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ITT Barton Model 288
Description
These 6" Differential pressure Indicating Switches are employed to energize alarm and control circuits at predetermined limits of flow through pipelines, liquid levels within pressurized vessels or pressure losses across devices such as filters. For monitoring flow rates, they are used in conjunction with a primary DP element such as an orifice or venturi.
Weatherproof, ITT Barton® Models 288, & 288A, are DP Indicating Switches. The 288A and 288C have NEMA-4 watertight die-cast aluminum cases (finished with a weather-resistant black epoxy resin paint). The durable lexan lens is secured in the bezel with an elastomer ring to reduce the possibility of accidental breakage. This ring also acts as a seal between the bezel and the case to ensure a moisture, fume and dust-free atmosphere for the jewelled indicator movement and switch mechanism.
Theory of Operation
The Die-cast Aluminum indicating switch housing is attached directly to the actuating unit (224 DPU). The indicating switch assembly consists of a drive arm with integral switch actuator cam, linkage, and a jewelled movement assembly to which the indicating pointer is attached. Also included are the Micro switches and associated linkages, switch setpoint indexes and setpoint locks. Changes in differential pressure is sensed by the differential pressure units bellows and transmitted as rotary motion through the torque tube, to the drive arm assembly of the indicating switch. The linkage and movement assembly respond to the action of the drive arm assembly to position the pointer on the scale to the indication relative to the differential pressure sensed by the DPU and simultaneously actuate the switch when the desired setpoint is reached. It does this because the drive arm has an integral switch actuating cam and is attached to the torque tube shaft which rotates between 8-10 degrees with the motion of the torque tube shaft. Two cam follower roller/actuator arm assemblies, one for each switch, respond to drive arm movement by opening and closing the switches as they ride on and off the cam. The levels of differential pressure at which the switches actuate are adjustable with high and low alarm switch adjustment indexes below the scale plate.
Minor adjustments to the switch setpoint can be made without removing the scale plate. Barton Models 288A/288C can have upto 4 alarm switches, but one or two alarm switches are standard. Each switch can be connected to operate normally-opened or normally-closed. The switches setpoints are adjustable between 5-95% of the scale range. SPDT and DPDT switch configurations are available.
Specifications
Housings and Safe Working Pressures
Forged Brass (FG Brass)......................SWP 500 PSI (34.5 bar)
Brass ....................................................SWP 1000 PSI (68.9 bar)
Carbon Steel ........................................SWP 1500, 3000, & 6000 PSI (103.4, 206.9 & 413.8 bar)
316 Stainless Steel...............................SWP 500,1500, 3000, & 6000 PSI (34.5, 103.4, 206.9 & 413.8 bar)
Cast Aluminum ....................................SWP 400 PSI (27.6 bar)
Alloy Steel ............................................SWP 10,000 PSI (689.5 bar)
Bellows Material
316 Stainless Steel
Beryllium Copper
Inconel 625
DP Ranges
0-30" W.C to 0-1000 PSI (ranges limited by the SWP and housing materials chosen.)
Actuating Unit.......................................Model 224 DPU
Dial Size.................................................6 Inches (150mm) Diameter
Temperature Limits.............................-40°F/C to + 180°F (+82°C) (+40°F minimum for water filled units- "D" Fill)
Adjustments........................................ Zero and Span (Micrometer-type)
Mounting..............................................Flush/Panel, Wall, and 2"Pipe/Yoke,
Indicator Case.....................................Aluminum Alloy, Powder Coated, Enamel or Epoxy Finish
Lens......................................................Polycarbonate
O-Rings (Wetted).................................Buna-N, Viton, or EPT (Special available upon request)
Overall Dimensions.............................per configuration and DPU housing rating
Weight ..................................................6 to 9.5 lbs (approx.) Weight depends on DPU configuration/materials.
Accuracy (DP Range)
Switches Disengaged.........................................±1% of full scale
At Switch Actuation........................................... ±1.5% of full scale
Switch Deadband ............................................. 5% of full scale
Repeatability.......................................................0.25% of full scale
Components
Bellows Construction - Individual diaphragms, stamped and formed from 316 stainless steel, Inconel 625 or beryllium copper, are assembled using highly specialized techniques, the results — exacting linearity characteristics, a long cycle life, and freedom from effects of work hardening commonly encountered with the hydraulically formed or mechanically rolled type bellows.
Torque Tube - eliminates possibility of leakage and need for lubrication. The needle bearing (inboard end) and ball bearing (on follower drive arm) operate with a minimum of friction — resulting in a high degree of sensitivity over the life of unit.
Temperature Compensator - An auxiliary free-floating bellows, attached to HP bellows, automatically protects unit from zero/calibration drift when ambient temperature changes.
Self-Draining/Venting Connection on the top and bottom of the pressure housing provides automatic draining of liquids or venting of gases.
Calibration Springs - The strength of the range-springs determines the differential pressure range of the unit. Each range-spring assembly is stamped with DP range it produces. They have an extremely low hysteresis characteristic and exceptional temperature stability.