[lentulusgracchus]

In other words, a safety valve should automatically close when not signaled to stay open.

You can't do that with blowout preventers because of the serious entailed consequences of an inadvertent activation of the rams. Each BOP stack has an inflatable "bag"-type preventer called a Hydril, which is separate from the main stack. There is also a TIW valve, a kind of check valve, inside the drillpipe. Higher rated are the hydraulic ram sets, which usu. include a set of

• a) pipe rams which close on the drillpipe offering a tight seal (all rams are pressure-rated and benchmarked and absolutely massive),

• b) shear rams which can crush and cut drillpipe like it was a plastic straw, achieving a "scissors" seal after the DP separates and the drillstring drops away, and

• c) blind rams, which are just a flush-faced pair of opposed rams which, after the DP is out of the way, or when you're out-of-hole, close tightly together and offer a very tight seal.

This stuff is serious equipment, very bulky and heavy-duty.

Rams are tested religiously, and the MMS and Coast Guard sometimes come out to look over the drilling contractor's men's shoulders. This is no place to play. Blowout preventers stacks are one of the most serious pieces of safety equipment in the oil patch, and when gas comes to surface, people's lives depend on their working first time, every time.

This time, they didn't -- and the Coasties and MMS and BP are going to know why.

[Gene Eric]

Thanks for the detailed info!

I take it that once the rams are actuated the seal is permanently closed? To reopen, the rammed section needs to be replaced?