Automation of the tightness control of the purge valve of the gas manifold of boiler plants. Tightness control. Gas Methods Design Guidelines for Automated Equipment

One of the ways to solve the problem of automating the tightness control of hollow products, for example, shut-off valves, is the development of a multi-position reconfigurable stand for automatic control of the tightness of products with compressed air, according to the manometric method. There are many designs of such devices. Known automatic control of the tightness of products, containing a table with a drive, an elastic sealing element, a rejecting device, a source of compressed gas, a copier and a device for clamping the product.

However, automation of the process is achieved due to the significant complexity of the design of the machine, which reduces the reliability of its operation.

Known machine for monitoring the tightness of hollow products, containing sealing units with leakage sensors, a test gas supply system, mechanisms for moving products and a rejection mechanism.

The disadvantage of this machine is the complexity of the process of monitoring the tightness of products and low productivity.

Closest to the invention is a stand for testing products for tightness, containing a rotor, a drive for its stepping movements, control blocks placed on the rotor, each of which contains a comparison element connected to a rejecting element, an element for sealing a product containing an outlet tube and a drive for its movement, which is made in the form of a copier with the possibility of interaction with the output tube.

However, this device does not allow to increase productivity, as this reduces the reliability of product testing.

Figure 1.6 shows an automated chamber-based leak tester. It consists of a chamber 1, in the cavity of which a controlled product 2 is placed, connected to the air preparation unit 3 through a shut-off valve 4, a membrane separator 5 with a membrane 6 and cavities A and B, a jet element OR-NOT OR 7. Cavity A of the membrane separator 5 is connected to the cavity of the chamber 1, and cavity B through the nozzle 8 - with the output 9 OR of the jet element 7. To its other output 10 NE OR is connected a pneumatic booster 11 with a pneumatic lamp 12. The cavity B is additionally connected by a channel 13 to the control input 14 of the jet element 7, atmospheric channels 15 of which are provided with plugs 16.

The device works as follows. The controlled product 2 is supplied with pressure from the air preparation unit 3, which is cut off by the valve 4 when the test level is reached. to the control input 14 of the jet element 7. Thus, in the absence of leakage from the controlled product 2, the jet element 7 is in a stable state under the action of its own output jet. In the presence of a leak from the product 2 in the internal cavity of the chamber 1 there is an increase in pressure. Under the influence of this pressure, the membrane 6 bends and closes the nozzle 8. The pressure of the air jet at the outlet 9 of the jet element 7 increases. At the same time, the jet disappears at the control input 14, and since the jet element OR - NOT OR is a monostable element, it switches to its stable state when the jet exits through the output 10 NOT OR. In this case, the amplifier 11 is triggered and the pneumatic lamp 12 signals the leak of the product 2. The same signal can be fed into the jet sorting control system.

This device is built on the elements of jet pneumoautomatics, which increases its sensitivity. Another advantage of the device is the simplicity of design and ease of configuration. The device can be used to control the tightness of gas fittings by compression methods at low test pressure, if the diaphragm seal is used as a sensor connected directly to the controlled product. In this case, the presence of abnormal leakage can be controlled by opening the membrane and nozzle.

Figure 1.6 ? Leak test device

Figure 1.8 shows a device that automates the control of the tightness of pneumatic equipment, for example, electro-pneumatic valves, that is, products similar to the gas fittings considered in the dissertation.

The tested product 1 is connected to the pressure source 2, the electromagnetic bypass valve 3 is installed between the output 4 of the product 1 and the exhaust line 5. The electromagnetic shut-off valve 6 with its input 7 is connected during the test with the output 4 of the product 1, and the output 8 - with the pneumatic input 9 of the converter 10 of the leakage measurement system 11, which is made in the form of a heat flow meter. The system 11 also includes a secondary unit 12 connected to the control input 13 of the converter 10, the pneumatic output 14 of which is connected to the exhaust line 5. The valve control unit 15 includes a multivibrator 16 and a block 17 for delay and pulse formation. One output of the multivibrator 16 is connected to the control input 18 of the shut-off valve 6, the other - to the control input 19 of the valve 3 and the block 17 connected in the control process to the drive 20 of the tested product 1. The calibration line 21 consists of an adjustable throttle 22 and a shut-off valve 23. It connected in parallel to product 1 and serves to configure the device.

Leak control is carried out as follows. When the valve control unit 15 is turned on, a pulse appears at the output of the multivibrator 16, which opens the valve 3 and the delay and pulse generation unit 17. The same pulse opens the tested product 1 after a set delay time by applying an electrical signal from block 17 to actuator 20. In this case, the test gas is vented through valve 3 into exhaust line 5. After a time set by multivibrator 16, the pulse is removed from valve 3, closing it, and is fed to the inlet 18 of the shut-off valve 6, opening it. In this case, the gas, the presence of which is due to leakage from the product 1, enters the leakage measurement system 11 and, passing through it, generates in the converter 10 an electrical signal proportional to the gas flow rate. This signal enters the secondary unit 12 of the leak measurement system, in which it is corrected, and the amount of gas flow through the closed test item 1 is recorded.

The disadvantages of this device include the following. The device is designed to control the tightness of gas fittings of only one type, equipped with an electromagnetic drive. At the same time, only one product is controlled, that is, the process is inefficient.

Figure 1.8 shows a diagram of an automated device for monitoring gas leaks using a compression method with a pneumatic-acoustic measuring transducer. The device consists of intermediate blocks and providing control of large leaks (more than 1 /min) and a pneumo-acoustic block for monitoring small leaks (0.005 ... 1) /min. The pneumo-acoustic converter unit has two amplifying manometric stages, consisting of micromanometers 1, 2 and acoustic-pneumatic elements 3, 4, interconnected through a distribution element 5. The measurement results are recorded by a secondary device 6 of the EPP-09 type, connected to the unit through distributor 7. Controlled product 8 is connected to the test pressure source through the shut-off valve K4. The operation of the device is carried out in a continuous-discrete automatic mode, which is provided by the logical control unit 9 and valves -. Controlled product 8 with the help of block 9 is connected in series to the blocks and, by the corresponding inclusion of valves and, where the preliminary value of leakage of the test gas is determined. In the case of a small leakage value (less than 1 /min), the product is connected by means of a valve to the pneumo-acoustic unit, where the leakage value is finally determined, which is recorded by the secondary device 6. The device provides gas leakage control with an error of no more than ± 1.5%. Supply pressure and element tube - tube in block 1800 Pa.

This device can be used for automatic control of gas fittings with a wide range of allowable gas leaks. The disadvantages of the device are the complexity of the design due to the large number of measuring units, as well as the simultaneous control of only one product, which significantly reduces the productivity of the process.

Figure 1.8 Automated device for monitoring gas leaks by compression.

Devices that provide simultaneous testing of several products are promising for monitoring the tightness of gas fittings. An example of such devices is an automatic device for checking the tightness of hollow products, shown in Figure 1.14. It contains a frame 1 fixed on the uprights 2 and covered by a casing 3, as well as a turntable 4 with a drive 5. The turntable is equipped with a faceplate 6, on which eight sockets 7 for products 8 are evenly located. The sockets 7 are made removable and have cutouts 9. Sealing nodes 10 are fixed on the frame 1 with a step twice as large as the pitch of the nests 7 on the faceplate 6. Each sealing unit 10 contains a pneumatic cylinder 11 for moving the product 8 from the slot 7 to the sealing unit and back, on the rod 12 of which a bracket 13 with a sealing gasket 14 is installed In addition, the sealing unit 10 contains a head 15 with a sealing element 16, which is communicated through pneumatic channels with the air preparation unit 17 and with the leakage sensor 18, which is a membrane pressure sensor with electrical contacts. The rejection mechanism 19 is mounted on the frame 1 and consists of a rotary lever 20 and a pneumatic cylinder 21, the rod of which is pivotally connected to the lever 20. Good and rejected products are collected in the appropriate bins. The machine has a control system, the current information about its operation is displayed on the board 22.

The machine works as follows. Controlled product 8 is installed at the loading position in the slot 7 on the faceplate 6 of the turntable 4. The drive 5 performs a step rotation of the table by 1/8 of a full turn at certain time intervals. To control the tightness by actuating the pneumatic cylinder 11 of one of the sealing units 10, the product 8 rises in the bracket 13 and is pressed against the sealing element 16 of the head 15. After that, a test pressure is supplied from the pneumatic system, which is then cut off. The pressure drop in the product 8 is recorded by the leakage sensor 18 after a certain control time, which is set by the table 4 step. Thus, when the table is rotated by one step, one of the following operations is performed at each of its positions: product loading; lifting the product to the sealing unit; tightness control; lowering the product into the socket on the faceplate; unloading of good products; removal of defective products. The latter enter position VIII, while the lever 20 under the action of the pneumatic cylinder rod 21 rotates in the hinge, and with its lower end passes through the cutout 9 of the socket 7, removing the product 8, which falls into the hopper under its own weight. Similarly, suitable products are unloaded at position VII (the unloading device is not shown).

The disadvantages of the device are: the need to lift the product from the faceplate in the sealing unit to control the tightness; the use of a membrane pressure transducer with electrical contacts as a leakage sensor, which has low accuracy characteristics compared to other types of pressure sensors.

The conducted studies have shown that one of the promising ways to improve the manometric method of tightness control is the joint use of bridge measuring circuits and various differential type transducers.

The pneumatic bridge measuring circuit for tightness control devices is based on two pressure dividers (Fig. 1.9).

Fig.1.9

The first pressure divider consists of a fixed throttle fli and an adjustable throttle D2. The second one consists of a constant choke Dz and an object of control, which can also be conditionally considered a choke D4. One diagonal of the bridge is connected to the test pressure source pk and the atmosphere, the second diagonal is measuring, a PD converter is connected to it. To select the parameters of the elements and adjust the bridge circuit, consisting of laminar, turbulent and mixed chokes, the dependence is used:

where R1 R2, R3, R4 are the hydraulic resistances of the elements D1, D2, D3, D4, respectively.

Given this dependence, the possibility of using both balanced and unbalanced bridge circuits, as well as the fact that the hydraulic resistance of the supply channels is small compared to the resistance of the chokes and therefore it can be neglected, then on the basis of the above pneumatic bridge circuit it is possible to build devices for monitoring the tightness of various objects. At the same time, the control process can be easily automated. It is possible to increase the sensitivity of the device through the use of unloaded bridge circuits, i.e. install transducers having R = in the measuring diagonal. Using the formulas for gas flow in subcritical mode, we obtain dependencies for determining the pressure in the inter-throttle chambers of an unloaded bridge.

For the first (upper) branch of the bridge:

for the second (lower) branch of the bridge:

where S1, S2, S3, S4 are the flow area of ​​the channel of the corresponding throttle; Рв, Рн - pressure in the interthrottle chamber of the upper and lower branches of the bridge, рк - test pressure.

Dividing (2) by (3) we get

Dependence (4) implies a number of advantages of using a bridge circuit in devices for tightness control by the manometric method: the pressure ratio in the interthrottle chambers does not depend on the test...

Let us consider schematic diagrams of devices that provide control of tightness by the manometric method, which can be built on the basis of pneumatic bridges and various types of differential pressure converters into electrical and other types of output signals.

On fig. 1.10 shows a diagram of a control device in which a water differential pressure gauge is used in the measuring diagonal of the bridge.

Figure 1.10 Scheme of a control device with a measuring diagonal of the bridge - a water differential pressure gauge

The test pressure pk is supplied through constant throttles to two lines. One line - the right one is measuring, the pressure in it varies depending on the amount of leakage in the controlled object 4. The second line - the left one provides a reference counterpressure, the value of which is set by an adjustable throttle 2. Typical devices can be used as this element: cone - cone, cone - cylinder, etc. Both lines are connected to a differential pressure gauge 5, in which the difference in the heights of the liquid columns h is a measure of the pressure drop in the lines and at the same time allows you to judge the amount of leakage, because proportional to it:

It is possible to automate the process of reading the readings of a water differential pressure gauge through the use of photoelectric sensors, fiber-optic converters, and optoelectronic sensors. In this case, the water column can be used as a cylindrical lens that focuses the light flux, and in the absence of water, it can be scattered. In addition, water can be tinted to make it easier to read the readings and act as an obstacle to the light flow.

This device provides a high accuracy measurement of the leakage value, and therefore can be used for calibrating other control and measuring devices and certifying test leaks.

On fig. 1.11 shows a device for measuring leakage in object 4, in which a jet proportional amplifier 5 is used in the measuring diagonal of the bridge. Under the pressure of the jet coming out of the booster, arrow 6, loaded with spring 7, deviates. Deviation of the arrow corresponds to the amount of leakage. The reading is carried out on a graduated scale 8. The device may be provided with a pair of closing electrical contacts that are triggered when leakage exceeds the allowable one. The use of a jet proportional amplifier makes it easier to adjust the device to a given level of leakage, and increases the accuracy of control.

Figure 1.11 Scheme of a control device with a jet proportional amplifier

However, given that the amplifier has a hydraulic resistance Ry0, the bridge circuit is loaded, which reduces its sensitivity. In this case, as an adjustable tuning throttle 2, it is advisable to use a bubbling tank 9 filled with water and a tube 10, one end of which is connected to the throttle 1, forming a counterpressure line with it, and the second end has an outlet to the atmosphere and is immersed in the tank. Regardless of the value of the test pressure pk, the pressure pp will be established in the tube 10, which is determined by the dependence:

where h is the height of the water column displaced from the tube.

Thus, the adjustment of the back pressure in the bridge circuit is carried out by setting the appropriate h and the immersion depth of the tube. Such an adjustable throttle device provides high accuracy in setting and maintaining backpressure. In addition, it is practically cost-free. However, control chokes of this type can be used in circuits operating at low pressure (up to 5-10 kPa) and mainly in laboratory conditions.

The use of bridge circuits with pneumoelectric membrane transducers in tightness control devices ensures their operation in a wide range of pressures pk with sufficient accuracy. A diagram of such a control device is shown in fig. 1.12.

It consists of constant chokes 1 and 3, as well as adjustable choke 2. Membrane transducer 5 is connected to the measuring diagonal of the bridge, while one of its chambers is connected to the measuring line of the bridge, and the second to the counter pressure line. At the beginning of the process of monitoring the tightness of the object 4, the membrane b is in the rest position, balanced by the pressures in the inter-throttle chambers of the bridge, which is fixed by closing the right pair of electrical contacts 7. If the object is leaking, i.e. when a leak occurs, a pressure difference will occur in the converter chambers, the membrane will bend and contacts 7 will open. If a leak occurs more than the permissible value, the membrane deflection will ensure the closure of the left pair of electrical contacts 8, which will correspond to a defective product.

Figure 1.12 Scheme of a control device with a pneumatic diaphragm transducer

The relationship between the membrane stroke and the pressure difference in the chambers in the absence of a rigid center and a small deflection is established by the dependence:

where r is the radius of the membrane, E is the modulus of elasticity of the membrane material,

Membrane thickness

Given the dependence and leakage Y according to the formula, dependence, you can choose the structural elements and operating parameters of this converter.

Transducers with flat membranes, in addition to electrical contacts, can be used in conjunction with inductive, capacitive, piezoelectric, magnetoelastic, pneumatic, tensometric and other output transducers of small displacements, which is their great advantage. In addition, the advantages of pressure transducers with flat diaphragms are their structural simplicity and high dynamic properties.

On fig. 1.13 shows a diagram of a device designed to control tightness at low and medium test pressures.

Figure 1.13 Diagram of a control device with a two-input three-membrane amplifier

Here, in the pneumatic bridge, consisting of constant throttles 1 and 3, adjustable throttle 2 in the measuring diagonal, a comparison element 5 is used, made on a two-input three-membrane amplifier USEPPA type P2ES.1, the blind chamber A of which is connected to the counterpressure line, and the blind chamber B is connected with measuring line. The output of the comparison element is connected to an indicator or a pneumoelectric transducer 6. The comparison element is powered separately from the bridge and at a higher pressure. Adjustable throttle 2 sets the differential pressure between the measuring line and the backpressure line proportional to the maximum allowable leakage. If, during the control, the leakage through the object 4 is less than the permissible value, then the pressure pi in the measuring line will be higher than the counterpressure pi, and there will be no signal at the output of the comparison element. If the leakage exceeds the allowable value, then the pressure in the measuring line will become less than the back pressure, which will lead to the switching of the comparison element and a high pressure will appear at its output, this will cause the indicator or pneumatic electric converter to work. The operation of this scheme can be described by the following inequalities. For control objects with an allowable leakage value:

For control objects with leakage exceeding the allowable:

This device can be used in automated stands to control the tightness of valves. An additional advantage is the ease of implementation of the design on typical elements of pneumatic automation.

On fig. 1.14 shows a device for measuring and controlling leakage in object 4, in which a differential bellows transducer 5 is connected to the measuring diagonal of the bridge. The pressure value corresponding to the allowable leakage is set by the adjustable throttle 2.

Bellows 6 and 7 are interconnected by a frame on which an indication system is fixed, consisting of an arrow 8 with a scale 9 and a pair of adjustable closing electrical contacts 10. The device is configured in accordance with the dependence:

Figure 1.14 Scheme of a control device with a differential membrane transducer

In the event of a leak, the pressure pi in the bellows 7 begins to decrease, and it contracts, and the bellows 6 will stretch, because pn remains constant, while the frame will begin to move and the arrow will show the amount of leakage. If the leakage exceeds the allowable one, then the corresponding movement of the bellows will close the electrical contacts 10, which will give a signal about the marriage of the control object.

This device can operate at medium and high test pressure. It can be used in automated stands for checking the tightness of high-pressure shut-off valves, where relatively high leak rates are allowed and their absolute values ​​need to be measured.

• 1. The use of pneumatic bridge circuits in conjunction with various types of differential transducers significantly expands the possibilities of using the manometric method for automation of tightness control.
• 2. Automated devices for tightness control based on bridge circuits can be implemented on standard logic elements, as well as serial differential sensors used to control various technological quantities, which significantly speeds up their creation and reduces the cost.

Checking the tightness of the valves of the shut-off valves installed in series in front of the burner, carried out before ignition of the burner after purging gas outlet. The procedure for checking depends on the degree of automation of the burner and its thermal output and is determined by the project. The check is made by creating a pressure difference on both sides of the valve and monitoring the change in pressure.

Leak testin manual mode(Fig. 109). When checking the tightness of two shut-off valves 1,2 installed in series before the burner, it is necessary to control the pressure between them. To do this, in front of the tap on the safety pipeline 5 a fitting is installed to which a pressure gauge is connected 4.

Work procedure:

Install a pressure gauge on the fitting (the shut-off valve in front of the burner is closed, and the valve on the safety pipeline is open);

Close the valve on the safety pipeline and if the installed pressure gauge does not show a change in pressure, then the first stop valve along the gas flow is tight;

With shut-off valves in front of the burner closed, open and close the first of them along the gas flow. The pressure gauge will show the gas pressure equal to the pressure in the supply gas pipeline, and if this pressure does not change, then the second shut-off valve along the gas flow and the valve on the safety pipeline are tight. If the valves are not tight, ignition of the burners is prohibited.

The check can also be performed using shut-off valves on the branch, while it becomes possible to check both the valve itself on the branch and the protection slam-shut.

Leak testin automatic mode .

An electric shut-off valve is installed in front of the burner and on the safety pipeline, and instead of a pressure gauge, a tightness control relay (pressure sensor) is installed.

Checking is carried out in the same way as in manual mode. mode(Fig. 109), but with automatic control.

Leak test,when installing a double solenoid valve and a tightness control unit upstream of the burner(Fig. 110). The tightness test is carried out before each burner start-up. If the double solenoid valve is not tight 1 the gas supply is stopped. When not in use, both solenoid valves are closed.

Leak control unit 2 consists of: solenoid valve 3 , internal pump 4 and built-in pressure switch (pressure sensor) 5 , which are sequentially placed on the bypass of the first valve along the gas flow.

Before the tightness test, the gas pressure in front of the double solenoid valve corresponds to the operating pressure ( R slave). At the beginning of the test, the solenoid valve 3 opens and internal pump 4 creates more gas pressure ( R con) in the control area between the solenoid valves, compared to the gas pressure in the outlet gas pipeline. When the required control pressure is reached, the pump switches off. A built-in pressure switch monitors the test area and if the pressure does not change, then both valves of the double solenoid valve are tight.

The furnaces and flues of gasified installations must be ventilated before being put into operation. The ventilation time is determined by calculation and set by the instruction, but not less than 10 minutes, and for automated burners - by the start-up (ignition) program.

Before starting gas into the burner, the tightness of the shut-off valves in front of the burner is checked. The shut-off valve on the gas pipeline in front of the burner opens after ignition of the ignition device.

Starting gas after conservation, repair, seasonal shutdown boiler room or production

The start-up of gas after conservation, repair, seasonal shutdown, as well as the initial start-up of gas after the completion of installation work is carried out by the owner enterprise or a specialized organization (according to the contract). The inclusion of gas-using equipment is formalized by an act prepared with the participation of a representative of the operating organization.

Before starting gas and gas networks, it is necessary:

Inspect equipment;

Ventilate the room;

Carry out control pressure testing of gas pipelines;

Remove the plug on the gas pipeline;

Blow gas pipelines with gas;

Take a gas sample and verify that the purge is complete. Purging is gas-hazardous work and is carried out according to a work permit.

Stop boiler room (manufacturing) for conservation (for repairs, seasonal stop)

Before stopping the gas-using installation for repair, its external inspection is carried out in accessible places in order to check the technical condition and clarify the scope of work. The shutdown of gas-using equipment is documented by an act prepared with the participation of a representative of the operating organization.

Operating procedure:

According to the instructions, the equipment is stopped (if necessary, hydraulic fracturing);

Gas pipelines must be disconnected and purged with air. Disconnection of the internal gas pipeline is carried out with the installation of a plug on the gas pipeline behind the shutoff valves. This is a gas-hazardous job and is performed under a work permit.

The shut-off valves on the purge pipelines must remain in the open position after the gas pipeline is turned off.

When the gas supply system or separate gas-using equipment is turned off at a long period or for repair the consumer is advised to notify the supplier at least three days in advance.

The shutoff valve drives are de-energized (fusible links are removed) and locked with locks, the keys to which are handed over by shift, and warning signs are hung on the shutoff valves.

Work performed at withdrawal from the reserve gas-using installation

Conclusion from reserve gas-using installation is a gas-hazardous job and is performed under a work permit or in accordance with the production instructions. The work is carried out by a team of workers consisting of at least two people under the guidance of a specialist:

· take off plug on the way to gas-using installation

The order of turning on the burners of gas-using installations depends on the design of the burners, their location on the gas-using equipment, the type of ignition device, the presence and type of safety and regulation automation.

· the sequence of actions during the ignition of the burners is determined in accordance with the requirements of the production instruction, developed on the basis of existing standards and instructions.

Start-up of a gas-using plant (see fig. 96) produced according to written order of the person responsible for the safe operation of gas consumption facilities, in accordance with the production instructions . Personnel must be warned in advance by the responsible person about the start time of work.

Before firing up a gas-fired boiler, the tightness of the shut-off valve in front of the burners must be checked in accordance with the regulations in force.

If there are signs of gas pollution in the boiler room, switching on electrical equipment, kindling the boiler, as well as using open fire is not allowed.

Before starting the gas, it is necessary:

Using a gas analyzer or by smell, check the room and make sure that there is no gas contamination;

According to the operational documentation, make sure that there is no prohibition on commissioning;

Inspect the position of the shut-off valves on the gas pipeline to the installation: all valves, except for valves on the purge pipelines, safety pipelines, in front of instrumentation and automation sensors, must be closed;

Make sure that the equipment for burning gas fuels of the furnace, gas ducts, air ducts, shut-off and control devices, instrumentation, headsets, smoke exhausters and fans are in good condition, as well as check the presence of natural draft;

Make sure that the gates on non-working units are closed;

Blow out the general boiler (general workshop) gas pipeline if the first installation is put into operation;

Turn on the smoke exhauster and the fan, before turning on the smoke exhauster to ventilate the furnace and gas ducts, you must make sure that the rotor does not touch the casing of the smoke exhauster, for which the rotor is turned manually;

gas start:

Open the shut-off valves at the gas pipeline outlet to the unit; fix, in the open position of the slam-shut protection; slightly open the control valve of automatic control by 10%; blow off the outlet to the unit, take a gas sample from the fitting on the purge pipeline;

Make sure that there are no gas leaks from gas pipelines, gas equipment and fittings by washing or using a device (leak detector);

Check the compliance of the gas pressure on the pressure gauge, and when using burners with forced air supply, additionally, the compliance of the air pressure with the set pressure;

Ventilate the furnace, gas ducts and air ducts for 10-15 minutes. and adjust the draft of the melted boiler by setting the vacuum in the upper part of the furnace 20-30 Pa (2-3 mm w.c. st.), and at the level of gas burners at least 40-50 Pa(4-5 mm w.c. Art.);

Close the air damper;

Check the tightness of the valves of the shut-off valves installed in front of the burner;

Using a portable gas analyzer, take a sample of air from the top of the furnace, make sure that there is no gas in it.

Ignition of gas burners.

The ignition of gas burners must be carried out by at least two operators.

Manual ignition forced air burners:

Open the tap to the portable igniter and ignite the gas coming out of the igniter;

With stable operation of the igniter, bring it into the furnace to the mouth of the main burner being turned on;

Close the tap on the safety pipeline;

Open the first shut-off valve along the gas flow in front of the burner, and then slowly open the second shut-off valve along the gas flow, letting gas into the burner;

After igniting the gas, slightly increase its supply, making the flame stable;

Open the air damper;

By increasing the gas supply, then air, while controlling the rarefaction in the furnace, bring the burner to the minimum mode according to the regime map;

Remove the igniter from the furnace and close the tap in front of it;

Put the rest of the burners into operation in the same way.

The kindling of the gas-using installation is carried out within the time specified by the instruction.

Protection and automatic control are put into operation according to the instructions.

Information about the work performed is recorded in the journal.

Ignition of injection burners produced in a similar way, and since If there is no fan, the furnace is ventilated without a fan. After igniting the gas, open the air washer,

adjust the vacuum in the furnace and, by increasing the gas supply, while monitoring the vacuum in the furnace, bring the burner to the minimum mode according to the regime map.

Ignition of the burners with the help of the RZZU:

Turn the control key of the gas-using installation to the “Ignition” position. In this case, the RCPD is activated: the time relay is turned on, the gas solenoid valve (PZK) of the igniter opens, the ignition device is turned on (when the igniter flame goes out, the flame control electrode of the RCPD gives an impulse to deflect the high-voltage transformer);

If the igniter flame is stable, close the safety gas valve and fully open the shut-off valve in front of the main burner.

Personnel actions in case of accidents (incidents) on burners

In case of separation, flashover or extinction of the flame during ignition or in the process of regulation, it is necessary:

immediately stop the gas supply to this burner (burners) and the ignition device;

ventilate the furnace and gas ducts for at least 10 minutes;

find out the cause of the problem;

report to the responsible person;

After eliminating the causes of the malfunctions and checking the tightness of the shut-off valve in front of the burner, at the direction of the person in charge, according to the instructions, re-ignite.

Startinto the work of the PIU (GRU) and ignition first burner

but. The hydraulic fracturing is put into operation in accordance with the production instructions.

b. The start-up of the gas-using installation is carried out in accordance with the production instructions.

in. Before ignition of the first burner, the valve on the purge gas line must be open.

Worksperformed at decommissioning of the gas-using installation in reserve

Stopping (see Fig. 96) of gas-using equipment in all cases, except for emergency, is carried out at the written direction of the technical manager, in accordance with the production instructions. If necessary, training of personnel is carried out.

Work order:

Set the operating mode of the burners of the installation to the minimum, according to the regime map;

Lock in the open position of the protection slam-shut;

- for forced burners by giving air, close the air damper in front of the burner, and then the second shut-off valve along the gas flow on the gas pipeline to the burner, and for injection burner close the second shut-off valve along the gas flow to the burner, and then the air washer;

Check visually the cessation of combustion;

Close the control valves and open the valve on the safety pipeline;

Remove other burners of the plant in the same way;

Close the shut-off valves at the outlet to the installation;

Open the purge pipeline and the safety pipeline;

Close slam-shut protection;

Open the air damper (washer) and ventilate the furnace for 10 minutes;

Turn off the fan (if any) and the smoke exhauster, close the air damper (washer) and the gate;

Make a journal entry.

The shutdown of gasified boilers with control and safety automatics and with complex automatics is carried out in accordance with the production instructions.

10.Maintenance and repair

TR 870. Mandatory requirements. installed to gas distribution networks during the operation phase (including maintenance and current repairs)

To establish the possibility of operation of gas pipelines, buildings and structures and technological devices of gas distribution and gas consumption networks after the deadlines specified in the project documentation, their technical diagnostics should be carried out.

Deadlines for the further operation of objects of technical regulation of this technical regulation should be established based on the results technical diagnostics .

Ensuring the safety of gas-fired heat engineering equipment is one of the most important tasks facing the designers and maintenance personnel of boiler houses.
The solution of this problem in practice is complicated by the wear and tear of equipment, its physical and moral aging, the malfunction of individual elements of automation equipment, as well as the insufficiently high level of qualification and low technological discipline of the maintenance personnel, which can lead to serious accidents accompanied by human casualties.
Investigation of emergencies, especially those related to safety devices, is often difficult due to the lack of objective information about the causes that led to their occurrence.
One of the most important elements, the condition of which largely determines the level of safety of gas boilers, is the purge valve of the gas manifold.
Leakage of the purge valve shutter is one of the reasons for the leakage (loss) of gas through the purge gas pipeline into the atmosphere, and in the presence of a malfunction of other elements of the gas shut-off valves, it creates dangerous prerequisites for unauthorized ingress of gas into production facilities and furnaces of boiler units.
Existing design solutions for the automation system do not provide for the possibility of continuously monitoring the tightness of the purge valve.
We were witnesses of accidental discovery of leaks in the purge valve of the gas collector, when, at the stage of commissioning, during the check of the automatic ignition system of the standby boiler unit, with the igniter solenoid valve turned off, after a spark was applied, a steady burning of the igniter flame occurred. The maintenance personnel of the boiler house did not have the information to detect this malfunction in a timely manner and take the necessary measures to eliminate it.
In order to prevent such situations, it is proposed to install a glass water seal filled with
glycerin. The control circuit consists of a gas collector pipeline, a gas cock 1, a purge valve 2, a water seal 3, a filler neck 5.
The gas cock 1 is necessary in case of leakage of the purge valve during the operation of the boiler, as well as in case of inspection or replacement of the valve. The passage of gas is determined by the bubbles in the hydraulic seal during the blowdown and operation of the boiler.
If the first solenoid valve is leaking, gas leakage can be seen in the form of bubbles that rise in the liquid when the burner is at rest.
If the blow-off valve is leaking during burner operation.
The device is designed in such a way that when the gas pressure drops, glycerin does not penetrate into the pipeline.
Another advantage of this device is that the pipe section between the valves is not filled with air during long periods of inactivity.
The proposed technical solution contains well-known elements and can be implemented on the basis of standard industrial devices. The costs of implementing the proposed technical solution are insignificant and incommensurable with the losses that may arise as a result of an emergency caused by a leak in the purge valve of the gas manifold.

Head of the Laboratory for Non-Destructive Testing of Kontakt LLC Ktitrov Konstantin Borisovich
Head of the Department for EPB ZiS LLC "Contact" Melnikov Lev Mikhailovich
Engineer of the 1st category LLC "Contact" Katrenko Vadim Fedorovich
Engineer-expert of Contact LLC Keleberda Alexander Ivanovich
Expert LLC "Contact" Kuznetsov Viktor Borisovich

Introduction

Chapter 1 Analysis of the state of the problem of automation of tightness control and statement of the research problem 9

1.1 Main terms and definitions used in this study 9

1.2 Features of gas valve tightness control 11

1.3 Classification of gas test methods and analysis of the possibility of their application to control the tightness of gas fittings 15

1.4 Review and analysis of means of automatic control of tightness according to the manometric method 24

1.4.1 Transducers and sensors for automatic leak detection systems 24

1.4.2 Automated systems and leak detection devices 30

Purpose and objectives of the study 39

Chapter 2 Theoretical Study of the Gauge Leak Test Method 40

2.1 Determination of gas flow regimes in test objects ... 40

2.2 Investigation of the compression method of leak testing 42

2.2.1 Investigation of time dependences in the control of tightness by compression method 43

2.2.2 Investigation of the sensitivity of tightness control by compression method with a cut-off 45

2.3 Study of the method of comparison with the continuous supply of test pressure 51

2.3.1 Scheme for checking tightness by the method of comparison with the continuous supply of test pressure 52

2.3.2 The study of time dependences in the control of tightness by the method of comparison 54

2.3.3 Investigation of the sensitivity of the tightness control by the method of comparison with the continuous supply of test pressure 65

2.3.4 Comparative assessment of the sensitivity of tightness control by compression method with cut-off and the comparison method 68

you water to chapter 2 72

Chapter 3 Experimental Investigation of the Parameters of Leak Testing Circuits Based on the Comparison Method 75

3.1 Experimental setup and research methodology 75

3.1.1 Description of the experimental setup 75

3.1.2 Technique for the study of leak control circuits 78

3.2 Experimental study of the tightness control scheme based on the comparison method 81

3.2.1 Determining the characteristic p = f(t) of the lines of a leak detection circuit 81

3.2.2 Studies of the temporal characteristics of the lines of the tightness control circuit according to the comparison method 86

3.2.3 Investigation of the static characteristic of the measuring line of the leak detection circuit 91

3.3. Experimental study of a tightness control device based on the comparison method 97

3.3.1 Investigation of a model of a device for monitoring tightness with a differential pressure sensor 97

3.3.2 Evaluation of the accuracy characteristics of devices for tightness control, made according to the comparison scheme 100

3.4 Probabilistic assessment of the reliability of product sorting during tightness control according to the comparison method 105

3.4.1 Experimental study of the distribution of the pressure value equivalent to the leakage of test gas in a batch of products 105

3.4.2 Statistical processing of the results of the experiment to assess the reliability of sorting 108

4.3 Development of leakage sensors with improved performance 126

4.3.1 Construction of the leakage sensor 127

4.3.2 Mathematical model and algorithm for calculating the tightness sensor 130

4.4 Development of an automated leak test bench.133

4.4.1 Design of the automated multi-position stand 133

4.4.2 Selecting parameters for leak detection circuits 142

4.4.2.1 Method for calculating the parameters of the tightness control circuit according to the compression method with a cut-off 142

4.4.2.2 Method for calculating the parameters of the leak control circuit according to the comparison method 144

4.4.3 Determining the performance of an automated leak tester 146

4.4.4 Determining the parameters of seals for an automated stand 149

4.4.4.1 Method for calculating the sealing device with a cylindrical collar 149

4.4.4.2 O-ring design method 154

General conclusions and results 157

References 159

Appendix 168

Introduction to work

An important problem in a number of industries is the increased requirements for the quality and reliability of manufactured products. This causes an urgent need to improve existing, create and implement new methods and means of control, including tightness control, which refers to flaw detection - one of the types of quality control systems and products.

In the industrial production of shut-off and distribution valves, in which the working medium is compressed air or another gas, the existing standards and technical conditions for its acceptance regulate, as a rule, one hundred percent control of the "tightness" parameter. The main unit (working element) of such fittings is a movable pair "plunger-body" or a rotary valve element, which operate in a wide range of pressures. Various sealing elements and lubricants (sealants) are used to seal gas fittings. During the operation of a number of gas valve structures, a certain leakage of the working medium is allowed. Exceeding the permissible leakage due to low-quality gas fittings can lead to incorrect (false) operation of the production equipment on which it is installed, which can cause a serious accident. In domestic gas stoves, an increased leakage of natural gas can cause a fire or poison people. Therefore, exceeding the allowable leakage of the indicator medium with appropriate acceptance control of gas fittings is considered a leak, i.e., a product defect, and the exclusion of marriage increases the reliability, safety and environmental friendliness of the entire unit, device or device in which gas fittings are used.

Checking the tightness of gas fittings is a laborious, lengthy and complex process. For example, in the production of pneumatic mini-equipment, it takes 25-30% of the total labor input and up to 100-120% of the time.

assemblies. This problem can be solved in large-scale and mass production of gas fittings by using automated methods and control tools, which should provide the required accuracy and performance. In real production conditions, the solution of this problem is often complicated by the use of control methods that provide the necessary accuracy, but are difficult to automate due to the complexity of the method or the specifics of the test equipment.

About ten methods have been developed for testing the tightness of products using only a gaseous test medium, for the implementation of which over a hundred different methods and means of control have been created. The development of modern theory and practice of tightness control is devoted to the research of Zazhigin A. S., Zapunny A. I., Lanis V. A., Levina L. E., Lembersky V. B., Rogal V. F., Sazhina S. G., Trushchenko A. A., Fadeeva M. A., Feldmana L. S.

However, there are a number of problems and limitations in the development and implementation of tightness control tools. Thus, most high-precision methods can and should be applied only to large-sized products, in which complete tightness is ensured. In addition, restrictions of an economic, constructive nature, environmental factors, and safety requirements for maintenance personnel are imposed. In serial and large-scale production, for example, of pneumatic automation equipment, gas fittings for household appliances, in which a certain leakage of the indicator medium is allowed during acceptance tests and, consequently, the requirements for control accuracy are reduced, the possibility of its automation and provision on this basis of high performance of the appropriate control and sorting equipment, which is necessary for 100% product quality control.

An analysis of the features of the equipment and the main characteristics of the gas tightness testing methods most used in industry made it possible to conclude that it is promising for automating the control of tightness.

the accuracy of gas fittings using the comparison method and the compression method that implement the manometric method. In the scientific and technical literature, little attention has been paid to these test methods due to their relatively low sensitivity, however, it is noted that they are most easily automated. At the same time, there are no recommendations on the selection and calculation of the parameters of tightness control devices, made according to the comparison scheme with a continuous supply of test pressure. Therefore, research in the field of gas dynamics of blind and flow tanks, as elements of control circuits, as well as gas pressure measurement technology as the basis for creating new types of transducers, sensors, devices and systems for automatic control of the tightness of products, promising for use in the production of gas fittings.

In the development and implementation of automated devices for monitoring tightness, an important question arises about the reliability of the control and sorting operation. In this regard, a corresponding study was carried out in the dissertation, on the basis of which recommendations were developed that allow, with automatic sorting by the "tightness" parameter, to exclude the ingress of defective products into suitable ones. Another important issue is to ensure the desired performance of automated equipment. The dissertation gives recommendations on the calculation of the operating parameters of an automated test stand for tightness control, depending on the required performance.

The work consists of an introduction, four chapters, general conclusions, a list of references and an appendix.

The first chapter discusses the features of monitoring the tightness of gas fittings, which allow a certain leak during operation. The review of methods of gas tightness testing, classification and analysis of the possibility of their application for automating the control of gas fittings is given, which made it possible to choose the most promising - the manometric method. Devices and systems that provide automation of tightness control are considered. The goals and objectives of the study are formulated.

In the second chapter, two methods of tightness control that implement the manometric method are theoretically investigated: compression with pressure cut-off and the method of comparison with continuous supply of test pressure. The mathematical models of the studied methods were determined, on the basis of which their time characteristics and sensitivity were studied under various gas flow regimes, different line capacitances and pressure ratios, which made it possible to identify the advantages of the comparison method. Recommendations on the choice of parameters for tightness control schemes are given.

In the third chapter, the static and temporal characteristics of the lines of the tightness control circuit are experimentally investigated by the method of comparison at various values ​​of leakage, line capacitance and test pressure, and their convergence with similar theoretical dependencies is shown. The operability was experimentally checked and the accuracy characteristics of the device for tightness control, made according to the comparison scheme, were evaluated. The results of evaluating the reliability of product sorting by the "tightness" parameter and recommendations for setting up the corresponding automated control and sorting devices are given.

In the fourth chapter, a description of typical schemes of automation of the manometric test method and recommendations for the design of automated equipment for tightness control are given. The original designs of the tightness sensor and the automated multi-position stand for tightness control are presented. Methods for calculating the tightness control devices and their elements, presented in the form of algorithms, as well as recommendations for calculating the operating parameters of the control and sorting stand, depending on the required performance, are proposed.

The Appendix presents the characteristics of gas tightness testing methods and time dependences for possible sequences of changing gas flow regimes in a flow tank.

Features of control of tightness of gas fittings

The developments and studies presented in the dissertation are related to gas fittings, in the manufacture of which the existing standards and technical conditions regulate one hundred percent control of the "tightness" parameter and a certain leakage of the working medium is allowed. Under the gas fittings considered in this paper, we mean devices intended for use in various systems in which the working medium is a gas or a mixture of gases under pressure (for example, natural gas, air, etc.), to perform the functions of cut-off, distribution etc. Gas fittings include: valves, distributors, valves and other means of industrial pneumatic automation of high (up to 1.0 MPa) and medium pressure (up to 0.2 ... at low pressure (up to 3000 Pa). Both finished products and their constituent elements, individual components, etc. are subjected to a tightness test. Depending on the purpose of the products, the conditions in which they are operated and the design features, various requirements are imposed on them in relation to their tightness.

The tightness of gas fittings is understood as its ability not to let the working medium supplied under excess pressure through the walls, joints and seals. In this case, a certain amount of leakage is allowed, the excess of which corresponds to the leakage of the product. The presence of leakage is explained by the fact that the main unit - the working element of such devices is a movable, difficult to seal pair: spool-body, nozzle-flap, ball, cone or saddle valves, etc. In addition, the design of the device, as a rule, contains fixed sealing elements: rings, cuffs, oil seals, lubricants, defects of which can also cause leakage. Leakage of gas fittings, i.e. the presence of leakage of the working medium exceeding the allowable one, can lead to serious accidents, breakdowns and other negative results in the operation of the equipment in which it is used. The stopcock (Fig. 1.1) is an important part of household gas stoves. It is designed to regulate the supply of natural gas to the burners of the stove and cut it off at the end of work. Structurally, the valve is a device with a rotary valve element 1, mounted in a split housing 2, which has channels for the passage of gas. The points of interface of the crane parts need to be sealed to ensure its maximum possible tightness. Sealing is carried out with a special graphite grease - sealant, manufactured in accordance with TU 301-04-003-9. Poor sealing leads to the leakage of natural gas during the operation of the stove, which, in the conditions of a limited space of domestic premises, is explosive and fire hazardous, in addition, the ecology (human habitat) is violated.

In accordance with the following requirements are established when testing the tightness of a shut-off valve. The tests are carried out with compressed air at a pressure of (15000±20) Pa, since higher pressures may damage the sealing lubricant. Air leakage must not exceed 70 cm3/h. The permissible volume of switching channels and capacities of the control device is not more than (1 ± 0.1) dm3. Control time 120 s.

Leakage of compressed air in the laboratory, in accordance with recommended control using a volumetric device (Fig. 1.2). The device consists of a measuring burette 1, to which air under pressure is supplied through channel 2, a reserve vessel 3, a vessel 4 to maintain the required level and a connection point for the test tap 5. It is allowed to control using other devices, the luxury of which does not exceed that of the volumetric device ± 10 cm3/h. Leakage control is carried out by measuring the volume of water displaced.

Gas fittings of medium and high pressure, which must be tested for tightness, include pneumatic valves, switches, adjustable throttles and other devices of pneumatic equipment, typical designs of which are shown in fig. 1.3 and 1.4. On fig. 1.3 shows a pneumatic valve with a cylindrical spool type P-ROZP1-S, a valve pneumatic valve with a flat spool type B71-33

channel 1 for the control signal, spool 2, body 3, cover with channel 4 connecting to the atmosphere, working channel 5 and sealing ring 6. In fig. 1.4 shows a crane pneumatic distributor with a flat spool type B71-33, consisting of a body 1, a cover 2, a flat rotary spool 3, a handle 4, a roller 5, working channels 6, 7, 8, 9, a channel 10 connecting with the atmosphere and a channel for compressed air supply 11. The presence of a regulated leak in pneumatic equipment is explained by the fact that its designs contain flat spools, cylindrical spools with a sealing gap, valve and crane devices, which involve leakage of compressed air from one cavity to another or leakage into the atmosphere through gaps and leaks . The allowable leakage value of a particular pneumatic device is set by the developer on the basis of GOST and is indicated in its technical specification. The allowable leakage values ​​for various types of pneumatic devices at the nominal compressed air pressure set for this device are given in table 1.1. Pneumatic equipment is used in control systems of various industrial equipment, therefore, increased leakage of the working medium and, as a result, a drop in pressure can lead to the failure of the device or cause false operation, i.e. lead to an emergency, equipment breakdown.

When testing for tightness of pneumatic equipment, difficulties arise due to the variety of designs, a wide range of allowable leakage of the indicator medium (0.0001 ... 0.004) m3 / min; different values ​​of test pressure (0.16...1.0) MPa and control time (from tens of seconds or more). In addition, contamination of the indicator medium (compressed air) should not exceed class 1 according to GOST 17433-91, ambient temperature 20±5C. The error of measuring and control instruments, by which the amount of leakage is determined, should not exceed ± 5% . To control the tightness of pneumatic equipment, pressure sensors (signaling devices) and specially designed equipment are used. An analysis of these devices is given in section 1.4.

Investigation of the sensitivity of tightness control by compression method with a cut-off

Leak test sensitivity is the smallest test gas leakage that can be measured during product testing. Table 2.2. Time dependences for various sequences of gas outflow modes from a blind chamber Variants of pressure ratio Sequence of changes in outflow modes in the transient process choke, i.e., with corresponding gas leaks through leaks in the test object. Let us express the gas leakage Y in terms of the mass flow rate G. Let us assume that regardless of the gas outflow regime, at a conductivity value f, the leakage is equal to Ud, and at a conductivity / the leakage is equal to U. For a turbulent supercritical regime, after substituting formulas (2.5) into (2.15), we obtain: With the same test duration /, - (as a result of transformation (2.19) and (2.20), we obtain the relation (2.21) Substituting (2.21) into (2.18), we obtain the relation Since in (2.23) the LU will have the same absolute value, regardless of the relations Ud U or Ud U, then, to simplify the calculations, we assume that Ud U. Then (2.23) can be represented as an expression - the pressure response pA to the change in AC leakage. If, in dependence (2.25), the value Art is taken equal to the sensitivity threshold pp of the manometric measuring device , then we obtain a formula for determining the smallest change in leakage Uch, which can be recorded during tightness control by the method under study.In accordance with the definition, this value on U, is the sensitivity of tightness control by compression method with cut-off in turbulent supercritical mode

Transformation (2.25) with respect to p0 makes it possible to obtain an expression for determining the test pressure depending on the sensitivity of the tightness control Uch in turbulent supercritical mode. compression method with a cut-off in turbulent subcritical mode Transformation (2.36) relative to p0 allows you to obtain an expression for determining the test pressure depending on the sensitivity Uch of tightness control in turbulent subcritical mode 2.41) and (2.42) we obtain the relation

Investigation of the comparison method with continuous supply of test pressure The general provisions and scheme of the leak test according to the comparison method with cut-off of the test gas source are discussed in Section 1.3.2. However, as the analysis showed, a method of comparison with a continuous supply of test pressure is promising for further research. This is explained by the fact that shut-off, distribution and switching gas fittings in real conditions operate under constant operating pressure and, according to technical characteristics, allow a certain amount of leakage. Therefore, to test the tightness of this class of devices, it is advisable to use the control scheme with a continuous supply of test pressure, as the most appropriate for the actual conditions of their operation. In addition, the need to cut off the pressure source during each test is eliminated, which greatly simplifies the design of the control device and facilitates the automation of the test process. 2.3.1 Diagram of tightness control according to the method of comparison with continuous supply of test pressure is a diagram explaining the control of tightness by the method of comparison with continuous supply of test pressure. The circuit consists of a measuring line IL and a reference pressure line EL, the inputs of which are connected to a common source of test pressure pQ, and the outputs are connected to the atmosphere. The reference pressure line contains an input pneumatic resistance (throttle) with a conductivity /J, a capacitance with an adjustable volume Ge and an output pneumatic resistance with an adjustable conductivity /2, which are designed to adjust the circuit. The measuring line contains an input pneumatic resistance with a conductivity /t, and a test object RO, which can be represented as a container with a volume of Ki, having a leak equivalent to the pneumatic resistance with a conductivity f4. The measuring and reference lines form a pneumatic measuring bridge. Comparison of pressures in the lines of the circuit is carried out by means of a differential pressure gauge measuring device, which is included in the diagonal of the pneumatic bridge. In this scheme, the measuring device has a conductivity /= 0, so the pressure /r, and pH in the lines do not depend on each other. Each line of the circuit represents a flow capacity. When checking the tightness according to the scheme shown in fig. 2.2, leakage is understood as the volume flow of gas through all through leaks of the test object in the steady state flow of test gas in the lines of the circuit. This mode corresponds to the same mass flow of gas through the input and output resistance in the line.

Technique for the study of tightness control schemes

An experimental study was carried out using serial industrial samples of shut-off valves for household gas stoves (at low test pressure), shut-off and distribution equipment for pneumatic automation (at medium and high test pressure), as well as leak models. In this case, the following method was used: 1. The length of the pneumatic line from the outlet of the air preparation unit to the stabilizer w Fig. 3.3 Special equipment for experimental research: a - variable capacitance; b - throttle with a diameter of 0.1 mm; c - control leaks: 1 - cylinder; 2 - cover; 3 - piston; 4 - volume lock; 5 - inlet fitting; 6 - outlet fitting; 7 - collet clamp; 8 - replaceable tube (inner diameter 0.1 mm) pressure at the inlet of the experimental setup was no more than 1.5 m. 3. The contamination of the test gas did not exceed the requirements of class 1 according to GOST 17433-80. 4. Setting the value of the test pressure supplied to the models of circuits and the tightness control device was carried out by adjusting the screw of the pressure stabilizer of the experimental setup. 5. The measurement of the test pressure at the inlet of the circuit models and the tightness control device was carried out by exemplary pressure gauges of class 0.4 with measurement limits 0 ... 1; 0...1.6; 0...4 kgf/cm. 6. Measurement of pressure in the reference and measuring lines of the circuit models and the tightness control device was carried out by exemplary pressure gauges of class 0.4 with measurement limits of 0...1; 0...1.6; 0...4 kgf/cm and a liquid micromanometer with a relative measurement error of 2%. 7. In studies at medium (up to 1.5 kgf/cm "0.15 MPa) and high test pressure (up to 4.0 kgf/cm" 0.4 MPa), the required leakage was set using adjustable throttles, previously calibrated by the rotameter with a relative measurement error of 2.5%. 8. In studies at low test pressure (up to 0.3 kgf / cm "" ZOkPa), the required leakage was set by means of control leaks made in the form of metal slit capillaries from L63 brass (Fig. 3.3, c). The capillaries were obtained by drilling holes with a diameter of 1 mm and subsequent flattening of the end section with a length of "20 mm. Calibration of control leaks was carried out with air at a pressure of 15 kPa using a volumetric device with a relative error of 2%. setting equal capacitances in the lines - by means of variable (adjustable) capacitances. 10. Measurement of the pressure drop between the lines in the control device model was carried out by a differential pressure gauge with a relative measurement error of 2% and measurement limits of 0 ... 25 kPa and 0 ... 40 kPa. 11. When taking time characteristics, the time was counted using an electronic stopwatch with a relative measurement error of 0.5%. 12. Measurements of the corresponding parameters (pu, Ap, I) for each studied characteristic or parameter of the model of the circuit or leak control device were carried out with repetition of readings at least 5 times. 13. The processing of the results of each experiment was carried out by finding the average values ​​of the parameters for each experiment. Based on the data obtained, the corresponding characteristics were constructed. The description of the points of the methodology for the study of individual characteristics is given in the relevant sections of this chapter. Investigation of the characteristic p = /(/) of the lines of the tightness control circuit. pressure in its lines during the time of control at high and low test pressure, which are used in the control of tightness in various gas fittings. Section 2.3.1 showed that this control scheme contains two lines, each of which can be represented as a flow tank. The study used an experimental setup shown in fig. 3.2, as well as the recommendations of Chapter 2 that all parameters of the measuring and reference lines of the circuit should be equal, so the experiment was carried out only with the measuring line. For this, the valves 15 connecting the reference line to the test pressure source and the measuring line to the differential pressure gauge 14 were closed.

To determine the characteristic p = /(/) of the flow capacity of the line at a high test pressure, a standard manometer 8 with an upper measurement limit of 4.0 kgf/cm (400 kPa) class 0.4 and an electronic stopwatch were used. The following parameters were set in the experiment: test pressure/?o=400 kPa; air leakage value U = 1.16-10-5 m3/s; the total volume of the flow tank and pneumatic channels is V "0.5 dm3. The amount of air leakage Y was set by a variable throttle 10 of type P2D.1M calibrated according to the rotameter, while the control leak 9 was blocked by valve 15. In the interval of intensive pressure increase, the readings of pressure gauge 8 were taken after 10 s. To construct the experimental characteristic p = /(/), the arithmetic mean values ​​from five experiments were taken as the values ​​of the pressure change.

Recommendations for the design of automated equipment...

Let's consider the main stages of technical design of automated equipment for tightness control. At the first stage, a technological analysis of the range and volume of a batch of products is carried out. At the same time, it should be taken into account that the number of products in a batch should be large enough (if possible, correspond to medium and large-scale production) in order to ensure the necessary loading of the designed control equipment without its readjustment. If the production is multi-product, and the batch size is small, then it is recommended that products of various production batches and types be combined into groups according to general specifications for tightness control, which allows the use of a single control scheme and instrumentation, as well as grouping according to similar designs of product cases and their input channels, which allows the use of common sealing elements, loading and fixing devices in the design. Here it is also necessary to analyze the suitability of product designs and the requirements of technical conditions for their tightness tests to automate this operation. Rational grouping of products allows you to design equipment with maximum performance and minimal readjustment to control different types of products. For example, high-pressure pneumoautomatic devices can be grouped according to the same specifications for compressed air leakage control (by the test pressure of 0.63 MPa and 1.0 MPa, as well as the same allowable leakage), according to a similar design of the inlet pneumatic channel, which allows using in the developed equipment in the first case, a common control block, and in the second, the same sealing device (end or internal lip). This stage is completed by determining the performance of the designed equipment, an example of the calculation of which is considered in the section

At the second stage of design, the need for reconfiguration of the designed device is determined, which should include: the ability of the control system to function taking into account different times for testing products under pressure; reconfiguration of the control and measuring unit for different allowable values ​​of test gas leakage, as well as for different levels of test pressure. Then it is necessary to make a choice of a control method and means of its implementation. Preliminary technical conditions for carrying out tightness control should be considered when analyzing the terms of reference. Here, as a rule, preference should be given to typical, wide-range control and measuring devices. But in some cases, it is recommended to develop a special control unit that fully meets the requirements of the designed machine or semi-automatic machine, for example, according to the requirement for device readjustability, test pressure range. Examples of calculation and application of control equipment are discussed in sections 4.3 and 4.4.

At the third design stage, the level of automation and reconfigurability of the entire device is selected. Leak testing machines include devices that carry out the entire process of tightness control, including sorting, as well as loading and unloading products without the participation of an operator. Automated devices (semi-automatic) for tightness control include devices in which the operator participates. It can carry out, for example, loading - unloading of the tested product, sorting into "Good" and "Reject" according to the information of the control and measuring unit, equipped with an automatic recording element. At the same time, the general control of the device, including the drive of the transport device, clamping - unclamping (fixing), sealing the product, control time delay and other functions are carried out automatically. Prospective schemes for automation of tightness control by the manometric method are considered in Section 4.2.

After assessing the level of automation, the next important task is to select and analyze the layout diagram, which should be drawn to scale. It allows you to rationally arrange all the devices of the designed equipment. Here, special attention should be paid to the choice of the loading position - unloading of the product, the trajectory of the movement of the loading equipment. The problems are related to the fact that the loaded products (test objects), as a rule, have a complex spatial configuration, so it is difficult to orientate, capture and hold. Because of this, the creation of special orientation and handling equipment is required, which is not always acceptable for economic reasons, so manual loading may be a rational solution. As an adequate solution to the issue, it is recommended to consider the use of industrial manipulators and robots. Examples of the selection and calculation of the parameters of some auxiliary equipment are given in the section

The next important design stage is the choice of a control system and the synthesis of a control scheme. Here, one should adhere to the recommendations and methods for developing control systems for process equipment given in the literature. The choice of an air preparation scheme is quite simple, as it is well technically developed and covered in the literature. But underestimating the importance of this issue can lead to increased contamination of compressed air (mechanical impurities, water or oil) used as a test gas, which will seriously affect the accuracy of control and the reliability of the equipment as a whole. The requirements for the air used in pneumatic control and measuring devices are set out in GOST 11662-80 "Air for supplying pneumatic devices and automation equipment1. In this case, the pollution class must not be lower than the second according to GOST 17433-80.

When choosing a test pressure supply scheme, one should take into account its mandatory stabilization with high accuracy, the need to connect to a rotary clock table or other moving equipment, as well as the simultaneous supply of a large number of control units. These issues are discussed on the example of an automated leak test bench in Section 4.4.

At the final stage, an expert evaluation of the project of an automated device for tightness control is carried out. Here it is advisable to evaluate the project collegially, according to certain criteria, with the involvement of specialists from the department where the implementation of the developed device is expected. Then an economic evaluation of the project is carried out. Based on the conclusions made, final decisions are made on the further development of working documentation, the creation and implementation of an automatic or automated device for tightness control for this project.

Kavalerov, Boris Vladimirovich