From Newsday, today, June 5, 2010:
FORGET "top cap" or "junk shot."
How about "seabed retread"?
That's what Northport native Alia Sabur, 21, a college grad at age 14 and youngest-ever professor at 18, calls her plan to stop the gushing BP oil well.
The proposal: Insert a diversionary pipe into the damaged well, then hold it in place by inflating rubber tires fastened around it, creating a firm seal. Sabur went to Louisiana Thursday to discuss the idea with a BP executive and has talks scheduled next with company scientists, she said.I'm hoping that Alia's solution didn't depend on using compressed air to inflate the tires. Water pressure at 5,000 feet is approximately 2,200 pounds per square inch (psi). For oil to flow out of the broken pipe, its pressure must exceed the water pressure.
So, lets assume that the oil pressure is 2,250 psi. Whatever you pushed into the pipe to be inflated, must be pressurized to something in excess of the opposing oil pressure or it would simply blow back out. To obtain a good seal, the pressure would have be nothing less than 75 to 100 psi greater than the oil pressure. Fairly simple fluid mechanics...
The problem is that you must pressurize the required 5,000 linear feet of 4 inch pipe to approximately 2,350 psi. That volume of air required would be 3,349,530 cubic feet of air.
Therefore, in what pressure vessel do you store this 3,349,530 cubic feet of air, compressed to 2,350 psi? How do you compress such a vast volume to that pressure? What means do you have to maintain that air pressure over time? In short, air pressure cannot succeed.
A possible solution is hydraulic pressure. Although I have not seen any reference to Alia's choice of fluid (gas or liquid). If using liquid, you don't need a vast volume of pre-compressed fluid.
What you need is a carefully designed, multi-o-ring seal plug. This seal would have to be installed on the end of the pipe. The pipe must be thick enough to avoid expanding under pressure, except at the plug end that inserts into the oil pipe. When pressurized, the thinner wall adapter at the end of the pipe would expand, stretching the o-rings until a seal is obtained. An external (around the outer diameter of the pipe) compression seal should be employed as well. Fluid within the pipe (sea water and oil) would be an acceptable pressure medium. The limited volume of natural gas will compress, but will eventually compress into a liquid.
On the outside of the pipe, an externally threaded compression seal ring would be pushed onto the leaking pipe's outside diameter. A compression nut would then be threaded onto the seal ring. This would squeeze onto the pipe very tight, providing a redundant seal and retain the internal plug in place.
The big problem now is that when they failed to cut the pipe cleanly, they used shears instead. This will prevent inserting a plug seal or an external seal because the end of the pipe is no longer round. It was a mistake not to try cutting the pipe again after the saw became jammed. A clean cut would have provided vastly more options.
Likewise, I do not understand why if they were going to shear cut the pipe, why didn't they simply pinch it off as much as possible. If you reduce the orifice, you reduce the volume of flow. Flow velocity would increase at the leak, but the volume of oil would be greatly reduced. A reduction in flow is desirable is it not?
It seems to my reasoning that BP panicked when they realized that the saw had became stuck. Rather than expend a day or two to make another attempt to cut the pipe cleanly, they over-reacted and used shears to sever the pipe. They succumbed to the political pressure rather than use sound engineering judgment.
Having shear-cut the pipe, BP elected to try and contain the leak by capturing the oil with yet another dome.
I'm trying to understand why they didn't try to pinch off the pipe off as much as possible first.
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