Why are the hatches round? Those that close and open the entrance to the sewer system. Those that have to be bypassed so that misfortune does not happen. They entered so habitually daily life that many people do not notice a foreign object in their path and automatically step over the dangerous place.
There are also car owners who diligently drive around the places where the sewage system exits to the surface in order to maintain the suspension. For this reason, the question of the shape of the lid can be quite worrying. large number people.
Why was this form chosen?
Man is a being of a higher order, thanks to his ability and desire to discover the world, seek and find answers to questions of interest. And people are curious about a lot of things. Why are huge elephants afraid of mice? Where do fallen stars go? How to do magic wand? Why is the manhole cover without corners and extra hinges?
Of course, there are squares, stars, and triangles on the asphalt. But this happens so rarely that it can be classified as an exception. And the pattern is a hatch in the shape of a circle. And there are several reasons for this:
1. Ideal shape for sewer wells– round. They are easier to maintain. The likelihood of blockages is minimal. It is clear that to cover wells it is most rational to use covers of the same shape, but with a slightly increased diameter.
2. The production of round lids costs factories less than the production of other shapes. This is mainly due to material savings. What is a circle? This is pretty lucky geometric figure. With a limited amount of material, choosing exactly this form will allow you to get maximum area(compared to other figures). After all, the ratio of the cross-sectional area of a circle to the circumference is greater than that of squares or rectangles.
3. You can also save on thickness if you choose the right hatch shape. The resulting load is evenly distributed, reducing internal pressure, only in a circle. Therefore, the lid can be thinner, even while maintaining its strength and reliability.
4. Sewer hatch covering the well round section, will not fall inside. Not from any position. And this additional measures safety 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 moving the heavy lid to the side.
With rectangular hatches it’s a little different. There the tension is concentrated in the corners. You will have to tinker with such covers.
6. Round options easier to move not only because of the distribution of the load, but also simply because of the absence of corners. Typically, sewer covers are made of cast iron. This is very heavy material. And any product made from it is almost unbearable. The circle can be placed on its 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 of the machine. Therefore, the production of round hatches is more than justified.
Many people wonder why sewer hatches They make them round, but not everyone knows that this shape is considered the most practical. It is safer to use round lids, and at the production stage of products, metal is saved. Of course, in addition to round ones, there are hatches of other shapes on city streets, for example, square ones, but they are quite rare. This is explained by a whole series of factors.
Security Considerations
Despite their small dimensions, the lids weigh about 50 kilograms, because they are made of cast iron. And the weight of products located on the roadway exceeds 78 kilograms - after all, they must withstand the weight of passing cars. According to the rules, hatches located on sidewalks must carry loads of up to 12 tons, and those intended for installation on the road - up to 25 tons.
Given the significant weight of the covers, it is very important to follow safety rules when working in a sewer well. If the product falls through the hatch onto the heads of the workers, tragedy cannot be avoided. Fortunately, the round lids are designed to never fall down the well. Products shaped like a square or rectangle can easily fall off, because their diagonals are always larger than any of the sides.
Ease of use
Considering the large weight of cast iron covers, dismantling them is quite difficult, especially if they are square. To move such hatches from place to place, you will need several adults. Round lids are much easier to handle because they can be rolled on an edge. You can cope with this task even alone.
There is no need to rotate the round lid, trying to adjust it to the shape of the hole. It will take the desired position no matter which side you place it on.
Increased strength
Since the covers that are used to protect engineering systems, are subjected to heavy loads during operation, care must be taken to ensure that these products have improved strength indicators. The easiest way to achieve this is to make the hatch round, because products of this shape have improved strength compared to square ones.
Photo: standard sewer manhole
In addition, if you carefully examine the structure of the hatch, you will notice that towards the middle of the circle it is slightly convex. This is not an accident: this shape ensures the most even distribution internal tension in the product. Rectangular covers do not have this property; the loads in them are distributed unevenly and lead to increased wear of the metal.
Cast iron is a brittle material, so cracks and chips may appear on its surface as a result of mechanical stress. Round hatches are made in such a way as to prevent the destruction of the metal: it is much more difficult to break off a piece from them than from square or rectangular-shaped products.
The load concentration points of a round hatch are evenly distributed around the entire circumference. With square products, stress is concentrated only in the corners, and this is very risky, because you cannot transfer the entire load to just one part of the part.
Economic feasibility
In addition to improved consumer properties, the round shape saves metal. With the same perimeter length, a circle always has an area greater than that of a rectangle. Thus, the production of round hatches is economically feasible, because savings on materials can reach 30%. It turns out that instead of three square lids, four round ones can be made at the same cast iron consumption.
Considering the low cost of round manholes, city-wide savings on the installation of sewer wells look impressive. In addition, round covers are widely used to protect other communication systems, such as waste pipelines, gas pipes or underground electrical networks.
The advantages of round hatches include not only metal savings, but also a very small percentage of rejection. Reducing the number of reference lengths is the key to a low probability of errors leading to the appearance of various defects.
Photo: open sewer manhole operating on the principle of doors Who is responsible for the hatches
Sometimes hatches are equipped with hinges - this is done in order to avoid theft, which has become especially noticeable in the last two decades. Cast iron products are in demand at metal collection points. Additionally, the hatches can be locked - in this case they resemble a door.
Most sewer wells, including their covers, are municipally owned, although some may be owned by legal entities And apartment buildings. If the object is ownerless, at the request of local government representatives it is registered with the body that registers property rights. Then, if the owner is not found, the hatch is transferred to the balance of one of the specialized companies.
The eternal question: “Why is the hatch round?”
Almost all manholes in the city are covered with special round covers. If you carefully study such objects, it turns out that they are the same all over the world. This involuntarily prompts the question: “Why are the covers on sewer manholes round? Why do the technical objects themselves have exactly this shape, and, for example, not square?” It turns out that the answers lie on the surface.
Some details about sewer manholes
The described items are made of cast iron or concrete. They are specially made heavy and unbearable, so that no one would have the desire to take a “useful” thing with them. Opening a technical hole on your own is not so easy, and this is specially provided for in the design for the safety of passers-by.
Sewer hatches have a conditional classification. They are divided according to the material of manufacture and the type of communications passing under the launch shafts. Therefore, experts highlight:
- Drainage systems.
- Storm drains.
- Electrical networks.
Hatches are made from high-strength cast iron and plastic, a special polymer-sand mixture, composite materials and reinforced concrete. But they are all invariably round in shape. Why, let's find out.
Logical explanation
So why is a manhole round? The described technical object consists of several parts - a round shaft, an inspection room and a lid.
The viewing room can have different shapes. It all depends on what communications are laid in the well. Dimensions are chosen taking into account the ease of their maintenance. But the mines are invariably made round. The diameter of the oval is 0.7 meters. They are assembled from brick and additionally equipped with a ladder that helps the service worker to go down without hindrance.
The top of such a hatch must be closed with a lid. It prevents entry into sewer systems various kinds of third-party objects that can provoke accidents. Almost everywhere the lid has a round shape. Why not square? Because in any position, such a lid will never fall inside and hit the person located there.
A square lid can easily fall inside under the influence of vehicles, slipping through at an angle. After all, the diagonal of a square is always greater than any of its sides. A circle has the same radius, no matter how you look at it.
Manufacturers typically produce lids that weigh more than 50 kg. This is done so that no heavy traffic of cars could move them.
Other explanations for the shape of the hatches
It is very rare to find such a form
There are several more explanations to help understand why manhole covers are round:
- Firstly, a circle has a higher ratio of cross-sectional area to circumference than a square or rectangle. This allows the lid production process to reduce material costs and save on product production.
- Secondly, the round shape reduces the internal forces that invariably occur when installing any cover on an object. And this also provides savings on the production of the product, since in this case it is possible to produce lids of smaller thickness.
- Thirdly, the round shape helps reduce the production of defective products. By reducing the number of reference lengths, the likelihood of errors leading to the appearance of uneven protrusions and other characteristic defects is reduced.
And one more thing. The round lid is much easier to transport for one person. He can just roll her to the place. A square or rectangular one will have to be carried in several hands.
The above arguments show that the choice of form is explained by elementary practicality.
Fun facts
There are known cases around the world of using lids of other shapes. For example, in the American city of Nashua you can still see sewer wells covered with triangular covers. Their sharp corners indicate the direction of flow waste water, and until recently this helped repair teams to navigate well. But today their use is considered unsafe, so the prefecture is dismantling them and replacing the triangles with circles.
Other forms are also found
Now you know why sewer manholes are made round. But why they are made so massive and heavy is also an interesting question. Although the explanation lies on the surface. The weight ensures relative safety from theft and delivery of the described products to metal collection points. About 10 years ago, a wave of characteristic crimes swept across the country. Lids began to disappear en masse, so the designers came up with an interesting solution.
Most modern sewer wells are not simply covered on top with a massive object that one person cannot carry away. The lids were placed on strong hinges, and they turned into real doors, which were additionally locked.
There is no way to leave the well open, especially those in which storm drain and plumbing. Their depth sometimes reaches 6 meters, and at the bottom of the technical room there are many protruding pipes and pieces of fittings. If a person falls there in the dark, it will end in death. Therefore, those who are responsible for sewer manholes - and this is the district administration - have a great responsibility for safe use of this technical structure.
Who else could be responsible for the hatches?
But the Russian people are still accustomed to seeing such a hatch
There are wells that are not in municipal ownership, but are part of the property apartment building or to the property of a specific legal entity.
All ownerless objects are first registered by the body that registers property rights. This happens at the request of the local government. Then, through the court, everyone can challenge their own right. If there are no volunteers within a year, all ownerless objects are transferred to the departments of specialized companies.
Generalization on the topic
The round shape of sewer manholes is more practical than all other types. Over many years of operation of sewerage structures it has been proven that round holes are more technologically advanced and have a longer service life. And all because such a hatch is more resistant to temperature changes.
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 are hatches round? The interview question is 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 find it difficult to answer”, this means that when faced with challenging 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. In the corridor leading into the room there are three switches.
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!
Logical tasks are given to job candidates to evaluate them analytical skills. Anyone can face similar questions. But even if this doesn’t happen to you, it will be simply interesting to study them for preparation.
Job seekers who encounter puzzles during the interview process should not panic or become confused. As a rule, in most cases it is enough to show your thoughts and ways to solve the problem. It may well be that the problem does not have a correct solution or an unambiguous answer. Under no circumstances should you say “I don’t know” or “I don’t know,” just think out loud.
So that you know what to be prepared for and don’t get confused, we have collected the most popular puzzle questions and prepared answers and recommendations for them. Who knows, maybe you will come across exactly these tasks.
Sewage hatches
This is perhaps the most common question among all puzzles.
Question: Why are sewer manholes round?
Answer: There are several options. Since the diameter of the circle is the same, no matter how you twist it, a round hatch cannot fall into the well. A square, for example, has a diagonal larger 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 hallway. For what minimum opening of the doors can you determine which switch belongs to which light bulb?
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 light bulbs remains on - this is the first switch, then we feel the remaining light bulbs - the warm one will be the second switch, and the cold one will be the third, respectively.
Cake
Question: How to divide a cake into 8 equal parts using three cuts?
Answer: First you need to make 2 cuts crosswise, dividing the cake into 4 equal parts. And then cut the cake in half horizontally. So what if the pieces are not tall, but you have 8 equal parts. You can also, after the first two cuts, stack the pieces on top of each other and halve them with one cut.
Dead man and match
Question: Found among the field dead man with a match in his hands, no traces. Why did he die and under what circumstances?
Answer: A man died from a fall from a plane that began to lose altitude, and an accident was inevitable. There was not enough one parachute for all the passengers and they drew lots. He got a short match and was forced to jump without a parachute.
Bus and balls
Question: How much tennis balls will it fit on the bus?
Answer: The recruiter himself does not know the exact correct answer, since it is not specified what kind of balls and bus they are - their sizes are not known, and no one has thoroughly checked this. Therefore, your train of thought is important here, you can only guess. Give the approximate length, width and height of the bus, and the dimensions of one ball. Calculate the volume of the bus and the ball - this way you will find out how many balls will fit into the empty bus. Reduce approximately this value taking into account the seats and other parts of the bus, make allowances for the fact that the balls are not square and give your answer. In this case, the process of finding an answer is more important than the answer itself. The question options may be different: the balls are soccer balls, instead of a bus there is a room, etc.
Pills
Question: The doctor gave the patient 4 tablets of two types - 2 tablets of each, which cannot be distinguished by appearance. The tablets should be taken in two doses: one tablet of each type in the morning and the same 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 undergo treatment and survive?
Answer: Of course, we can say that it is better to go to the doctor and ask for more, after all, it is 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 evening.
In conclusion
Remember that, first of all, such tasks and puzzles are intended to test the candidate’s behavior in non-standard situations, to assess the ability to think, creatively and logically. Unfortunately, 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 the desire to come to an answer will show you with the best side and increase your chances of getting a position.