Medical Gas Systems Lab
Count the beds and rooms by department, get the terminal units for oxygen, medical air, surgical air, vacuum and nitrous oxide, then the diversified design flows, the main pipe sizes and the plant: liquid oxygen VIE, cylinder reserve, air compressors and vacuum pumps. Links to the Healthcare Electrical Lab for essential power.
How to use: edit the department list (beds or rooms, flows for the first and each extra bed), then the pipe lengths and plant settings. Flows are typical HTM 02-01 style values to check against the current tables. Tap i for help.
1. Inputs
2. Medical gas system
Zone schematic from plant to terminal units, a 3D hospital with risers and the liquid oxygen level between deliveries.
3. Checks
4. Terminal units and design flows
5. Mains and plant
6. How it works
Terminal units and diversity
Each bed or room gets terminal units for the gases its clinical use needs: typically oxygen, medical air and vacuum at every ward bed, with surgical air and nitrous oxide in theatres. Not every outlet flows at once, so HTM 02-01 gives design flows as a first-bed figure plus a smaller amount for each extra bed. The lab uses that form with editable typical values.
Pipe sizing
Oxygen, medical air (MA4) and nitrous oxide run at a nominal 400 kPa, surgical air (SA7) at 700 kPa, and vacuum at about -60 kPa or lower. Mains are degreased medical copper (EN 13348) sized so the drop from plant to the furthest terminal stays small. Each zone has an area valve service unit (AVSU) and an area alarm.
Plant
Oxygen usually comes from a liquid oxygen vacuum insulated evaporator (VIE) with a cylinder manifold as secondary and an emergency reserve. One litre of liquid oxygen gives about 861 litres of gas. Medical air and vacuum plant use several machines so the design flow is met with one out of service. All medical gas plant and alarms go on the essential (generator backed) supply.
Concept sizing tool. Final terminal unit schedules, design flows and plant come from HTM 02-01 (or NFPA 99 or AS 2896) tables, the clinical brief, the medical gas supplier and the authority (DHA, DoH, MOHAP or the NZ DHB).