Helical pressure gauge
The helical elements produce more free-end traveland torque than spiral elements. Other advantages include a higher range of operating pressure with sufficient over range protection. The operating range is affected by coil diameter, wall thickness, the number of coils used, and the material of construction, which is the same as may be used in C-tube elements . Applications of helical elements include direct reading for the following: indicators, recorders, controllers, switches, transmitters, and differential instruments when pressures are applied to both sides of the elements.
Applicationsof helical Pressure Gauge:
Up to 100,000 PSIG (690 MPa)
Up to 600 ° F (316 ° C) with stainless steel Bourdon tube; lower with others; ± 1% zero shift per 50 ° F (28 ° C) ambient variation
Materials of Construction:
Minimum span 15 PSI (100 kPa); maximum span 100,000 PSI (690 MPa)
$50 to $300 for indicators and switches, $500 to $1,200 for direct recorders, and$750 to $1,800 for direct controllers and transmitters. Quartz helix units range for$2,500 for an electronic transmitter to $18,000 for an IEEE and RS-232 program-mable, stable-alone station.