The safety valve in the heating system is a protective device for heat generators and other equipment, characterized by ease of operation. Its main function is the discharge of unplanned loads arising in various situations.
In addition, this device is engaged in regulating the flow of coolant in the heating system. All other equipment is very dangerous, as a result of high pressure water jacket is considered to be explosive.
Appointment
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 a water heating system and hot water supply, pressure reaches its limit values quite rarely.
A sharp increase in pressure is possible for the following reasons:
- The coolant volume is beyond the permissible values as a result of a failure of the automation.
- A sharp increase in temperature.
Safety valve in the heating system: device diagram
This device consists of a housing and two cast elements. The casing is made of tap brass manufactured by 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 outward.
In turn, the membrane located in the seat, equipped with a sealant, is spring-loaded. The upper part of the spring abuts against a metal washer mounted on a rod and screwed to a plastic handle. A handle is required to adjust the safety valve in the heating system.
Consider in more detail the varieties of these devices.
Coupling valve
These devices are made of brass. This type is straight-through, in other words, it opens by means of pressure. 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 stem with 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 can withstand the temperature of the coolant up to 1200 ° C.
Check valve
The non-return valve is a safety device that prevents the backflow of the coolant in the heating system when the pressure drops.
Operating principle
Today, there are 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.
Lever and cargo
This type of safety valve externally represents locking equipment, the design of which provides for a special load connected with a spool using a lever. Moving the load in the direction of the length of the lever controls the force with which the spool is pressed against the seat. When the coolant pressure in the heating system exceeds the norm, the safety valve opens and excess fluid flows through the outlet pipe.
Spring loaded
Currently, a 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 from the lever-cargo device. By changing the compression ratio 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 rules. You can find them in special regulatory documents. 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 device must be installed on the supply pipe immediately 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 the 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 the places between the valve line, the device of stop valves is unacceptable.
- Discharge pipes should be discharged into a sewer system or other safe place. On this line, the installation of locking devices is completely unacceptable.
The choice
It is very important to make the right choice of safety valve for the heating system, which will prevent boiling of the boiler and lower pressure. For the valve to work correctly, it is necessary:
- Choose spring equipment in which the spring will counteract the pressure of the coolant.
- Decide on the size and type of device so that the pressure in the heating system does not exceed acceptable values, since it is precisely this that should help the system work.
- An open valve must be selected if water is discharged into the atmosphere, and a closed valve if water is discharged into a return pipe.
- It is advisable to choose a full-lift and a low-lift valve taking into account the throughput.
- When discharging water into the atmosphere, it is recommended that open-type devices be installed. For boilers operating on liquid fuel, low-lift valves should be selected; for gas-fired boilers, full-lift valves.
Payment
Calculation of the safety device must be carried out in accordance with the methodology presented in SNiP II-35 "Boiler installations".
Since manufacturers rarely specify in the technical specifications 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 valve size as a result of this calculation is somewhat overestimated. In any case, after selecting the device, it is necessary to compare the heating power 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 permissible value. For this reason, the calculation of this device should be reduced to calculating the maximum allowable increase in the volume of the coolant and determining possible sources of excess pressure.
Sources of volume growth can serve:
- Overheating in a heat exchange or boiler unit with subsequent vaporization. During vaporization, the liquid is able to increase its volume by 461 times, therefore, this factor is predominant when choosing a valve.
- The failure of the control automation of the make-up lines of boiler rooms and independent heating systems. It may also be a predominant factor in valve selection.
- The heat carrier, heating in a heat exchange or boiler unit, increases in volume. When heated, the specific increase in volume is from 0 to 100 ° C, which is only 4%, therefore, when choosing the size of a device of this type, this is not a fundamental point.
The selected equipment should ensure the discharge 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 pipe of the valve must be equal to or greater than the diameter of the pipe obtained in the calculation. In addition to matching the diameter of the pipe, it is necessary to check the safety device for dumping the calculated increase in the volume of 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 escape through the safety equipment.
When choosing this device, it should also be remembered that its full opening is achieved when the pressure in the heating system is higher than the value when triggered by 10%, and complete closure when the pressure drops below the response parameter by 20%. Based on this, it is advisable to choose equipment with a set pressure above about 20-30% of the actual pressure of the system.
Nominal diameter
Determination of the conditional diameter of this safety device is carried out by means of special techniques that were developed by the state technical supervision. For these purposes, it is advisable to invite qualified specialists.
In the absence of such an opportunity, it is recommended to use the following principle: the diameter of the valve must be not 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 safety valve of the heating system is adjusted so that the critical pressure is about 10-15% higher than the working pressure. The performance of the device can be checked by forcing its opening. The safety valve of the heating system must be adjusted annually before the start of the heating season.