A pigtail is a short, high-pressure tail from a gas cylinder to a manifold header. It is the most frequently handled pressure part in any plant — connected and broken every time a cylinder is changed, sometimes several times a week, for years. Nothing else on this site sees that many make-and-break cycles, and that, not the pressure, is what a pigtail has to be designed around.
What this service does to a hose
Cycles at the collar. Every cylinder change is a bend, a twist and a pull applied by hand at the fitting. The transition from flexible corrugation to rigid ferrule is a stress concentration, and it is exactly where the operator’s hand applies the load. Pigtails fail at the collar, essentially always. A short assembly makes it worse, because a short hose has very little live length to distribute the bend over — see bend radius and live length.
Pressure that is genuinely high. Industrial gas cylinders are filled to 150–200 bar and higher. Our published small-bore ratings are honest about where that sits: DN6 single braid is rated 120 bar at 20 °C and 180 bar double braided. Above that figure a braided corrugated pigtail is not the right part, and we will say so rather than stretch the table. Tell us the cylinder fill pressure, not the regulated downstream pressure, because the upstream side of the regulator is what the pigtail sees.
Whip. A failed high-pressure tail is a projectile. Restraint is not optional and it is not something a hose specification can substitute for.
What is in the cylinder. Oxygen turns this into a cleanliness problem. Acetylene excludes copper alloys anywhere in the assembly. Hydrogen brings its own leak-tightness and permeation questions. The tube is the least of it.
What we would fit
| Element | What we would supply | Why |
|---|---|---|
| Hose | 316L annular corrugated, small bore — typically DN6 to DN12 | The bore is set by the flow to the header, which is usually modest |
| Braid | Double braid as standard on this duty | The pressure is high and the assembly is handled; there is no case for single here |
| Ends | The cylinder connection family the gas requires, plus a header connection to match your manifold | Cylinder valve outlets are gas-specific by design, to prevent cross-connection |
| Guard | Spring guard or reinforced sleeve at both ferrules | It moves the bend away from the stress concentration that fails |
| Cleaning | Cleaned for oxygen service where the gas is oxygen or an oxidiser | This is a documented process, not a wipe-down — see the oxygen page |
What we would not fit, and what happens
An unguarded short assembly. All the handling load lands on two millimetres of metal at the collar.
A generic connection at the cylinder end. Gas-specific valve outlets exist precisely so that the wrong gas cannot be connected. Defeating that with an adaptor is dangerous.
Interlock hose. Not pressure-tight, in a duty defined by pressure.
Any hydrocarbon grease at the joint on oxidiser service. The grease is the fuel and the cylinder is the oxidiser.
What we need to size it
| We need | Because |
|---|---|
| The gas, precisely — including whether it is an oxidiser | It decides the cleaning, the seals and the cylinder connection |
| Cylinder fill pressure, not the regulated pressure | The pigtail sits upstream of the regulator |
| Bore required and the flow to the header | Small bore keeps the stored energy down; oversizing it is not free |
| Cylinder valve outlet type and the header connection | Both are defined families and both must be right |
| How often cylinders are changed | It is the fatigue duty, and it decides the guarding |
| Whether batch certification or burst testing is specified | It decides whether this is work we can take at all |