Hedland offers a complete line of over 15,000 variable area flow meters to measure oil, hydraulic oil, phosphate esters, water and water-based fluids, as well as air and other compressed gases.

1. Variable Area Flow Meters

2. Variable Area Flow Meters
• Port Sizes: 1/4” - 1.5” and 3”
• Measure: Oil, Water, Air
• Accuracy: ±2% of full scale
• Repeatability: ±1%
• Other specifications:
• Flow ranges: 0.02 - 300 GPM (0.1 - 1100 LPM)
• Construction: Aluminum, brass and T303 stainless
• Connections: SAE, NPTF, BSPP, Code 61/62 flange
• Pressure up to 6,000 psi (414 bar) maximum
• Temperature up to 240 °F (116 °C)
• High Temp units to 400 °F (204 °C)

3. General Design Features
• Operates in any position
• Easier to read linear scale
• 360° Rotatable guard/scale
• No flow straighteners or special
piping required
• Reverse flow bypass option
• Good viscosity stability to
(400 SUS / 90 cSt)

4. Effects of Viscosity
• Hedland’s sharp-edged orifice ensures operating stability and accuracy over a wide
viscosity range.

5. Effects of Viscosity

6. Effects of Density
Corrections for more or less dense fluids can be made to
standard scales using the following correction factor:
√ 1.0 / specific gravity, water/water-based meters
√ 0.876 / specific gravity, petroleum-based meters
Example: Measuring liquid propane with petroleum meter
• Fluid ~ Liquid Propane (LPG)
• Scale Measured Flow ~ 25 gpm
1. Select (LPG) specific gravity from the Fluid Selection
1.31
.876
.51

Chart = 0.51
2. Since petroleum meter is utilized, select petroleum
formula
3. Multiply scale reading by 1.31, 25*1.31= 32.75 (actual
flow of liquid propane)

7. Pneumatic Flow Meters
• Multi-pressure scale • Single-pressure scale

8. Pneumatic Flow Meters
• Compressibility of Gases
• Significant
• Density varies with
• Pressure
• Temperature
• Effects of Specific Gravity
• Any changes from standard has
a proportional effect on meter
accuracy

9. Pneumatic Flow Meters
• Example: Measuring Natural Gas with a Air meter
• Line Pressure =140 psig
• Temperature = 40° F
• Fluid = Natural Gas 0.6 SG
• Pressure correction:
• Temperature:
• Specific Gravity:
• Total correction factor :
.861
114.7
1 
14.7


140
f
.971
460

2 
530

40
f
.775 3 f  0.6 
.861*.971*.775 .648 total f

10. Pneumatic Flow Meters
• To determine actual flow vs. indicated flow
scfm
scfm indicated
25 ( )
( )  
f
scfm actual
.648( )
total
38.6
• To determine which standard meter is required
to achieve a flow of 85scfm
scfm flow f scfm total 85 (max )*.648( ) 55.1

11. Pneumatic Flow Meters
To determine which standard meter is required
to achieve a desired flow of 85 scfm
scfm flow f scfm total 85 (max )*.648( ) 55.1
• H671A-050
• H771A-050
Actual scale range
5scfm(min flow) .648( f ) 7.7cfm(actual) total 
50scfm(max flow) .648( f ) 77.1cfm(actual) total 

13. Flow-Alert® Flow Switches
Available in single or double switch
• Reed
• SPST-N.O. 10W, 50V and .5 A max
• SPST-N.C. 5W, 50V and .5 A max
• Changes state when internal magnet is in
proximity - returns to original condition when
magnet moves away
• Micro
• 220 VAC @ 10A and 125VDC @ .5A
• Single(1) or Double(2) prewired single-pole, double-throw
(SPDT)

14. MR Flow Transmitter
• Output options and Power requirement
• 0-5V Output requires 10-30Vdc@.75W max
• 0-10V Output requires 12-30Vdc@.75W max
• 4-20mA Output loop powered 30Vdc max
• Digital rate and total flow indication
• Operates as part of a totally integrated electronic
process control/ data acquisition system
• Non-contact sensor electronics
• In-field compensation for specific gravity and viscosity
• Rating: NEMA 12 and 13 (IP 52/54)

15. Applications
• Agriculture
• Irrigation systems
• Pesticides and Ag Chemicals
• Coolant Flow on Thermal Transfer Equipment
• Telecom
• Coolant Flow on Calorimeters
• Automotive
• Case Drain – Hydraulic Power Units
• Engine Coolant Test Systems
• Transmission Flush Systems
•Compressed Air Systems

16. Applications
• General Manufacturing
• Monitor air compressor output
• Monitor air supply to balance systems
• Semicon
• Coolant Flows
• Flush Flows
• Fluid Power
• Case Drain – Hydraulic Power Units

17. Thank You
+44 (0)1280 817304 sales@bellflowsystems.co.uk www.bellflowsystems.co.uk