Meriam Process Technologies www.meriam.com ph: 800.817.7849 fax: 216.281.0228
The Meriam Model 1120 Differential Pressure Unit is a proven and reliable
sensing element used in all Meriam Bellows Gauges. It is available in ranges
as low as 0-30” w.c. or as high as 0-500 PSI. The light weight and compact
differential pressure unit incorporates a rupture-proof and leak-proof bellows
plus other features that ensure ruggedness and reliability. This basic unit is
suitable for activating indicators, recorders, transmitters, switches, and
controllers and is available as a separate assembly for that purpose.
The 1120 consists of a high and a low pressure bellows connected to each
side of a center plate. The bellows are enclosed in end housings which in turn
are bolted to the center plate. The interior of the bellows and center plate is
completely filled with a clean, low freezing point, non-corrosive fill fluid. As
differential pressure is applied, this fill fluid moves between the bellows
through a field adjustable dampening valve in the center plate. Other external
dampening devices are not required for measurements of pulsating differential
pressure. Also, the Meriam 1120 incorporates a special design which
completely isolates the process fluid from the center plate.
When differential pressure is applied to the high and low pressure connections,
the high pressure bellows contracts, forcing fluid through the center plate into
the low pressure bellows which expands. The resulting linear motion of the low
pressure bellows is converted to a 6° rotary motion of the output shaft through
temperature compensating linkage. Over-range protection up to the pressure
rating of the housing is provided by two fluid shut off valves located on this
linkage. The output shaft is part of a low friction, “O” ring sealed shaft and
bearing assembly which carries the rotary motion to the external area of the
bellows unit and into the instrument case.
56
Bellows Gauges
for Differential Pressure,
Flow and Level
1226X Explosion-Proof Switch
Meriam’s 1226X Explosion-Proof
Indicating Switch is CSA and U.L. listed,
meeting N.E.C. requirements for Class I,
Division I, Group D hazardous environ-
ments. Class I, Group D atmospheres
include gasoline, hexane, naphtha,
benzine, butane, propane, alcohol,
acetone, benzol, lacquer, solvent vapors,
and natural gas.
The explosion-proof housing is made from a strong, light-weight
aluminum alloy that is both non-rusting and non-sparking. A large
glass window provides full viewing of the 6” indicator. Front of
board, panel or pipe mounting can be supplied.
1120 Series Indicators
Indicator models 1123, 1124 and 1126 have 3”, 4½” and 6” dials
respectively. A variety of scales for differential pressure, flow and
level can be supplied. The 1120 Series is widely used in industrial
process plants, power plants, pollution control facilities and in the
cryogenic gas industry.
1220 Series Indicating Switches
The Series 1220 Differential Pressure Indicating Switches are used
for on-off control or alarm. They also indicate flow, liquid level or
other process variables. These units are furnished with one or two
SPDT type switches with actuation set points easily adjustable over
most of the range of the instrument. The calibrated travel of the
pointer is 270° which gives good differential pressure indication
and switch resolution. Dials can be supplied with linear scales for
differential pressure, square root scales for flow, or custom scales
for level. The Series 1220 Switches are used extensively in power
plants, compressor stations and cryogenic applications.
1126P-2 Portable Indicator
The 1126P-2 is designed for por-
table applications. Typical exam-
ples are periodic measurements
of the pressure drop across
filters, balancing of flow rates in
heating and cooling systems and
checking of back flow prevention
devices. Meriam’s 1126P-2 con-
sists of an 1126 D/P Indicator with 3-valve manifold and piping, 2
hoses and quick disconnects. Each instrument system is assembled
as a complete package with all the accessories mounted in a rug-
ged, light weight case. When used as a flow measuring device, the
instrument normally comes with a 0-100% square root scale. With
all flow elements designed for the same differential, multiplying the
scale reading by the primary element’s full flow design value gives
readings directly in flow units. Scales in flow units, inches of H
2
0,
PSI and metric units are also available.
(4 pages)
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