THE SUBSEA BOP CONTROL SYSTEM. A subsea control system not only provides hydraulic power to close or open the BOP stack, it also provides and controls power for operating remote valves and latching and unlatching system components. On rigs with a subsea BOP, this power is regulated through a complex control system. Since the stack cannot be observed and the closing system is complicated, procedures for shutting in the well must be known and strictly followed to insure the well is properly shut in.
There are three general classifications of subsea systems: hydraulic, electro-hydraulic (EH) and electric (MUX).
In the hydraulic system, when a function operating button on a remote panel is pressed, electric current switches a solenoid and opens an air drive. The air drives an air cylinder that shifts a four-way valve on the accumulator manifold.
If the operating button is in the center, or blocked, position, no fluid movement is possible. The manifold sends high pressure fluid down a pilot line to the subsea pod. In the pod a hydraulic piloted function (or regulating) valve shifts and allows hydraulic fluid from the subsea accumulator or surface system to operate
the selected blowout preventer or valve. Both the electro-hydraulic and the multiplex systems use electric signals sent to the control pods for faster reaction time in deeper water environments. A subsea control panel contains both a flowmeter and a pressure read-back gauge.
When the system is functioned the flowmeter indicates the volume of hydraulic fluid used to complete the operation. The flowmeter readout is then compared to the theoretical volume required. In this way the driller or other operator can determine if the component functioned properly. The pressure read-back gauge indicates the system re-charging to the correct operating pressure.
Locate the proper function control.
Activate the control panel’s master switch if the panel has one. It is usually labeled Push and Hold to Operate.
Firmly depress proper function control.
Check the Read Back Pressure gauge to see if it drops and then returns.
Check the flowmeter to see if the proper number of gallons is used.