• Generates a constant flow of compressed air to purge a downpipe
  • All-pneumatic design does not include integral transmitter
  • Provides 1:1 pressure signal to a compatible indicator or external transducer through 1/4 in. airline tubing
  • Holds a fixed pressure differential across a precision orifice to ensure constant flow rate of 1 cfh (cubic foot per hour), making it possible to maintain a linear 1:1 response of the sensing system
  • Back pressure sensed is equivalent to the hydrostatic head pressure due to actual liquid depth
Unit of Measure

Specifications

Series

 N/A 780

Type

 N/A Purge Control Level Transmitter

Temperature [Min]

 N/A -16 ºC0 ºF

Temperature [Max]

 N/A 54 ºC120 ºF

Material

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

Fittings

 N/A Swagelok; (1) 3/8 in. Tube, (2) 1/4 in. Tube (Compatible with Copper or Poly Tubing)

Pressure Output

 N/A 25 to 650 in. SafeGard Range

Depth Measurement [Max]

 N/A 1,937 inH2O49.0 mH2O

Purge Control

 N/A 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)

Electronic 4 to 20 Milliampere (mA) Output

 N/A D/P Purge Control or D/P LiquiSeal™ transmitter provides a 4-20 mA output over a two wire cable to an indicator or the analog I/O of a PLC. Using twisted pair shielded cabling permits transmission distances of several thousand feet to a remote receiver.

Direct Current (DC) Power Supply Voltage (Unregulated)

 N/A 14 to 40 V

Repeatability

 N/A ± 0.20% of Calibrated Span

Flow Rate (Air Purge)

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

Pressure Ranges

Burst Pressure

 N/A 200 psi

Compressed Air Requirement

 N/A 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.)

Operating Limit (Maximum Pressure)

 N/A 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.

Options and Accessories

LiquiSeal™ Purge Control Service Parts

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

Downpipe Check Valve

 N/A 6363: Downpipe float check valve, 3/4" NPT connections

6563-10: Downpipe float check valve, 3/4" NPT outlet, 3/8" tube inlet
  • Prevents siphoning or backflow of liquid through a downpipe installed in tank level gauging applications
  • Utilizes a specially designed float pin that rises up to seal the valve shut when liquid enters from the downpipe through the bottom of the unit
  • The advantage of a float check is that it doesn't create a pressure drop that would affect the level gauge reading (Spring-loaded check valves can impact the accuracy of a downpipe or bubbler system if installed at the tank entry point)
NOTE: Not recommended for use with heavy diesel fuel oil or other high viscosity liquids. Installation in conjunction with a gate valve will permit removal of check valve for inspection and cleaning. (We recommend cleaning the check valve once per year to ensure reliability.)

Material: 304 Stainless Steel, Nylon (float), FKM (seals)
Maximum Pressure: 150 psig
Inlet/Outlet: 3/4" NPT-female
Weight: 1.2 lb (0.5 kg)

SafeGard Option

 N/A 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.

Tank Top Fittings

 N/A 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

Application

Application

 N/A
  • Tank level indication
  • Marine
    • Tank level, draft monitoring and vessel management
    • Ballast water
    • Fuel oil
    • Fresh water
    • Lube oil
    • Brine
    • Preload
    • Holding

Tank Gauging Applications

 N/A A complete tank level gauging system can be configured using either pneumatic Purge Controls or D/P Purge Controls. The output signal can be routed to either a analog column display or digital readout.

Indication is then provided directly as the total weight or volume of liquid in the tank.

Features

Downpipe Level Sensor

 N/A 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™ Purge Control

 N/A 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.

Pneumatic Output Signal

 N/A 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.

Downpipe Liquid Level Sensor

 N/A 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.

Pneumatic Output to Indicator

 N/A Purge Control continuously purges tank downpipe and creates pressure corresponding to hydrostatic head of liquid. This pressure signal is conveyed through 1/4 in. airline tubing to a compatible electronic or pneumatic column indicator.

Electronic Output to Indicator

 N/A D/P Purge Control senses hydrostatic pressure due to liquid depth and transmits a proportional 4-20 mA output. KING-GAGE® indicator correlates level to tank geometry to display actual volume amount (or weight) of liquid in tank.

Hazardous Zone Service

 N/A 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.

Additional Information

Additional Information

 N/A
  • 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.

Warnings

Product Warranty

 N/A 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.

Prop 65 Warnings

 N/A
WARNING: This product can expose you to chemicals including Lead and Nickel, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov