Jasper, GA--The traditional way to measure the level of cryogenic liquids in tanks is with a mechanical differential pressure gage. Usually, the gage comes calibrated in inches of water, and a conversion table on the wall translates that readout to gallons. Pounds are the normal unit for liquid CO.
Mechanical gages get the job done, but exhibit several shortcomings. Most possess a limited range, requiring different gages for tanks of different size. Most lack either an alarm or a remote-reading capability.
Developed by engineers at Technical Manufactured Products, a versatile electronic liquid-level gage offers a variety of benefits. Transducers measure the pressure at the top and bottom of the tank. An electronic package calculates the differential pressure and presents the readout in units selected by the user. High accuracy, remote readout and alarm capability, and a single model that covers all sizes of tank are among the advantages of the electronic unit.
Pressure ports are located both at the top and bottom of the gage. Most users employ the bottom ports for input and mount a standard pressure gage on the top, low-pressure port. Gages powered by a 9V battery use a "push-to-read" button on the front. Continuous readout requires an ac adapter.
On installation, the user sets the full-tank reading, and also sets the display to read percent full, inches of HO, or gallons. The adjustable low-level alarm flashes a light on the face of the gage and includes contacts for a remote alarm. All selections are made with DIP switches and adjustable pots, accessible with the cover open.
Exacta-Gage, the basic unit, covers vertical tanks ranging from 250 to 15,000 gallons in capacity-one size fits all. A variation on the basic gage is Porta-Gage for horizontal tanks. Cylindrical horizontal tanks are more difficult to measure than vertical tanks. One inch level when the tank is near full represents much less liquid than when the tank is half full. An additional circuit board in the Porta-Gage contains the dimensions of the tank and the math to display percentage full readings. "The electronics give us much greater accuracy than mechanical gages on both horizontal and vertical tanks," says TMP's Jagat Trivedi. Porta-Gage is a natural for over-the-road tank trucks, but is not yet certified for flammable liquids.
Tela-Gage for remote readout by modem is another variation that requires an additional circuit board. In addition to level, Tela-Gage also measures tank pressure and stores the last 650 pressure and level readings in memory. Readings may be taken at regular intervals (every hour is standard) or only on demand. Remote operators can interrogate the gage, and either low level or low pressure can trigger the gage to call the operator.
Additional details...Contact Jagat Trivedi, Technical Manufactured Products, Box 488, Jasper, GA 30143, (706) 692-3360.