MEDICAL OXYGEN SUPPLY
London, which, again, share a VIE. I asked what determines the oxygen flow rate in a hospital medical gas pipeline system. He said: “Go back to the analogy of very cold liquid oxygen in a thermos flask. As the liquid exits into the ambient air, the warmer temperature warms it up – akin to changing water to steam – and it changes into a gas. Within the VIE plant,” he continued, “there is a control panel, usually from an oxygen supplier such as BOC or Air Products. This panel incorporates two regulators, which control the maximum flow rates that go through them. While flow rates vary from hospital to hospital, the equipment is typically set up to deliver between 1200 and 1800 L/min. Before the pandemic, most control panels allowed a maximum flow rate of 3000 L/min.” As well as the regulators, each VIE incorporates a vaporiser – as the liquid oxygen passes through this it is exposed to the ambient temperature, and ‘gases off’. It then goes through the control panel, which allows the gas to enter the medical gas pipeline at the pre-selected flow rate. Stafford Scopes explained: “During the pandemic, some hospital vaporisers proved to be small to accommodate the sizeable liquid oxygen flows passing through them, with the danger they would not be able to warm the liquid sufficiently to turn it into gas. The liquid could then get into the control panel and freeze it up.” Such a scenario tends, he emphasised, to occur only when oxygen flow is ‘well above the design flow rate of the equipment’.
An FLO2
dashboard screenshot. Gas pressure reduced
A typical oxygen flow rate for a large teaching hospital under ‘normal circumstances’ might, Stafford Scopes explained, be 300-400 L/min, and thus a vaporiser able to deliver anything up to 3000 L/min ‘would appear to be grossly oversized’. He said: “The VIE’s vaporiser and control panel jointly determine the oxygen flow, while the control panel also reduces the gas pressure from perhaps 10.5 bar to a typical line pressure of 4 bar, for distribution throughout the hospital. The key issue for healthcare estates teams during the pandemic’s ‘peaks’ was that the required higher flow rates were not being reached, or sustained – which was part of the reason that, for example, London’s Charing Cross Hospital installed
an oxygen concentrator (HEJ – October 2020), which we supplied, because the Estates team there realised that the hospital’s existing VIE simply couldn’t cope with the calculated flow rates they needed with all the extra COVID patients.”
Having set the context, Stafford Scopes went on to explain how the FLO2 system was developed. He said: “With many hospitals keen to be able to monitor their oxygen flow and pressure rates in real time, a number installed flowmeters for the first time at strategic points on their medical gas pipeline infrastructure in the Spring and Summer of last year. However, this generally still meant engineers having to go round and manually take readings from the meters at regular intervals. Some hospitals subsequently linked the flowmeters to their BMS systems, for instance using BACnet protocol technology to transmit the data from meter to system. “Designated users could then access, view, and analyse, flow rate and other key data via the BMS ‘front-end’. However, this tends only to be accessible from certain terminals on site. For this reason,” Stafford Scopes continued, “and also in response to a call for help from a long-standing customer, Shane King, head of Estates Operations at London’s Imperial College Healthcare NHS Trust, we developed FLO2 Scopes explained that FLO2
’s main
hardware component is a compact ‘box’, which simply bolts onto the flowmeter, and sends flow rate and other data (depending on the transducers fitted) every five seconds to the company’s servers, where the data is hosted, and is then viewable via SHJ’s web-based customer portal, K’nect. The data is accessible ‘at any time, and on any device’, via K’nect to authorised personnel at any contracted SHJ customer. FLO2
A screenshot from an FLO2 gauge, and a graph of VIE output over a 24-hour period. 34 Health Estate Journal June 2021
to users if oxygen supplies are reaching maximum capacity.
.” Stafford
issues text or email alerts
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