Factbox: How BP's containment cap works, next steps

HOUSTON/WASHINGTON (Reuters) - BP Plc says its containment cap on a seabed oil leak in the Gulf of Mexico collected 14,800 barrels on June 7, the highest capture rate in four days.

That brings the cumulative total of oil collected to 42,500 barrels.

As the global energy giant slowly increases that rate, it is moving to re-use equipment installed for a previous failed attempt to clog up the pipe known as "top kill." The equipment will now be adapted to siphon more of the leak and to interrupt containment efforts if a hurricane blows through the Gulf.

Here is an explanation of how both operations are supposed to work, as well as other technologies BP is using to try to bring the well under control:

CONTAINMENT CAP

* On June 3, BP placed the cap with a seal on the remnant of the pipe jutting from the top of a lower marine riser package, or LMRP, which sits atop a failed blowout preventer at the wellhead.

* Oil and gas continued to gush from under the cap because four vents were open as BP pumps nitrogen and methanol into the cap through a pipe attached to a drillship one mile above at the ocean's surface.

* The chemicals are intended to stabilize pressures and combat cold temperatures as the pumping action helps expel seawater from the cap.

* The aim is to prevent seawater from mixing with the gas, which can form ice-like hydrates and block the flow of oil and gas to the drillship.

* About 1,000 barrels a day of oil was flowing to the drillship as of early Friday. In subsequent days, the amount rose to 10,500, then 11,100 and reached 14,800 as of midnight on Monday.

* If the nitrogen lowers pressure as intended, the vents will close, the flow to the drillship will increase and the amount of oil gushing from the cap should decrease. On Sunday, BP closed one of the vents.

* U.S. government scientists estimated the leak's flow could increase by 20 percent before the seal works as intended. They are analyzing data to determine if that estimate turned out to be right.

* Oil that is channeled to the drillship will be stored for later processing at a refinery ashore and the natural gas is being flared.

BACKUP CAPS/DOMES

* If the first containment cap fails, BP has several backup caps of varying sizes at the seabed, on the way or being manufactured.

ENHANCEMENT TO LMRP CAP PLAN

* BP will use seabed equipment installed to conduct the top kill to enhance the containment cap system.

* The top kill involved pumping heavy drilling fluid into the failed blowout preventer to try to smother the leak. Mud was pumped from a ship to a service rig and down to a manifold, which routed the fluid to "choke and kill" hoses connected to the blowout preventer.

* With the system expected to be ready by mid-June, BP will reverse direction and pull oil and gas from the blowout preventer through the hoses and manifold to a vessel at the surface.

HURRICANE PREPAREDNESS

* BP also is planning a system to allow the drillship connected to the containment cap to suspend operations and move if a hurricane approaches.

* BP will use a "free-floating" pipe that stretches from the LMRP to about 300 feet below the drillship. Then a hose will connect the pipe to the ship.

* The system would involve a new, bigger cap designed to have a tighter seal to replace the current containment cap.

* Described by BP as a "long-term option," the system would allow the company to disconnect the hose from the pipe and move the ship out of a storm's path, then return when the weather calms to resume the operation.

* When disconnected, the leak would spew from the end of the pipe.

* The system is expected to be implemented in late June or early July.

* The Atlantic hurricane season began on June 1.

THE RELIEF WELLS

* Drilling continues on two relief wells intended to intercept and cap the leaking well beneath the seabed. The first was begun on May 2 and the second on May 16. Both are expected to be finished in August.

(Reporting by Kristen Hays; Editing by Eric Beech)