738-4918-138

738

LiquiSeal™ Purge Control Level Transmitter

0 to 277 inH₂O thru 0 to 830 inH₂O /0 to 7.0 mH₂O thru 0 to 21.0 mH₂O

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

200 psig

Swagelok; (1) 3/8 in. tube, (1) 1/4 in. tube x 1/4 in. National Pipe Thread (NPT) (Compatible with Copper or Poly Tubing)

± 0.22% Full Scale

1,937 inH₂O

4 to 20

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).

0 to 30 psid

300% Over-Range

0 to 30 psid

The above model but adds an integral differential pressure (D/P) transmitter converting pneumatic pressure into 4-20 mAdc electronic output.

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.

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

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). Includes an integral differential pressure (D/P) transmitter converting pneumatic pressure into 4 mAdc to 20 mAdc electronic output.

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.)

All pneumatic instrumentation requires extremely clean, dry and oil-free compressed air. It must be noted that failure to use adequately filtered compressed air will result in unsatisfactory performance. Use of a compressed air coalescing filter (such as the King Air-Guard or King Air Control Station) upstream in the supply line is expressly recommended.

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.

Purging a downpipe with compressed air creates a force balance, resulting in pneumatic pressure equal to the hydrostatic pressure due to liquid depth in the tank. The LiquiSeal™ Purge Control works as a constant flow regulator, providing a continuous flow of air (1 cfh) into the downpipe. Pressure is created as liquid is purged from the downpipe.

This pneumatic pressure is the basis for the tank level measurement because it is equal to the hydrostatic (liquid) pressure which is directly proportional to liquid depth. For any increase or decrease of depth, there will also be a corresponding change in the pneumatic pressure.

When equilibrium exists (i.e., air pressure = liquid pressure), the continuous flow of air escapes through the open end of the downpipe. This air bubbles up through the liquid hence the reason why this type of level sensing is often termed a "bubbler".

A complete tank gauging system can be configured using pneumatic components or can include electronic transmitters and indicators. Pneumatic sensors and indicators are inherently safe and explosion proof since there are no electrical components involved. A pneumatic system transmits a pressure signal through small bore tubing (typically 1/4" OD) to the pneumatic indicator. The location of the indicator may be up to several hundred feet from the LiquiSeal™ control.

An electronic system using the D/P LiquiSeal™ generates a 4-20 mA signal to the indicator. This electronic signal can be transmitted over several thousand feet using twisted pair (2-wire) cable. The indicator can be either an analog column display or digital readout, depending upon preference.

Since the primary element of either system is merely an open-ended pipe, the variety of material selections assures compatibility with tank contents. It may also be readily replaced by the user from any conveniently available source.

LiquiSeal™ control provides compressed air flow to downpipe. The tubing (3/8-in. OD) also conveys the resulting pressure due to liquid depth. The purge control then retransmits an isolated pneumatic signal or 4-20 mA electronic signal to the indicator.

TL-190: Differential Calibration Kit

The KING-GAGE® D/P Transmitter is also offered in a hybrid version combined with an air flow control for pneumatic sensors or downpipe (bubbler) systems. These combination units allow for direct 4-20 mA signal from the tank using the integrated differential pressure transmitter.

D/P Sensor Controls are designed for use with KING-GAGE® pneumatic diaphragm sensors. The air control portion of these units creates a 1:1 pneumatic pressure directly proportional to liquid depth in the tank. Acting as a force balance, the pneumatic pressure offsets the hydrostatic pressure exerted against a diaphragm at the tank. The electronic transmitter then converts this pressure into a 4-20 mA output signal.

D/P LiquiSeal Controls and D/P Purge Controls are used in conjunction with a downpipe (or bubble tube) extending down through the liquid contents of the tank. This type of sensor also acts as a force balance. A continuous purge of compressed air into the pipe displaces the liquid and creates a pneumatic pressure equivalent to hydrostatic head pressure. The transmitter converts this pressure into a 4-20 mA output signal.

LiquiSeal™ Purge Control Service Parts

7333-10: Replacement filter element
7334-9: Air control section kit
7334-21: Sensor section kit (Includes 7366-1 orifice check valve and 6448-22 Titanium diaphragm)
7336-1: Orifice/check valve
6448-22: Sensor diaphragm, titanium
9316-4: O-ring for D/P top plate

Length of pipe penetrates hull a point below minimum water line. Output from the purge control proportional to liquid depth is transmitted to the indicator which displays actual draft measurement.

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

The LiquiSeal™ Purge Control can be used to sense tank levels or measure ship's draft. The output signal (pneumatic or electronic 4-20 mAdc) can be transmitted to KING-GAGE® indicators in the engine room, control center or ship's bridge.

Applications Include:

• Ballast water tanks
• Fuel oil tanks
• Day tanks
• Bunker oil tanks
• Liquid cargo tanks

Purge Controls

• 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.

D/P Sensor Control

• Piezoresistive element for less frequent recalibration
• 4 mA to 20 mA two wire output for monitoring or control
• Better than ±0.02% span repeatability

Liquid level gauging demands a high degree of accuracy and repeatability. This is especially true for quality control in batch processing operations. That is why KING-GAGE® D/P Transmitters are specifically designed to provide optimal performance in tank gauging applications. They utilize a precision piezoresistive sensor element that provides longer term stability. Guaranteed accuracy is within ± 0.2% F.S. and repeatable to within ± 0.02% of calibrated span.

LiquiSeal™ Downpipe Purge Control

• Level sensor for ballast and service tanks or ship's draft
• Externally mounted at the tank or remotely
• Pneumatic or electronic (4 mA to 20 Ma output)

The downpipe level sensor is a highly refined version of a bubbler system using a precision air flow controller. A downpipe is an extremely simple yet effective method of sensing the hydrostatic pressure due to liquid depth. It can be used for tank gauging or ship’s draft measurement.

LiquiSeal™ Purge Control is a fully integrated air purge regulator and pressure transmitter. It can be mounted directly adjacent to the tank or remotely up to 50 feet away. 3/8" air line tubing connects the LiquiSeal™ unit to the pipe extending downward in the tank. A supply of compressed air is required for system operation.

The rugged brass construction is especially suited to the rigors of marine service. Beneath a durable gloss epoxy finish, the machined brass body and housing resists corrosion while affording maximum protection. For explosion hazard areas, an all-pneumatic version of the LiquiSeal™ can be used without the need for intrinsic safety provisions.

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.

Unit includes (1) water-resistant Hubbell cord grip.