Start and Stop Pressure Sensor or Differential Pressure Sensor

Properly stopping and starting pressure sensors and differential pressure sensors is one of the skills that users need to master. Because during the daily use, checking the zero position for the pressure sensor and differential pressure sensor and periodically discharging the sensor will involve the starting and stopping of the sensor.

• Stopping and starting steps for the pressure sensor locally installed

The installation method of the pressure sensor locally installed on site is basically the same as the spring pressure gauge, that is there is only one sampling valve and some have a discharge valve.

1. Stopping method for locally installed pressure sensor

When stopping the pressure sensor installed locally, close the sampling valve, then slowly open the discharge valve to remove the measured pressure. If the pressure sensor does not have a drain valve, be sure to loosen the connector threads of the sensor slowly to relieve pressure. During operation, be careful to prevent the medium pressure from hurting people.

2. Starting method for locally installed pressure sensor

Starting the pressure sensor installed locally simply needs to open the sampling valve.

• Stopping and starting steps for the pressure sensor remote installed

The remote installed pressure sensor is connected with at least three valves and a pressure guiding tube. In addition to sampling, the sampling valve also cuts off the process medium drain valve. After the drain valve is shut off, the pressure guiding tube can be flushed and the condensate or gas in the pressure guiding tube can be removed. The shut-off valve for connecting the pressure guiding tube to the pressure sensor is also called secondary valve.

1. Stopping method for the pressure sensor remote installed

When stopping the pressure sensor, first close the secondary valve of the sensor. Then, the pressure can be removed through the drain liquid valve, drain gas valve at the measuring chamber of pressure sensor or through the drain valve at the pressure guiding tube. The sampling valve should also be closed if necessary. For sensors containing isolation fluid, do not open the drain valve at will to remove pressure.

2. Starting method for the pressure sensor remote installed

For pressure sensors used for general measured medium, it is only needs to open the secondary valve to start the sensor. However, for steam pressure measurement, the pressure guiding tube has been emptied. Therefore, close the secondary valve and the drain valve before opening the sampling valve. Then open the drain valve to flush the pressure guide tube. Then close the drain valve and wait for more than half an hour. After the steam condensate is accumulated in the pressure guide tube, open the secondary valve. At this time, use the exhaust valve of the sensor's measuring chamber to remove air. When doing the above operations, switch the control system associated with it to manual mode.

• Stopping and starting steps for the differential pressure sensor

The differential sensor is connected with at least five valves. Two of the sampling valves are used to sample and cut process medium. Two drain valves are used to flush the pressure guiding tube or to remove condensate and gas from the pressure guiding tube. The connection between the pressure guiding tube and the differential pressure sensor is a three valves manifold or five valves manifold. Most of the operations to stop and start the differential pressure sensor are the operation to three valves manifold.


1. Stopping method for the differential pressure sensor

When stopping the differential pressure sensor, the steps to close the three valves manifold are as follows. First close the negative pressure valve. Then open the balancing valve. Finally close the positive pressure valve. If the differential pressure sensor need to be stopped for a long time, positive and negative pressure valves in the three valves manifold as well as primary valve all should be closed. The balance valve should be opened to ensure that the pressure on both sides of the measurement chamber in differential pressure sensor are equal and in a balanced state.

2. Starting method for the differential pressure sensor

When starting the differential pressure sensor, the steps to start the three valves manifold are as follows. First open the positive pressure valve. Then close the balancing valve. Finally open the negative pressure valve.
For some differential pressure sensors starting and stopping, for example, differential pressure sensor for steam flow measurement, differential pressure sensor with isolator, level differential pressure sensor with balanced container. When opening and closing the three valves manifold, do not open the positive and negative pressure valves and the balancing valve at the same time. Because even if it is opened for a short time at the same time, it is possible to cause the condensate in the balance container and the isolation liquid in the separator to be lost. It will cause the instrument indication inaccurate. In severe cases, even the differential pressure sensor will not start. If necessary, users need to use the drain liquid valve and exhaust valve on the differential pressure sensor to exhaust the air or condensate.