Bleed screw: the working principle and its impact on the efficiency of the heating system

Modern heating systems in buildings and industrial buildings, public and residential applications have a common technological element - bleed screw: principle of this device is to remove unwanted gaseous substances from the working circuit in order to maximize the efficiency of heating system. On appointment and technical characteristics of this device will be discussed in this article.

What is a bleed screw: operating principles and specifications

A huge number of closed hydraulic systems used in high technology industries (car, Heating engineering, mechanical engineering, etc.)., is used the removal of gaseous substances (air) from the working circuit, reducing the effectiveness of their work. This is especially true of heating systems.

Majewski valve operates like a conventional closure valve operating type - this opening / closing Hermetic compound of the area gaseous or hydraulic fluid with increased pressure in the region of the medium with normal physical conditions. Historical prototype of modern designs Majewski valve was the most common type of faucet sedelchatogo.

But not control technical water from heating systems using conventional water cranes require special design that makes it difficult or completely eliminating the loss of water from the heating networks. Advanced solution to this problem was the bleed screw, endures a lot of improvements in connection with the development of engineering.

Bleed screw: photo

Whatever the technical performance or considered valve Majewski, a principle of operation of this device always corresponds to its intended technological purpose the regulations and standard intra - a valve for venting STD 7073V (TU 36-710-82) of the heating systems for industrial and domestic application.

Structurally, it is performed as an air shutoff valve needle-type (hence the second name) as a combined plug for radiator with built-in mechanism for bleed air. Since standard STD 7073V regulated constructive dimensions, the air valve for radiators (aka Majewski) has an outer diameter landing half inch (1/2 "), three quarters of an inch (3/4 "), one inch (1"), etc. Various crane with a diameter of orifice (DN) 15, 20 and 25 mm allow its use not only the radiators but also in different nodes heating system. The technical characteristics include parameters such as working pressure (PN) - 10 atm (1 MPa) and a working temperature - up to 120 degrees Celsius.

valve design Majewski

The main element of a valve is the locking screw, is screwed into the mechanism housing and having tapered end portion, thereby ensuring a tight fit in the "saddle" diameter through hole 1.5-2 mm. The outer part of the screw is a four-sided or hex head (a special key for bleed screw) with a slot under ordinary screwdriver. Air passage upon opening of the valve body of the screw is performed with longitudinal grooves.

The air at the outlet of the groove enters the chamber, a sealed sleeve (typically made of resin) and having an outlet diameter commensurate with the through hole. Since the valve body is established by means of a threaded joint having a stuffing gasket and the valve mechanism in a closed position tightly closes the through hole, during operation of the heating system mounted crane ensures complete tightness of the system.

Useful advice! When selecting a valve must take into account the corrosion resistance of the material of which it made parts. Since many manufacturers produce products made of chrome-plated steel with a small term of operation, preference should be given to products made of brass or stainless steel.

Majewski Crane on a heated towel rail

If there are spaces in the radiator connected to the heating system or hot water system must be used with a heated towel rail bleed screw. Properties mounting such replaceable elements without having a complete set of these valves can lead to the accumulation of air in the upper areas of internal space towel warmer and most problematic - is to create "air pockets" to stop the process circulation coolant and in the heating circuit and hot water circuit. Presence crane Majewski on the towel warmers can eliminate the negative.

Bleed screw: the principle of the automatic air vent

The increasing use in heating systems are automatic air vent for radiators. This special Majewski crane structure which provides discharge of gas accumulations in the automatic mode. Consider further how the automatic air vent. Its design presupposes the existence of the float in the vertical channel. Without the presence of the gaseous medium backs the float through the lever spring with the inner tube, whereby the sealed system.

Under the conditions of occurrence of the gaseous medium, the float falls, weakening of the spring pressure on the stopper, the latter opens the outlet and the gaseous mixture coming out. By substituting the volume of the gas component, the coolant fills the float chamber and the float rises, closing through the spring with the outlet stopper. In case of breakage of the float mechanism via Majewski key can manually generate bleeding accumulated gas mixture.

The need to use a crane Majewski in heating systems

After mounting and filling of the heating system circuit coolant (water, antifreeze, industrial oils) in radiators air always remains. It forms the so-called air pockets and stops the circulation of the working fluid. This leads to a loss of efficiency of the heating system, since the boiler is operating at a predetermined temperature, and the radiators "cold". Without the use of a crane Majewski can not do in a given situation.

After the end of the heating season in the coolant medium the degassing phenomenon. A certain amount of dissolved air in the coolant when the temperature falls and the resting position is released from the liquid and accumulates, forming the same "air pockets". Therefore, before start of heating is required to top up the coolant system and use the crane Majewski possible.

Another negative factor in the formation of gas accumulations in the heating process is formation of hydrogen at a water hydrolysis reactions and the inner walls of metal pipelines and radiators. This is especially true of radiators made of aluminum without a protective anticorrosion treatment. With the application of the system bleed screw this problem is solved completely.

Lineup and manufacturers bleed screw: the price

Currently, the sanitary ware market represented a large number of crane models Majewski, both domestic and imported using different materials and components. Buying one or another form, as can be and need to buy a metal key for Majewski crane. The keys are commercially available and in plastic.

The following table provides information about the types and prices of the bleed screw:

product name	Trademark	Material	price, rub.
Bleed screw diameter of 10, 15, 20 mm	"Promart" Ltd., Kazan	chrome-steel	21-51
Py bleed screw diameter of 16 mm and 10, 15, 20 mm	"MetPromInteks" Ltd., Moscow	chrome-steel	63,8
The key to the bleed screw is 5 mm, Meibes SX 11202	"KOMFORT.RU" Ltd., Moscow	silumin	18
The key for radiator tubes and crane Majewski	"MantehBryansk" Ltd., Bryansk	polymer plastic	118
Manual bleed screw, diameter 15 mm	"OK Resa» Ltd., Permian	chrome-steel	152
Bleed screw Demin Dokum Classik Art, diameter 15-20 mm	LLC "Laboratory heat", Mr. Rostov-on-Don	brass	138
Air vent for a radiator circuit	PP "Termoklimat" Mr. Yaroslavl	stainless steel	259
Bleed screw (automatic)	"TECHNO-GROUP», Mr. Kirov	stainless steel	230
ball valve with bleed screw diameter of 15 mm (1/2 ")	LLC "TECOM" Mr. Krasnoyarsk	chrome-plated brass	243
TEE Majewski crane	LLC "Siberia GOST" Mr. Omsk	chrome-steel	596
Crane with a three-way cock Majewski (G1 / 2 - G1 / 2)	LLC "AKVA-KIP" Mr. Moscow	chrome-steel	245
Majewski tap filter with diameter 15 mm	"Promarmatura" Ltd., Barnaul	chrome-plated brass	474
Bleed screw automatic RR 374 full bore, for cast-iron radiators	"SantehKlass" Ltd., Moscow	chrome-steel	700

Useful advice! If you need to buy a bleed screw, always agrees landing sizes Places installation of valves in the elements of the heating system with parameters bought. In the case of non-compliance need to purchase additional adapters and consumables.

Features of use and adjustment of the crane Majewski

Consider the case when the system is installed and assembled, but not mounted on the radiator bleed screw. Then you can do it yourself. For this it is necessary to unscrew the stub tube on the opposite side of working fluid entry to the radiator and in their place screw selected valves.

Useful advice!Regardless of whether the pressure at the stuffing box of the threaded portion of the valve body will be expedient to use sealing tape on the thread or tow FUM for better sealing.

As the bleed screw works

Adjustment of the outlet radiator bleed screw needs to be done so that it was directed to the opposite side of the wall and preferably with a slope to the bottom.

With regard to the installation of the crane Majewski on the towel, then it needs to be placed in the upright position using a special tee. Using the latter allows you to translate the work mounted crane axis from vertical to horizontal. It is his preferred location technology makes it possible to fulfill the requirement of the instructions: bleed-hole must be directed to the opposite side wall and sloping toward the floor.

An important issue is the use of bleed screw for cast iron radiators. Cork plugs-they do not have mounting holes for standard valves. However, many craftsmen found a way to install valves for fighting air due to the operation of drilling and threading in the body of the cast-iron caps. But as practice shows - such "kustarschina" can lead to the disruption of the thread at the phenomena of water hammer when the coolant pressure could grow tenfold. The output of this situation is the installation of the landing adapted to the size plugs of cast iron radiators air vent automatic type. The more so because they have no fear of clogging.

It should be added that in the case where the heat transfer fluid may contain particles of solid waste (scale, welding flux, hemp thread, ink, etc.)., then before the crane is desirable to set the standard mechanical filter water supply.

Valve Majewski: how to use

Consider how to use the bleed screw, or more simply: how to pull the air? Majewski Crane provides a fairly simple process bleed air from the heating system. Particular attention should be paid to the time when the heating system has a fuel pump to increase the coolant flow rate. Required before surgery bleed air should be turned off. Firstly, in order to reduce the pressure within the circuit and, secondly, to stop the process of mixing the air bubbles around the coolant volume.

Subject to a small set of rules can independently carry out work on the removal of trapped air in the system:

• apply a small capacity and a dry cloth to be set below the outlet opening Majewski crane;
• cook key to turn the adjusting screw of the valve;
• for secure carry a sliding or open-end wrench for possible further tightening the tap into the radiator.

The wrench (or a screwdriver) on the head of the adjusting screw, you must gradually make the opening operation (twisting screw) until the hissing sound of air escaping. Hold at this position prior to screw drip fluid exiting the radiator. It is desirable that it is poured into the prepared container. Then smoothly screw the bolt to the complete cessation of fluid leakage. For this purpose, a dry rag wipe the valve body and visually observe the output of the valve opening. If fluid leakage is not observed - the tap is sealed.

In cases where after the opening of the valve there is leaking water from the threaded connection body should gently pull the thread using the wrench until no education drops. It will also help to learn how to pull air from the radiator video and instructions found on the Internet.

Majewski Crane pneumatic systems

Technical features Majewski crane is its structural uniqueness. It can also be used to remove not only air, but also liquid, namely - from the pneumatic systems with high pressure air. Typically, the compressed air entering the system from the compressor, comprises a number of above-norm of water vapor. Technologically excess moisture shown on freezing of special devices and various filters.

For a long time operation in stationary (tube) highways may accumulate a significant amount of water. It accumulates in the lowest areas of pneumatic and sprayed over the entire contour. Water entering the operating compressed air from the pneumatic devices and the equipment is very undesirable. In these cases, the aid comes bleed screw. Only in this case it is mounted in the lowermost point of the contour and etching process is accumulated since the ejection liquid (water), and terminates the clean air outlet. Then the valve closes and the system again becomes hermetically closed.

Related article:

heating circuit 2-storey private house: types of routing calculation and equipment The constituent elements of the system, the purpose of the device, the rules of calculation and installation. Classification by wiring and methods.

Thus, it became clear as a bleed screw works. Its main function is to remove accumulated air from the system, which plays an important role in terms of efficiency and economy. It really affects the economy of cash costs in the operation. Market accessibility, simple valve design allows independently and without the involvement of specialists in the plumbing does not only produce air bleed operation of the circuit of the heating system, but also to establish or to perform the replacement of the crane. Neither one nor the other operation in itself does not imply large financial and physical costs, and most importantly - time.