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Dwyer Series HF In-Line Flow Sensors

Low Cost, Durable Flow Monitors have a patented design based on a floating sharp-edged orifice disk and variable area flow measurement to yield accuracy of ±2.5% over center one-third of scale. This unique design allows accurate performance with fluid viscosities up to 500 SSU. All internal wetted parts are contained inside a sealed metal tubular casing assuring a virtually maintenance-free unit. Flowing media forces linear motion of a spring loaded, sharp edge orifice disk and ring shaped transfer magnet which both ride on a tapered center shaft. The transfer magnet drives a clearly visible magnet follower located outside the flow tube, protected under the clear Lexan® tube. A ring on the magnet follower indicates flow rate on the direct reading scale. Rubber bumpers are provided for external impact resistance.

Designed for single-direction flow, Series HF Monitors are recommended for use with system filtration of a least 74 microns or a 200 mesh screen. Some applications may also require magnetic filtration.

Brass and stainless steel models are calibrated for water with 1.0 specific gravity. For a fluid with a significantly different specific gravity, a correction factor can be determined by using the following formula.
Click to See Dimension Graphic
Connection Size
"A" Reference
"B" Wrench Flats
"C" Reference
1/4" to 1/2" NPT 1-7/8" (48mm) 1-1/4" (32mm) 6-9/16" (167mm)
3/4" to 1" NPT 2-3/8" (60mm) 1-3/4" (45mm) 7-1/8" (181mm)
1-1/2" NPT 3-1/2" (90mm)
2-5/8" (58mm)
10-1/8" (258mm)
Service: Compatible gases or liquids
Wetted Materials: Body: Aluminum, brass or 304SS ; Seals: Buna-N or Viton; Magnet: Teflon coated Alnico ; Other internal parts: 304SS
Viscosity: 500 SSU
Temperature Limits: HFA, HFB and HFS Models: 240 °F (116 °C); HFH Models: 400 °F (204 °C)
Pressure Limits: HFA Models: 600 psig (41 bar); HFB and HFH Models: 3500 psig (240 bar); HFS Models: 6000 psig (413bar)
Accuracy: ±4% FS over entire range; ±2.5% over center third of the measuring range
Repeatability: ±1% of full scale
Shipping Weight: 1/8 to 1/2" FNPT Models - 2lbs; 3/4 to 1" FNPT Models - 3.5lbs ; 1-1/2 FNPT Models - 11lbs
Aluminum Body for Oil Based Fluids
Model Number
Connection Size
Range, GPM
HFL-2-05 1/2" NPT(F) 0.5-5
HFL-4-25 1" NPT(F) 2-25
Brass body for water based fluids (non-steam) Wetted Parts: Brass, Teflon coated Alnico, 304 SS and Buna-N
Model Number
Connection Size
Range, Water GPM (LPM)
HFB-2-05 1/2" NPT(F) 0.5-5.0 (1-19)
HFB-3-15 3/4" NPT(F) 2-15 (7.5-55)
HFB-3-20 3/4" NPT(F) 2-20 (7.5-75)
HFB-4-35 1" NPT(F) 5-35 (19-130)
HFB-5-50 1-1/2" NPT(F) 5-50 (19-189)
HFB-5-100 1-1/2" NPT(F) 10-100 (38-379)
HFB-6-150 2" NPT(F) 20-150 (76-568)
HFB-6-75 2" NPT(F) 8-75 (31-284)
304 Stainless Steel body for high-pressure fluids Wetted Parts: 304 SS, Viton and Teflon
Model Number
Connection Size
Range, Water GPM (LPM)
1/2" NPT(F)
0.2-2.0 (0.75-7.5)
HFS-2-10 1/2" NPT(F) 0.5-10 (1.9-38)
Brass Body High Temperature 400°F for water based fluids.  Wetted Parts: Brass, Teflon coated Alnico, 304SS and Viton
Model Number
Connection Size
Range, Water GPM (LPM)
HFH-2-05 1/2" NPT (F) .05-5.0 (1-19)
1/2" NPT(F)
1-10 (3.8-38)
HFH-4-35 1" NPT(F) 5-35 (19-130)
Flow monitor shall have sharp-edged orifice disk, sealed (aluminum)(brass)(304SS) chamber and magnetically coupled outer indicator protected by a clear Lexan® window. Unit shall be Dwyer Model No. HF____
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