In the previous topic, we discuss about the annular preventer and today we would like to give you more details regarding ram preventers. The ram preventers were invented by James Smither Abercrombie and Harry S. Cameron in 1922.
This preventer consists of two rams which extend into the center of the wellbore in order to shut the well in (see the image below). The ram preventers can be hydraulically or manually operated. When people would like to shut the well in using the ram preventer, they will go to the hydraulic option first. If the hydraulic is not properly operated, the manual system will be utilized.
In order to provide the wellbore sealing, the rams must compose of top seals and packers which are made of the special elastomer. For more understanding, please take a look at the diagram of Cameron BOP below.
(Courtesy of Cameron)
When the well is shut in, the packer will seal around drillstring or tubular and the top seal will be pushed against the BOP body. With both top seals and packer, the well is securely shut in when
In the drilling industry, there are four types of rams preventers which are Pipe Rams, Variable Bore Rams (VBR), blind rams and blind-shear rams.
Pipe Rams – it closes around the drill string or tubular in order to restrict the flow. The size of the rams must match with drill string size in order to properly shut the well in. The rams are designed to hold pressure from the bottom only. Personnel should not close the ram in tool joint or open hole (closing without pipe in the well)
(Pipe Rams – Courtesy of Cameron)
Variable Bore Rams (VBR) – It is similar to the pipe rams but it can use with a wider range of outside diameter of pipe. You can see that the packer can be varied depending the force push against the rams. Please see the image below for more understanding.
(Variable Bore Rams (VBR) – Courtesy of Cameron)
Blind Rams – This rams are used to close the wellbore when there is no drilling string in the wellbore and the blind rams cannot shear the pipe. Most operators and drilling contractors don’t consider using this rams but they prefer blind-shear rams because the blind-shear rams can cut the pipe.
Blind Shear Rams – The blind shear rams have two applications – 1 seal the wellbore without pipe in the wellbore, 2 cut the pipe prior to shutting the well in.
(Blind Shear Rams – Courtesy of Cameron)
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Reference book: Well Control Books