Standards development work carried out under the UK National Flow Programme will deliver enhanced accuracy for a key measurement technology used in the oil and gas industry. The revised standard ISO/TR 15377:2018 was published in January. It provides guidelines for the specification of orifice plates, nozzles and Venturi tubes beyond the scope of ISO 5167.
The research involved the revision of the existing standard, ISO/TR 15377:2007. It was carried out by Principal Consultant, Dr Michael Reader-Harris. The revision was necessary because research showed that the equation used in the standard to describe the behaviour of orifice plates with drain holes was unsatisfactory.
“The equations used to develop the old standard were based on engineering judgement rather than experimental data,” Michael explains. “To address this issue, we collected a robust set of data on the performance of orifice plates with drain holes. Equations based on our new data were then incorporated into the revised standard.”
Orifice plates with drain holes are used by operators to measure gas flows that are intermittently wet, for example when some liquid is introduced into a pipeline over a short period of time for cleaning. Drain holes let this liquid drain away.
“The new standard will reduce the uncertainty of measurements using these devices,” Michael says. “It will enable people to use this technology who have not used it before, as they thought that the standard wasn’t robust enough. There are many such devices in use, including a surprisingly large number in dry networks.”
Michael’s work involved calibrating meters in a single-phase fluid, using a comprehensive range of designs and pipe dimensions (from 2-inch to 8-inch diameters).
“The project was more complicated than we expected,” Michael reports. “This was due to orientation issues and the relationship between the flows through the different holes in the devices. We investigated these effects thoroughly to find out exactly what was going on.”