Dwyer HF User Manual

BULLETIN F-55

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Series HF IN-LINE FLOW MONITORS

Specifications - Installation and Operating Instructions

Series HF Flow Monitors combine the

simplicity of a sharp edged orifice disk with a
variable area flow monitor to provide a low cost
way to measure flow at high pressures. These
monitors are tubular , with all internal wetted parts
sealed within the body casing. Running through
the body is a tapered shaft which is centered in
the bore by pilot disks at each end. Surrounding
the shaft are a sharp-edged floating orifice disk,
a transfer magnet and return spring. The disk
and transfer magnet are held in the “no flow”
position by a biased return spring. As flow moves
through the monitor, it creates a differential
pressure at the orifice disk forcing the disk and
transfer magnet against the return spring. As
flow increases, the differential pressure at the
disk increases, forcing the disk and transfer
magnet to move along the tapered center shaft.
As flow decreases, the biased return spring
forces the disk and transfer magnet down the
center shaft, returning to the “no flow” position.
In metal casing monitors, disk and magnet
movement are not visible so a magnet follower is
located outside the body casing, magnetically
coupled to the internal transfer magnet. As flow
increases, motion of the internal magnet moves
the magnet follower outside the body casing,
under the scale.

Valve

Size

1/8 NPT

1/4 to 1/2 NPT

3/4 to 1 NPT

1-1/4 to 1-1/2 NPT

2 NPT

“A”

Reference

1.25

1.875

2.375

3.500

3.500

“B”

Wrench Flats

0.875

1.250

1.750

2.250

2.250

“C”

Reference

4.813

6.562

7.125

10.125

12.625

SPECIFICATIONS

Service: Compatible gases or liquids.
Wetted Materials: Body: Aluminum, brass or

304 SS; Seals: Buna-N or Fluoroelastomer;
Magnet: PTFE coated Alnico; Other internal parts:
304 SS.

Maximum Viscosity: 500 SSU.
Temperature Limits: HFA, HFL, HFB and HFS

Models: 240°F (116° C); HFH Models: 400°F
(204°C).
Pressure Limits: HFA Models: 600 psig (41 bar);
HFL, HFB and HFH Models: 3500 psig (240 bar);
HFS Models: 6000 psig (413 bar).
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˝ female NPT

Models; 2 lb (0.9 kg); 3/4 to 1˝ female NPT
Models: 3.5 lb (1.59 kg); 1-1/2˝ female NPT
Models: 11 lb (5 kg); 2˝ female NPT Models: 13.5
lb (6.12 kg).

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, IN 46361,U.S.A. Fax: [phone] e-mail: [e-mail]

Phone: [phone] www.dwyer-inst.com

Aluminum body for air or other non-corrosive gases:

Wetted Parts: Aluminum, PTFE coated Alnico, 304 SS and Buna-N

Model

Number

HFA-0-01
HFA-1-12
HFA-1-22

Connection

Size

1/8˝ female NPT
1/4˝ female NPT
1/4˝ female NPT

Range, Air

SCFM

2-12
2-12
4-23

Max. Pressure

Drop, PSID

Aluminum body for oil based fluids:

Wetted Parts: Aluminum, PTFE coated Alnico, 304 SS and Buna-N

Model

Number

HFL-2-05
HFL-4-25

Connection

Size

1/2˝ female NPT

1˝ female NPT

Range, GPM

Oil

0.5-5
2-25

Range, LPM

Oil

1-19

7.5-95

Brass body for water based fluids (non-steam):

Wetted Parts: Brass, PTFE coated Alnico, 304 SS and Buna-N

Model

Number

HFB-0-01
HFB-0-02
HFB-2-05
HFB-3-15
HFB-3-20
HFB-4-35
HFB-5-50

HFB-5-100

HFB-6-75

HFB-6-150

Connection

Size

1/8˝ female NPT
1/8˝ female NPT
1/2˝ female NPT
3/4˝ female NPT
3/4˝ female NPT

1˝ female NPT
1-1/2˝ female NPT
1-1/2˝ female NPT

2˝ female NPT

2˝ female NPT

Range, GPM

Water

0.05-1

0.2-2

0.5-5
2-15
2-20
4-40
5-50

10-100

8-75

20-150

Range, LPM

Water

.19-3.8
.75-7.5

1-19

7.5-55

7.5-75
19-130
19-189
38-379
31-284
76-568

304 Stainless Steel body for high-pressure fluids:

Wetted Parts: 304 SS, Fluoroelastomer and PTFE

Model

Number

HFS-0-01
HFS-2-02
HFS-2-10

Connection

Size

1/8˝ female NPT
1/2˝ female NPT
1/2˝ female NPT

Range, GPM

Water

0.05-1

0.2-2

0.5-10

Range, LPM

Water

0.19-3.8

0.75-7.5

1.9-38

3.32

3.32

3.61

Max. Pressure

Drop, PSID

6.08

8.41

Max. Pressure

Drop, PSID

1.98

5.58

7.18

10.2

6.2

15.2

9.25

25.59

14.95

39.86

Max. Pressure

Drop, PSID

1.98

5.58

8.68

Brass Body High Temperature 400˚F for water based fluids:

Wetted Parts: Brass, PTFE coated Alnico, 304 SS and Fluoroelastomer

Model

Number

HFH-2-05
HFH-2-10
HFH-4-35

READING THE MONITOR

Note the red reference line running 360° around the
white magnet follower. This line moves in direct
proportion to the movement of the internal orifice
disk. When fluid is flowing, the flow rate is read by
aligning the red reference line with the closest scale
graduation.

SPECIFIC GRAVITY OR DENSITY EFFECT

Standard water monitors are calibrated with water
and oil monitors are calibrated with .873 S.G. oil.
Flow indication will read high for heavier fluids and
low for lighter fluids. A correction factor for other
specific gravities can be established using the

Connection

Size

1/2˝ female NPT
1/2˝ female NPT

1˝ female NPT

Range, GPM

Water

0.5-5
1-10
5-35

Range, LPM

Water

1-19

3.8-38

19-130

following formulas.
For Water Monitors use:

Actual = Observed Reading x 1.0

For Oil Monitors use:

Actual = Observed Reading x 0.873

VISCOSITY EFFECT

The Series HF Flow Monitor incorporates a unique
floating sharp-edged orifice disk which provides
greater operating stability and accuracy over wide
ranging viscosities up to 500 SSU.

Max. Pressure

Drop, PSID

7.18

8.68

13.46

√

√

S.G.

S.G.

BASIC APPLICATION INFORMATION

The flow monitor can be installed directly in the fluid
line without flow straightening or special piping.
They are suitable for measuring the flow rate of most
liquids which do not contain particles larger than 74
microns.

1. The magnetic follower is sealed inside the Lexan
tube to allow use in areas where the unit might be
sprayed or washed with soap water.

2. Mount the monitor in a location allowing easy
access for reading and maintenance.

3. The monitor should not be located near hot pipes
or equipment which could damage the window tube
and/or scale.

4. Mount the monitor at least 1 ft (.3 m) from large
electric motors which can weaken or demagnetize
the internal magnet.

5. Aluminum should not be used for water.

WARNINGS AND PRECAUTIONS

1. These monitors are designed to operate in
systems that flow only in one direction, matching the
direction indicated by the arrow on the flow scale.
Operation in the reverse direction can damage the
monitor or other system components.

2. The window tube is made of polycarbonate which
can be safely cleaned with soap and water. many
other cleaning agents can damage this material,
causing discoloration or crazing. To check
compatibility, call General Electric’s polycarbonate
Compatibility Reference Line at 1(800)845-0600,
USA.

3. To maintain accuracy and repeatability, many
internal parts are precision machined and thus
require filtration or at least 74 micron or 200 mesh
screen.

4. All monitors are tested and calibrated using a light
hydraulic oil. Units are well drained, but some oil
residue may remain. Please check compatibility with
your fluid. Cleaning may be required before use. See
“Cleaning and Inspection.”

5. When installing aluminum or brass monitors onto
steel pipe, take caution not to over tighten
connections. Threads could strip if over tightened.

6. Aluminum and brass monitors should not be used
in systems where piping is not supported. Heavy
weight can cause the monitor to bend and
malfunction.

7. Do not exceed the maximum operating pressure
or temperature limit.

8. Pressure and flow surges can disengage the
outer magnet follower from the transfer magnet. If
this occurs, a shock suppressor should be used to
avoid repetitive malfunctions.

9. Caution should be used when using Teflon
thread tape on joints. Leave at least 1/8˝ (3 mm) of
exposed pipe on the end.

10. These monitors use an internal transfer magnet
in their design. Because of this be aware of the
following:
a. Keep computer disks or tapes away from these
units.
b. If metal particles are flowing through this device,
a magnetic filter may be required.

BASIC INSTALLATION

Series HF Flow Monitors are installed in-line and are
direct reading. They can be mounted in a vertical or
horizontal position as long as flow is in the direction
of the arrow on the side. No straight pipe is required
before or after the monitor. If necessary, 90° elbows
can be installed on both ends without significant
flow variation. When installing, apply a small amount
of pipe thread sealant tape or pipe thread sealant to
assure a good seal. Locate filter, if used, in front of
monitor and in a location allowing easy access for
routine maintenance. Refer to Warnings and
Precautions for additional information.

FLUID FLOW IN REVERSE DIRECTION

These monitors will not allow flow in the reverse
direction, opposite to the arrow on the scale. In the
reverse direction unit will act like a leaky check
valve.
If the application requires occasional reverse flow,
install a check valve in parallel with the monitor
which will force flow around the unit when reversed.
This type of check valve can be obtained from your
local fluid component distributor.

WARNING: Do not remove monitor from
system without proper and adequate safety
measures if fluid or gas is toxic, corrosive or
flammable. Shut down system and relieve
pressure before removing flow monitor from
system.

DISASSEMBLY

Important: It is not necessary to remove the window
tube or window seals to clean the monitor. Note
how the unit is disassembled to aid in reassembly.
Warning - Shut down system and relieve pressure
before removing monitor from flow line.

1. Use a clean, dry cloth to remove all foreign matter
from exterior of monitor, especially around threaded
connections.

2. Remove monitor from flow line.

3. With the arrow on the scale pointing upward,
secure the unit in a vice using the flats on the inlet
connection. DO NOT apply wrench or vice to Lexan
tube.

4. Use a wrench on the flats provided on the outlet
connection and turn counter-clockwise to loosen.
Either port may come loose. Do not remove end
connection at this time.

5. Remove monitor from vice. Hold unit so the end
connection that has been loosened is on top.
Remove loose connection.

6. Tilt open end of monitor over a clean cloth to
expose inner cartridge. Remove inner cartridge
assembly from body casing. NOTE: Because the
transfer magnet is coupled magnetically to the
magnet follower, you will notice a light resistance
when removing the cartridge. If cartridge does not
slide out, insert a wooden dowl in opposite end of
monitor and push or rap lightly on dowel until
cartridge breaks free. IMPORTANT: If inner cartridge
does slide out freely, it may be a sign of
contamination. Locate and remove the source of
contamination before returning monitor to service or
the problem will reoccur. It may be necessary to
install finer filtration or a magnetic filter in the

®

system. The transfer magnet is a powerful Alnico
magnet. Keep it away from metal chips and filings.
They can be difficult to remove when reassembling
and will cause premature failure.

7. Examine inner cartridge assembly for
contamination. If the inner cartridge assembly has
no contamination and is working properly,
reassemble unit and return to service. If
contamination is found, proceed to Cleaning and
Inspection.

CLEANING AND INSPECTION

1. Soak inner cartridge assembly in a suitable
cleaning solvent or soap and water. Caution: When
using a compressed air hose, wear proper eye
protection.

2. Remove parts from solvent. Use compressed air
and/or scrub lightly with a soft brush to remove any
remaining contaminants. Remove any magnetized
particles from transfer magnet.

3. Remove any contaminants from inside body
casing.

added, mainly have self-generated contamination.

4. If inner cartridge assembly or body casing
cannot be cleaned, is scored, pitted or damaged
beyond repair, replace monitor.

5. Clean polycarbonate window with soap and
water or a compatible cleaning solvent.

6. Clean and inspect O-ring assemblies for nicks
and cuts. Replace as necessary.

7. After monitor is cleaned, reassemble in reverse
order of disassembly.

8. Clean and inspect monitor every six months.
Properly filtered monitor will provide years of
trouble free service. If unit is not properly protected
by a filter, damage and malfunction can occur.
Damage caused by excessive contamination is not
covered by warranty.

9. If the cartridge clip is removed or lost, a new clip
should be used. Cartridge retainer clips are Waldes
No. 5105-12H for 1/4˝ and 1/2˝ models, No. 5105­18H for 3/4˝, 1˝, 1-1/2˝, and 2˝ models.

RECOMMENDED FILTRATION

The manufacturer recommends system filtration of
at least

a 74 micron filter or a 200 mesh screen. If
inadequate filtration has caused monitor failure, it
will normally fail in the open position. Some
systems may require a magnetic filter. Important:
Monitor damage caused by excessive
contamination is not covered by warranty.

STABILIZED CONTAMINATION

The goal of filtration is to create effective protection
from system contamination. Proper filtration
stabilizes contamination to allow fluid components
to function properly. A fluid system is considered
stabilized when “contamination in” equals
“contamination out.” Proper filtration must reduce
initial contamination to a stabilized level within an
acceptable time period. The entire system should
be stabilized in time to prevent premature wear or
damage to monitor components.

CONTAMINATION SOURCES
Fresh Fluid - When new or fresh fluid is stored

inside holding tanks, the fluid may be
contaminated with scale or metal flakes from inside
the tank. To prevent this type of contamination,
filter fresh fluid before adding to the system.

New Machinery - When building new machines, a
certain amount of built-in contamination is
unavoidable. Typical built-in contamination might
include dust, dirt, chips, fibers, sand, flushing
solutions, moisture, weld splatters and pipe
sealants. Flushing the system before operation can
reduce contamination but cannot eliminate it
entirely. Unless the system is flushed at a high
velocity some contamination will not be dislodged
until the system is in operation. System
contamination can cause fluid component
malfunction.

Environmental Contamination - When
performing routine maintenance, the systems fluid
is commonly exposed to environmental
contamination. Exercise caution during routine
maintenance to prevent this type of contamination.
Change breather filter and system air filter regularly.

Self-Generated Contamination - Self-generated
contamination is a product of wear, cavitation, fluid
breakdown and corrosion. Systems that are
carefully flushed, maintained and have fresh fluids

©Copyright 2009 Dwyer Instruments, Inc Printed in U.S.A. 7/09 FR# 50-440843-00 Rev. 3

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, IN 46361,U.S.A. Fax: [phone] e-mail: [e-mail]

In this case, proper filtration can help prevent fluid
component malfunction.

COMPRESSIBILITY OF AIR AND GASES

Air and gases are extremely compressible. Gas
density increases as pressure increases. In most
cases, correction factors should be used to obtain
accurate readings. See correction factors below.

CALIBRATION

All standard Dwyer Instruments,Inc. air flow monitors
are calibrated for air with a specific gravity of 1.0 at
100 psig and 70°F (6.89 bar and 21.1°C). Monitors
are calibrated in SCFM, Standard Cubic Feet per
Minute. A standard cubic foot or air is defined as a
cubic foot of air at 70°F at atmospheric pressure,

14.7 PSI at sea level. Since most industrial
pneumatic systems typically operate at 90-100 PSI,
standard Dwyer Instruments, Inc. Monitors are
calibrated for inlet conditions of 100 PSI at 70°F.
When operating the monitor at other pressures or
temperatures, a correction factor should be used to
maintain the original design accuracy of the monitor.
When inlet pressure of the monitor is at or near 100
PSI, the air flow can be read directly from the monitor
scale. When pressure is other than 100 PSI, use the
following correction factor tables.

CORRECTION FACTORS FOR AIR AND GASES

SCFM (indicated) x (CF) = SCFM (actual)
CF = (f1) x (f2) x (f3)
Note:It is not necessary to use all correctionfactors.

TABLE 1
(f1) PRESSURE CORRECTION FACTORS

f1=

TABLE 2
(f2) TEMPERATURE CORRECTION FACTORS

f2=

TABLE 3
(f3) SPECIFIC GRAVITY CORRECTION FACTOR

f3=

INTERNAL GAGE PRESSURE

System pressure will vary from location to location in
a typical dynamic air or gas system. Because of this,
it is important that an accurate pressure gage be
used to determine flow conditions as close as
possible to the inlet port of the flow monitor.

Phone: [phone] www.dwyer-inst.com

14.7 + psig
––––––––––

√

114.7 psia

√

√

530
––––––––
460 + °F

1

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Sp. Gr.