Dwyer Instruments 25, 27, MM-80, M-700 Pa, 28 Instructions And Operation

Dwyer Mark II Manometers come in a vari­ety of ranges. Make sure the oil being used
is for the correct manometer.

Mark II #25, 27, MM-80 and M-700 Pa use
red gage oil (specific gravity 0.826).

Mark II #26, 28 and MM180 use blue gage
oil (specific gravity 1.9).

If additional oil is required, call or fax nearest
Dwyer office listed at bottom of page.

INSTALLATION

Position manometer on a vertical surface.
Drill two 1/8˝ or 9/64˝ holes on a vertical line
315/16˝ apart. Loosely mount manometer
with self-tapping screws provided. Adjust
gage until level bubble is centered in level
vial, then secure the manometer tightly.

For portable use, order optional A-612
Portable Stand.

FILLING

Turn the zero set knob counterclockwise until
it stops, then turn clockwise 3 full turns. This
puts zero in approximately the middle of the
travel adjustment in either direction. Remove
the fill plug and fill with gage fluid until fluid
reaches zero on scale. Minor adjustments
can be made to adjust zero by adjusting zero
knob. Replace fill plug. If gage is overfilled,
remove excess by inserting pipe cleaner
through the fill port to blot up excess oil.

MAINTENANCE

Check oil level regularly and adjust zero with
zero adjust knob. Be sure tubing connec­tions are disconnected and gage is open to
atmosphere before adjusting zero.

Clean with mild soap and water. Avoid any
cleaning fluids which may result in damaging
the gage.

ACCESSORIES

Each Mark II manometer includes two tubing
connectors for 1/8˝ pipe or sheet metal
ducts, two mounting screws, 3/4 oz. bottle
of indicating fluid, red and green pointer
flags, 8´ of double column tubing and instruc­tions.

Mark II Series Molded Plastic Manometers

Specifications - Instructions and Operation

Bulletin D-58

DWYER INSTRUMENTS, INC.

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

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

Mark II Model No. 25

inclined-vertical manometer,

(shown with optional A-612 portable stand)

FLOW

PsPt

PITOT TUBE
(SECTION
ENLARGED
TO SHOW
DETAIL)

AIR FILTER GAGE

Mount gage within 3 ft. of filter bank. Install
tubing adapters on each side of filter. Run
tubing from clean side of filter to positive
pressure side of gage (left fitting). Run
downstream side to low pressure side of
gage (right fitting). Install green and red
arrows adjacent to indicating tube to indi­cate filter condition.

AIR VELOCITY METER

A pitot tube should be used for air velocity
readings. Install the pitot tube and gage
carefully to ensure accuracy. Select a loca­tion for the pitot tube with al least four diam­eters of smooth straight sections of duct
both upstream and downstream. Install
pitot tube in the center of duct with tip
directed into air stream. Connect the right
angle (leg parallel to tip) to negative (right fit­ting) and straight pitot tube connection to
positive (left connection) of gage. The veloc­ity reading shown on the gage is the center
or maximum velocity. For average velocity
across the full area, multiply by a factor of

0.9.

No’s. 27 and 28 require pitot tube at addi­tional cost. See Bulletin F-41-F.

The velocity indicated is for dry air at 70°F,

29.9˝ barometric pressure and a resulting
density of 0.075 lb/ft

3

. For variation from
these standard conditions, corrections may
be based upon the following data.

AIR VELOCITY CALCULATIONS:

Air Velocity = 1096.2

where Pv = velocity pressure in inches of

water

D = Air density in lb/ft

3

Air Density = 1.325 x

where P

B = Barometric Pressure in inches

of mercury

T = Absolute Temperature (indicat-

ed temperature °F plus 460)

Flow in cu. ft. per min. = Duct area in square
feet x air velocity in ft. per min.

PITOT TUBE SENSES TOTAL AND STATIC PRESSURES. MANOMETER
MEASURES VELOCITY PRESSURE-(DIFFERENCE BETWEEN TOTAL AND
STATIC PRESSURES).

PB

T

Pv

D

√

APPLICATIONS MARK II MANOMETER

DWYER INSTRUMENTS, INC.

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

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

©Copyright 2004 Dwyer Instruments, Inc.

FR# 67-440215-00 Rev. 11

Printed in U.S.A. 1/04