BOP Closing & Opening Ratio
The hydraulic operating pressure a BOP actually needs to close or open, given wellhead pressure and the tool's own rated mechanical ratio.
The Formulas Used
Where This Fits
This is the mechanical link between a wellhead pressure reading and what the closing unit actually has to supply to hold it — directly relevant on the BOP equipment page and any time the accumulator function test is checked against real closing pressures rather than a generic target. As wellhead pressure climbs during a well control event, this is the quick check for whether the rig's accumulator system has enough working pressure margin above what a given ratio actually demands at the current shut-in pressure.
Frequently Asked Questions
What is a BOP closing/opening ratio?
It's the mechanical advantage built into an annular preventer or ram design — the multiple by which hydraulic operating pressure gets converted into the actual sealing or opening force against wellbore pressure. A 7:1 closing ratio means the operating system needs to supply pressure at only 1/7th of the wellhead pressure it has to hold closed against.
Why is the opening ratio usually a smaller number than the closing ratio?
Closing has to generate enough force to seal against full wellbore pressure, which needs a large mechanical advantage. Opening only has to overcome the preventer's own sealing element resistance and whatever residual pressure remains, a much smaller force — so opening systems don't need as much mechanical advantage and are built with a lower ratio.