High and Low Viscosity Liquids - Helical
Helical Screw Flowmeters
Meter Selection
Helical Screw Flowmeters measure variable viscosity fluids up to 5000 cSt and higher at flow rates giving up to the normal maximum pressure drop of the meter. For low flowrates, greater viscosity can be accommodated. (CentiPoise mPa.s divided by Specific Gravity equals CentiStokes mm2/s). Meters are selected for materials compatibility, service pressure and temperature conditions. Electrical warming or hot fluid heating jackets can be included. Secondly, the application maximum allowable pressure drop and flowrate/viscosity determines the meter size.
OM Series Meter Data
Minimum flowrates relate to viscosity and sensor selection as well
| Meter Type |
Meter Size |
Nom. Flowrate litres/minute | Pressure bar max |
Temperature ºC Min Max |
Pulses/ Litre max ^ |
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| min | N max | E max* | min | max* | |||||
| OME Series | 13 | 1/2" | 0.1 | 10 | 15 | 40 | -20 | 100 | 1214 |
| 20 | 3/4" | 0.3 | 30 | 45 | 40 | -20 | 100 | 321 | |
| 32 | 1" | 1 | 100 | 150 | 40 | -20 | 100 | 78 | |
| OMG Series | 13 | 1/2" | 0.1 | 10 | 15 | 250 | -20 | 250 | 1216 |
| 20 | 3/4" | 0.3 | 30 | 45 | 250 | -20 | 250 | 640 | |
| 32 | 1" | 1 | 100 | 150 | 250 | -20 | 250 | 234 | |
| 52 | 1 1/2" | 3.5 | 350 | 525 | 160 | -20 | 250 | 71 | |
| 68 | 2" | 7 | 700 | 1050 | 100 | -20 | 250 | 40 | |
| 100 | 4" | 20 | 2000 | 3000 | 40 | -20 | 250 | 16.8 | |
| 140 | 6" | 50 | 5000 | 7500 | 40 | -20 | 250 | 8.85 | |
| OMH Series | 13 | 1/2" | 0.1 | 10 | 15 | 420 | -20 | 250 | 1216 |
| 20 | 3/4" | 0.3 | 30 | 45 | 420 | -20 | 250 | 640 | |
| 32 | 1" | 1 | 100 | 150 | 420 | -20 | 250 | 234 | |
| 52 | 1 1/2" | 3.5 | 350 | 525 | 420 | -20 | 250 | 71 | |
| 68 | 2" | 7 | 700 | 1050 | 420 | -20 | 250 | 40 | |
| OMK Series | 13 | 1/2" | 0.4 | 10 | 15 | 40 | -20 | 100 | 1216 |
| 20 | 3/4" | 1.2 | 30 | 45 | 40 | -20 | 100 | 640 | |
| 32 | 1" | 4 | 100 | 150 | 40 | -20 | 100 | 234 | |
| 52 | 1 1/2" | 7 | 350 | 525 | 40 | -40 | 100 | 71 | |
| 68 | 2" | 14 | 700 | 1050 | 40 | -40 | 100 | 40 | |
| OMX Series |
Special high pressure versions up to 1034 barg pressure | ||||||||
| * Use of ext. range above N max - nominal maximum is related to service conditions. | |||||||||
| ^ optionally, these pulses/litre values can be increased - consult our engineers. | |||||||||
OMG: The body is of grey cast iron with ball-race bearings and nitrated steel rotors. The 'O'-seals are FPM. Maximum pressure drop is 20 bar.
Flowrate over-run: The nominal maximum flowrate is increased by 50% for lubricating fluids, at less than 120ºC and with certain limitations of viscosity. The OMG20 meter can operate down to 0.015 I/min with clean,viscous lubricating fluids.
OMH: This high pressure meter, in sizes up to OMH68, is rated to 420 bar maximum. Specification is as type OMG except the body which is in nodular graphite cast iron. The sensor is selected for the application pressure. A special series of meters based on the OMH type design is available to 690 bar with 316 stainless steel external construction. (Over-run as OMG) OMH100 is available - contact factory.
OMK: The body is 304 or 316L stainless steel. Rotors are filled-PTFE, not requiring bearings. The 'O'-seals are Kalrez and FEP covered silicon as standard. The standard temperature range is -20 to +40°C with optional high temperature type: +20 to 100°C. Maximum pressure drop is 4 bar.
Flowrate over-run: The nominal maximum flowrate is increased by 50% for lubricating fluids, at less than 40ºC with certain limitations of viscosity and within the 4 bar maximum pressure drop allowed.
OME: The body is of aluminium with ballrace bearings and nitrated steel rotor. The O-seals are FPM. Maximum pressure drop is 2 bar. Sensor is not wetted. Over-run is limited to the maximum pressure drop and has to be a lubricating fluid.
Litre Meter - Comprehensive Instrumentation
The Helical Screw Flowmeters operate with all Litre Meter Signal Processing and Display Instruments. These offer comprehensive facilities and are detailed in the Litre Meter Pelton Wheel section. Alternatively, the flowmeter can be directly equipped with an NPN open collector, PNP or TTL output. The frequency of the output can be derived from the application flowrate and the 'pulses per meter' meter factor for each meter as tabulated in this section above.
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