Ashcroft 1259SD4.5, 1259SL4.5, 1279SS4.5 Installation and Maintenance Instructions

SELECTION

Pressure Ranges

– Select a gauge with a full scale pressure
range of approximately twice the normal operating pressure.
The maximum operating pressure should not exceed approxi­mately 75% of the full scale range. Failure to select a gauge
range within this criteria may ultimately result in fatigue failure
of the Bourdon tube component.

INSTALLATION

Always use a wrench on the flats of the gauge socket to screw
the gauge in place. When a fitting is being screwed to the
gauge, hold a wrench on the socket flats instead of twisting
against the gauge socket screws which are intended to hold
the gauge mechanism in the case.

When gauges are mounted on the wall or panel, make sure
they are connected free from piping strains. Also see that the
mounting surface is flat, or insert washers under the flange of
the gauge case to obtain three-point suspension. Preferably,
the last length of piping leading up to the gauge should be flex­ible tubing. This will ensure that the gauge is free from strain.

Install gauges where they will be free from the effects of
mechanical vibrations as this will wear out any gauge quickly.
Tr y to mount the gauge on a wall nearby and connect the
gauge to the machine which vibrates badly by means of
flexible line assembly.

Protect gauges from frequent pressure pulsations by using
liquid-filled or Duragauge Plus

®

with a throttle screw in the
socket of the gauge, needle valves, pulsation dampeners or
pressure snubbers.

When any gauge is used for steam pressures, a siphon filled
with water must be installed between the gauge and the line.
When the system is subject to occasional vacuum, provide a
leg of piping which cannot be emptied by the vacuum effect. A
drain cock or plug should be installed at the bottom of this leg
to enable occasional cleaning out of the sediment. The head
effect of this piping leg should be compensated for by resetting
the pointer of the gauge.

OPERATING CONDITIONS

The operating conditions to which a gauge will be subjected
must be considered. If the gauge will be subjected to severe
vibration or pressure pulsations, liquid filling the gauge may be
necessary to obtain normal product life.Other than discolora­tion of the dial and hardening of the gasketing that will occur
as ambient temperatures exceed 150°F, metal case Dura­gauges (that are not liquid filled) can withstand continuous
ambient temperatures as high as 250°F. Liquid filled gauges
can withstand 200°F but glycerin fill and acrylic window will tend
to yellow. Accuracy will be affected by approximately 1.5% per
100°F. Gauges with welded joints will withstand 750°F (450°F
with silver brazed joints) for short times without rupture,
although other parts of the gauge will be destroyed and cali­bration will be lost. For temperature limits on other gauges see
the appropriate bulletin.

PROPER USE

Apply pressure slowly. do not open gauge cock or valve too
quickly – this imparts a severe strain on the Bourdon tube
which may rupture it, or result in shortened life. When the
service itself is subject to sudden pressure applications, use
a needle valve or the Ashcroft Gauge Saver.

Avoid overpressure. See that the apparatus is provided with a
relief valve and that the range of the gauge is higher than the
set pressure of the relief valve.

Sudden pressure release has the same detrimental effect and
should be compensated for in the same manner as for the
pressure applications mentioned above. On hydraulic presses,
Catalog Number 1056 or 1009DH Gauges with slotted link
should be specified. See Special Service Bulletin SG-1.

MAINTENANCE

Replace broken glasses and thus keep dirt out of the working
bearings and teeth of the movement mechanism.

Never oil gauge movements or linkages except with high grade
instrument oil. Regular oil attracts dirt and becomes gummy,
thus causing the gauge to act sluggish and inaccurate.

Installation and Maintenance Instructions for

ASHCROFT®Pressure Gauges, Gauge Parts
and Ring Designs, Engineering Data

© Dresser, Inc., Dresser Instrument, 250 E. Main St., Stratford, CT 06614-5145, 203-378-8281, 203-385-0499 Fax, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M008-10031-10/00 (250-1997B) GBE

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CORRECTION IN % 0F PRESSURE SCALE

020406080100120 140 160 180 200 220 240 260 280 300 320 340 360 380 400

TEMPERATURE IN °F

<– 75° ROOM TEMP.WHEN CALIBRATED

HEAT AFFECTS GAUGE ACCURACY

Approximate error or change in calibration of a Bourdon

tube type pressure gauge caused by changes in temperature.

Example: Gauge working at 500 psi pressure at 280°F. temperature

would have a –3% correction and would read 3% or 15 psi fast.

The drawing below shows a typical solid front, lower connec­tion Duragauge with all of the parts designated by their stan­dard names. The use of these names will facilitate the
ordering of parts and eliminate any misunderstanding in
describing gauge construction.

When ordering parts – specify as much of the following data
as possible:

Size (Dial Diameter); Case Material (Stainless

Steel, Polypropylene, Aluminum or Phenol);

Case Type (Open

Front or Solid Front);

Ring Design (Slip, Internal Threaded,

External Threaded, Bayonet, Snap or Hinged);

Connection

Location

(Lower or Back); Connection Size (1⁄

4˝ or

1

⁄

2˝);

Bourdon Tube/Socket (Material Indicated on Dial); Dial Range
(Specify type number if possible; otherwise, mention whether
parts are for Duragauge, General Service Gauge, Special
Application Gauge, Receiver Gauge or Test Gauge.)

Installation and Maintenance Instructions for

ASHCROFT®Pressure Gauges, Gauge Parts
and Ring Designs, Engineering Data

1. Preliminary Gauge Calibration Setting –

(SOLID FRONT GAUGE SHOWN)

2. Calibration –

a. At zero pressure (or at full vacuum for compound

or vacuum gauges), assemble pointer to pinion
shaft in the horizontal position.

b. Apply pressure equal to full range and adjust the

slide in the segment slot until the pointer has
rotated 270° (vertical position).

c. Reduce pressure to zero and reset pointer, if nec-

essary, to horizontal position. If pointer adjust­ment was required, repeat step (b) above.

d. Apply pressure equal to mid-scale and drive

pointer firmly onto pinion.

e. Recheck calibration at the lower and upper ends

of the scale.

3. Linearity Adjustment –Although the procedure out­lined above should produce a correctly calibrated
gauge, linearity adjustment may be required. If the
pointer reads correctly at the bottom of the scale
and low at the top of the scale, rotate the movement
to increase the angle between the link and the seg­ment. If the pointer reads high, rotate the movement
in the opposite direction.

1279 case used to
clearly illustrate the
gauge components.

Note: The socket, tube and tip assembly is furnished as one

integral unit. The movement is supplied complete.

Rear Cover

Phenolic Case

Micrometer
Poin ter

Gasket

Window

Threaded Ring

Dial

Gasket

O-Ring

Bourdon Tube System

Rotary
Geared
Movement

1 LOOSEN MOUNTING

SCREWS SLIGHTLY

2 ROTATE MOV’T

TO DISENGAGE
SEGMENT FROM
PINION. WIND
HAIRSPRING,
RE-ENGAGE
SEGMENT

SEGMENT SCREW

3 TIGHTEN MOV’T

SCREWS

LINK SCREW

TYPICAL CONSTRUCTION DETAILS

CALIBRATION PROCEDURE

© Dresser, Inc., Dresser Instrument, 250 E. Main St., Stratford, CT 06614-5145, 203-378-8281, 203-385-0499 Fax, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M008-10031-10/00 (250-1997B) GBE