The safety valve in the heating system is a safety device for heat generators and other equipment, which is easy to operate. Its main function is to relieve unplanned loads that occur in various situations.
In addition, this device regulates the flow of coolant in the heating system. All other equipment is very dangerous as the water jacket is considered explosive as a result of the high pressure.
Destination
The main purpose of the safety valve is to protect the heating system from 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 coolant is out of range as a result of a failureautomation.
- A sharp increase in temperature.
Safety valve in the heating system: device diagram
This device consists of a housing and two molded elements. The body is made of plumbing brass, manufactured using hot stamping technology. The main component of the valve is a steel spring. With the help of its elasticity, it sets the pressure force that will act on the membrane that blocks the passage to the outside.
In turn, the membrane, located in the seat, equipped with a seal, is pressed by a spring. The upper part of the spring rests against a metal washer fixed on the stem and screwed to the plastic handle. The handle is required in order to adjust the safety valve in the heating system.
Let's take a closer look at the varieties of these devices.
Clutch valve
These devices are made of brass. This type is direct-flow, in other words, it opens by means of pressure force. Despite the fact that this is the cheapest option, it is also quite reliable. The sleeve safety valve in the heating system has a simple design: a stem with a gasket and a thread on both sides.
Brass device
This equipment has a more complex design. It must be installed in the heating system immediately after the circulation pump. The stem and spring in this design are made of stainless steel. The brass safety valve in the heating system is able to withstand coolant temperatures up to 1200 °C.
Return valve
The non-return valve is a safety device that prevents the backflow of coolant in the heating system when the pressure drops.
Operation principle
Today, you can find two main types of valves - spring and lever-weight. And before choosing a safety valve for a heating system, it is necessary to consider these types in more detail.
Lever and cargo
This type of safety valve is externally a shut-off equipment, the design of which provides for a special weight connected to the spool with 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 against the seat. When the pressure of the coolant in the heating system exceeds the norm, the safety valve opens and excess fluid flows out through the outlet pipe.
Spring loaded
Currently, the spring type valve is more popular. It differs from the previous version in that the spool rod is pressed not by means of a lever with a load, but by means of a spring. The principle of operation as a whole is not much different fromleverage device. By changing the degree of compression of the spring, the valve is adjusted.
Mounting Options
To ensure reliable and safe operation of the valve in the heating system, it is recommended to install in accordance with all regulations. 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 still remain, among them:
- In the heating system, this device must be installed on the supply pipeline directly after the boiler. If the power of the heat generator is large, it is allowed to install two valves.
- The safety valve on the return pipe of heating systems is installed only to ensure hot water supply at the highest point of the boiler.
- It is also unacceptable to narrow the channel in places between the main valve, the installation of shutoff valves is unacceptable.
- Drain pipes should be discharged into the sewer system or other safe place. It is absolutely unacceptable to install locking devices on this line.
Choice
It is very important to choose the right safety valve for the heating system, which will prevent the boiler from boiling and reduce the pressure. For the valve to work correctly, you must:
- Select spring equipment in which the spring will oppose the coolant pressure.
- Determine the size andtype of device so that the pressure in the heating system does not exceed the permissible values, since it is it that should help the system work.
- An open valve must be selected if water is discharged into the atmosphere, and a closed one if water is discharged into the return pipeline.
- Full-lift and low-lift valve should preferably be selected taking into account the throughput.
- When discharging water into the atmosphere, it is recommended to install open-type devices. Low lift valves should be selected for oil fired boilers, full lift valves for gas boilers.
Calculation
Calculation of the safety device must be carried out in accordance with the methodology presented in SNiP II-35 "Boiler installations".
Since manufacturers rarely indicate the actual height of the stem in the technical specifications, in the calculation this parameter is equal to 1/20 of the seat diameter. For this reason, the valve size is somewhat oversized as a result of this calculation. In any case, after selecting the device, it is necessary to compare the thermal output of the heating system with the maximum power recommended in the technical description for the selected size.
The installation of a safety valve is required to protect the heating system from exceeding the pressure level above the maximum allowable value. For this reason, the calculation of this device should be reduced to calculating the maximum allowable increase in the volume of the coolant andidentify possible sources of overpressure.
Sources of volume growth can be:
- Overheating in a heat exchanger or boiler unit with subsequent vaporization. During vaporization, the liquid is able to increase its volume by 461 times, so this factor is predominant when choosing a valve.
- Failure of automatic control of make-up lines of boiler houses and independent heating systems. This may also be the overriding factor in valve selection.
- The coolant, heating up in the heat exchanger or boiler unit, increases in volume. When heated, the specific volume increase is 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 must ensure the discharge of the calculated amount of coolant, according to the most significant volume growth factor.
Safety valve in the heating system: selection
The diameter of the inlet pipe of the valve must be equal to or greater than the diameter of the pipe obtained from the calculation. In addition to matching the diameter of the nozzle, it is necessary to check the safety device to reset 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 when the valve is opened, the more liquid will be released through the safety valve.equipment.
When choosing this device, it should also be remembered that its full opening is achieved when the pressure in the heating system exceeds the value when triggered by 10%, and full closure - when the pressure drops below the trigger parameter by 20%. Based on this, it is desirable to choose equipment with a set pressure higher by about 20-30% of the actual system pressure.
Nominal diameter
Determination of the nominal diameter of this safety device is carried out using special methods that were developed by the state technical supervision. For these purposes, it is advisable to invite qualified specialists.
If this is not possible, it is recommended to use the following principle: the diameter of the valve must not be less than the outlet pipe of the boiler unit. In this case, a significant margin is obtained, which will ensure the security of the system.
The heating system safety valve is set so that the critical pressure is approximately 10-15% higher than the working pressure. The operation of the device can be checked by forcefully opening it. The heating system safety valve must be adjusted annually before the start of the heating season.
