LVDT Based Position Sensors Offer Greater Longevity In Harsh Environments

Offshore Drilling uses Long-Stroke Hydraulic Cylinders

Accurate sensing of linear position in hydraulic cylinders takes on more complex design considerations when targeting applications where a rugged outdoor environment is the operational norm.

Environmental considerations include:

  1. Heat – Not just ambient temperatures but the temperature of hydraulic fluid rises with continued operation and can increase the effective operating temperature range.
  2. Vibration – Applications for hydraulic cylinders in heavy duty construction equipment, drilling and, Mining equipment, etc., present severe challenges for certain types of sensors, most notably rod-based magnetostrictive sensor designs.
  3. Water & Humidity – Concerns include their effect on sensitive electronics needed to support the core position sensing technology.
  4. Electromagnetic Interference – Placement of the sensor technology near strong electromagnetic sources, can unintentionally affect the performance of certain sensor technologies.
  5. Field Replacement – When a sensor fails in the field, operations may need to be halted to perform a replacement. The time required to make the replacement depends on whether the part is readily available at the job site, and how much disassembly may be required to perform the repair. Minutes are dollars in these environments and a zero tolerance policy for failure modes in the design of such equipment is appropriate.

LVDT Position sensors solve one part of this problem by simplifying the support electronics  required for highly accurate position sensing, and allowing the encapsulation of the electronics in such a way as to provide excellent immunity to most environmental conditions.  CPI’s SL series sensors present a unique LVDT based implementation combined with a type of draw-wire sensor technology that has some highly attractive characteristics in the high reliability, high electromechanical endurance sector.

  1. Heat  -Because the LVDT solution contains fewer sensitive electronic parts operating temperature range is extended to 300F where magnetostrictive are limited to about 185F
  2. Vibration – With no rod or sensitive electronics, and a sealed LVDT, vibrational sensitivity is maximally reduced.
  3. Moisture – Our implementation can be completely sealed and is designed to mount on either the oil or the gas side of the cylinder.
  4. EMI – The nature of the LVDT sensor technology makes it more immune to EMI and the draw-wire sensor technology is mechanical and completely immune to any EMI environment.
  5. Field Replacement – Instead of needing to stock rod-type magnetostrictive sensors in many sizes, a single SL series sensor can accommodate many different stroke lengths and can even fit perfectly into the existing center bore of a previous magnetostrictive sensor implementation.

In summary, many hydraulic cylinder applications could benefit from a more robust, drop-in replacement for existing position sensors. Especially those where operators can least afford downtime of equipment.

To get For more information, contact CPI for a discussion of your sensor needs.