Overview 

MD/JAJ series wellhead safety hydraulic cutoff device is a kind of equipment to ensure the safety of well site production. When there is overpressure at the wellhead, pipe explosion and fire in the station, this device can automatically cut off the wellhead gas source to prevent the occurrence and spread of disasters and accidents, thus protecting the safety of station equipment and personnel.

 Performance features

1) automatic valve closing in case of overpressure
2) automatic valve closing in case of pressure loss 
3) automatic valve closing in case of fire
4) manual emergency valve closing
5) manual well opening and closing according to production requirements
6) valve position display 
7) no electricity and no one can work 
8) high pressure sensing accuracy and reliable action
9) fast valve opening and closing, especially the time from receiving signal to closing is less than 2 seconds
10) Compact structure, simple operation, few faults and convenient maintenance.

Main technical parameters 

1) Nominal diameter: DN25-DN600
2) Nominal pressure: 0. 5-105MPa
3) Overpressure sensing range: 0. 5-40 mpa
4) Loss of pressure sensing range: 0. 5-10 mpa
5) Pressure sensing accuracy: 1% of the set pressure
 6) Closing response time: ≤2S

Working principle

This device controls the automatic closing of its hydraulic block valve through the hydraulic control system placed in the control cabinet. The pressure source of the device is provided by the manual pump, which enters the hydraulic block valve and the accumulator respectively through pipelines. A master control valve is arranged on the pipeline of the hydraulic block valve to control the closure of the hydraulic block valve. The master control valve is controlled by a secondary low-pressure control loop, and the pressure source is provided by the manual pump through a pressure reducer to reduce the pressure to the required pressure, thus forming the control back pressure of the master control valve. Set high and low pressure pilot valves, fire alarm fusible plugs and manual ESD control points on the secondary low pressure control circuit respectively. When unqualified signals (such as wellhead overpressure signal, pipeline leakage pressure loss signal and fire signal) are detected at each control point, or an action signal is given artificially, the corresponding control valve acts or the fire fusible plug melts to release the pressure of the secondary low-pressure circuit. At this time, the back pressure of the main control valve causes the pressure of the hydraulic block valve actuator to be released through the control port of the main control valve and the quick release valve, and the actuator piston realizes safe well shut-in under the action of spring force.