Description
BOP Control System Inspection & Testing
The following are the minimum requirements that apply for the design of the Blowout Preventer control unit for the surface BOP’s and it is off course helpful in the rig inspection of the BOP Control Unit:
For annular preventers, the closing time should not exceed 30sec for the size smaller than 18 3/4” nominal bore and 45sec for those of 18 3/4” and larger.
Hydraulic operating equipment shall have at least a 3,000psi accumulator unit equipped with two regulator valves, one to reduce the operating fluid pressure to 1,500 psi and the other for further reduction of pressure for bag type preventer operations.
The capacity of the accumulators should be, at least, equal to the volume (V1), necessary to close and open all BOP functions installed on stack at least once, plus 25% of V1. The liquid reserve remaining on accumulators should still be the minimum operating pressure of 1,200 psi (200 psi above the pre-charge pressure).
The control panel shall be fitted with visual and acoustic alarms for signalling of low accumulator pressure, as well as control fluid reservoir low level.
A minimum of two air-driven pumps and one electrically driven triplex pump is required for charging the accumulators. The combination of air and electric pumps shall be capable of charging the entire accumulator system from the pre-charge to full charge pressure within 15min or less.
In addition to the hydraulic master control panel, the BOP control unit shall include at least one graphic remote control panel located on the rig floor near the Driller’s console (Check also Driller Job Descriptions). Off-shore units shall have an additional graphic remote control panel located at a safe distance from the rig floor usually in tool pusher’s office or adjacent to the escape route from drilling unit. Each remote control panel shall be connected to the control manifold in such a way that all functions can be operated independently from each panel.
A safety device shall be installed on the BOP control manifold and remote panels to prevent accidental operations of BOP controls such as the closure of the rams (pipe or shear) on the drilling string while drilling or tripping.
The BOP end of the control hoses must be flexible and fire proofed.
The BOP accumulator electric-driven pump shall be connected to an emergency power source.
Purpose of The Rig Inspection Of BOP Control Unit.
Verify the functionality of all the components of the BOP control unit (hydraulic and electro-hydraulic), the alarms, the pressure integrity of control lines, etc.
THE PROCEDURES OF THE RIG INSPECTION OF BOP CONTROL UNIT
1. Follows the Drilling Contractor test procedures for the BOP control unit.
2. For each control element, test functionality and response.
3. Repeat tests with all surface control panels (main and remote)
4. Pressure test control hoses.
5. Attach to the report the drawing of the BOP stack and surface control system schematic with the references for all components tested along with the result of tests.
Rig Inspection of the Accumulator Bottles
1 Bleed off the pressure manifold of accumulator Unit in the BOP Control Unit.
2 Check precharge accumulator pressure to be in accordance with systems specifications.
RIG INSPECTION FOR RECHARGING TIME TEST.
1 With accumulator pressure bled off to zero, start recharging with the electrical pump and record the time to reach 3000 PSI.
2 Repeat the same test using air pumps only.
3 Record the following
All bottles Precharged at …… psi.
Number of bottles with wrong precharge No
Recharging time with electrical pumps. min
Recharging time with air pumps.
OTHER ITEMS TO BE IN MIND WHILE INSPECTING WELL CONTROL SYSTEM PRIOR OF INSTALLATION
The control unit prior to installation should be tested for precharge pressure. The bottom valves of accumulator bottles should be opened and all fluid drained off to reservoir. Check nitrogen precharge pressure on each accumulator bottle and if required, it should be charged to recommended pressure. This should be done after changing to new drill site.
Check reservoir fluid to be free from any foreign material or for bacterial growth. Change reservoir fluid if required.
Pressure clean all the lines prior to installation.
Check for leakage from diaphragm and change if required.
Check air lubricator. Clean and fill up with the manufacturer’s recommended lubricating oil.
Check seal rings and air passage ports of remote control interface and interconnect cable assembly for any damage and plugging.
Control unit should be tested each time when the BOPs are tested. It should be done prior to pressure testing BOP stack. The test should be conducted with a drill pipe lowered in the stack as follows :
1. Record initial accumulator pressure and regulate operating Pressure to annular preventer to 53 kg/cm2 (750 psi).
2. Switch off power supply to all pumps.
3. Close annular preventer, and one ram BOP on pipe. Open the hydraulically operated choke valve. All this should be done simultaneously.
4. Record time required to close annular and ram BOPs as stated above and in opening of hydraulic valve.
5. Record final accumulator pressure. This should be at least 14.06 kg/cm2 (200 psi) above the precharge pressure.