PRESSURE & VACCUME CALIBRATION (NABL Accreditation No. C 086)


PRESSURE & VACCUME CALIBRATION (NABL Accreditation No. C 086) The primary calibration standards for pressure at IDEMI are the Dead Weight Testers which use the measurements of force and area to produce a pressure to calibrate instruments with great accuracy. The force is derived from weight and the area is that of a piston and a cylinder.

Following table gives the list of Dead Weight Testers used in the laboratory along with their operational ranges and accuracies. When using the DWTs, corrections for temperature and variation due to acceleration in gravity (Nominal Pressure x g/9.80665) are also incorporated.

For low pressure measurements (0.1 – 1.0 Bar) a mercurial manometer of Wallace and Tiernan make with an accuracy of ± 0.02% of full scale is used. The manometer has inbuilt setting for temperature and gravity correction.

An electronic standard (Ruska DDR – 6000)
is used for measurement of pressure up to 2000 psig with an accuracy of ± 0.004% of the full scale. Here nitrogen or argon is used as the medium of calibration. This is a very precision instrument employing quartz bourdon tube as the sensor adopting the Force Balance Technique. Strain gauge bonded type sensors ( 0 – 1000 psig ) with 3 ½ digits readout are also used with an accuracy of ± 0.05% of F.S. Digital Pressure Indicator Heise Model 711 of range –1 to 7 kg/cm2 and accuracy ± 0.05% of F.S. is also used for calibration. The laboratory is also equipped with standard test gauge covering a range from 0 – 3000 kg/cm2 with accuracies of ± 0.1% to ± 0.2% F.S. The Standard Test Gauges are calibrated with our Dead Weight Testers calibrated at the National Physical Laboratory, New Delhi.

Dead Weight Tester Calibration

The calibration of Dead Weight Tester is done by using the Cross-Float System. The dual base system covers a Pneumatic Range (0.25 to 35 Bar) and Hydraulic Range (2 to 1400 Bar). The different subsystems of the DWT Calibration System consist of the following :
1. Pneumatic Dual Base System Model P7120 with piston cylinder unit of range0.025 to 35 Bar and accuracy class 0.0055% reading accuracy class 0.0055% reading with traceability to NIST.
2. Hydraulic Dual Base System Model P7300 with 2 piston cylinder (LP/HP) units of ranges 2 – 70 Bar and 70 – 1400 Bar and accuracy class 0.005% reading with traceability to NIST.
3. Mass Set : This consists of nominal masses WT3 covering a range up to 100 Bar and F2 Trim Mass Set.
4. Additional Equipment include the Ruska 2455 – 2470 adaptor kit with 2 float sensor and RTD thermometer for both hydraulic and pneumatic sections.
5. Ruska 2455 Dead Weight Gauge Monitor with Ruska with Prompt software
6. Precision Electronic Balances Sartorius Make Model LP120005 – 0CE of range12000g with readability of 0.1 g and Model LP 1200S – 0 CE of range 1200 g with readability of 0.001 g.

                               In this method, using the pressure balance between the Standard Piston and the under Test Piston with known masses the effective cross-section area of UUT is calculated as a function of different pressures. The actual balance when floatation occurs is sensed electronically using inductive type sensors, with a Ruska Cross Float Indicator. The actual masses can be computed with Digital Precision balances. Thus one can calibrate DWTs by the Primary Cross Float Method. In this method, using the pressure balance between the Standard Piston and the under Test Piston with known masses the effective cross-section area of UUT is calculated as a function of different pressures. The actual balance when floatation occurs is sensed electronically using inductive type sensors, with a Ruska Cross Float Indicator. The actual masses can be computed with Digital Precision balances. Thus one can calibrate DWTs by the Primary Cross Float Method. Corrections applied are for gravity, temperature, buoyancy fluid density and computations are accomplished using the Win Prompt Calibration Software. The Win Prompt Calibration Software increases calibration efficiency by providing full-colour windows-based measurement and also in endowed with the capability for customizing calibration procedures and reports. The software stores all the calibration coefficients for working standards, including piston/cylinder effective area, thermal coefficient of expansion, pressure deformation coefficients and all calibrated mass values. It includes environmental parameters, including local gravity, head corrections and ambient air density. It also performs the necessary calculations of pressure-to-mass and mass-o-pressure in both English and ST units. The above integrated system for calibration of DWTs affords ease of use, very high accuracy and precision.

Pressure Laboratory: -
Commissioned very low pressure controller/Calibrator, Make : Ruska, Model : 7250 IP. Range : 0 to 10 InWC & 0 to 30 InWC. with an uncertainty ± 0.02% of reading.

Calibration of Magnehelic Gauges, low pressure Gauges, Manometers, Indicators, & in low pressure instruments mainly used in pharmaceutical industries etc.
No. DWT Type Range Accuracy
1. Budenberg Hydraulic Dead Weight Tester Model 380H 0 - 1200 kg/cm2 ± 0.05% of the pressure being measured
2. Budenberg Hydraulic Dead Weight Teste 100 – 3500 kg/cm2 ± 0.05% of the pressure being measured
3. Budenberg Air Dead Weight Tester Model 350A 1 to 1 kg/cm2 ± 0.12% of the pressure being measured
4. Budenberg Air Dead Weight Tester Model 452 0.1 to 7 kg/cm2 -