Dwyer Magnehelic User Manual

Magnehelic®Differential Pressure Gage

1/8 FEMALE NPT
HIGH PRESSURE
CONNECTION

1-3/4

(44.45)

1/2

(12.70)

1/8 FEMALE
NPT LOW
PRESSURE
CONNECTION

1

1/16

(17.46)

17/32

(13.49)

ø4-3/4 (120.65) PANEL CUTOUT

ø5

(127)

ø4-47/64
(

120.27)

3/16

(4.76)

2-17/32
(64.29)

15/32

(11.91)

ø4-1/2

(114.3)

1-1/4

(31.75)

ø5-1/2

(139.70)

MOUNTING RING

R

UBBER PRESSURE RELIEF
PLUG WILL UNSEAT ITSELF
W

HEN GAGE IS

OVERPRESSURIZED

(3) 6-32 X 3/16 (4.76) DEEP HOLES
E

QUALLY SPACED ON A Ø4-1/8
(104.78) BOLT CIRCLE FOR
P

ANEL MOUNTING

1/8 FEMALE NPT
H

IGH PRESSURE

CONNECTION

1-3/4

(

44.45)

1

/2

(12.70)

1/8 FEMALE NPT
L

OW PRESSURE

CONNECTION

11/16

(17.46)

15/32

(

11.91)
1-11/16

(42.86)

Ø4-1/2
(

114.3)

1-1/4

(

31.75)

1

7/32

(13.49)

.025 (.64) SPACE CREATED BY 3

SPACER PADS WHEN SURFACE

M

OUNTED. DO NOT OBSTRUCT.

P

ROVIDES PATH FOR RELIEF OF

OVERPRESSURE.

1/8 FEMALE
N

PT HIGH
PRESSURE
C

ONNECTION

1/8 FEMALE
N

PT LOW
PRESSURE
C

ONNECTION

7

/16

(11.11)

Ø4-3/4

(

120.65)

*The blowout plug is not used on models above 180 inches of water pressure, medium or high pressure models,

STANDARD GAGE ACCESSORIES: Two 1/8˝ NPT plugs for
duplicate pressure taps, two 1/8˝ pipe thread to rubber tubing
adapters and three flush mounting adapters with screws.

MP AND HP GAGE ACCESSORIES: Mounting ring and snap
ring retainer substituted for 3 adaptors, 1/4” compression fittings
replace 1/8” pipe thread to rubber tubing adaptors.

OVERPR ESSUR E P ROTEC TION: Standard Magnehelic
Diffe re nt ia l Pres su re Ga ge s are rated for a maximum pres­sure of 15 psig and should not be used where that limit could be
exceeded. Models employ a rubber plug on the rear which func­tions as a relief valve by unseating and venting the gage interi­or when over pr essur e rea ches approx imate ly 25 psig
(excludes MP and HP models). To provide a free path for pres­sure relief, there are four spacer pads which maintain .023˝
clearance when gage is surface mounted. Do not obstruct the
gap created by these pads.

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360 U. S.A.

or on gages which require an elastomer other than silicone for the diaphragm.

SPECIFICATIONS
Service: Air and non-combustible, compatible gases. (Natural

Gas option available.)

Wetted Materials: Consult factory.
Housing: Die cast aluminum case and bezel, with acrylic

cover. (MP model has polycarbonate cover).
Accuracy: ±2% of full scale (±3% on - 0, -100 Pa, -125 Pa,
10MM and ±4% on -00, - 00N, -60 Pa, -6MM ranges),
throughout range at 70°F (21.1°C).

®

Pressure Limits: -20˝ Hg to 15 psig.† (-0.677 bar to 1.034
bar); MP option: 35 psig (2.41 bar), HP option: 80 psig (5.52
bar).
Overpressure: Relief plug opens at approximately 25 psig
(1.72 bar), standard gages only. The blowout plug is not used
on models above 180 inches of water pressure, medium or
high pressure models, or on gages which require an elastomer
other than silicone for the diaphragm.
Temperature Limits: 20 to 140°F (-6.67 to 60°C).
temperature models available as special option.

Size: 4˝ (101.6 mm) diameter dial face.
Mounting Orientation: Diaphragm in vertical position.

Consult factory for other position orientations.
Process Connections: 1/8˝ female NPT duplicate high and
low pressure taps - one pair side and one pair back.

Weight: 1 lb 2 oz (510 g), MP & HP 2 lb 2 oz (963 g).
Agency Approvals: RoHS.

†For applications with high cycle rate within gage total pressure rating,
next higher rating is recommended. See Medium and High pressure
options.

Note: May be used with hydrogen when ordering Buna-N diaphragm.
Pressure must be less than 35 psi.

Phone: [phone] www.dwyer-inst.com
Fax: [phone] e-mail: [e-mail]

Bulletin A-27

*Low

INSTALLATION

Select a location free from excessive vibration and where the

mbient temperature will not exceed 140°F (60°C). Also, avoid

a
direct sunlight which accelerates discoloration of the clear plas­tic cover. Sensing lines may be run any necessary distance.

ong tubing lengths will not affect accuracy but will increase

L
response time slightly. Do not restrict lines. If pulsating pres­sures or vibration cause excessive pointer oscillation, consult
the factory for ways to provide additional damping.
All standard Magnehelic

alibrated with the diaphragm vertical and should be used in

c
that position for maximum accuracy. If gages are to be used in
other than vertical position, this should be specified on the

rder. Many higher range gages will perform within tolerance in

o
other positions with only rezeroing. Low range models of 0.5”
w.c. plus 0.25” w.c. and metric equivalents must be used in the

ertical position only.

v

®

Diffe re nt ia l P re ss ur e Ga ge s are

SURFACE MOUNTING

Locate mounting holes, 120° apart on a 4-1/8” dia. circle. Use
No. 6-32 machine screws of appropriate length.

FLUSH MOUNTING

Provide a 4-9/16” dia. (116 mm) opening in panel. Provide a 4­3/4” dia. (120 mm) opening for MP and HP models. Insert gage
and secure in place with No. 6-32 machine screws of appropri­ate length, with adapters, firmly secured in place.

PIPE MOUNTING

To mount gage on 1-1/4” - 2” pipe, order optional A-610 pipe
mounting kit.

TO ZERO GAGE AFTER INSTALLATION

Set the indicating pointer exactly on the zero mark, using the
external zero adjust screw on the cover at the bottom. Note that
the zero check or adjustment can only be made with the high
and low pressure taps both open to atmosphere.

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360 U. S.A.

OPERATION

ositive Pressure: Connect tubing from source of pressure to

P

either of the two high pressure ports. Plug the port not used.
Vent one or both low pressure ports to atmosphere.

egative Pressure: Connect tubing from source of vacuum or

N

negative pressure to either of the two low pressure ports. Plug
the port not used. Vent one or both high pressure ports to

tmosphere.

a
Differential Pressure: Connect tubing from the greater of two

ressure sources to either high pressure port and the lower to

p
either low pressure port. Plug both unused ports.
When one side of the gage is vented in dirty, dusty atmosphere,

e suggest an A-331 Filter Vent Plug be installed in the open

w
port to keep inside of gage clean.

. For portable use of temporary installation use 1/8” pipe

A

thread to rubber tubing adapter and connect to source of pres­sure with flexible rubber or vinyl tubing.

. For permanent installation, 1/4” O.D., or larger, copper or alu-

B

minum tubing is recommended.

AINTENANCE

M

No lubrication or periodic servicing is required. Keep case exte­rior and cover clean. Occasionally disconnect pressure lines to
vent both sides of gage to atmosphere and re-zero. Optional
vent valves should be used in permanent installations. The
Series 2000 is not field serviceable and should be returned if
repair is needed (field repair should not be attempted and may
void warranty). Be sure to include a brief description of the prob­lem plus any relevant application notes. Contact customer serv­ice to receive a return goods authorization number before ship­ping.

WARNING

Attempted field repair may void your warranty. Recalibration or
repair by the user is not recommended.

TROUBLE SHOOTING TIPS
Gage won’t indicate or is sluggish.

1. Duplicate pressure port not plugged.

2. Diaphragm ruptured due to overpressure.

3. Fittings or sensing lines blocked, pinched,
or leaking.

4. Cover loose or “O”ring damaged, missing.

5. Pressure sensor, (static tips, Pitot tube,
etc.) improperly located.

6. Ambient temperature too low. For
operation below 20°F (-7°C), order gage
with low temperature, (LT) option.

Phone: [phone] www.dwyer-inst.com
Fax: [phone] e-mail: [e-mail]