The effect of pressure-transmitting fluids in the characterization of a controlled clearance piston gauge up to 1 GPa

Abstract

The present paper describes the effect of different pressure-transmitting fluids (PTFs) on the systematic characterization of an oil-operated controlled clearance piston gauge (nominal diameter of the piston, 2.5 mm) in the pressure range up to 1000 MPa (1 GPa). Pure PTFs and mixtures of different PTFs are studied and four of them will be discussed here: namely (a) pure normal hydraulic oil (J-13), (b) a mixture of J-13 and an aviation turbine fuel (ATF), (JATF), (c) a pure di-ethyl-hexyl-sebacate oil (BIS) and (d) a mixture of white gasoline (G), J-13 and sebacate (GJBIS).The characterization is the measurement of the fall-rate of the piston as a function of applied jacket pressure (pj) with various PTFs using the method of Heydemann and Welch (HW model) (Heydemann and Welch 1975 Experimental Thermodynamics vol II, ed B Leneindre and B Voder (London: Butterworths) p 147). The analysis of the results is the determination of the cube root of the piston fall-rate (v1/3) with pj at different loads or measured pressures (pm). The linear portion of this v1/3–pj curve is extrapolated towards the null value of fall-rate, and the stall jacket pressure (pz) at different pm is obtained. It is observed that reasonably good fall-rate data could be obtained for J-13, JATF and BIS up to maximum pressures of 500 MPa, 700 MPa and 650 MPa, respectively. For GJBIS, these fall-rate data can be obtained up to a maximum pressure of 1 GPa. From the values of pz at different pm and also the values of the jacket pressure coefficient (d) along with other characteristic parameters in the HW model (Newhall et al 1979 Rev. Sci. Instrum. 50 964–8, Bandyopadhyay and Olson 2006 Metrologia 43 573–82), we have determined the relative standard uncertainties in the effective area (u(Ae)/Ae) for GJBIS up to 1 GPa for pj = 0 (free deformation mode) and pj/pm = 0.3. It is interesting to note that for pj = 0, at a pm of 100 MPa, u(Ae)/Ae is 74 × 10−6, while at a pm of 1 GPa, u(Ae)/Ae is 248 × 10−6. However, for pj/pm = 0.3, at a pm of 100 MPa, u(Ae)/Ae is 67 × 10−6, while at a pm of 1 GPa, u(Ae)/Ae is 125 × 10−6. A comparative study of u(Ae)/Ae has been elaborated with the four PTFs investigated. We have shown that at a pm of 100 MPa, u(Ae)/Ae is 202 × 10−6, 114 × 10−6, 66 × 10−6 and 67 × 10−6, for J-13, JATF, BIS and GJBIS, respectively, while at a pm of 500 MPa, u(Ae)/Ae is seen to be 97 × 10−6, 57 × 10−6, 46 × 10−6 and 56 × 10−6 for J13, JATF, BIS and GJBIS, respectively. Our measurements show that GJBIS is a convenient PTF for working up to 1 GPa. Finally, the results of the characterization are compared with the NPLI pressure scale through calibration of a NPLI secondary standard which is traceable to the LNE (France) pressure scale though direct comparison and participation in a recently concluded bilateral comparison with NIST (USA).

Standardisation of pressure measurement using pressure balance as transfer standard

“…(7,10,15,20,25,30,40, 50, 60 and 70) MPa and observations were repeated six times, three times each in increasing and decreasing orders of pressures, for each pressure point. The traceability of the NPL100MPN is established by cross-floating it against national primary pressure standard [17][18][19][20]. The NPL100MPN has also participated in several key comparison exercises, APMP.M.P.…”

Investigations on Measurement Uncertainty and Stability of Pressure Dial Gauges and Transducers

“…The primary and secondary pressure standards maintained are controlled clearance type piston gauges [4,[8][9]. Fig.1 shows schematically the usual circuit for the calibration of PDGs and PTs.…”

“…liquid column manometers (LCM), dead weight testers (DWT), quartz resonators (QR), pressure dial gauges (PDG), resistance / capacitance / inductance type pressure transducers / transmitters (PT). LCM and DWT measure pressure based on primary principle having well defined mathematical expression / model for measurand and are categorized as primary / reference instruments [3][4]. The evaluation of measurement uncertainty for such instruments is readily evaluated and can be characterized by the estimation of Type A and Type B standard uncertainties [5][6][7].…”

Least squares best fit line method for the evaluation of measurement uncertainty with electromechanical transducers (EMT) with Electrical Outputs (EO)

“…(for linear) [20] and Since the solution of the parabolic equation is itself very complex, the solutions for cubic parabolic and higher order would require the help of computer software. A computer software has been developed in QBASIC, which enables to solve such complex matrices and provide solutions [17][18].…”