Safety valve in the heating system. Scheme, selection, adjustment

The safety valve in the heating system is a protective device for heat generators and other equipment, which is distinguished by its simple operation. Its main function is to reset unplanned loads that occur in different situations.

In addition, this device is engaged in regulating the flow of coolant in the heating system. All other equipment is very dangerous, because as a result of high pressure, the water jacket is considered explosive.

Appointment

The main purpose of the safety valve is to protect the heating system against possible pressure drops. A similar situation is typical for houses with steam boilers. In the system of water heating and hot water supply, the pressure reaches the limit values quite rarely.

A sharp increase in pressure is possible for the following reasons:

• The volume of the coolant goes beyond the permissible values as a result of the failure of the automation.
• A sharp rise in the temperature regime.

Safety valve in the heating system: device diagram

This device consists of a body and two cast elements. The body is made of water brass, manufactured by the technology of hot stamping. The main component of the valve is a steel spring. With the help of its elasticity, it sets the force of pressure, which will act on the membrane, overlapping the passage outward.

In turn, the membrane, located in the saddle, complete with a seal, is pressed by a spring. The upper part of the spring rests against a metal washer fixed to the rod and screwed to the plastic handle. The handle is required in order to regulate the safety valve in the heating system.

Let us consider in more detail the variations of these devices.

Coupling valve

These devices are made of brass. This type is straight-flow, in other words, it is opened by means of a pressure force. Despite the fact that this is the cheapest option, it is also quite reliable. The coupling safety valve in the heating system has a simple design: a rod with a gasket and on both sides a thread.

Brass device

This equipment is more complex. It must be installed in the heating system immediately after the circulation pump. The stem and spring in this construction are made of stainless steel. The brass safety valve in the heating system can withstand the temperature of the heat carrier up to 1200 ° C.

Check Valve

The non-return valve is a safety device that prevents the counterflow of the coolant in the heating system when the pressure drops.

Operating principle

To date, you can find two main types of valves - spring and lever-cargo. And before you select the safety valve for the heating system, you need to consider these types in more detail.

Leverage-freight

This type of safety valve externally represents locking equipment, the design of which provides a special load, connected to the spool by means of a lever. The movement of the load in the direction of the length of the lever regulates the force with which the spool is pressed down against the saddle. When the heating medium pressure in the heating system exceeds the standard, a safety valve opens and excess liquid flows through the outlet pipe.

Spring

Currently, the most popular valve is a spring type. From the previous version, it differs in that the spool spindle is not pressed by means of a lever with a load, but by means of a spring. The principle of operation as a whole differs little from the lever-cargo device. By changing the degree of compression of the spring, the valve is regulated.

Mounting options

To ensure reliable and safe operation of the valve in the heating system, it is recommended to install in accordance with all the rules. You can find them in special regulatory documentation. The rules differ depending on the power and operating pressure of the system. But the basic principles are still preserved, among them:

• In the heating system, this appliance must be installed on the supply line immediately after the boiler. If the power of the heat generator is high, two valves are allowed.
• The safety valve on the return pipe of the heating system is installed only to provide hot water supply at the highest point of the boiler.
• Also, it is unacceptable to narrow the channel in the areas between the main valve and the shut-off valve is inadmissible.
• Dispose of the discharge pipes in a sewer system or other safe place. It is absolutely unacceptable to install locking devices on this line.

Selection

It is very important to make the right choice of the safety valve for the heating system, which will prevent the boiling of the boiler and lower the pressure. In order for the valve to work correctly, it is necessary:

• Select a spring equipment in which the spring will resist the pressure of the coolant.
• Determine the size and type of the device so that the pressure in the heating system does not exceed the permissible values, since it should help the operation of the system.
• The open valve must be selected if water is released into the atmosphere, and closed - if the water is discharged into the return pipeline.
• A full-lift and low-lift valve should preferably be selected taking into account the throughput.
• When dropping water into the atmosphere it is recommended to install devices of an open type. For oil-fired boilers, low-lift valves should be selected, and full-lift for gas boilers.

Calculation

The calculation of the safety device must be carried out in accordance with the procedure presented in SNiP II-35 "Boiler installations".

Since manufacturers rarely indicate in the technical characteristics the actual height of the rod, in the calculation this parameter is equal to 1/20 of the diameter of the saddle. For this reason, the size of the valve as a result of this calculation is somewhat overestimated. In any case, after selecting the device, it is necessary to compare the heating capacity of the heating system with the maximum capacity recommended in the technical description for the chosen standard size.

The installation of a safety valve is required to protect the heating system from exceeding the pressure level beyond the maximum permissible value. For this reason, the calculation of this device must be reduced to calculating the maximum permissible increase in the volume of the coolant and determining possible sources of excess pressure.

Sources of volume growth can serve as:

• Overheating in a heat exchanger or boiler unit followed by steam generation. During vaporization, the liquid is capable of increasing its volume by 461 times, so this factor is the predominant one when choosing a valve.
• The output of the automatic control system for the boiler feed lines and independent heating systems is out of order. This can also serve as a predominant factor in the selection of the valve.
• The heat carrier, heated in a heat exchange or boiler unit, increases in volume. When heated, the specific increase in volume from 0 to 100 ° C, which is only 4%, so when choosing the size of a device of this type, this is not a fundamental point.

The selected equipment should provide a reset of the calculated amount of coolant, according to the most significant factor of volume growth.

Safety valve in the heating system: selection

The diameter of the inlet fitting of the valve must be equal to or greater than the diameter of the nozzle obtained in the calculation. In addition to matching the diameter of the branch pipe, it is necessary to check the safety device for resetting the calculated increase in the volume of the coolant in the event of an emergency. It is also important to take into account the fact that the greater the pressure difference between the values in the discharge line and the opening of the valve, the greater the amount of liquid exits through the safety equipment.

When selecting this device, it should also be remembered that its full opening is achieved when the pressure in the heating system exceeds the value by 10%, and the complete shutdown is achieved when the pressure drops below the triggering parameter by 20%. Therefore, it is advisable to select equipment with an operating pressure higher than approximately 20-30% of the actual system pressure.

Nominal diameter

Determination of the nominal diameter of this safety device is carried out by means of special techniques that have been developed by the state inspection. For these purposes, it is advisable to invite qualified specialists.

In the absence of this possibility, it is recommended to use the following principle: the diameter of the valve should not be less than the outlet of the boiler unit. In this case, a significant reserve is obtained, which will ensure the safety of the system.

The safety valve of the heating system is set in such a way that the critical pressure is above the operating pressure by about 10-15%. The efficiency of the device can be checked by forcing it to open. The safety valve of the heating system must be adjusted every year before the start of the heating season.