Session chairs: Paul Holland, EffecTech (GB)
The session “Gas cylinder handling and treatment” will take place on Tuesday 18 June 2019 with the following lectures:
C.1 – The use of a new cylinder design for LPG / NGL calibration mixtures by Paul Holland, EffecTech (GB)
Calibration of instrumentation used for the measurement of liquid petroleum gas (LPG) and natural gas liquids (NGL) is problematic because of the two phases (gas / liquid) that form in conventional cylinders used store and dispense the reference liquid mixtures. Dip tube cylinders are used with an overpressure (pad) gas to propel the liquid mixture out of the cylinder. Unfortunately, this approach is not the best solution for volatile components as the gas / liquid equilibrium constantly changes as the liquid is depleted from the cylinder during use. A much better, but more expensive, solution is to use a constant pressure cylinder where a piston is used with an overpressure gas to prevent the two phases forming. When sampling from the liquid phase, the composition remains stable over the lifetime of the liquid reference mixture. This presentation will show the results of stability trials for a new type of cylinder for LPG and NGL reference liquids. These conventional cylinders can maintain a stable reference composition from when the cylinder is first used until the cylinder is almost empty, even for volatile mixtures containing ethane. This approach offers a high-quality analytical solution providing equivalent performance to piston cylinder technology with the convenience and lower cost of a conventional cylinder.
C.2 – Cylinder valves with integrated pressure regulators (VIPR) for specialty gases by Peter Adam, Linde (DE)
Investigations on the technical suitability of using VIPR’s for specialty gases applications will be demonstrated. Applications include pure gases as well as calibration gas mixtures. The mechanisms of controlling the flow of VIPR’s will be described based on ISO 22435 “Gas cylinders – Cylinder valves with integrated pressure regulators – Specification and type testing”. The experimental investigations include high purity tests, particle analysis and stability tests for particular gas mixtures. In the interest of consistency, the performance data of VIPR will also be compared with the data of standard cylinder regulators otherwise the results cannot be referenced. Therefore, most of tests have been done for VIPR and standard reference cylinder regulators as well. A new concept to build a mobile gas diluter by using the outlet flow values of two mini-VIPR’s will be presented. The gas diluter design is basically following the principal of dynamic preparation of calibration gas mixtures described in ISO 6145-6 “Gas analysis – Preparation of calibration gas mixtures using dynamic methods – Part 6: Critical flow orifices”. The composition is calculated from the flow data and the composition of the parent gases. The individual flow calibration of the VIPR’s will be described, and one of the most interesting applications of gas diluters, the generation of multi point calibrations, will be presented.
C.3 – Advanced build-in regulator for calibration gas mixture delivery by Jean-Luc Blanc, Air Liquide (FR)
Several factors can influence the composition of the pure gases and the gas mixtures used for calibration purposes. The transfer of calibration gas from the cylinder to the point of calibration is one of them. Re-connecting cylinders always has the danger of creating a leaking connection, which shall be avoided to maintain the integrity of the gas. In an optimum set-up, the pressure regulator should remain on the cylinder. This will help to reduce the number of purge cycles to flush the regulator prior to analysis. These purge cycles are time consuming and has to be done before each calibration to guaranty the cleanliness of this pressure regulator and avoid the back contamination in the cylinder. There is more and more demand for reducing the time of the analysis both in laboratory and process analyses. Moreover, for mobile analysers calibration shall be achieved on site using calibration gas mixtures. For safety reason it is not allowed to transport cylinders with connected regulator. Then, before each use of these calibration gas mixtures, it is necessary to purge the regulator for avoiding any modification of the mixture composition. A new advanced build in regulator is presented to improve the quality of the pure gases and mixtures while reducing the time for purging before use. This paper describes the design of this integrated pressure regulator valve, named LABTOP. The advantages of this new delivery system is also explained using the return of experience of early users.