Valves, as "small parts", are easily overlooked in firefighting. However, such "small parts" sometimes play a "big role". Valves are more like switches, and they are effectively controlled in some fire-fighting systems and equipment.

Wet alarm valve

In the event of a fire, a flame or high-temperature air flow activates the heat-sensitive elements of the closed nozzle, opening the sprinkler head and spraying the water. At this point, the water in the pipe network changes from static to flowing, so that the water flow indicator acts to send an electrical signal, indicating on the alarm controller that a certain area is already spraying water. As the nozzle is turned on, the water pressure in the upper part of the wet alarm valve is lower than the lower water pressure due to continuous discharge and pressure relief. Under the effect of pressure difference, the wet alarm valve that was originally in the closed state is automatically opened, and pressure water flows through the alarm valve to the fire extinguishing network. Turn on the access to the hydraulic bell, and the water flow impacts the water alarm to sound an alarm signal. According to the alarm signal of the water flow indicator or pressure switch, the control center automatically starts the fire pump to pressurize the water supply to the system to achieve the purpose of continuous automatic sprinkler fire.

The characteristics of the wet system are: 1 simple structure, convenient construction and management; 2 good economy; 3 fast fire extinguishing rate, high control rate; 4 wide application range, suitable for setting indoors temperature not lower than 4 °C and not higher than 70 °C inside buildings and structures.

Dry alarm valve

The dry system is developed from the wet system. Usually the pipe network is filled with compressed air or nitrogen, so it is suitable for places where the ambient temperature is lower than 4 °C or higher than 70 °C. The system consists of closed nozzles, piping systems, inflatable equipment, dry alarm valves, alarm devices and water supply facilities.

Before the dry alarm valve is activated, the pipeline in front of the dry alarm valve (connected to the water source) is filled with pressurized water. The pipeline behind the dry alarm valve is filled with compressed air and the alarm valve is closed. In the event of a fire, the thermal sensitive element of the closed nozzle moves, the nozzle opens, the compressed air in the pipeline is sprayed from the nozzle, the pressure on the outlet side of the dry valve drops, causing the front valve water pressure to be greater than the rear pressure, dry alarm The valve is automatically opened, the pressure water enters the water supply pipe, the remaining compressed air is pushed out from the open nozzle, and then the water is sprayed. When the dry alarm valve is opened, the access to the hydraulic bell and the pressure switch is also turned on, the water flow impacts the hydraulic bell and the pressure switch, and the pump is started to pressurize the water supply.

Dry automatic sprinkler system features: 1 after the alarm valve in the pipeline without water, not afraid of freezing, not afraid of high temperature; 2 due to the discharge process after the nozzle action, so the slower than the wet system speed; 3 because there is inflation Equipment, high investment in construction, the usual management is also more complex and demanding; 4 apply to places where the environment below 4 °C and 70 °C and should not use wet sprinkler system.

Dry alarm system and wet alarm system

The basic constitutional conditions of the dry system include the water source, pressure and regulation facilities, pressure gas source, alarm devices, pipe network and closed nozzles.

Necessary conditions for the wet system: adequate water supply, reliable water supply equipment, energy-driven equipment, such as pumps, water tanks and pressure water supply equipment, complete sets of valves, alarm and linkage facilities, piping and automatic sprinklers.

The main working process of the dry automatic sprinkler system differs from the wet sprinkler system in that there is an exhaust process after the former nozzle action, which will affect the speed and effectiveness of the fire extinguishing. For dry automatic sprinkler system with large pipe network volume, this adverse effect can not be neglected during design. Usually, an “exhaust accelerator” device is added to the dry alarm valve outlet pipe to speed up the alarm valve. The depressurization process allows the alarm valve to be started sooner, so that the pressure water can quickly enter the inflatable pipe network, shorten the exhaust time, and spray water early.

Groove valve to consider the installation and use

For projects with high speed requirements, the installation is simple and rapid. However, when there are irresistible factors, they can quickly replace the products and ensure that the pipeline maintenance speed is increased and the installation cost is even more important.

The grooved (clamp) connection valve is used as a new type of pipe connection method, and its application in international pipeline fluid control is more and more extensive. Extensive application makes the installation cost more important. For example, Shanghai Huhang Valve Co., Ltd. independently researches and designs and manufactures a series of new connecting valves while referring to similar advanced products from the United States and Germany. The external connection end of the valve body is provided with a flange or thread or a long straight section for welding, and is a short straight section with a groove, so as to save materials, simplify the valve production process, and reduce the valve cost. When designing the connection method of the valve, full consideration is given to the restricted environment of the product installation conditions. Design products with quick and easy installation. Compared with similar gate valve products, at least one-third of the time is saved in installation. The time for product installation and construction has been greatly improved, and for projects with high requirements for the speed of the construction period, for the maintenance features, when there are irresistible factors, the product can be quickly replaced and the pipeline maintenance speed can be improved, which has obvious advantages.