780-198-88

780

Purge Control Level Transmitter

Machined brass body with acrylic semi-gloss enamel finish; integral filter element is aluminum with acrylic semi-gloss enamel finish

None, 1/4 in. National Pipe Thread (NPT)

Without SafeGard Option

1,937 inH₂O

Unit incorporates differential air flow regulator with flow control orifice
Fixed differential set to nominal 10 psid
Output is 1:1 pneumatic pressure (hydrostatic force equivalent)

14 to 40 V

± 0.20% of Calibrated Span

Nominal 1 cfh (Cubic Feet Per Hour) at Specified Differential
Maximum Air Consumption Under 5 cfh (Cubic Feet Per Hour).

200 psi

35 psig to 150 psig supply pressure at control inlet. (Minimum supply pressure should be at least 20 psig greater than anticipated maximum liquid head pressure.)

Pressure above 300% nominal range (overrange) will result in damage to the transmitter (200% may cause a shift in calibration). Burst pressure is 200 psi and will cause catastrophic and physical failure of the pressure element.

7334-2: Safegard Service Kit
7334-19: Air Control Service Kit
7333-10: Replacement Filter Element Kit

An adjustable pressure-limiting control that permits pre-setting a maximum value for pressure output from the Purge Control. SafeGard range available as 25 inH₂O to 650 inH₂O or 650 inH₂O to 1750 inH₂O

A precision pneumatic control valve which will instantly close bubble-tight when subjected to a pre-set pressure. It is used to prevent over pressuring an indicator.

1-1/2" NPT Tank Top Fitting (for 3/4" Pipe) single purge line connection with tube fitting
7746-13: Carbon Steel, polyflo 3/8" tube
7746-15: Carbon Steel, Swagelok 3/8" tube
7746-18: 316 Stainless Steel, Swagelok 3/8" tube

1-1/2" NPT Tank Top Fitting (for 3/4" Pipe) with single 1/4" NPT purge port connection
2000FA: Carbon Steel
2000PA: PVC
2000SG: 316 Stainless Steel

1-1/2" NPT Tank Top Fitting (for 3/4" Pipe) with two 1/4" NPT purge/equalizer connection
2000FA-2: Carbon Steel
2000PA-2: PVC
2000SG-2: 316 Stainless Steel

When purged with compressed air liquid within the downpipe is displaced by air pressure equal to the hydrostatic force of liquid in the tank. If carefully regulated at a low rate of flow, air pressure will constantly maintain equilibrium against the force of the liquid. Air escapes out through the bottom of the pipe unless needed to increase pressure as liquid force (depth) increases.

The primary sensor element is typically 3/4 in. diameter pipe purchased from a local source. Always select piping material for compatibility with the tank contents. Downpipe purge systems can be used to measure virtually any type of liquid product including resins, asphalt or corrosive materials. Output is proportional to liquid depth and can be transmitted as an electronic 4-20 mA signal or pneumatically as a direct 1:1 pressure signal.

LiquiSeal™ D/P purge control is a fully integrated air purge regulator and level transmitter. Operation is based on the control regulating a continuous 1 cfh (cubic foot per hour) flow of compressed air into the tank downpipe.

An internal differential pressure sensor element converts resulting pressure into a 4-20 mAdc two wire signal.

An all-pneumatic version of the LiquiSeal™ purge control is available. It provides a 1:1 pressure signal to a compatible indicator or external transducer through 1/4 in. airline tubing.

All LiquiSeal™ purge controls feature an internal isolation diaphragm. Backpressure created by the continuous purging of the downpipe is applied to this internal diaphragm. Working as a pneumatic transmitter, an equivalent pressure is generated on the gauge side of the diaphragm. This process effectively isolates downstream components from contact with the liquid or vapor releases.

Purge Control or LiquiSeal™ Control provides air pressure signal to an external transmitter or compatible indicator (with integral transducer). Typically, 1/4" poly or soft copper tubing is used to convey the pressure signal up to 1000 feet from the tank.

Control regulates compressed air flow to pipe extending down toward tank bottom. Depth of liquid causes air pressure to increase or decrease proportionally. A differential pressure (D/P) transmitter provides a 4-20 mA signal that can be used for remote indication or process control functions.

The downpipe sensor and pneumatic components are fully compatible with explosion hazard environments. This makes pneumatic the sensible alternative for hazardous areas without the cost and complications of intrinsic safety barriers or explosion-proof products. Assumes only pneumatic components are situated in explosion hazard zone.

• Continuous level measurement
• Reliable, proven sensing technique
• Simple to install and maintain

A downpipe is the simplest type of liquid level sensor, often referred to as a "bubbler." This is merely a length of open ended pipe that extends downward into the tank. LiquiSeal™ or Purge Control differential pressure air flow regulators are highly refined versions of the basic bubbler air control.

788 D/P Purge Control is a more basic differential pressure regulator and air flow control. It generates a constant flow of compressed air to purge a downpipe. Its integral differential pressure transmitter provides 4-20 mAdc output proportional to liquid level. 780 Purge Control is an all-pneumatic version that does not include the integral transmitter. It provides a 1:1 pressure signal to a compatible indicator or external transducer through 1/4 in. airline tubing. The purge control holds a fixed pressure differential across a precision orifice to ensure constant flow rate of 1 cfh (cubic foot per hour). This regulated low flow rate makes it possible to maintain a linear 1:1 response of the sensing system. In this way, backpressure sensed is equivalent to the hydrostatic head pressure due to actual liquid depth.

All KING-GAGE®, a NOSHOK Company products are guaranteed to be free from defects in material and workmanship for one (1) year from the date of purchase.

Repair Services Warranty: 90 days limited warranty.