Hydraulic Deadweight Tester.
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Transcript of Hydraulic Deadweight Tester.
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.
DEADWEIGHT TESTER-TYPES
Pneumatic Deadweight
tester
Hydraulic Deadweight
tester
Oil type
Water /Alcohol Mixture
type A Pneumatic Deadweight tester
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.
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
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
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)
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)
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
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.
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
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.
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.
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.
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.
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.
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
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
HDWT:APPLICATIONS
Calibration of mechanical pressure
measuring instruments
Oil & Gas Plants
Thermal / Nuclear / Hydro Power Stations
Hydraulics and Pneumatics
High pressure test benches
APPLICATIONS: CONTINUED…
Research & Developments
Steel Plants
General Mechanical Engineering Industries
Rubber / Plastic Industries
Chemical Process Industries
Machine/Automobile Industries
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.
THANK YOU