The wellhead protective sensors.

It consist of valve basic components essentially for the smooth sourcing of the hydro-carbon to the surface reservoir which are as follows:
1.Regulator
2.The fusible plug
3.The p-pilot
4.U-valve

U-Valve:
For the well to flow sucessfully without the presence of the operator at the site there must be a means of ascertaining that the devices in the process network are adequately kept.So the U-Valve function as a security man over the behaviour of well flow processes.when the flow of the flowline is within the calibrated range,the gate of the valve remain open and hydrocarbon passes through it smoothly without any eruption.In an abnormal increase above the set -point or calibrated range of the pressure;the gate is forced to closed,thereby making the entire operation automatically safe.
The P-Pilot: the p-pilot is designed to sense or percieve the pressure abnormalility or change in pressure in the flow lines.The signal is transduced to the u-valve actuator,note that the p-pilot consistof the following components: piston,plunger,torgle valve,spring(low and high tension) and adjustable screw.
Sigma Valve:The basic function of this device is to bleed-off instrument gas or block it based on the percieveable condition.The signal is percieved or transduced by the sensor (p-pilot). It is a three-way
valve with a supply inlet and two outlets to the p-pilot and u-valve,whch consist of gasket, plunger and springway.
Fusible plug:The fusible plug is a mechanical elbow filled with lead and acts as a fire safety device.