Engineering Bulletin - EB04-005: Scope

Engineering Bulletin – EB04-005
GX 18 ¾-10,000 ABOP Open Chamber Head
Scope
of the lower annular. The third incident was in
This Engineering Bulletin identifies operating the upper part of the dual annular assembly.
conditions that could lead to damage of the Although a conclusive cause of the third incident
opening chamber head in Hydril’s GX 18 ¾- could not be fully identified, the investigation
10,000 Annular BOP when used in deep water has yielded the following probable causes:
applications.
1. One scenario that would cause the bending of
Background the opening chamber head is having an
improperly functioning check valve that would
The opening chamber head is used to prevent not allow trapped pressure above the opening
contamination of the opening chamber while chamber head to vent. The current check valve
changing out the packing unit. The opening is manufactured from a carbon steel material that
chamber head was first used in the GL Model is subject to corrosion in a seawater
ABOP’s, and has been used with the GL 18 3/4/ environment. The corrosion could cause the
- 5,000 subsea since the mid-70’s. The GX 18 ¾ check valve to stick and not allow trapped
- 10,000 Annular BOP incorporated this design pressure above the opening chamber head to
and has been in service since 1982. Currently, properly vent.
thirty four (34) GX 18-10 ABOP’s are being
used in deep water applications (> 4,000 ft) and 2. When the GX annular is used in subsea
some of these BOPS have been successfully applications, there is a large pressure head due to
operated at depths greater than 9000 feet. In water depth acting on the outside of the annular
normal operation, the cavity between the BOP. If the pressure in the opening chamber of
opening chamber head and the BOP head is the annular were to drop below the hydrostatic
isolated by the head seal on the wellbore side, sea head pressure and the pressure relief valve
and on the hydrostatic seawater pressure side, by fails to seal (due to the possible corrosion), a
a combination of the head to body seal, latch pressure load acting downward on the opening
screw seals and the pressure relief valve. chamber head could exist. In a water depth
greater than 3000 feet, the hydrostatic pressure
In the last two years, three incidents have load could be severe enough to permanently
occurred in which the opening chamber head has deform the opening chamber head. A scenario
been damaged. Each of these incidents has that could cause this type of loading would be if
occurred in the dual annular version (See Page the annular were fully closed then placed in a
3) of the GX 18 ¾ - 10,000. Two of these blocked position where by the annular packing
incidents resulted in the bending of the opening unit could passively force the piston downward
chamber head in the lower half of the dual into an open position. During the downward
annular. The bending in both cases was motion of the piston, if opening fluid were
determined to be caused by improper assembly restricted from entering the opening chamber of
Prepared By: Reviewed By:
___________________________________Date______________ ________________________________Date_______________
John Scoggins. William L. Carbaugh P.E.
Senior Mechanical Engineer Lead Engineer
Approved By: Approved By:
___________________________________Date______________ ________________________________Date_______________
Ed Hemphill Dave Wiley
Director of Engineering Director of Sales & Marketing
Revision: A1 HYDRIL is a registered trademark and service mark of Hydril Company LP 2004 Hydril Company LP All rights reserved Page 1 of 3
LATEST REVISION Printed on : Mon Sep 30 01:27:01 EDT 2013

the annular, a pressure lower than that of sea this cannot be avoided, ensure that the
head pressure could exist inside the opening hydraulic control circuit plumbed to the
chamber of the annular. This would result in a opening chamber of the annular can
pressure load being applied downward on top of provide enough flow as not to cause a
the opening chamber head. A low interflow pressure drop across the Opening
shuttle valve could restrict the opening chamber Chamber Head as described in Item 2
fluid flow enough to cause this condition to of the Background section of this
exist. document.
3. As referred to earlier in this section with the
other two accounts of damage to the opening • Ensure that the seals are installed in the
chamber head, improper assembly of the annular proper orientation when the annular
could result in damage to the opening chamber BOP is redressed with new seals. Refer
head. The GX annular is equipped with both to the GX BOP operations and
unidirectional and bidirectional seals. It is maintenance manuals for guidance on
important that the unidirectional seals be the proper seal orientation as well as
installed in their proper orientation to ensure that assembly/disassembly practices,
the proper seal integrity is obtained. lubrication recommendations, and
procedures.
Conclusion
• Periodic inspection for severe corrosion
and/or damage to the following
Hydril recommends the following to best components:
mitigate the previously stated conditions:
o Pressure relief valve
• Replacement of the pressure relief o Seals on the latch screws
valve with the stainless steel version o NPT plugs in the end of the
when the next available opportunity latch screws
arises. The replacement part number is o Annular head O-ring seal
1930644-01.
For further assistance with information
• During subsea operation of the GX 18 contained within this document or if assistance
¾-10,000 ABOP, avoid putting the is needed with other issues related to Hydril
annular control circuit in the “BLOCK” equipment, please contact your Hydril sales
position after closing the annular. If representative


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Engineering Bulletin – EB04-005

GX 18 ¾-10,000 ABOP Open Chamber Head

Prepared By: Reviewed By:

Approved By: Approved By:

LATEST REVISION Printed on : Mon Sep 30 01:27:01 EDT 2013

LATEST REVISION Printed on : Mon Sep 30 01:27:01 EDT 2013

LATEST REVISION Printed on : Mon Sep 30 01:27:01 EDT 2013

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