Automatic tank dewatering system designed to save you millions

By installing Agar ID-200 Interface Detectors, a US refinery was able to reduce its total HC being dumped to the WWTS by 82% with better interface/separation control (see attached Hydrocarbon Processing article). An 82% reduction in the amount of SLOP OIL being generated is equal to £1,990,424/year in savings/additional profit. Not just for the first single year, but continuing year after year.


Reduction in Slop Oil Waste

*Example from a US Refinery


Prevention is better than a cure.

The Agar System 3 represents the first and only interface control system to utilize this understanding of the oil/water interface as the basis for control. The system consists of a minimum of two or a maximum of four Agar energy absorption instruments: three designated for service in the vessel and one installed upstream of the unit in the crude feed line. In the System 3 control scheme, these probes provide continuous 4 to 20 mA output signals that are proportional to the % water concentrations at their individual locations inside the desalter.

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Click on the tabs below for more information.

Controls the brine outlet valve – using its ability to measure small amounts of oil in water to maintain a very high (and unstable) percentage of water several feet above the bottom of the vessel. This allows suspended oil in the water phase to separate, thus inhibiting oil undercarry as a primary control function. While Probe #1 establishes this lower limit for the emulsion layer anything that floats on the water phase stops here.
Monitors the % water content from its position in the oil phase just below the lower grid. This provides real-time detection of the rate and extent of emulsion growth (which must, by Probe #1’s control, occur in the upward direction). Probe #2’s monitoring function allows the operator to avoid downstream upsets by providing advanced warning of such growth, and allows time for the implementation of corrective measures to prevent grid loss (transformer “trip”).
Is an in-line monitor of the water content of the crude feed and is typically located as far as possible upstream of the desalter (generally at or near the tank farm). This probe provides advanced warning of wet/contaminated crude feed, which is necessary to avoid the upsets typically resulting from tank switching and/or the introduction of slop oil.

The fourth probe monitors the condition of the water phase below the control probe, alarming on the presence of suspended oil that does not readily separate and threatens the condition of the brine effluent. This is of particular value when low-quality sources of wash water (e.g. stripped or straight sour water) are utilized that can upset the separation process and form stable oil-in-water mixtures (reverse emulsions). This probe is also used during mud-wash cycles.

Technical Information

Operating Range
Emulsion Concentration 0-100% Hydrocarbon/ Water by Volume
Process Temperature Standard: 32°F to 300°F (0°C to 149°C)
High-Temp: 32°F to 450°F (0°C to 232°C)
Ambient Temperature -40°F to 131°F
Pressure Rating Up to 3000 PSI
Electrical Rating
ID-201, ID-202, ID-205 Probe Intrinsically Safe: Class 1, Div.1, Groups C & D, T3C
ATEX: II 1G EEx ia IIB T4 (-40ºC<Ta<+70ºC)
II 1G EEx ia IIC T5 (-40ºC<Ta<+65ºC)
Power Required 115/240 VAC 50-60 Hz or 12/24 VDC (±20%)
Normal Power Consumption 3 Watts
Maximum Power Consumption of 250 Watts (including lights)
PS-201 Enclosures Weatherproof (N4X) NEMA 4X
Explosion Proof (N4/7) NEMA 4/7 Class 1, Div. 1, Groups C&D
Wiring Connections Flame-Proof (N4/7) NEMA 4/7 ATEX: II 2G Ex d[ia] IIB T6 (-20ºC<Ta<+55ºC)
Barrier Terminal Block #18 AWG Maximum Diameter
Materials Of Construction
Standard Optional
Probe 316 Stainless Steel, Teflon & Peek Duplex, Hastalloy, Monel (Others available upon request)
Seals Aflas and Teflon Viton
Optional Process Connection
SH-2″/SS 2″ NPT Seal Housing, 316 Stainless Steel
SH-2″/SS 2″ NPT Seal Housing, Carbon Steel
CF-¼”/SS ¼” NPT Compression Fitting, 316 Stainless Steel
CF-¼”/CS ¼” NPT Compression Fitting, Carbon Steel
Flange Connections        ANSI 150# to 1500#
Model Variations
ID- 201         ½” shaft; Standard: 48″ (4 Ft.); Minimum: 12″ (1 Ft.); Maximum: 120″ (10 Ft.)
ID-202 For probe lengths greater than 10 feet, sturdier 1 ¼” shaft assemblies from 5 foot sections via threaded connections.
ID-205 Shaft replaced by cable for suspension of antenna down through the top of the tanks, wells, platform legs, caverns, etc.
Standard Output Option
ID-201/420 Powered 4-20 mA into 400 Ohms Maximum; 4 mA = Oil, or Lowest Water Content
ID-201/RL Relay Contact 1A; 115V; NO and NC; (SPDT); Fail Safe On Water or Oil
Adjustable Trip Point
ID-201/RL/420 Relay and 4-20mA Options
ID-201/RL/LI Relay with Local Indicating Lights; Amber = Oil, Blue = Water


CSA-US Canadian Standards Association /UL Specifications ATEX European Committee for Electrical Standardization GOST-R Russian Approval, ROSTECHNADZOR Safety JRIIS Japanese Research Institute of Industrial Safety