An autoclave or steam-in-place line is a modest duty repeated relentlessly: 121–134 °C saturated steam, two or three bar, several cycles a day, for the working life of the plant. Nothing about any single cycle is demanding. Fifteen thousand of them are, and the assembly has to survive them while remaining something a validation engineer will accept.
What this service does to a hose
Cycling, not magnitude. Saturated steam at 121 °C is at 1.1 barg; at 134 °C, 2.1 barg. Against a DN25 assembly rated 38 bar cold and 24 bar hot that is nothing. But each cycle takes the assembly from ambient to sterilising temperature and back, and each transition is a thermal strain applied at the collar where the flexible corrugation meets the rigid ferrule. This is a fatigue duty dressed up as a pressure one, and it is why the installation geometry matters far more here than the pressure table does.
Condensate is the process, not a nuisance. A sterilisation cycle only works if the steam reaches every surface, which means air has to be displaced and condensate has to drain. A hose looped below the line is an air pocket on the way up and a water trap on the way down, and an air pocket is a cold spot that never reaches sterilising temperature. This is the commonest reason a line fails validation, and it is a routing problem.
The bore has to be as clean afterwards as before. Corrugation valleys hold condensate and whatever the condensate carried. On a genuinely hygienic line that is the argument for a smooth PTFE-lined bore, and on a utility-side SIP line it is usually acceptable to run unlined — but which side of that line you are on is a decision for your quality function, not for us.
What we would fit
| Element | What we would supply | Why |
|---|---|---|
| Hose | 316L annular corrugated; PTFE smooth bore where full drainability is required | The corrugation valley is the crevice, and crevices are what audits find |
| Braid | 316L, sized on the derated pressure at 134 °C | Comfortable at these pressures, but stated properly rather than assumed |
| Ends | Tri-clamp as standard; DIN or ISO to order | It has to break down for inspection without tools that damage the face |
| Welds | Crevice-free, full penetration, with the bore condition stated | A weld with a crevice in it is where the audit stops |
| Finish | Internal Ra stated as a number, not described in words | “Polished” is not a specification; an Ra figure is |
What we would not fit, and what happens
An assembly with a crevice anywhere in the wetted path. It will be found, and it will be found by an auditor rather than by you.
Interlock hose. Not pressure-tight and impossible to clean or verify.
A hose supported so it sags into a low point. The sag is where the condensate sits and the cold spot forms.
A finish described rather than measured. If your specification needs an Ra, tell us the number and we will tell you whether we can meet and certify it, or whether that part goes out.
What we need to size it
| We need | Because |
|---|---|
| Sterilising temperature and hold time, and cycles per day | It is the fatigue duty, and it is the number nobody sends |
| Whether the line is product-contact or utility side | It decides liner, finish and documentation |
| Required internal surface finish as an Ra figure | A number we can measure and certify, or one we must decline |
| End connections — tri-clamp, DIN or ISO, and the size | It has to break down for inspection |
| Routing, and whether a continuous fall to drain is achievable | If not, the design needs fixing before the hose is quoted |
| Documentation required — material certificates, weld records, finish records | It changes the route through the works, and the price |