Analysis on the problems of automatic sprinkler system and pressure switch

In common automatic sprinkler system, the wet alarm valve group is one of the important components of this system.The wet alarm valve group is composed of wet alarm valves, water source control valves, delayers, hydraulic alarm bells, pressure switches, filters, water test valves and other components.It is responsible for the test and inspection of water supply devices and alarm facilities, alarms, drainage and other functions. It is an important component of the automatic sprinkler system.However, in specific projects, there are many problems in the design and construction of the wet alarm valve group.The following are common problems:

Wet alarm valve in automatic sprinkler system

1. Improper setting of wet alarm valve

When a fire occurs in a building, the pressure switch installed in the wet alarm valve group should be able to operate as soon as possible after the sprinkler moves to spray water, and the sprinkler pump is activated in time to provide sufficient water and pressure for the system to extinguish the initial fire.Therefore, the wet alarm valve should be placed as close to the protected area as possible to reduce the length of the water distribution pipeline.

However, in some large-scale commercial buildings and community construction projects, designers tend to centrally install wet alarm valves in the pump room far away from the protected building. Valves and pipelines are located outdoors underground, and the distance is long, resulting in large resistance losses. The pressure switch takes a long time to start the spray pump，The control valve connected to the inlet and outlet of the alarm valve must be in a normally open state, so the valve should be a signal valve, and its signal should be reversed to the fire control center，When the signal valve is not used, a lock shall be provided to lock the valve.

2. The water source control valve adopts ordinary gate valve

In order to ensure a continuous water supply in the sprinkler system pipe network, the water source control valve must be in a normally open state.Therefore, the valve should be a signal valve, and its signal should be reversed to the fire control center;When the signal valve is not used, a lock shall be provided to lock the valve.However, in specific projects, a small number of designers did not make it clear in the design drawings, and some construction units used ordinary gate valves without signals and locks.

3. The laying of the pressure switch signal line does not meet the requirements

Generally speaking, because the pressure switch is installed between the outlet of the retarder and the hydraulic alarm bell, as long as the retarder is full of water, when the water pressure in the pipeline reaches a fixed value, the pressure switch will act to alarm, and the alarm and control signals should be transmitted separately. To the fire control center and the sprinkler pump control cabinet to report the fire alarm and automatically start the sprinkler pump.Therefore, the alarm and control circuit of the pressure switch should be buried in the wall through the metal pipe. If it is an open application, fire-resistant paint should be applied to the outside of the metal pipe.

However, in specific projects, a small number of construction units not only failed to lay the lines as required, but only laid the alarm lines to the fire control center, and did not lay the control lines to the sprinkler pump control cabinet. As a result, Once the alarm control cabinet of the fire control center fails, the spray pump cannot be started automatically.Some construction units use electric contact pressure gauges instead of pressure switches to automatically start and stop the spray pump, which does not comply with the control principle that the spray pump can only be stopped manually.