What you need to know about the shape of manholes. Why are manhole covers round? Other explanations for the shape of the hatches

Hello always, dear friend!

There is a type of question that is generally considered to be a quick wits question. Sometimes this is true. But more often such questions are asked at once with several purposes.Why hatches round is an interview question just one of this series. Although it is found less and less, for it has already lost its former originality and the effect of surprise.

Let's remember that at the interview they want to evaluate not so much “Who are you?” As “What are you?”.

1. How do you respond to this question? - the first goal of your interlocutor.

He wants to understand the degree of your emotional maturity.

2. Will you be looking for an answer to this question? - the second goal.

Let's remember that the employer is interested in several, which he never asks directly. One of them: will you solve the problems that will inevitably arise in the course of your work.

Either you will look for reasons why the problem cannot be solved, or you will pass problems onto other people, including the leader.

3. The very content of the answer - the third goal.

Can you solve problems that require ingenuity and analytical thinking, logic?

If instead of answering you say “I don’t know” or “I’m at a loss to answer,” this means that when faced with a difficult task, you will most likely fold.

How to react?

Let's agree right away that we define this question “why are hatches round” as, and not manipulative and not. Therefore, we answer constructively.

The worst thing you can do is puff out your cheeks and freeze something like this:

"Listen, what does this have to do with the subject of our meeting?"

After that, consider that you have not passed the test, although in fact you are right. The reason is that you did not accept the rules of the game that are offered to you. I repeat, this question is constructive and is not an attack on your personality. Therefore, it should be answered constructively.

Let's remember the principles of answering constructive interview questions:

1. If you get asked questions, that's fine. If you are not asked about anything, how will they know that you are the best candidate?
2. As a consequence of point # 1: Just give the interlocutor the right to ask any questions. Any question is your opportunity to be better than other candidates. You will answer confidently and calmly, and there is no reason to be afraid or nervous.
3. Majority are asked to get to know you better, and not to hear the correct answer. That's why you came so that they would know what a wonderful candidate you are.

How to answer?

1. Listen to the end.
2. Verbal reaction - and with the tips of the lips (teeth closed!), A slight nod.
3. A short pause.
4. Answer.

The simplest and most logical answer to this question:

Round hatch - cannot fall into a well. No matter how hard you try and twist it. The square has a diagonal longer than its sides, and when lifted, it can slide down into the well. Drown or even injure someone. Besides -the diameter of the top of a round hatch is usually larger than that of the bottom, and it cannot slide inward under any circumstances.

In addition, round hatches are easier to move - they can be rolled.

A couple more questions from the same series

About cake

Myself Question: How to divide the cake into eight identical pieces using 3 cuts?

Answer: First, you should make a cross-to-cross cut, thereby dividing the cake into 4 equal parts. Next, make one cut horizontally in half along the entire diameter. The pieces are lower, but the problem is solved - you have 8 equal pieces.

Second option: after your two cuts, we have 4 pieces. We can put them on top of each other. Then split all four pieces in half with one cut.

About light bulbs

There are three light bulbs in the room. There are three switches in the hallway leading to the room.

Question: How many times do you need to open the door to determine which light bulb corresponds to which switch?

Answer: It is enough to open the door once. We turn on 2 switches at the same time, then turn off one. We enter the room: we see that one lamp is on. She is from the first switch. We place our palm on each of the remaining two bulbs. Which is warm from the second switch, respectively cold from the third.

In the event that, if any intelligible answer does not come to mind, start thinking out loud. Trying to find a suitable one is much better than a nervous reaction or a “hard to answer” answer. Keep in mind that some of these questions don't have a definite answer at all.

Your attempts to find the answer, the train of thought, the options for solutions are often more important than the answer itself.

Thank you for your interest in this article. I would be grateful for your comment (at the bottom of the page).

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Have a good day and good mood!

Why are the hatches round? Those that close-open the entrance to the sewer system. Those that have to be bypassed so that misfortune does not happen. They have become so accustomed to everyday life that many people do not notice a foreign object on their way and automatically step over a dangerous place.

There are also car owners who diligently go around the drainage points to the surface in order to preserve the suspension. For this reason, the question of the shape of the lid can be of concern to a fairly large number of people.

Why was this form chosen?

Man is a being of a higher order, thanks to his ability and desire to discover the world, to seek and find answers to questions of interest. And people are curious about a lot. Why are huge elephants wary of mice? Where do the fallen stars go? How to make a magic wand? Why is the hatch cover without corners and unnecessary hinges?

Of course, there are squares, stars, triangles on the asphalt. But this happens so rarely that it can be classified as an exception. And the pattern is a circle-shaped hatch. And there are several reasons for this:

1. The ideal shape for sewer wells is round. They are easier to maintain. The likelihood of blockages is minimal. It is clear that to close the wells, it is most rational to use covers of the same shape, but in a slightly increased diameter.

2. Manufacturing of round caps is cheaper for factories than other forms. This is mainly due to material savings. What is a circle? This is a pretty good geometric figure. With a limited amount of material, the choice of just such a shape will allow you to get the maximum area (compared to other shapes). After all, the ratio of the cross-sectional area of ​​a circle to the length of a circle is greater than that of squares or rectangles.

3. You can also save on thickness if you choose the right shape of the hatch. The resulting load is evenly distributed, reducing the internal pressure, only in the circle. Therefore, the lid can be thinner, even while maintaining its strength and reliability.

4. The sewer hatch covering the round well will not fall inside. From no position. And these are additional safety measures for performing plumbing work.

5. Each point on the circumference of the hatch is a stress concentration point. The even distribution of the load, which was already mentioned above, has another advantage. It is this shape that makes it easier to open the well by shifting the heavy cover to the side.

With rectangular hatches, it is a little different. There the tension is concentrated in the corners. You will have to tinker with such covers.

6. Round variants are easier to move not only because of the distribution of the load, but also simply because of the lack of corners. As a rule, sewer covers are made of cast iron. This is a very difficult material. And any product made of it is almost overwhelming. The circle can be put on an edge and rolled.

In addition to the above reasons, one more important point should be mentioned. There is such a production pattern: the fewer protrusions and corners a part has, the less rejects will come out from under the machine. Therefore, the production of round hatches is more than justified.

Job candidates are asked logic puzzles to assess their analytical skills. Anyone can face similar questions. But even if this does not happen to you, it will be just interesting to study them for preparation.

Jobseekers who are faced with puzzles during the interview process should not panic and get lost. As a rule, in most cases, it is enough to show the course of your thoughts and the ways of solving the problem. It may well be that the problem does not have a correct solution or an unambiguous answer. In no case should you say “I don’t know” or “I’m at a loss to answer”, just think aloud.

So that you know what to be ready for and not get confused, we have collected the most popular puzzle questions and prepared answers and recommendations for them. Who knows, you may come across these tasks.

Sewer hatches

This is perhaps the most common question among all the puzzles.

Question: Why are the sewer manholes round?

Answer: There are several options. Since the diameter of the circle is the same, no matter how you twist it, the round hatch cannot fall into the well. A square, for example, has a larger diagonal than its sides, so the lid could fall off. You can also answer that round hatches are easier to transport and move.

Light bulbs

Question: There are 3 light bulbs in a closed room, and 3 switches in the corridor. For what is the minimum door opening you can determine which switch belongs to which lamp?

Answer: For one discovery. We turn on 2 switches at the same time, after a while we turn off the second one. We go into the room: one of the bulbs remained on - this is the first switch, then we probe the remaining bulbs - warm and will be the second switch, and cold, respectively, the third.

Cake

Question: How to divide a cake into 8 equal parts with three cuts?

Answer: First you need to make 2 cross-to-cross cuts, dividing the cake into 4 equal parts. And then cut the cake horizontally in half. So what if the pieces are not high, but you have 8 equal parts. After the first two cuts, you can also fold the pieces on top of each other and halve them with one cut.

Dead man and match

Question: A dead man was found among the field with a match in his hands, there are no traces. What did he die of and under what circumstances?

Answer: A man died from a fall from an airplane, which began to lose altitude, and the accident was inevitable. One parachute was not enough for all passengers and they drew lots. He got a short match and was forced to jump without a parachute.

Bus and balls

Q: How many tennis balls can the bus fit?

Answer: The recruiter himself does not know the exact correct answer, since it is not specified what the balls and the bus are - their sizes are not known, and no one has thoroughly checked it. Therefore, the course of your thoughts is important here, you can only guess. What are the approximate length, width and height of the bus, the size of one ball. Calculate the volume of the bus and the ball - this is how you will find out how many balls can fit on an empty bus. Decrease approximately this value, taking into account the seats and other details of the bus, make an allowance for the fact that the balls are not square, and give an answer. In this case, the process of finding an answer is more important than the answer itself. Variants of the question may be different: balls - football, instead of a bus - a room, etc.

Pills

Question: The doctor gave the patient 4 tablets of two types - 2 tablets each, which cannot be distinguished by their appearance. The tablets should be taken in two doses: in the morning, one tablet of each type and in the evening. If the dosage is violated or the pills are not taken, the patient will die. It so happened that the tablets were mixed. How to get treatment and survive?

Answer: Of course, we can say that it is better to go to the doctor and ask for more, still a matter of life and death. But these may be the only pills on Earth, the doctor may disappear under mysterious circumstances, etc. So you still have to answer. In addition, everything is quite simple: you need to divide each tablet into 2 parts and drink half of each tablet in the morning and in the evening.

Finally

Remember that, first of all, such tasks and puzzles are designed to test the candidate's behavior in non-standard situations, to assess the ability to think, creative and logical approach. Alas, there are often cases when the interviewer cannot correctly interpret the results of such questions, or does not understand their purpose at all. But even in this situation, confident behavior and a desire to come to an answer will show you your best side and increase your chances of getting a job.

Round? And what else could they be? In theory, the hatch can be square or rectangular. But such a construction is rather an exception to the rule. The hatch is not a simple access door, it must be securely closed. It should be easy to maintain and safe to use.

If convenience is not for everybody, then it is the round design of the lid that can provide reliability at the level of standard loads. The configuration of the base depends on its shape, which, in fact, is the sewer hatch.

Waste system

Sewer networks are a complex of structures designed for collection and disposal from users to treatment facilities. The easiest way to do this is to dig a trench, pipes are laid into it, through which drains will be discharged.

To be able to service the system at a certain distance, observation shafts are required. In the conditions of urban infrastructure with dense buildings, it is possible to lay sewer networks only along the roads or directly under them. In this case, during heavy traffic, the hatches must be securely closed. But why are the sewer manholes round? They must be strong enough to withstand the maximum possible traffic loads.

In a big city, the number of inspection hatches and all kinds of mines can be in the hundreds of thousands. After all, this is not only a sewage system, it is also a communications network: water supply, heating systems, electricity, gas, telephony, and so on.

Inspection wells

For ease of access to communications, the well shaft is usually round. Sewer rings used for the construction of such structures are most often made of reinforced concrete.

The cylindrical shape of the well is most suitable for maintenance. It is more convenient to carry out work in such mines. They are suitable for ventilation, since air circulation in a cylindrical object is more intensive.

The size of the cover, the area of ​​the base and the inner diameter are selected in accordance with the purpose of the inspection shaft. In this case, all elements of the system will correspond to each other as much as possible. The location, possible loads, traffic intensity are taken into account.

It depends on the shape of the lid. On the one hand, service personnel must have convenient access to underground utilities. On the other hand, the well must be reliably closed in order to exclude the possibility of foreign objects getting inside, to ensure the safe movement of pedestrians and the passage of vehicles. A round lid is best suited for this, which means that the hatch itself must be of this shape.

Depending on the purpose, they are divided according to the type of communications laid under them: engineering cable networks, water supply, gas mains, heating mains, storm and waste sewerage. The size of the manhole varies from country to country. In Russia, standard dimensions (645 and 800 mm) are most often used. Manholes that are not manufactured in accordance with GOST are designed and developed by manufacturers in accordance with the order and specific technical conditions.

This configuration has several advantages. Previously, hatches were made in various shapes. They could be square, rectangular, oval, or even triangular to indicate the direction of water flow. However, the round shape of the lid was found to be the most suitable.

She will never fall into the well, no matter how she is turned. The round lid is easier to open, so the point of application of the force will be the same anywhere in the circle. It can be rolled by placing it on its edge. In manufacturing, such a design is more cost-effective.

The round shape of the lid is less prone to sagging. It can withstand a lot of stress at the same thickness, which means it can be made thinner without losing quality. During production, round castings give a lower percentage of rejects (shells, pores, cavities).

Material

The base and hatch covers for those in charge are most often made of cast iron. This material has strength, which makes it possible to withstand heavy loads, and corrosion resistance for long-term The weight of the structures is sufficient so that passing vehicles cannot accidentally lift and move the cover. are made by remelting secondary raw materials, they are cheaper than steel counterparts.

In places where there is no heavy car traffic, it is impractical to install heavy and powerful structures. Recently, hatches made of plastic, polymers and composite material have appeared. They are lighter, cheaper, have a sufficient margin of safety, and a long service life.

In private houses, sewer rings made of reinforced concrete are used for arranging sewage systems, equipping inspection wells and septic tanks. In this case, it is quite justified to install the same base for the hatch on them from above. The cover is also made of concrete. It is made with a larger diameter, does not fit into the groove, but simply closes the hatch hole. The massive structure is quite heavy, it is impossible to accidentally move it. This provides the necessary operational safety.

Specification and labeling

For increased loads on the roads, heavy hatches (class T) are used. They can be over 100 kg in weight and over 100 mm in thickness. Where car traffic is not foreseen, light hatches (class L) are used. Structures for gardens, lawns and other areas (class A) have a diameter of 540 mm and a thickness of 50 mm.

Why are sewer hatches round and marked? This is done for the convenience of recognizing their belonging to. Their covers have letters: ГС - gas network, MG - main gas pipeline, PG - fire hydrant, etc.

Quite often, when hiring a candidate for a position, they are interested in why the sewer manholes are round. This is a very unexpected question that takes a person by surprise, and he begins to think about it. So you can quickly determine a person's thinking, assess his level of intelligence and the ability to get out of difficult situations. If a person hesitates, thinks about it for a long time and gives a completely illogical and incorrect answer, then one can judge his inability to think creatively and quickly. But what is really interesting is why the manholes are round and not square. There are different theories and answers. Let's try to figure them out.

Manhole cover

The cover is an integral part of the manhole cover, which must be present. In addition, it should be comfortable and ergonomic, and should not crash when hit by a car wheel. It also has a small hole through which you can check the gas content of the well.

With all this, the cover is most often made of cast iron and is very heavy. Its large weight is justified by the complexity of theft, however, it is precisely because of such a large weight that it is often stolen for subsequent delivery for scrap. And although it is prohibited by law to accept sewer manholes at scrap metal collection points, this does not stop thieves. Someone generally uses them in everyday life for different purposes.

However, now is not about that. In most countries, the lids are indeed round, but there are exceptions. In some states of the USA and even in India, they are made in the form of squares and triangles. Therefore, it cannot be argued that all covers on manholes are round. Why is the round shape most often found? As mentioned above, there are different versions.

Logical version

The very first version explains the shape of the caps by economy. The fact is that it is the round shape with minimal cost that allows you to create such a hole into which a person would easily crawl. For example, for a person to freely penetrate to the well through a square hatch, the hole would have to be made slightly larger in area. Consequently, in the manufacture of a hatch for such a hole, more metal would be spent, and this is economically unprofitable. It is believed that the production of round hatches is 40% more profitable compared to the production of square ones, and on a large scale this is a fairly solid figure.

Due to the round shape, the covers do not fall down

The second version, which explains why the sewer hatches are round, is that this shape does not allow the hatch to fall down. That is, under no circumstances, no matter how anyone tries, he will not be able to push the lid into the well itself. But the square cover of the sewer manhole can fall into the well if you try to shove it with an edge along the diagonal of the hole.

It is also believed that the round shape has a good feature - it distributes the loads more evenly when a car hits it. Consequently, this allows a slight reduction in the section size (thickness), which ultimately leads to additional cost savings.

Round well - round cover

However, it is strange to ask at all why the sewer hatches are round, because the well itself is round, so when developing the covers, no one even thought about using a square shape. Moreover, if you need to quickly move the cover of the round hatch from the well, you can simply roll it with an edge, which even one person can handle. But rolling a square hatch will not work - it must either be transported, or carried by two or even three. However, some lids have special "tendrils" that prevent them from rolling with an edge.

It is also believed that opening a round manhole cover is easier due to the fact that any point of its circumference is simultaneously a stress concentration point. As for the square covers, there are only two similar points - the corners of one of the sides.

It just happened so

In general, no one knows why the sewer hatches are round. Very few people think about it, but looking for an answer to this question is simply stupid. It's like asking why the curbs are rectangular. There is no unequivocal answer to this question, because when the first sewer wells appeared, no one at all thought about making them in other forms. It just so happened, and all attempts to explain why the hatches are round are, to put it mildly, far-fetched. The only more or less logical option is the inability to drop the hatch into the well itself. This is possible with a square lid, since the diagonal length of the lid itself will be longer than the side length. This makes sense, but even this explanation does not suit many.

Other forms

Note that hatches are not always round. Different countries may have their own forms. In India, triangular shapes are often found, and in some countries they can represent a generally indefinite geometric figure. Square shapes are not uncommon in the United States and other countries in America. There are even hatches with eight corners, and models in the shape of a rhombus or semicircles are very rare.

But we must admit that most often they are just round. This form is the most popular, comfortable and ergonomic.

Conclusion

So, we figured out why the hatches are round. You can answer this question in different ways. If you really become a bore, then you can calculate how much metal is needed to make a square cover for a hole into which a person would freely crawl. Then the resulting value must be compared with the weight of the metal required to make the cover for the round hole. With the same metal cross-section, it turns out that more metal will go to the square hatch due to the presence of corners in the square.

You can also calculate how evenly the forces are distributed when the car wheel hits the hatch. It turns out that the loads are distributed more evenly around the entire perimeter of the circle. In the case of a square or triangle, this is not the case.

In general, now you know why manholes are usually round, and you understand what you need to answer if suddenly asked about it during an interview. Most likely, this is the only case when such information can help. However, if we are talking about an interview, then it is not at all necessary to answer correctly. You can answer with a joke or even say that the hatches from sewer wells are not always round, it is just that it is customary in our country. Sometimes even the person who asks such a stupid question does not know himself why the hatches are round at all. However, you now know the exact answer. Despite the many good versions, the most logical and plausible version seems to be with the shape of the lid, because of which it simply cannot go into the sewer hole.