Ashcroft 1327D - Pressure Gauge Comparator User Manual
Page 8
One Weight Box:
10 inch (25 cm) width; 10 inch (25 cm); 10 inch (25 cm)
height
Storage space dimensions are larger than actual size of
tester carrying case and deadweight carrying case by
approximately _ inch, (1.3 cm), in order to facilitate ease of
handling in storage.
Note: For catalog numbers 1305D, DH-100, 1305DM,
DMH-150, 1305DB, DBH-700 and 1305DA, DAH-
700 allow storage space for two weight boxes.
3.3 Operation 1305D
3.3.1 Piston and Cylinder Selection
The 1305D Tester is a dual range device in that most
-models utilize two interchangeable piston and cylinder
assemblies for measurement of pressure throughout the
entire range. Each piston and cylinder assembly has a
minimum and maximum operating range. First, determine
what pressure points need to be measured and select the
appropriate assembly. The pressure range of the assem-
blies is shown in Table 2-1. When priming the pump the
high pressure piston and cylinder assembly should be used.
3.3.2 Priming the Pump
The offset pipe (64 or 66 Figure 2-1) should already be
secured in place and the reservoir should contain the
operating fluid (refer to Installation Section 3.2).
Close the release valve (37) by turning it clockwise and
open the air vent by loosening the filler plug (35) a few
turns. The shuttle valve (51) should be pulled outward
from the pump body, the end of the knob approximately
even with the edge of drip pan. In this position the high
volume displacement mode is selected and the pump is
self-priming. Operate the pump handle several times using
full strokes, until you see fluid appear in the outer pump
body outlet.
The cone seat (82) is located in the base of the outer-
pump body outlet and serves as the sealing surface
between the bottom of the piston and cylinder assembly
and the pump body. Confirm the coned end of the seat is
facing up and the cylindrical end of it is facing down.
Thread the high pressure piston and cylinder assembly
(79) or (67) into the outer body outlet as shown, using the
wrenches provided.
Operate the pump handle a few more times until fluid is
observed at the end of the offset pipe. Connect the gauge
or other device to be tested to the offset pipe. For purpos-
es of priming, the device must be designed to withstand
the full operating pressure of 10,000 psi (70,000kPa). If a
lower range device must be used, extreme care must be
exercised to avoid overpressuring its pressure element.
Seal the connection to the device by tightening nut adapter
(62) and adapter (60) until the coned end of the pipe is
forced into its inlet. If necessary, rotate the device for view-
ing by loosening nut adapter (62), set it to the proper posi-
tion and retighten nut adapter.
Again, operate the pump handle a few more times. After a
few strokes positive pressure will develop and the pump
handle will begin to resist pumping action. Raise the pump
handle to its uppermost travel position. Loosen the bleed
screw (30) a half turn counter clockwise and slowly oper-
ate the pump handle through a downward stroke until fluid
flows steadily from the bleed vent. Close the bleed screw
just prior to completing the downward handle motion.
Repeat this action until no air bubbles are observed in the
fluid flow. (Note – the bleed screw must be closed when
the handle is being raised). Push the shuttle valve in
towards the pump body and continue pumping to the
desired test pressure. Open the release valve (37) to vent
the pressure. To check operation pull the shuttle valve out-
ward, close the release valve and operate the pump han-
dle several times. When handle resistance is felt, push the
shuttle valve inward and continue pumping within the
range of the test device.
Entrapped air will prevent the pump from operating in the
high pressure valve position or cause it to achieve only
partial pressure. Repeat the above bleed procedure as
necessary to assure all air is removed. Once air is
removed the pump will continue to operate without further
attention providing the reservoir level is maintained.
3.3.3 Weights
The weight set consists of a selection of various masses
that will produce desired pressure increments when oper-
ated with the appropriate piston and cylinder assembly.
Each weight is stamped with two pressure values. When
applied to the high pressure piston and cylinder assembly
the equivalent pressure value is indicated next to the letter
“H”. Conversely, when applied to the low pressure piston
and cylinder assembly the equivalent pressure value is
indicated next to the letter “L”. The piston and piston plat-
form also contribute to the total mass. Their equivalent
pressure value is stamped on the top of the platform.
During normal operation, selected weights are added to
the plate and piston assembly to equal the desired pres-
sure value.
3.3.4 Levelness
The deadweight tester must be level to function properly.
The unit may be leveled by placing a bubble type level on
top of the piston plate and revolving it slowly. Shims may
be used between drip pan and bench to level the piston
plate. The unit is level when the position of the bubble
does not change within the glass as it is rotated on top of
the piston assembly.
3.3.5 Making the Test
Add weight to the piston plate to give desired calibrating
pressure.
Pull the shuttle valve (51) outward from the body and close
the pressure release valve (37). Operate the pump handle
until the fluid pressure forces the piston to raise the
weights. When pumping, the weights should be rotated
slowly to decrease cylinder wall friction. If pump handle
resistance is difficult and the weights have not risen, push
the shuttle valve inward and continue pumping. With the
shuttle valve pushed in, the fluid displacement of each
stroke is reduced, thereby requiring less effort to continue
pumping.
The piston assembly has a maximum lift of
3
⁄
4
inch (1.9
cm). It is recommended that readings be taken at mid-
point, or
3
⁄
8
inch (1 cm) lift. Small adjustments to the piston
lift can be made with the pump handle or the displacement
valve (41).
Improper readings will result if the piston plate is so low
that it rests on the bushing, or so high that the internal
stop on the piston assembly is touching the underside of
the bushing.
Spin the weights by hand and take readings only when the
weights are spinning. Speed of rotation is unimportant,
although a slow speed is more convenient and
recommended.
To release pressure, turn valve (37) counterclockwise slowly.