Hydraulic Deadweight Tester.

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HYDRAULIC DEADWEIGHT TESTER

description

final year project

Transcript of Hydraulic Deadweight Tester.

Page 1: Hydraulic Deadweight Tester.

HYDRAULIC DEADWEIGHT TESTER

Page 2: Hydraulic Deadweight Tester.

DEADWEIGHT TESTER

The most accurate and stable

pressure standards

Widely used in industry,

academics and research

institutes to calibrate pressure

measurement devices like

pressure transmitters, pressure

gauges & hydro-testing of

pipeline.

Page 3: Hydraulic Deadweight Tester.

DEADWEIGHT TESTER-TYPES

Pneumatic Deadweight

tester

Hydraulic Deadweight

tester

Oil type

Water /Alcohol Mixture

type A Pneumatic Deadweight tester

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HYDRAULIC DEADWEIGHT TESTER

To calibrate an analog gauge,The deadweight

tester conveniently provides hardware for all

three of these functions –

To generate , control & measure

hydraulic pressure.

It utilizes a piston-cylinder assembly for

measuring hydraulic pressure.

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WORKING PRINCIPLE

The basic principle is that

P= F/A

where the pressure (P) acts on a

known area of a sealed piston (A),

generating a force (F). The force of

this piston is then compared with

the force applied by calibrated

weights

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HYDRAULIC DWT-CONSTRUCTION

1 - Hand pump

2 - Testing Pump

3 - Pressure Gauge to be calibrated

4 - Calibration Weight

5 - Weight Support

6 - Piston

7 - Cylinder

8 - Filling Connection

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WORKING

The testing pump (2) is connected to

the instrument to be tested (3), to

the actual measuring component and

to the filling socket. A special

hydraulic oil is used as the pressure

transfer medium. The measuring

piston is then loaded with calibrated

weights (4). The pressure is applied

via an integrated pump (1).

(2)

(3)

(4)

(1)

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WORKING :CONTINUED

This pressure is applied until the loaded

measuring piston (6) rises and 'floats' on

the fluid. This is the point where there is a

balance between pressure and the mass

load. The piston is rotated to reduce

friction as far as possible. Since the piston

is spinning, it exerts a pressure that can

be calculated by application of a derivative

of the formula P = F/A.

Force(F)

PRESSURE(P)

CROSS SECTIONAL AREA(A)

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PISTON-CYLINDER ASSEMBLY

•Both the piston and

cylinder are made from

Tungsten Carbide.

•Tungsten Carbide has

very small pressure and

thermal expansion

coefficients,

• Protected in a solid

stainless steel housing

Piston

Cylinder

Housing

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HOW HDWT MEASURES PRESSURE

It allows the operator to know

or calculate the pressure when

the system is in a specific state.

This state, known as

Floatation, is achieved when

there is enough force from the

hydraulic

pressure medium to support the

piston in a floating state.

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CONTINUED……

The resulting pressure is

proportional to how much force is

applied by the mass loaded.

The mass produces a force because

it is accelerated by gravity.

When the piston is floating, the

pressure (P) is derived by

P=F/A

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CALIBRATING AN ANALOG GAUGE

The operator connects the gauge in

parallel with the piston.

He then applies the same pressure to both

at the same time.

The operator sets each test pressure in a

previously defined sequence, one at a

time.

At each point, the operator records the

analog gauge reading and the calculated

pressure from the deadweight tester.

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CONTINUED…

The test data is checked against the

specified tolerance .

Further if gauge requires adjustment,

registered

procedures are used to bring gauge into

tolerance.

Then a second test sequence is run to

confirm that

the adjustments were correct.

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CHECKS FOR ACCURATE CALIBRATION…

Leaks are eliminated, or at least reduced to the point

of insignificance.

That all fluid heads have been identified and

corrective actions applied.

The test medium is not contaminated with another

fluid.

The test device has been correctly zeroed if

applicable to the calibration.

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HYDRAULIC DWT:SPECIFICATIONS

Accuracy better than 0.015% of

reading.

Over All Range : 0.2-2000 bar,

10-30000 psi, 0.2-2000 kg/cm².

Various Pressure Unit available:

Bar,kg/cm², psi, MPa, kPa.

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SPECIFICATIONS: CONTINUED

Pressure generated by a ram

screw.

Operating Fluid : Hydraulic

Oil

Distilled Water can also be

used as fluid.

Masses manufactured from

stainless steel and aluminium.

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FACTORS AFFECTING CALIBRATION

Local fluctuations in the gravity value

Temperature of piston-cylinder system

Air pressure

Room temperature

Humidity

Effect of pressure on piston effective area

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DWT:USES

Primary standard for ranges up to 1500 psi (100 bar)

(pneumatic) or 15,000 psi (1,000 bar) (hydraulic).

Reference instrument for testing, adjusting and calibrating

pressure measuring instruments in factories and calibration

laboratories.

Self contained, complete system suitable for on-site

measurements/calibrations

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HDWT:APPLICATIONS

Calibration of mechanical pressure

measuring instruments

Oil & Gas Plants

Thermal / Nuclear / Hydro Power Stations

Hydraulics and Pneumatics

High pressure test benches

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APPLICATIONS: CONTINUED…

Research & Developments

Steel Plants

General Mechanical Engineering Industries

Rubber / Plastic Industries

Chemical Process Industries

Machine/Automobile Industries

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ADVANCEMENTS

Local gravity adjustment being introduced.

Kerosene being used in place of transformer oil

to increase length of rotation of piston.

To efficiently use `gas` as working medium

despite its high compressibility & energy.

Preserving effective area of piston-cylinder assembly.

Dual column & Re-Entrant type Deadweight testers.

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THANK YOU