Annulars Hydril Gk
The 'GK' annular preventer is designed for surface installations and is also used on offshore platforms and subsea. Standard operation requires both opening and closing pressure. Seal off is affected by hydraulic pressure applied to the closing chamber, which raises the piston, forcing the packing unit into a sealing engagement. Main features include:
- Only two moving parts (piston and packing unit) mean few areas are subjected to wear. The BOP is thus safer and more efficient requiring less maintenance and less downtime.
- Piston is designed to be well pressure assisted. This ensures a more positive seal off under kick conditions for a higher margin of safety.
- Field replaceable wear plate in the BOP head serves as an upper non-sealing wear surface for the movement of the packing unit, making field repair fast and economical.
- Piston stroke measurement provides indication of packing unit life without disassembly.
- Three choices of packing unit rubber compounds
- Figure 27 - Type 'GK' Annular Blowout Preventer
1.6.1 Hydril 'GK' Stripping Operations
During well control operations, drill pipe can be rotated and tool joints stripped through a closed packing unit, while maintaining a full seal on the pipe. Longest packing unit life is obtained by adjusting the closing chamber pressure just low enough to maintain a seal without any leakage as the tool joint passes through the packing unit. As a large diameter tool joint passes through the packing unit it expands. A responsive regulator valve must control the hydraulic surge pressure caused by packing unit expansion. Better control may be achieved with the addition of a surge absorber (accumulator) to the closing chamber. Pre-charge the accumulator to half the closing pressure required to effect seal off. Slow stripping speeds will give longest packing unit life.
Average Closing Pressure (psi) To Establish Initial Seal Off In 'GK' Blowout Preventers For Surface Installations
|
OD (Ins) |
7 1/16 3M |
7 1/16 5M |
7 1/16 10M |
7 1/16 15M |
7 1/16 20M |
9-3M |
9-5M |
9-10M |
11-3M |
11-5M |
11-10M |
13 5/8 3M |
13 5/8 5M |
13 5 /8 10M |
16-2M |
16-3M |
16 % 5M |
18-2M |
|
6 5/8 |
350 |
700 |
600 |
350 |
450 |
500 | ||||||||||||
|
5 |
400 |
350 |
450 |
450 |
500 |
800 |
650 |
700 |
400 |
500 |
550 | |||||||
|
4 1/2 |
350 |
400 |
350 |
2100 |
2200 |
400 |
450 |
380 |
450 |
450 |
500 |
900 |
650 |
700 |
500 |
500 |
600 |
600 |
|
3 1/2 |
400 |
450 |
550 |
2100 |
2200 |
500 |
600 |
570 |
550 |
525 |
700 |
1000 |
7000 |
1200 |
600 |
600 |
650 |
650 |
|
2 7/8 |
400 |
450 |
750 |
2100 |
220 |
550 |
650 |
760 |
650 |
800 |
800 |
1100 |
750 |
1400 |
700 |
700 |
750 |
700 |
|
2 3/8 |
500 |
500 |
850 |
2100 |
2200 |
650 |
750 |
860 |
750 |
900 |
1100 |
950 |
1400 |
800 |
800 |
850 |
740 | |
|
1 90 |
600 |
600 |
900 |
750 |
850 |
850 |
920 |
1000 |
1500 |
900 |
950 |
950 |
850 | |||||
|
1 66 |
700 |
700 |
1000 |
850 |
950 |
1000 |
950 |
1000 |
1500 |
1000 |
1000 |
1050 |
950 | |||||
|
CSO |
1000 |
1000 |
1150 |
1050 |
1150 |
1150 |
1150 |
1150 |
1500 |
1200 |
1150 |
2200 |
1150 |
1150 |
1150 |
1150 |
The pressure above is a guideline. Maximum packing unit life will be realised by the use of the lowest closing pressure that will maintain a seal. For subsea applications, see the appropriate Operator's Manual for computation of best closing pressure.
Recommended test pipe for maximum packing unit life
The pressure above is a guideline. Maximum packing unit life will be realised by the use of the lowest closing pressure that will maintain a seal. For subsea applications, see the appropriate Operator's Manual for computation of best closing pressure.
Recommended test pipe for maximum packing unit life
* Reference only replaced by 'GX'
- Average closing pressures to establishing initial seal off pressure-surface installations.
Figure 28 — Packing Unit Testing
Figure 28 — Packing Unit Testing
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