Model P91

SKU: P91

Capacitance Probe, Floating Probe for Oil Skimmer

The Delta Controls Model P91 Capacitance Probe is designed for interface measurement. The probe floats on the top surface of oil in a skimmer basin or separation vessel. A vertical sensing rod, with parallel ground reference rods, is supported by outrigger floats. The sensing rod goes through the floating oil and into the water.

The P91 measures the distance from the top of the oil to the interface between the water and the floating oil. This measurement is then converted into a 4-20 mA direct current signal equivalent to the thickness of oil present. Optionally, an on/off differential control signal can be produced to control a drainage pump or skimmer trough.

The interconnection allows pull up for testing and maintenance as well as acting as a tether in large pond applications. The P91 is typically used in petroleum refineries, machinery manufacturing plants, oil field salt water disposal companies, and similar industrial operating companies.


  • Measures from 2 in to 36 in (50 mm to 900 mm) of oil floating on water
  • Supports oil or water total elevation change up to 50 ft (15 mm)
  • Works on large tank tramp oil collectors
  • Works well with fresh or salt water
  • Entire transmitter may be submerged to 50 feet (15 meter)
  • For highly corrosive and offshore applications, 316 Stainless Steel electronic housings are optional
  • Optional Hastelloy® C-276
  • Unaffected by foam, bubbles, and froth
  • Functions well with lip type rotatable skimmers


  • Electronic Module: Remote from sensor
  • Range: ≤ 6 in to ≤ 36 in (150 mm to 900 mm)
  • Specific Gravity (Oil): 0.70 min
  • Attachment Cable: 0.0620 in 316 Stainless Steel
  • Interconnection:Oil resistant
  • Rubber Tubular Jacket over Signal Cable: ≤ 60 ft (20 m)
  • Available Wetted Materials: 316 Stainless Steel, PTFE
  • Floats and Frame Support: 316 Stainless Steel
  • Sensing Rod Jacket and Seals: PTFE extruded and welded PTFE

Required Ordering Information

  • Detailed model number
  • Tag or nameplate detail (if required)
  • Documentation/testing tiers (if required, refer to Additional Resources in the product catalog)
  • Process fluid or material name
  • Process fluid or material dieletric constant
  • Maximum process temperature
  • Maximum process pressure
  • Upper and lower materials required for interface service

Additional Information


Capacitance Probe, Floating Probe for Oil Skimmer

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