Most assemblies that fail early were specified from three pieces of information when they needed seven. This page sets out what we need and, more usefully, why each one changes the answer.
The seven inputs
1. Size
Two numbers, not one. The bore is set by the flow you need to pass — but a corrugated bore resists flow more than smooth pipe of the same diameter, so sizing the hose to match the pipe can starve the line. As a working rule, allow twenty to forty per cent more bore than the equivalent pipe where flow rate is critical.
The length is set by the installation geometry and the movement. A hose that is long enough to reach is not necessarily long enough to move. Tell us the face-to-face distance and the movement separately; do not net them off.
2. Temperature
We need both the medium temperature and the ambient temperature, because they load different parts of the assembly. A hose carrying cold product through a hot bay, or hot product past an operator walkway, has requirements that a single number will not capture.
Temperature also determines the pressure the assembly may carry — see temperature derating. And note that maximum and minimum both matter: austenitic stainless is comfortable at −196 °C, but the fittings, gaskets and any liner may not be.
3. Application
What the assembly is actually doing. A pump connection, a loading arm, a burner hose, a steam lance, a tank farm crossover and a CIP drop are all "a hose" and none of them are the same product. The application tells us the failure mode we are designing against, and that usually determines the accessories more than the hose itself.
4. Media
Name it, and give the concentration and whether it is wet or dry — those two qualifiers change the answer more often than the chemical name does. Chlorine is a good example: dry chlorine is workable in austenitic stainless with care, wet chlorine is not.
Tell us about entrained solids too. Abrasive particles erode corrugation valleys and are the reason an internal liner exists. See media compatibility.
5. Pressure
Working pressure, and the pressure at the highest temperature the line reaches — not the ambient figure. Also tell us about surge, water hammer, pressure shock and any vacuum condition. Vacuum is frequently omitted from enquiries and it is a completely different load case: a bellows or hose that is comfortable at 16 bar internal may collapse under full vacuum unless it was designed for it.
Our pressure basis
Every rated working pressure we publish is a quarter of burst — a safety factor of four — and is quoted at ambient temperature, 20 to 23 °C. Above that, apply the temperature factor before you compare the rating with your line pressure.
Test pressure is 1.5 times working pressure and every pressure-retaining assembly is tested before despatch. For pulsating or shock service, halve the working pressure before doing anything else — a line that surges is a fatigue problem, and the published static figure does not describe it.
6. End connections
Type, size, standard and material at both ends — they are frequently different. Where a flange is involved, give the standard and rating, not just "flanged": PN16 and ANSI 150# are not interchangeable. See end fittings.
7. Dynamics
This is the input most often left blank and the one that most affects service life. Does the assembly move? How far, how often, and in which direction? A hose that flexes once during installation and a hose that flexes forty times a minute are different products even if every other parameter is identical.
Give us the movement type, the amplitude and the frequency. See movement types and bend radius and live length.
Two things that are not on the list but should be on your enquiry
- The governing code. If the project runs to ASME B31.3, EN 13480 or a client specification, tell us at enquiry. It changes the documentation and sometimes the design.
- The certification you need. EN 10204 3.1 material certificates, third-party inspection, positive material identification — all straightforward if planned into the order, all disruptive if requested after manufacture.
