Design and Development of an Indigenous Cross-Floating Pressure Calibration System up to 140 MPa

Precise and accurate pressure measurements play a prominent role in several scientific applications. The pressure balances (PBs) are used as a primary standard for pressure measurements which requires utmost accuracy. In the case of calibration and characterization of these PBs, the method of cross-floating is an internationally accepted practice used for the comparison of 2 PBs for determining their metrological parameters, i.e. effective areas, distortion coefficient and zero pressure area etc. The present paper describes the work which has been carried out to develop a cross-floating pressure balance calibration system for an organization engaged in R&D activities and providing calibration services to the process industries. The study also describes some of the newly designed, developed, upgraded and fabricated components and devices for a cross-floating system in hydrostatic pressure range up to 150 MPa. The whole system consists of an upgraded hydraulic screw pump, newly designed, developed and fabricated oil reservoir, cross-float valve, use of two commercially available needle valves in combination with a pressure balance supplied by the customer with associated pressure fittings and connector in the pressure transmitting circuit. The characterization of the pressure balance was also done using the newly developed components/parts and instruments at 12 calibration points in the high pressure range (7–140) MPa and 11 calibration points in the low pressure range (0.2–7) MPa. The development process was started in the year 2018 and completed in the month of November 2020. The combined relative measurement uncertainty (at coverage factor, k = 2) associated in high pressure range is found to be 59.3 × 10⁻⁶ and 42.3 × 10⁻⁶ with associated pressure and effective area, respectively. Similarly, in low pressure range the combined relative measurement uncertainty (k = 2) is found to be 62.2 × 10⁻⁶ and 47.3 × 10⁻⁶ with associated pressure and effective area, respectively. The results obtained are found in excellent agreement with the values of uncertainty and the effective area reported by the manufacturer. This newly developed system will help the customer in providing in-house traceability to their own instruments as well services to the industries.