Why sewer? What you need to know about the shape of sewer manholes. Sewer cover shape

Have you ever wondered why, there are sewer manholes everywhere? round, and not square? Manhole covers are made of cast iron, sometimes concrete. This is so that the lid is heavy and cannot open spontaneously. If speak about cable duct, then most often there are two of them, a shut-off and a protective one. The first one weighs much lighter, it is usually made of steel and is needed to protect the cable from theft. They place it just under the protective cover, and on the cover itself they simply write the purpose of the hatch.

The simplest and most logical explanation

A square-shaped lid can easily fall into a hatch, for example, slip through at an angle. This may be because the diagonal of the square is larger than its sides, that is, the lid may fall into the hole. And a circle has the same diameter, no matter how you turn it. And since the diameter of the upper surface of the hatch is always larger than the lower one, the cover will never fall inside the hatch, no matter what position it is in. Round cover turns out to be safer than covers of other forms, since they will not fall on the heads of workers who are inside the hatch.

The most frivolous explanation

There is an explanation that, of course, seems funny. The hatches are round because the holes are round. Although, on the other hand, it is easier to dig a round hole than to align the corners of a square or rectangular or triangular hole. And in general, for example, it makes no sense to make a sewer well square, because you will have to spend extra effort and extra time. In addition, round holes are more technologically advanced, they have a longer service life, and are resistant to temperature changes and transformation.

So, there is some truth in this statement too.

The fact is that round hatches are easier to transport. That is, the square cover only needs to be carried, and one person is unlikely to cope with this, because the hatch cover is very heavy. It will take at least two men to carry the manhole cover to the right place. And the round one can be rolled, which is something one adult man can do. Moreover, without experiencing any particular difficulties. Moreover, when closing the hatch with a round lid, there is no need to rotate it, aligning it with the hatch opening. There is some truth in this too; round hatches are much more convenient. Moreover, they are easy to manufacture, because again, you will have to tinker with square hatches; their corners may be damaged during transportation, for example, knocked off.

By the way, the question “Why are hatches round” is asked by recruiters to candidates. They say that the answer to this question allows you to assess the general level of intelligence, how capable it is of solving problems and tasks. By asking this question, experts want to see whether the candidate employee has the willingness and ability to enter into discussions and how the candidate solves the task or refuses to solve it. It is also very important how the candidate answers the question, seriously or jokingly. By the way, worldwide famous company Microsoft has long used this question when testing specialists they are going to hire.

To sum it up, it is easiest to say that The lid should be round, including manhole covers!

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Hello always, dear friend!

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

Let's remember that during an interview they want to evaluate not so much “Who are you?”, but rather “What are you like?”

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

He wants to understand your level of emotional maturity.

2. Will you look for the answer to this question? - second goal.

Let's remember that the employer is interested in several questions that he never asks directly. One of them is whether you will solve 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 shift the problems onto other people, including your manager.

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

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

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

How to react?

Let’s immediately agree that we define this question “why are hatches round” as, and not manipulative and not. That's why we respond constructively.

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

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

After this, consider that you have not passed the test, although in essence 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 questions in an interview:

If they ask you questions, that's good. If they don't ask you anything, how will they know that you are the best applicant?
As a consequence of point No. 1: Simply 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.
Majority They are asked to get to know you better, 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?

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

The simplest and most logical answer to this question is:

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

In addition, round hatches are more convenient to move - it can be rolled.

A couple more questions from the same series

About the cake

The question itself: How to divide a cake into eight equal pieces using 3 cuts?

Answer: First, you should make a cut crosswise, thereby dividing the cake into 4 equal parts. Next, make one cut horizontally in half along the entire diameter. The pieces turned out 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 cut all four pieces in half using one cut.

About light bulbs

There are three light bulbs in the room. There are three switches in the corridor leading into the room.

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

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

In the event that no intelligible answer comes to mind, start thinking out loud. Trying to find the right one is much better than a nervous reaction or a “I don’t know” answer. Keep in mind that some of these questions do not have a clear answer at all.

Your attempts to find an answer, a train of thought, and solutions are often more important than the answer itself.

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

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Have a nice day and good mood!

In fact, at first they were different: in many countries other shapes were used, but the “winner” was still round. They are used all over the world to this day.

What is the difference between manhole covers? Everything except the form. On top of them, at the dawn of their mass use, there could be images of various coats of arms, motives of events, and memorable dates. Today everything is much simpler: a simple pattern and information about the manufacturer of the lids and the customer for their production. Large companies sometimes place “decorative” ones near their offices.

So why are hatches round?

Because well tunnels and cross-section sewer pipes also round. Therefore, there is simply no point in using another shape; round is the most convenient.
Because round manhole covers never fall into the well. But square ones, for example, can do it without problems.
Because it's cheaper. To cover a round “hole” with a diameter of 60 centimeters with a square lid, the area of such a lid should be 0.36 square meters. At the same time, perform this task you can use a round hatch with an area of 0.28 sq. m. Noticeable difference?

Because it’s more convenient to carry them this way. Or roll, because the weight is not small - from 50 to 110 kg: one person may not be able to handle it. What if they were also square?

Because round hatches are more convenient for installation and dismantling. They have load concentration points along the entire perimeter, and in square ones - only in the corners.

However…

“Who cares why sewer manholes are round,” you ask? I would like to answer that no one is interested in this, but there are precedents. And they happened at very serious events, in the offices of reputable companies. The fact is that sometimes HR managers like to ask unexpected questions during interviews to see how a person behaves in force majeure situations. Just ask someone out of the blue, why are hatches round? Do you think you will immediately hear a clear answer? No! So they torment applicants for high positions in the private sector with insidious and at the same time stupid questions.

Quite often, when hiring a candidate for a position, they ask why sewer manholes are round. This is very unexpected question, which takes a person by surprise and he begins to think about it. This way you can quickly determine a person’s thinking, assess his level of intelligence and 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's 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 lid is component hatch manhole, which must be present. In addition, it should be comfortable and ergonomic, and should not rattle when a car wheel hits it. It also has a small hole through which you can check the gas contamination of the well.

With all this, the lid is most often made of cast iron and is very heavy. Its large weight is justified by the difficulty of theft, but it is precisely because of such a large weight that it is often stolen for subsequent scrap metal. And although the law prohibits the acceptance of sewer manholes at scrap metal collection points, this does not stop thieves. Some people use them in everyday life for different purposes.

However, this is not about that now. 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 said that all manhole covers are round. Why is it most common? round form? As mentioned above, there are different versions.

Logical version

The very first version explains the shape of the lids by economy. The fact is that it is the round shape with minimal costs allows you to create a hole that a person can easily crawl through. For example, for a person to freely enter a well through square hatch the hole would have to be made a little larger in area. Consequently, when making a hatch for such a hole, more metal would be spent, and this is not economically viable. 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 respectable figure.

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

The second version, which explains why sewer manholes are round, is that this shape prevents the manhole from falling down. That is, under no circumstances, no matter how hard anyone tries, will he be able to push the lid into the well itself. And here square cover sewer hatch may fall into the well if you try to insert it with its edge diagonally across the hole.

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

For a round well - a round lid

However, it is strange to even ask why sewer manholes 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 round hatch cover from the well, you can simply roll it on its edge, which can be done even by one person. But rolling a square hatch will not work - it must either be transported or carried by two or even three people. However, some lids have special “antennae” that make it impossible to roll them edgewise.

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

It just happened that way

In general, no one knows why sewer manholes are round. Few people think about this, but looking for an answer to this question is simply stupid. It's like asking why curbs have a rectangular cross-section. There is no definite answer to this question, because when the first sewer wells appeared, no one thought about making them in other shapes. It just happened that way, 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 greater than the length of the side. This makes sense, but even this explanation does not suit many.

Other forms

Note that hatches are not always round. IN different countries forms can be different. Often found in India triangular shapes, and in some countries they may represent a generally indefinite geometric figure. Square shapes- not uncommon in the USA and other American countries. There are even hatches with eight corners, and very rarely there are models in the shape of a diamond or semicircles.

But it is worth recognizing that most often they are 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 want to get really boring, you can calculate how much metal is needed to make a square lid for a hole that a person could easily fit into. The resulting value must then be compared with the weight of metal required to make the cover for the round hole. With the same cross-section of metal, it turns out that more metal will be needed for a square hatch due to the presence of corners in the square.

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

In general, now you know why sewer manholes are usually round, and you understand what you need to answer if you are suddenly asked about this at an interview. Most likely, this is the only case where 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 are from sewer wells not always round, it’s just the way it is in our country. Sometimes even the person who asks such a stupid question doesn’t know why hatches are round in the first place. However, you now know the answer for sure. Despite the many good versions, the most logical and plausible version seems to be the one with the shape of the lid, due to which it simply cannot fit into the sewer hole.

A familiar, familiar detail of the urban landscape are sewer manhole covers, which are round in shape almost everywhere, in all countries of the world.

Why round – we will try to answer this question in detail.

Safety

The manhole cover of the sewer well is a massive piece of cast iron. It weighs more than 50 kilograms, and the weight of hatches located on the roadway exceeds 78 kilograms.

This is not surprising, because a manhole cover located on the sidewalk of the street must withstand a load of 12 tons, and a manhole cover lying on the road must withstand a load of as much as 25 tons. This weight is due to the thickness of the cover, calculated taking into account the given load and the strength of the cast iron.

Now imagine the following situation: the manhole cover is open and lies next to the hatch, and below, people are working in the well. If someone accidentally moves the round lid, then in the worst case they will simply close the hatch. In this case, a rectangular or square lid can fall into a hole directly on the heads of the workers, because the diagonal of a square or rectangle is always larger than any of its sides. Therefore, the round shape of the lid is the safest in this case.

Strength

Engineers have long known that round objects are much stronger than square ones. The sewer hatch is not only round, but also slightly convex in the middle: this shape provides the greatest resistance to mechanical load directed from above.

Internal stresses in a hatch of this shape are evenly distributed over the metal, while in square, rectangular and any other covers, under the influence of a load, the stresses are distributed unevenly, which leads to faster wear and, consequently, more frequent replacement of covers.

In addition, we should not forget that cast iron is a rather fragile material, and if you drop a rectangular lid, a corner may well break off. To crack a round manhole cover, you will have to put in a lot more effort.

Judging by the fact that almost all lids have been intact for decades (and some for more than a hundred years), under normal conditions it is almost impossible to damage a round lid.

Metal saving

Why is the round shape of hatches more optimal in terms of saving metal? With the same length of the perimeter of round and rectangular hatches, the area of the circle is always greater than the area of the rectangle or any other geometric figure.

If we translate this into economic indicators, it turns out that the circle is the most favorable form hatch, since the cover requires much less cast iron (saving up to forty percent) than a rectangular cover.

The optimal ratio of perimeter length to area makes it necessary to make round hatches not only for sewer wells, but also in much more serious structures - for example, between compartments of submarines or spaceships. Round hatches more economical and withstand greater loads than any other form of hatch.

Convenience of work

A round manhole cover is much more convenient when carrying out repair or maintenance work. If a rectangular lid needs to be lifted in order to be moved over a certain distance, which will require at least two adult men, then a round lid can be easily rolled by placing it on its edge, and this task can be completed alone.

And in order to fit the heavy cover into place, you do not need to rotate it, adjusting it to the configuration of the hole. The round lid will fall into place in any case, no matter which side you lay it on.

So, there are more than enough reasons why you need to make the manhole cover round.