If mud is observed coming from the weephole this would suggest that the piston rod mud seal requires replacing. Should leakage occur in either the wellbore or operating chamber the weephole will provide a vent to atmosphere. The function of the weephole is to isolate wellbore pressure from the pressure in the operating cylinder. Ram closing and Bonnet opening pressure (Red) Ram opening and Bonnet closing pressure (Blue)Īll ram type blow out preventers mentioned in this section incorporate a weephole and secondary sealing mechanism between the operating chamber and the interior of the BOP.
Hydraulic Control System of 'U' Preventers An important feature of the hydraulic system is that the rams are pulled back close to the bonnets before the bonnets begin moving toward the preventer body. Hydraulic control pressure draws the bonnets tightly against the preventer body bonnet bolts hold the bonnets closed. Ram opening pressure also closes the bonnets. An eyebolt on each end of the preventer body can be screwed into the top of each ram for lifting. When the bonnet bolts are unscrewed and closing pressure is applied, pressure pushes the ram inward and at the same time moves the bonnet away from the preventer body. The Ram closing pressure also opens the bonnets for ram change. As hydraulic fluid is displaced into the closing chamber of the BOP the piston moves inward pushing the ram into the well bore. Hydraulic fluid is directed through open and close lines which connect to the body of the BOP. The 'U' BOP is operated using a typical accumulator system with 1500 psi. Theses require a separate function to be deployed in order to lock the rams. Wedgelock system available for subsea operations.
#Force of ram pressure manual
A large manual locking screw facilitates locking and closing of the BOP if required.These effectively increase the closing area by 35%. Large bore shear bonnets are available for U type BOPs.The Ram bonnets are opened and closed using hydraulic pressure.Wellbore pressure acts on the ram to increase the sealing force and to maintain the seal in the event of hydraulic pressure loss. The Cameron 'U' BOP is a ram type preventer designed for both land and subsea operations. Subsea rams must close within 45 seconds.API RP53 requirements state that surface rams must close within 30 seconds.This section looks at three common types in use: Shaffer 'SL', Cameron 'U' and Hydril 'V'. Ram type BOPs are the most common type of blow out preventers.
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