Ashcroft A4A - Precision Dial Pressure Gauge - Manual (Page 2)

SAFETY PRECAUTIONS
Pressure gauge selection should be done in accordance with
recognized industry codes and safety practices to avoid the possi-
bility of misuse or misapplication which could result in personal in-
jury or damage to property. ASME B40.1 should be consulted by
those responsible for gauge selection and installation.
UNPACKING THE GAUGE
All Ashcroft
® A4A precision pressure gauges are shipped with a
piece of foam between the glass window and the pointer. This
foam secures and protects the movement from damage during
shipment. THIS FOAM MUST BE REMOVED PRIOR TO INSTAL-
LATION AND OPERATION OF THE GAUGE
To remove foam, first remove the zero adjust lock screw located
beneath the dial face. This is the screw located in the center of the
zero adjust knob. With this screw removed lift the bottom of the
bezel away from the gauge. Then lift the bezel up and off the align-
ment pin at the top of the gauge. With bezel assembly off, remove
pad. Reinstall bezel through reverse procedure. Be certain to align
the teeth for zero adjust mechanism prior to replacing dial adjust
lock screw.
GAUGE INSTALLATION
Unless otherwise specified at the time of order, Ashcroft
® A4A
gauges are calibrated in the upright or vertical position. Gauges
should always be mounted in the same position as they were cali-
brated to eliminate positional errors. Special calibration is required
for gauges to be mounted in any position other than vertical. Each
gauge has three holes for
1 ⁄
4
˝ screws spaced 120° apart on the
back of the bezel to facilitate panel mounting. Factory installed wall
mounting brackets are available as an option.
GAUGE OPERATION
Ashcroft
® A4A gauges are precision instruments. Certain proce-
dures and precautions are recommended in order to maximize
their performance. These are:
For liquid systems the trapped air should be purged from the sys-
tem using the bleeder cap on the end of the Bourdon tube. When
opening or closing the bleeder cap firmly hold the free end of the
Bourdon tube to protect the movement, Bourdon tube or linkages
from damage due to stress. To bleed air from system open bleeder
cap slightly and carefully apply pressure to the gauge to force fluid
through the cap. Allow the fluid to flow for several seconds to
purge trapped gas from the tube. Direct the fluid away from the
gauge to protect the movement from becoming contaminated.
Once this is done tighten cap.
It is good practice to pressurize the gauge to full scale for several
minutes prior to use. The pressure should then be removed and
the dial zeroed, if necessary. The dial adjuster is located at the
bottom of the dial. The smaller central knob is an adjustment lock
and the larger, outer knob is used for zero adjustment.
PRESSURE MEDIA
Care should be taken to assure that the process pressure media
are compatible with the gauge wetted materials. Hydrogen use
should be limited to gauges equipped with Beryllium Copper
Bourdon tubes. Consult factory for questions regarding media
compatibility.
Unless specially cleaned, the gauge wetted surfaces may include
cleaning solvent or hydrocarbon (oil) residue from the manufactur-
ing and calibration processes. These substances may be incom-
patible with specific installations or process media. Consult factory
for special factory cleaning options. DO NOT USE GAUGES ON
OXYGEN SERVICE UNLESS GAUGE HAS BEEN CLEANED
AND CERTIFIED FOR OXYGEN USE. Failure to comply with
these recommendations could result in damage to the gauge and
personal injury.
GAUGE ACCURACY & CALIBRATION
Ashcroft
® A4A precision pressure gauges are calibrated at the fac-
tory to ±0.1% F.S. accuracy and certified, traceable to the N.I.S.T.,
USA. (Note: For gauges equipped with 316 SS Bourdon tubes,
hysteresis may exceed 0.1% and is not guaranteed). Primary cali-
bration adjustments on the movement are sealed with liquid metal
and should not be altered. Tampering with these calibration points
may degrade the accuracy of the gauge and will void the warranty.
Under normal operation, a one-year calibration cycle is recom-
mended for your Ashcroft
® A4A precision pressure gauge(s).
Recertification services are available at the factory.
OPTIONAL FEATURES
• Bimetallic Thermal Compensation – is recommended for all
gauges that are to be installed in non-temperature controlled en-
vironments. This option maintains the 0.1% of span accuracy
over a range of –25 to +125°F. Gauges not equipped with this op-
tion may incur an additional 0.1% error per 5°F deviation outside
the operating temperature window of 68-72°F.