Reliability of shear rams
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docellen
Jul 27, 2010, 5:00:41 PM7/27/10
to blowout
The objective of this design task is to get maximum reliability from
the shear rams, in spite of failures in hydraulic systems, shuttle
valves, control systems, whatever. The first and most important thing
is ensure that there are two completely independent, tested-at-full-
pressure, shear rams in every BOP. It is not clear to me whether that
was the case with the Deepwater Horizon. I see the diagram released
by BP (Blowout Preventer Drawing at http://www.energy.gov/open/oilspilldata.htm)
shows two shear rams. I see this information replicated in various
drawings for newspapers. Then I read an article in the New York Times
(http://www.nytimes.com/2010/06/21/us/21blowout.html?_r=2) in which
there is extensive and emphatic discussion of the fact that DWH did
*not* have two shear rams. Does anyone know for sure what is in that
stack?
Back to the topic of how to improve the shear ram - I would add a
flange that could be quickly removed to insert a fat steel shaft to
force the shear closed. This should work even if the entire hydraulic
system is destroyed.
the shear rams, in spite of failures in hydraulic systems, shuttle
valves, control systems, whatever. The first and most important thing
is ensure that there are two completely independent, tested-at-full-
pressure, shear rams in every BOP. It is not clear to me whether that
was the case with the Deepwater Horizon. I see the diagram released
by BP (Blowout Preventer Drawing at http://www.energy.gov/open/oilspilldata.htm)
shows two shear rams. I see this information replicated in various
drawings for newspapers. Then I read an article in the New York Times
(http://www.nytimes.com/2010/06/21/us/21blowout.html?_r=2) in which
there is extensive and emphatic discussion of the fact that DWH did
*not* have two shear rams. Does anyone know for sure what is in that
stack?
Back to the topic of how to improve the shear ram - I would add a
flange that could be quickly removed to insert a fat steel shaft to
force the shear closed. This should work even if the entire hydraulic
system is destroyed.
MacQuigg
Jul 28, 2010, 2:27:41 PM7/28/10
to blowout
There is an even simpler option - just provide a port where an
external hydraulic supply can be inserted. See the sketch
emergency_hydraulics.png. Notice that emergency plug cuts off the
normal supply completely, so even if there are leaks on the supply
side, this should still work. It won't help if there is damage to the
piston or its seals. In that case, your fat steel shaft may be the
last line of defense.
external hydraulic supply can be inserted. See the sketch
emergency_hydraulics.png. Notice that emergency plug cuts off the
normal supply completely, so even if there are leaks on the supply
side, this should still work. It won't help if there is damage to the
piston or its seals. In that case, your fat steel shaft may be the
last line of defense.
EdMG
Jul 28, 2010, 4:00:45 PM7/28/10
to blowout
There is a diagram of a shear ram at http://en.wikipedia.org/wiki/File:MMS455b_shear_ram_section.png.
Looks like you could just replace the entire piston and shaft with a
new assembly. That interface between the piston and body of the BOP
might need some redesign to make it possible to do this underwater
using ROVs.
Looks like you could just replace the entire piston and shaft with a
new assembly. That interface between the piston and body of the BOP
might need some redesign to make it possible to do this underwater
using ROVs.
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