Boiler equipment, whether it be a boiler in a private house or a large boiler house in an enterprise, is a source of danger. A constant pressure boiler water jacket is potentially explosive.
To ensure safety, today many boilers and other heat generators are equipped with many protective systems and devices. One of the easiest and most affordable is a safety valve installed in the heating system. It is sometimes also called an explosive valve.
Causes and consequences of coolant overheating
The problem of increasing pressure in the heating system is especially important for solid fuel boilers. An emergency situation usually occurs when the water in the boiler circuit is overheated. As soon as the excess heat carrier boils in the boiler tank, it instantly turns into steam. This is followed by a sharp increase in pressure in the heating system of such a steam boiler.
As a result of overheating of the boiler, the risk of destruction of fittings and polymer pipes increases. Leaks can begin at the piping connections of the system, up to pipe ruptures. The worst thing is a boiler explosion or an electrical short in boiler equipment.
What is a safety valve for?
The troubles associated with overpressure in the heating system are extremely dangerous for people and buildings. Explosion valves are installed to prevent the severe effects of overheating. Since the boiler itself is a source of critical pressure increase, the valve should be located as close to it as possible. It is mounted on a supply heating pipe.
Manufacturers of heating equipment often produce their products already equipped with safety groups - a manometer, an automatic air vent and a relief valve. This group is usually mounted on the jacket of a heating boiler. If such equipment is not provided in the purchased boiler, then you must install it yourself.
When is a safety valve necessary?
Unlike solid fuel boilers, when using electric or gas, explosive safety valves are not installed. These devices have their own automation, and inertia is almost completely absent. This means that as soon as the temperature of the coolant reaches the set point, the electric element or gas column are switched off on their own. At the same time, the heating stops, which eliminates the risk of overheating, and, accordingly, increasing the pressure to critical values.
Solid fuel boilers, like stoves with a water circuit, are systems in which the use of safety valves is mandatory. Regardless of the automation in the solid fuel heat generators, after heating the liquid in the network to the nominal value, the furnace will continue to raise the temperature for some time, although access to the chamber is closed by the sensor, and the flame begins to die out. This is how the effect of inertia manifests itself. When the temperature in the furnace reaches 90-95 degrees (limit values for most boilers), vaporization is inevitable. The result may be a depressurization of the heating system or a boiler explosion.
If a safety valve is installed on the boiler in the system, then the pressure increase after boiling of the coolant will be prevented. The valve will itself release excess steam to the outside, reducing the pressure in the system to normal. After that, the valve closes and trips the next time only in the event of an emergency.
Safety valve device
The valve is made of tap brass using hot stamping technology. It consists of two parts having a semi-solid state.
The main element of the valve is a special spring. Depending on its elasticity, the pressure power is determined, which is on the membrane that closes the outlet to the outside. The nominal position of the membrane is in the saddle, tightened by this spring.
With its upper part, the spring abuts against a metal washer, which is mounted on a rod, the end of which is fixed to a plastic handle. It is she who allows you to adjust the explosive valve. The sealing parts and the membrane itself are made of polymer. The spring is steel.
Valve operating principle
While in standby mode, the entrance to the inner chamber is closed by a membrane. In the event of an emergency, the mixture of steam and water begins to abut against the membrane, opening it at peak pressure. As a result, the steam-water mixture penetrates into the chamber, and then goes out through the hole on the side.
After reducing the pressure, due to some water leaving the system, the membrane falls into place and blocks the water outlet. Sometimes such valves are activated often, especially when boilers operate at maximum capacity. This is undesirable since the boiler may lose its tightness and leak accordingly.
If traces of leakage from the safety valve are detected, it is urgent to inspect the boiler and the heating system, since its operation is a sign of the heating system in extreme conditions. However, sometimes an expansion tank may also be the cause of an emergency pressure release. Therefore, you must definitely check it out.
In addition to the valve in question, the PGVU valve can also be used - for dust and gas ducts. He has the same principle of action. However, in the case of its use, it does not matter at all whether the steam boiler is solid fuel or what exactly will be thrown out - water, steam or gas.
How to choose a safety valve
If a valve is not supplied with the boiler, it will have to be purchased separately. The choice is made based on the characteristics of the boiler installation. The thermal power and the maximum possible pressure of the coolant in the heating system matter.
For reference. Most solid fuel boilers of famous brands have a maximum allowable pressure of about 3 Bar, with the exception of STROPUVA products. They have a limit of 2 bar.
It is best to install a valve that provides for adjustment in several ranges. Naturally, the values of the boiler installed in the boiler room should be included in these ranges. After that, the valve is selected for power - here the passport to the boiler will help, which always indicates the unit's power limit for heat.
It is strictly forbidden to install an explosion valve after the pump responsible for the circulation of the coolant in the system. There is another rule. Stop valves must not be placed between the boiler and the relief valve.
For aesthetic purposes, it is recommended to connect a pipe to the valve outlet, through which excess hot liquid would go into the sewer.