Dwyer Magnehelic User Manual

Bulletin A-27

Magnehelic® Differential Pressure Gage

	025 (.64) SPACE CREATED BY 3		(3) 6-32 X 3/16 (4.76) DEEP HOLES
	SPACER PADS WHEN SURFACE	RUBBER PRESSURE RELIEF	EQUALLY SPACED ON A Ø4-1/8
	MOUNTED. DO NOT OBSTRUCT.	PLUG WILL UNSEAT ITSELF	(104.78) BOLT CIRCLE FOR
	PROVIDES PATH FOR RELIEF OF	WHEN GAGE IS	PANEL MOUNTING
	OVERPRESSURE.	17/32 OVERPRESSURIZED	1/8 FEMALE NPT
		(13.49)	HIGH PRESSURE
			CONNECTION
		1/8 FEMALE
		NPT HIGH
		PRESSURE
	1-1/4	CONNECTION	1-3/4
	(31.75)
		1/8 FEMALE	(44.45)
		NPT LOW
	Ø4-1/2	PRESSURE
	(114.3)	CONNECTION	1/2
			(12.70)

Ø4-3/4	15/32			11/16	1/8 FEMALE NPT
	(11.91)				LOW PRESSURE
(120.65)			7/16	(17.46)
	1-11/16				CONNECTION
			(11.11)
	(42.86)	17/32
			ø4-3/4 (120.65) PANEL CUTOUT
		(13.49)			1/8 FEMALE NPT
					HIGH PRESSURE
					CONNECTION
			ø5
	1-1/4		(127)		1-3/4
	(31.75)				(44.45)
	ø4-1/2		ø4-47/64
			(120.27)
	(114.3)				1/2
					(12.70)

ø5-1/2

15/32

11/16

1/8 FEMALE

(139.70)

(11.91)

3/16

NPT LOW

MOUNTING RING

2-17/32

(17.46)

PRESSURE

(64.29)

(4.76)

CONNECTION

*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.

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.

OVERPRESSURE PROTECTION: Standard Magnehelic® Differential Pressure Gages 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 pressure reaches approximately 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.

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). *Low 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.

	DWYER INSTRUMENTS, INC.	Phone: [phone]	www.dwyer-inst.com
		Fax: [phone]	e-mail: [e-mail]
	P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360 U.S.A.

INSTALLATION

Select a location free from excessive vibration and where the ambient temperature will not exceed 140°F (60°C). Also, avoid direct sunlight which accelerates discoloration of the clear plastic cover. Sensing lines may be run any necessary distance. Long tubing lengths will not affect accuracy but will increase 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® Differential Pressure Gages are calibrated with the diaphragm vertical and should be used in that position for maximum accuracy. If gages are to be used in other than vertical position, this should be specified on the order. Many higher range gages will perform within tolerance in 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 vertical position only.

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 4- 3/4” 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.

OPERATION

Positive Pressure: Connect tubing from source of pressure to either of the two high pressure ports. Plug the port not used. Vent one or both low pressure ports to atmosphere.

Negative Pressure: Connect tubing from source of vacuum or negative pressure to either of the two low pressure ports. Plug the port not used. Vent one or both high pressure ports to atmosphere.

Differential Pressure: Connect tubing from the greater of two pressure sources to either high pressure port and the lower to either low pressure port. Plug both unused ports.

When one side of the gage is vented in dirty, dusty atmosphere, we suggest an A-331 Filter Vent Plug be installed in the open port to keep inside of gage clean.

A.For portable use of temporary installation use 1/8” pipe thread to rubber tubing adapter and connect to source of pressure with flexible rubber or vinyl tubing.

B.For permanent installation, 1/4” O.D., or larger, copper or aluminum tubing is recommended.

MAINTENANCE

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.

	DWYER INSTRUMENTS, INC.	Phone: [phone]	www.dwyer-inst.com
		Fax: [phone]	e-mail: [e-mail]
	P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360 U.S.A.