Hydraulic Accumulator Charge Sensing

CPI Linear draw wire position sensor

In sub-sea applications used for mining oil and gas at the ocean floor, large and powerful hydraulic accumulators often get the job of providing emergency power on blow out preventers positioned on the sea floor.

If you’re a hydraulic accumulator manufacturer then you know that it’s all about pre-charge pressure. Accumulators are pressure vessels used to store hydraulic energy by compressing a blanked of nitrogen over an oil filled area. The accumulators are typically cylindrical type, with a stainless steel float that partially separates the oil from the nitrogen. They cylinders are piston type as membrane or gasket versions are too prone to leakage at high charges. The accumulator is designed to deliver hydraulic energy under controlled pressure to the connection pipes and hoses of the sledge assembly under emergency operating conditions.

CPI Linear Position Sensors are ideally suited to this application in a way that perhaps no other sensor in the world can lay claim to. Key elements of our sensor design make our operation as a charge sensing element much more robust and completely insensitive to high pressure our sub-sea deployment.

  1. CPI sensors use a sophisticated implementation of reliable draw wire technology to detect absolute piston position.
  2. The measurement translation uses an LVDT and is completely non-contacting.
  3. There are no sealed volumes in the unit. As such it is completely immune to pressure and has been tested in sea-water at 5000 ft depths.
  4. The sensor can be deployed internal or external to the cylinder and on the oil or gas side of the piston.
  5. Our custom design accommodates stroke lengths of over 7m.

The Undersea Economics of Hydraulic Accumulator charge sensing.

Because of the criticality of hydraulic accumulators used to power blow out preventers, operators need to be sure pressure is maintained in the cylinder. To insure this, periodic maintenance is typically conducted every 6 months or more to check and potentially replace cylinders that have failed or leaked in any way.

Imagine the potential cost savings if a reliable way of detecting and monitoring pre-charge pressure on the sea floor were available! Operators could save 10’s of thousands of dollars in expensive maintenance and replacement operations, deffering them until they were really needed.

Until now this has been difficult to achieve because the sensors available were even less reliable than the cylinders once deployed in such a harsh environment. But with linear position charge sensors like the CPI 1500, the sensor is no longer the first point of failure.

For more information, please contact CPI today.