Remote Liquid Level Indicating System

The liquid level indicator system is the product of specialists in boiler trim design. The indicator, a differential pressure device, is operated by the water vessel itself, using the weight difference between a constant head and variable head of water. Its accessories include a transmitting coil and signal conditioner to provide a dc milliampere signal to one or more secondary (repeater) indicators; a control module with magnetically or cam actuated switches to perform alarm, trip and shut-off functions.

Major Components of the System

Primary Indicator The primary (transmitting) indicator couples a reliable magnetically actuated indicating mechanism with a transmitting coil (LVDT) and armature assembly which is actuated by the indicator pointer. A signal conditioner energizes the transmitting coil receiving an output signal which is conditioned to dc milliampere output proportional of the primary pointer reading. Enclosures meet the condition of NEMA 1, 2 & 5 (See Page 9).

Indicator Operation The indicator combines two separate elements; (1) a sending element which responds to differential pressure and (2) an indicating system which presents response as a true reading of level.
     The sensing element measures and compares the variable head of the liquid in vessel to a constant head. Contained within a pressurized housing, the sensor is self-powered by the hydraulic forces imposed upon it.
     The indicating system is located outside the pressure zone and receives the actuating force through a permanent magnet coupling, thereby eliminating direct mechanical linkages and stuffing boxes.
     The high pressure, right-hand side of the indicator is connected to the constant head chamber which is installed above high water level.
     The low pressure, center-hand side is connected to the lower drum connection. The indicator diaphragm(19) responds to signals from both these sources. The pipe connected to the head chamber delivers a constant head pressure force from the chamber to the high pressure side of the diaphragm. The other pipe, which is connected to the lower fitting of the drum, produces a variable head pressure on the low pressure side of the diaphragm as the liquid level changes. Any change in the differential head pressure produces a force variation on the diaphragm. This variation results in motion of the pin (17) and the deflection plate (24). This plate, anchored at one end, is fitted at the free end with a permanent horseshoe magnet (25). Poles of the magnet straddle a spiral armature inside a pressure isolating well (34) threaded into the housing (13). A counter-balance pointer (11) is fastened to the outer end of the armature. When motion of the deflection plate changes the position of the horseshoe magnet, its movement along the well causes rotation of the spiral armature, which, in turn actuates the pointer to respond to every change in liquid level. The pointer moves over a standard ten-division vertical scale (dial).

Features and Benefits

Remote Reading
Transfers hard-to-see liquid level readings from inaccessible points down to eye level.

Continuous Indication
The primary sensing device is operated by the liquid in the boiler itself.

Foolproof
The actuating diaphragm can withstand high unbalanced pressure.

Complete
It can be linked with a control module that actuates sound and light alarm accessories to provide a complete indicating and controlling system.

Density Compensation
For changes in density at various operating pressures (0 to 3,000 psi; 0 to 207 bar).

No Mechanical Linkages
Located outside the pressure zone, the indicating system receives its signal through a magnetic coupling.

The information above is only a partial segment of our literature for this product. If you would like the complete literature for this product, contact K. Connelly Corp. for Literature requests.