Bi-Directional Pressure Transducers for Vapor Recovery

August 9, 2018

Figure 1: CS10 with -70 to +70mBar pressure range

Core Sensors offers a variety of high quality bi-directional pressure transducers for use in low pressure vapor recovery operations. Unlike a unidirectional pressure transducer that can measure pressures from zero to a defined positive pressure (i.e. 0 to 70mBar), bi-directional pressure transducers measure both positive and negative pressure (i.e. -70mBar to +70mBar).

Bi-directional pressure transducers are commonly found in Vapor Recovery Units (VRU’s) which monitor and recover light hydrocarbon vapors that collect at the top of oil and gas storage tanks. The positive end of the pressure transducers measurement range is used to monitor the increase in vapor pressure at the top of the storage tank and the negative end of the measurement range is used to monitor the suction when recovering the vapors from the tank. Recovering these vapors reduces the potential impact on the environment since they are not being vented or flared and also presents financial savings for a company by converting the collected vapors into a liquid state which can then be added back into the storage tanks.

Other applications to consider bi-directional pressure transducers include:

  • Landfill Gas Recovery
  • Digester Gas Recovery
  • Casinghead Pressure Reduction

Core Sensors utilizes 316L SS wetted material in the manufacturing process to allow for a wide media compatibility. Custom configurations are available including a Hastelloy C276 diaphragm material for added corrosion resistance.

Since bi-directional pressure transducers are very low pressure, it is important that the proper venting techniques are followed. Not properly venting the transducer can result in incorrect/inconsistent pressure readings and a reduction in expected lifespan of the equipment. Core Sensors uses two different venting methods depending on your electrical termination choice:

  • Transducers with cable connections have a vent tube that runs the length of the cable and exits the cable jacket with the rest of the conductors. Terminate the vent tube in a clean and dry area, preferably a weatherproof enclosure, to prevent moisture ingress.
  • Transducers with connectors have a vent hole on or near the connector instead of a vent tube. The exact location of the vent hole depends on the electrical connector being used. A PTFE patch is used internally over the vent hole to prevent moisture ingress. It is important to install the sensor in an area where minimal moisture will make contact with the sensors electrical connector.

Common pressure ranges include:

  • Calibrated Measurement Range
  • -70mBar to +70mBar
  • -150mBar to +150mBar
  • -350mBar to +350mBar
  • -1050mBar to +1050mBar
  • Equivalent PSI Range
  • ~ -1.015 to +1.015 PSI
  • ~ -2.175 to +2.175 PSI
  • ~ -5.076 to +5.076 PSI
  • ~ -15.228 to +15.228 PSI

Recommended Products

For applications where hazardous area approvals are not required, we recommend the CS10 Industrial Pressure Transducer. Figure 1 above shows a CS10 transducer with a +/-70mBar bi-directional pressure range, 4-20mA output signal, 1/4″ MNPT mechanical interface and a 1/2″ MNPT conduit fitting with integral cable. Visit the CS10 product page here for more information.

Core Sensors is preparing to release new hazardous area approved transducers manufactured in the USA. Hazardous area approvals will include CSA Class I, Division 1 Intrinsically Safe and Class 1, Division 2 Non-Incendive. Stay tuned to this post and core-sensors.com for release date information.

For more information, call us today at (862) 245-2673 to discuss your application with a knowledgeable Core sales representative.