Comparison of the application of normally open and normally closed differential pressure switches in different fields

Comparison of the application of normally open and normally closed differential pressure switches in different fields
In the industrial field, the normally open and normally closed states of differential pressure switches have different application scenarios. In chemical production, for some tanks storing hazardous chemicals, in order to prevent tank leakage, normally closed differential pressure switches are often used to monitor the pressure difference of the inlet and outlet pipelines of the tank. Under normal circumstances, the fluid flow inside the pipeline is stable, and the pressure differential switch contacts are closed. Once a leakage occurs in the tank, the pressure difference between the inlet and outlet pipelines will change, causing the normally closed pressure difference switch contacts to disconnect, triggering the alarm system to remind staff to take timely measures to avoid safety accidents caused by hazardous chemical leaks.
In some industrial processes that require precise control of fluid flow, normally open differential pressure switches are widely used. For example, in the pipeline transportation system of petrochemical industry, by installing throttling devices on the pipeline and cooperating with normally open differential pressure switches, the opening of the regulating valve can be controlled according to the changes in pressure difference, thereby accurately adjusting the flow rate of the fluid. When the flow rate in the pipeline changes, the pressure difference at both ends of the throttling device will also change accordingly. When the pressure difference reaches the set value of the normally open pressure difference switch, the switch closes and transmits a signal to the control system. The control system adjusts the opening of the regulating valve according to the signal to keep the flow rate within the set range.
In the field of HVAC, the normally open and normally closed states of differential pressure switches also have their own uses. On the water side of the air conditioning system, normally open differential pressure switches are usually used to monitor the resistance changes of equipment such as heat exchangers and water filters. When the heat exchanger or water filter is clogged, the pressure difference at both ends will increase. When the pressure difference exceeds the set value of the normally open pressure difference switch, the switch will close and send a signal to remind maintenance personnel to clean or replace the equipment to ensure the normal operation of the air conditioning system.
In the ventilation systems of some high-rise buildings, normally closed differential pressure switches are used for pressure control in stairwells and lobbies. In the event of a fire, in order to ensure the safe evacuation of personnel, it is necessary to maintain a certain pressure difference between the staircase and the front room to prevent smoke from entering the front room and staircase. The normally closed differential pressure switch is installed on the ventilation duct between the staircase and the front room, and the contacts are normally closed. When a fire occurs, the positive pressure air supply fan starts, and the pressure difference between the staircase and the front room reaches the set value, the contact of the normally closed pressure difference switch opens, controlling the bypass pressure relief valve to open and release pressure, keeping the pressure difference within a safe range.