Ashcroft 1305DMH-20 Manuale di installazione e manutenzione - Pagina 4

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The deadweight tester consists of a two stage hydraulic

pump containing a manifold which is pressurized during

operation. Integral to the pump is a shuttle valve that

allows the operator to regulate the speed of pressure in-

crease. One connection to the manifold includes a cylinder

and a free-floating precision machined piston with a plate

for holding calibrated weights. A second connection to the

manifold accommodates a gauge or other pressure mea-

suring device to be calibrated or checked. Incorporated

into the manifold is a hand operated displacement valve

that allows small adjustments in fluid volume to be made

without further operation of the pump handle or release

valve.

The tester is dual range having two interchangeable piston

and cylinder assemblies. One is a low pressure piston

having an effective area five times larger than that of the

high pressure piston. The low pressure piston is used for

making measurements below 2,000 psi (14,000 kPa). The

high pressure piston, with an area 1/5 that of the low pres-

sure piston, is used to measure pressure through 10,000

psi (70,000 kPa). The weight masses are pre-measured

and identified with the pressure values they produce when

operated with the interchangeable piston and cylinder

assemblies.

Pressure calibration points produced by the deadweight

tester are accurate to within ± 0.1% of the reading certified

traceable to the N.I.S.T. The tester provides consistent, re-

peatable accuracy, maintaining its pressure for an appre-

ciable length of time regardless of temperature changes,

slight leaks in the pressure system, or changes in volume

of the pressurized system due to movement of a Bourdon

tube or other device.

A hand jack set, three wrenches, spare O-rings, and a

special adapter for making connections to pressure outlets

that do not accommodate cone pipe seating, are included

with each unit.

All deadweight testers are supplied with lower and back

connection offset pipe assemblies, with pipe adapters for

⁄

NPT or

⁄

NPT connections.

An all metal, double-latched, top handle carrying case is

supplied with the complete tester for all fittings and attach-

ments. Deadweights are packed in metal, double-latched

storage-carrying boxes.

2.1.2 Theory of Operation – 1305D

The theory behind a deadweight tester can be expressed

as simply as force acting upon a known area. Pressure

produced by the pump is distributed by the manifold, to

the base of a precision machined piston and to a device

being calibrated or checked. Pre-selected weights loaded

onto the piston platform are acted upon by gravity and

develop a force that is to be equally opposed by the fluid

pressure from the pump. When equilibrium is achieved,

the pressure value is known, it being a direct result of the

sum of the forces from the weights, piston platform and

the piston divided by the effective area of the piston and

cylinder assembly.

With the 1305D two piston and cylinder assemblies are

supplied, one having an effective area 1/5 of the other.

When using the smaller piston and cylinder assembly, five

times more pressure is required to oppose the force of a

constant mass being acted upon by gravity. For this rea-

son the masses supplied with the tester are stamped with

two pressure values, the value being contingent on the

effective area of the piston and cylinder assembly selected.

2.1.3 Specifications – 1305D

Accuracy: Combined tolerance of weights and piston and

cylinder assemblies within 0.1% of reading. Weight toler-

ance within 0.05% of mass. Piston and cylinder is within

0.05% of rated mean effective area.

Deadweight: Non-magnetic die cast zinc alloy. Total

weight to produce maximum pressure of 10,000 psi

(70,000kPa) is 125 lbs. (56.7 kg).

Piston & Cylinder Assemblies: High strength stainless

steel piston and cylinder with brass collar and aluminum

weight platform.

Pump: Two stage, lever operated generates 10,000 psi

(70,000 kPa) with 28 pounds (12.7 kg) of force on lever

handle.

Pump Body: Aluminum, corrosion inhibited and coated

with baked blue epoxy finish.

Shuttle Valve: Stainless steel bypass valve that controls

rate of pressure increase and reduces operator effort

when working at high pressure.

Displacement Valve: A fine pitched threaded valve rod

permitting vernier adjustments to fluid volume and provide

precise pressure changes or adjustment of piston travel.

Limit stops prevent rod removal during normal operation.

Mounting: Four bench mounting holes located in base for

positive mounting to any level surface.

Instrument Connections: Two coned pipe assemblies

provide vertical calibration capability for back and lower

connected gauges. Standard

inch inter NPT fitting adapters are supplied.

Operating Fluid: 1305D – Light grade machine oils, au-

tomotive petroleum base SAE 20 oils or other equivalent

fluids suitable for use with Buna N O-ring materials. 1.5

pints required (.7 liters).

1305DH – Most hydraulic oils of phosphate ester base,

brake fluids, skydrol, pydraul etc., suitable for use with

Butyl or Ethylene-Propylene O-ring materials. 1.5 pints

required (.7 liters).

2.1.4 Certification:

Standard (CD-3) – Traceable calibration certificate

(accuracy/traceability statement only).

Optional (CD-5) – Certification document includes actual

(as left) weight values for each weight and piston, piston

diameter values, environmental data and test numbers.

Set includes numbered weights.

2.2 Product Description 1327D

2.2.1 Construction

The Ashcroft Type 1327D Portable Test Pumps are

rugged, versatile pressure transfer standards, used for

testing, setting, calibrating or repairing pressure measur-

ing devices with ranges up to 10,000 psi (70,000kPa). A

selection of high accuracy test gauges, with a precision of

±0.25% of span, are supplied as the standard to which the

device under test is compared.

The main component to the tester is a two stage hydraulic

pump containing a manifold which is pressurized during

operation. Integral to the pump is a shuttle valve that

allows the operator to regulate the speed of pressure in-

crease. One connection to the manifold has a straight pipe

with a precision test gauge attached serving as the refer-

ence standard. A second connection to the manifold ac-

commodates a gauge or other pressure measuring device

to be calibrated or checked. Incorporated into the manifold

is a hand operated displacement valve that allows small

adjustments in fluid volume to be made without further op-

eration of the pump handle or release valve.

of 20

⁄

inch internal NPT and

⁄