Mayevsky’s crane: principle of operation and its influence on the efficiency of the heating system

Modern heating systems for industrial and public buildings and housing have one common technological element – the Mayevsky crane: the principle of operation of this device is to remove unwanted gaseous substances from the working circuit in order to ensure maximum efficiency of the heating system. The purpose and technical characteristics of this device will be discussed in this article.

What is the crane Mayevsky: principle of operation and technical characteristics

A huge number of closed hydraulic systems used in high-tech industries (automotive, thermal engineering, mechanical engineering, etc.) use the technology of removing gaseous substances (air) from the working circuit, reducing the efficiency of their work. This is especially true of heating systems.

The Mayevsky valve functions in the same way as a conventional shut-off valve works – this is the opening / closing of a hermetic connection from an area of ​​gaseous or hydraulic medium with increased pressure to an area of ​​medium with normal physical conditions. The historical prototype of the modern constructions of the valve of Mayevsky was the most common type of a tap valve.

However, uncontrolled intake of industrial water from heating systems using ordinary water taps required a special design that impeded or completely eliminated the loss of water from heating networks. The best solution to this problem was the crane Mayevsky, which has undergone many improvements in connection with the development of engineering thought.

Regardless of the technical performance of the Mayevsky valve, the principle of operation of this device always corresponds to its direct technological purpose and the rules of the intra-industry standard – this is a tap for air flow STD 7073B (according to TU 36-710-82) from industrial and domestic heat supply systems.

Structurally, it is performed as a needle-type air shut-off valve (hence the second name) in the form of a combination cap for a radiator with a built-in mechanism for air bleeding. Since the STD 7073B standard regulates the design dimensions, an air valve for radiators (he is Mayevsky) has an outer diameter of half an inch (1/2?), Three-quarters of an inch (3/4?), One inch (1?), And so on. d. The sizes of the crane with the nominal diameter (DN) of 15, 20 and 25 mm make it possible to use it not only in radiators, but also in different nodes of the heating system. The technical characteristics include parameters such as operating pressure (Ru) – 10 atm (1 MPa) and operating temperature – up to 120 degrees Celsius.

The main structural element of the valve is a locking screw, which is screwed into the body of the mechanism and having a conical shape of the end part, thereby ensuring a tight fit into the “saddle” of a through hole with a diameter of 1.5-2 mm. The outer part of the screw is a four-sided or hexagon head (under a special key for a Mayevsky crane) with a slot for an ordinary screwdriver. For the passage of air when the valve is opened, the screw body is made with longitudinal grooves.

The air at the exit of the grooves enters the chamber, hermetically sealed with a cuff (usually made of polymer) and having an outlet opening in diameter commensurate with a through hole. Since the valve body is installed using a threaded connection with a gland seal, and the valve mechanism in the closed position tightly closes the through hole, the installed valve during operation of the heating system ensures complete tightness of the system.

Helpful advice! When choosing a valve, it is necessary to take into account the corrosion resistance of the material from which its parts are made. Since many manufacturers produce products made of chrome-plated steel with a short lifetime, preference should be given to products made of brass or stainless steel.

If there is a radiator in the premises connected to the heating system or to the hot water supply system, it is necessary to use a heated towel rail with a Mayevsky tap. Features of installation of such replaceable elements without the presence of these valves in the assembly can lead to air accumulation in the upper zones of the internal space of the heated towel rail and the most problematic is to create air plugs that stop the circulation of the coolant both in the heating circuit and in the hot water circuit. The presence of a Mayevsky crane on a heated towel rail allows you to eliminate this negative.

Increasing use in heating systems are automatic air vent for radiators. This is a special design of the Mayevsky crane, which ensures the discharge of gas accumulations in automatic mode. Consider next how the automatic air vent works. Its design assumes the presence of a float in the vertical channel. Without the presence of a gaseous medium, the float props up through the lever a spring with an inner plug, due to which the system is sealed.

Under conditions of gas environment, the float falls, weakening the spring pressure on the plug, the latter opens the outlet, and the gas mixture comes out. When replacing the volume of the gas component, the coolant fills the float chamber and the float floats, closing the outlet through the spring with the stopper. If the float mechanism breaks with the Mayevsky key, it is possible to manually release the accumulated gas mixture.

After installing the heating system and filling the circuit with coolant (water, antifreeze, technical oils), air always remains in the radiators. It forms the so-called air plugs and stops the circulation of the working fluid. This leads to a loss of efficiency of the heating system, since the boiler operates at a given temperature, and the radiators are “cold”. Without the use of the crane Mayevsky in this situation is not enough.

After the end of the heating season in the environment of the coolant occurs the phenomenon of degassing. A certain amount of dissolved air in the coolant when the temperature drops and the state of rest is released from the liquid and accumulates, forming the same “air plugs”. Therefore, before starting to start heating, it is required to add coolant to the system and, if possible, use a Mayevsky crane.

Another negative factor in the formation of gas accumulations in the heating system is the formation of hydrogen in the hydrolysis reactions of water and the inner walls of metal pipes and radiators. This is especially true of radiators made of aluminum without protective anti-corrosion treatment. With the use of the Mayevsky crane in the system, this problem is completely solved.

Currently, a large number of models of Mayevsky cranes, both domestic and imported using various materials and components, are on the market of sanitary products. When buying this or that type, it is also possible and necessary to buy a metal key for the Mayevsky crane. The keys are also available in plastic.

The table provides information on the types and prices of Mayevsky cranes:

Helpful advice! If there is a need to buy a Mayevsky crane, be sure to match the mounting dimensions of the installation locations of the valves in the elements of the heating system with the parameters purchased. In case of discrepancy, additional purchase of adapters and consumables will be required.

Consider the option when the system is installed and assembled, but Mayevsky’s cranes are not mounted on the radiators. Then you can do it yourself. To do this, unscrew the plugs from the opposite side of the working fluid inlet to the radiator and screw in the selected valves in their place.

Helpful advice! Regardless of the presence of the clamping gland on the threaded part of the body of the crane, it would be advisable to use on the thread of the sealing tape FUM or tow for better sealing.

The adjustment of the outlet of the Mayevsky radiator cranes must be made so that it is directed in the opposite direction from the wall and preferably with a slope to the bottom.

As for the installation of the Mayevsky crane on the heated towel rails, it is required to place it in a strictly vertical position with the help of a special tee. The use of the latter allows the working axis of the mounted crane to be transferred from vertical to horizontal. This is his preferred technological location makes it possible to fulfill the requirement of the instruction: the bleed hole should be directed in the opposite direction from the wall and have a bias towards the floor.

An important issue is the use of the crane Mayevsky for cast iron radiators. Corks, plugs they do not have mounting holes for standard valves. However, many craftsmen have found a way to install taps for air bleeding due to the operation of drilling and tapping in the body of a cast-iron plug. But as practice shows, such a “handicraft industry” can lead to a breakdown of the thread with water hammer phenomena, when the pressure of the heat-transfer agent can grow tenfold. The way out of this situation is the installation of automatic type vent valves fitted to the landing dimensions of cast-iron radiators of air vent valves. Especially since they are not afraid of clogging.

To this, it should be added that in the case when the coolant may contain solid particles of debris (scale, welding flux, tow threads, paint, etc.), then it is advisable to install a mechanical standard filter for the water supply system in front of the tap.

Consider how to use the crane Mayevsky, or more simply: how to lower the air? Mayevsky’s crane provides a fairly simple process of bleeding air from the heating system. Particular attention should be paid to the moment when the fuel pump is installed in the heating system to increase the circulation rate of the coolant. Be sure to turn off the air before the operation. First, in order to reduce the pressure inside the circuit and, secondly, to stop the process of mixing air bubbles throughout the coolant volume.

If you follow a small set of rules, you can independently carry out work to remove accumulated air in the system:

• apply a small container and dry cloth, which must be installed under the outlet of the Mayevsky crane;
• prepare a key for turning the valve adjusting screw;
• for safety, have a sliding or open-end wrench for possible additional tightening of the valve in the radiator.

Wearing a key (or inserting a screwdriver) on the head of the adjusting screw requires a smooth opening operation (unscrewing the screw) until a hissing sound of outgoing air appears. Hold the screw in this position until the beginning of the drop of liquid from the radiator. It is desirable that it merge into the prepared container. Then gently screw in the screw until the liquid stops flowing. To do this, use a dry cloth to wipe the valve body and visually observe the valve outlet. If no leakage of fluid is observed – the valve is hermetically closed.

In cases when after opening the valve water is flowing out from under the threaded connection of the housing, it is necessary to gently tighten the thread using a wrench until the formation of drops completely stops. They will also help you learn how to take out air from the heating radiator videos and instructions found on the Internet.

Technical feature of the crane Mayevsky is its constructive uniqueness. It can also be used to remove not only air but also liquids, namely, from pneumatic systems with high air pressure. Typically, compressed air entering the system from a compressor contains an excessive amount of water vapor. Technologically excess moisture is selected by special freezing devices and various filters.

For a long time of operation in a stationary (pipe) lines can accumulate a significant amount of water. It accumulates in the lowermost zones of the pneumatic lines and splashes around the entire contour. Water entering pneumatic devices and equipment using compressed air is very undesirable. In these cases, the crane Mayevsky comes to the rescue. Only in this case it is mounted to the lowest point of the contour and the process of bleeding starts with the release of accumulated liquid (water), and ends with the release of clean air. Then the valve closes and the system becomes hermetically closed again.