Ashcroft 1305DMh-150 Kurulum ve Bakım Kılavuzu - Sayfa 12

Test Ekipmanları Ashcroft 1305DMh-150 için çevrimiçi göz atın veya pdf Kurulum ve Bakım Kılavuzu indirin. Ashcroft 1305DMh-150 20 sayfaları. Deadweight tester and portable pump

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a 50 degree F (28 degree C) change in temperature. The

pressure will, therefore be less than indicated at high

temperatures.

4.4 Mass, Height, and Buoyancy

The density of air at room temperature and sea level

pressure is about 0.0012 grams/c.c., and the mass of the

piston assembly and weights under these conditions will

be reduced by about one part in 7,000 or .014%. When

the submerged part of the piston has a uniform cross

section, as with the 1305D Deadweight Tester, a buoyancy

correction is not necessary. In other designs, the piston is

sometimes enlarged to provide a stop for its upward mo-

tion or for increased strength. If these enlargements are

submerged in liquid, a buoyancy correction is necessary.

4.5 Absence of Friction

By rotating the weights and piston, friction effects are

greatly reduced.

4.6 Head of Transmitting Fluid

Oftentimes, the gauge being tested, or the point at which

pressure is being measured, is not at the same level as

the lower end of the piston. A correction, therefore, should

be made for the pressure distance between these points;

the height is considered positive when the gauge is above

the piston. When oil is used in the gauge tester, the cor-

rection will be approximately 0.03 psi (.2 kPa) for each

inch (2.54 cm) difference in level.

4.7 Method of Operation

It is important that the piston be kept floating in mid-posi-

tion, either spinning or oscillating.

4.8 Levelness

The piston assembly should be vertical to within ±1 de-

gree. A 3 degree tilt to piston axis may cause a .13% of

1% error. The deadweight tester is manufactured and

tested to 1/10th of 1% accuracy, to this degree of level-

ness. A tilt piston/cylinder axis causes excessive friction,

due to side loading of the piston against the cylinder.

4.9 Cleanliness

The weights have been manufactured and tested to a

precision of 0.05%. A buildup of dirt and grease may

cause the weight value to exceed its original tolerance and

produce erroneous pressure readings.

Periodically clean the weights to assure proper

performance.

5.0 MAINTENANCE INSTRUCTION

5.1 General Maintenance

The Deadweight tester and test pump are designed to

serve as precise pressure measuring standards. They are

precision built units and should be cared for in the same

manner as other sensitive laboratory equipment. General

maintenance is limited to cleaning and replacement of

O-ring packings, which can be done with tools supplied

with the equipment and requires only limited disassembly

of the gauge tester.

The piston supporting the weight platform has been man-

ufactured to very close tolerances. It has an area accuracy

of 1/20th of 1% and a weight accuracy of 1/20th of 1%.

The deadweights have been certified traceable to N.I.S.T.

with the accuracy of the finished weights better than

1/20th of 1%. To maintain deadweight tester accuracy,

handle the weights with care and keep the piston and cyl-

inder in clean condition.

The tester should be flushed with a solvent occasionally,

preferably every six months, so that operating fluid is al-

ways clean. This will prolong component life, and provide

protection against possible sticky action between the

piston and cylinder. After cleaning, always lubricate parts

before assembly.

If a deadweight tester is not used for long periods of time,

or if a piston and cylinder assembly is being replaced, the

piston should be removed from the cylinder and coated

with the hydraulic fluid, so that it never operates in a dry

state. When removing or replacing the piston, it should be

rotated back and forth.

Should a piston or cylinder wear excessively, the tester will

leak oil at a high rate, and will not be operable. A new pis-

ton and cylinder assembly should be installed.

Piston wear will result from improper or contaminated

lubrication, excessive dirt, or from several years of

continuous use.

5.2 Cleaning

Both the Tester and Test Pump should be cleaned thor-

oughly whenever the operating fluid is seriously contam-

inated with dirt, grit, or chemicals. A good practice is to

clean the test unit prior to anticipated periods when the

unit will not be in use.

5.3 To Disassemble for Cleaning

(See Figure 2-1, Figure 2-2 and Figure 5-1)

It is necessary to disassemble only those components

which come in contact with the operating fluid. Complete

disassembly is rarely necessary.

a. Remove pipe extension assembly (58) or piston and

cylinder assembly(67) and (79).

b. Then remove lower or back connection pipe assembly

(64, 66).

5.4 Removing Pump Handle and Piston

a. Remove four retaining rings (8).

b. Slide out two clevis pins (9).

c. Remove clevis (10).

d. Lift hand assembly (4) with piston pin (7) piston (20)

O-ring packing (12, 19) and back-up ring (11)

attached to it, out of piston sleeve (6).

e. Remove back-up washers (18, 11) and O-ring pack-

ing

(12, 19).

f. Unscrew piston (20)

g. Remove piston sleeve (6) and O-ring packing (45, 16)

and back-up washers (46, 17)

5.5 Removing Reservoir and Fill Tube

a. Unscrew filler plug (35) from reservoir.

b. Remove gasket (36).

c. Remove reservoir (5) by removing three screws (24).

d. Twist reservoir to free O-ring packing (21) seat.

e. Remove O-ring packing (21) from body (2).

f. Remove fill tube assembly (23) and O-ring packing (27).

g. Remove plug (22).

5.6 Removing Shuttle Valve, Shuttle Valve Plug

and Check Valve

a. Remove set screw (33) and spring (32).

b. Slide shuttle valve piston (31) out of body (2). Operate

back and forth as necessary to dislodge pin (31)

engagement.

c. Remove shuttle pin (31) by pushing it into the shuttle

valve piston cavity using a plastic shaft less than

inch (3mm) in diameter.

d. Unscrew shuttle valve plug (43) and remove O-ring

packing (27).

e. Remove check valve spring (14) and check valve (44).

f. Remove O-ring packing (15) from check valve (44).

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