Model IPT


Capacitance Interface Transmitter, Refinery Desalter

The Delta Controls Model IPT transmits a 4-20mA signal proportional to the interface position in a water/oil separation vessel. Process conditions can range up to 2500 psig (27 MPa) and up to 500 °F (250°C)

The transmitter sensing probe can be removed from the vessel without disturbing or de-pressurizing the process. The probe is withdrawn up into a chamber located above a block valve. The valve is then closed and only the withdrawal chamber is depressurized. The sensing probe can then be cleaned in place or completely removed.

Applications include refinery desalters, crude oil production separators, reclaimed oil plants, and paper mill soap collection tanks.

Measuring Desalter Interface

Measurement of the water/oil interface position in refinery desalters has commonly been attempted with analog type capacitance level transmitters. Unfortunately, the measuring probe of this type device becomes coated with carbon, water emulsions, and other material. This coating and buildup creates interface position errors and eventually renders the output signal meaningless. This is true even when a “buildup proof” unit (as is claimed by some manufacturers) is used. Cleaning the probe and recalibrating normally restores the signal accuracy. Unfortunately, this mandatory frequent probe cleaning has not been practical because a pressurized desalter has to be shut down before this type of continuous transmitter can be removed. A modern refinery will not tolerate the frequent shutdowns and recalibration expense required by this type transmitter.


Model IPT Product Diagram - Delta Controls Corporation

The new Delta Model IPT especially designed probe type interface transmitter does not require shutdown of the desalter. The sensing probe can be extracted, cleaned, and reinserted without disturbing operation of the desalter unit. Only infrequent cleaning of the probe is required. The IPT design allows this infrequent cleaning to be safely and easily done. The Model IPT assembly is mounted on top of a desalter isolation valve which permits its removal without depressurizing the desalter. The sensing probe, normally inserted down in the process fluid, is withdrawn into a chamber above the valve whenever access to the probe is desired. The block valve is then closed beneath it, permitting depressurization of only the withdrawal chamber. The sensing probe can then be cleaned or even complete removed. The desalter interface position is monitored by operating the manual try cocks during the cleaning procedure.

How the Model IPT Senses Interface Position in a Desalter Water/Oil

The percentage ratio of oil/water around the probe determines how energy is radiated away. The energy transfer is at a minimum when it is covered with crude oil and at a maximum when it is covered with water. The Model IPT transmitter is calibrated by locating two interface elevation points in the desalter and pushing a button. The IPT then automatically calculates a curve through those points. The result is a 4-20 mA output signal which is proportional to the elevation of the interface position. This elevation is displayed on the integral LCD screen. The amount of energy flowing is always very small, microamp at millivolt amounts.


  • Run Your Desalter on Automatic Control
  • Continuous Interface Position Signal from 1 up to a 5 Foot (1500mm) Elevation Range
  • Improves Refinery Efficiency
  • Lower Cost of Operation and Maintenance
  • One Piece Design for Low Cost Installation
  • Sensor Can be Removed for Cleaning Without Shutting Down Desalter
  • Pushbutton Calibration at Any Time
  • 2 Wire 4-20 mA Signal; Optional HART® Protocol
  • 24VDC Loop Supply


  • Output 4-20 mADC loop signal, isolated. Optional HART® Protocol
  • Loop Impedance, maximum: 550 Ohm @ 24 VDC; 1000 Ohm @ 35 VDC
  • Range: 11,000 sensitivity units (refer to Delta probe Engineering notes #00-00039 and #9900040 for details)
  • Linearization Curves Cubic Polynomial
  • Display: LCD Screen, 2 line, 8 character, Alphanumeric
  • Calibration Entry: Four pushbutton entry switches
  • Memory Protection Non-volatile
  • Voltage Requirements: 13-35 VDC Loop Power
  • Ambient Temperature Range:
    • From 30 to 125ºF (0 to 50ºC), for good readability of display
    • From -20ºF to +175ºF (-30 to 80ºC), for transmitter function
  • Housing Aluminum, Class 1, Division 1, Groups BCD; 4x, CSA (Canada); NRTL/C (U.S.)
  • Process connections: 4” (100mm) recommended; 2” (50mm) minimum; ANSI or equivalent DIN, JIS Flanges
  • Wetted materials: Carbon steel, 316 stainless steel, and PTFE are basic; others available
  • Insertion and other Dimensions: As required by desalter design
  • Required Application Data: Please complete Data Sheet 00-IPT05
  • Maintenance: Frequency of cleaning required is determined by the crude oil being run. The time period will normally be in terms of months.
    • Retract sensor up into chamber; close block valve;
    • Clean buildup off with steam or solvents;
    • Open block valve and reinsert sensor into desalter.

HART® is a registered trademark of FieldComm Group

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