Pneumatic conveying is an abrasion duty. Cement, fly ash, alumina, lime and mineral powders travel at fifteen to thirty metres a second and they take material off the inside of whatever they travel through. A hose on this duty is a wear part with a predictable life, and the honest engineering question is not how to make it last forever but how to make its life long enough and its replacement easy.
What this service does to a hose
Abrasion, concentrated at every bend. Particles travelling in a straight line carry on travelling in a straight line when the pipe turns. They strike the outer wall of the bend, and that impact is where all the wear happens. In a hose the geometry makes it worse: a corrugated bore presents the leading face of every convolution to the flow, and those faces erode first. This is why an annular corrugated hose is a poor choice on abrasive conveying and why interlock, with a smoother effective bore and a much heavier strip section, is the standard answer.
The corner case is the whole design. A hose installed with a generous sweeping radius has the wear spread over a long arc. The same hose bent tightly concentrates every impact into a few centimetres and wears through there in a fraction of the time. Radius is not a comfort question on this duty, it is the life of the part.
Static. Dry powder moving fast through a conveying line generates a great deal of charge. Where the powder is combustible — and many mineral and organic powders are — the assembly must be part of a bonded, earthed system. A welded stainless interlock assembly is electrically continuous, which helps, but the earthing has to be designed rather than assumed. See anti-static and bonded assemblies.
Interlock is not pressure-tight. This is the constraint that decides where interlock can be used at all. A dilute-phase conveying line at half a bar is fine. A dense-phase system at three or four bar is not an interlock duty, and at that point the conversation changes.
What we would fit
| Element | What we would supply | Why |
|---|---|---|
| Hose | SS 304 or 316 interlock, heavy gauge strip, for dilute-phase conveying and ducting | The strip section is the wear allowance and it is far thicker than a corrugation wall |
| Packing | Fitted where the duty needs the seam to resist dust escape | It is dust containment, not pressure containment |
| Alternative | PTFE-lined corrugated hose where the line is genuinely pressure-tight duty and the powder is fine | A smooth bore removes the convolution faces that erode |
| Ends | Flanged, with the assembly built so it can be replaced without cutting pipework | It is a wear part; plan the replacement into the design |
| Routing | The most generous radius the layout allows, and no tight bends | Radius is the life of the part |
What we would not fit, and what happens
Annular corrugated hose on abrasive conveying. The convolution faces erode and the assembly is scrap in months.
Interlock on a dense-phase pressure line. It leaks powder and it always will.
A tight radius anywhere in the run. All the wear lands in one place.
An unbonded assembly on a combustible powder. Charge accumulates and the consequence is not a hose failure.
What we need to size it
| We need | Because |
|---|---|
| The material, its particle size and its hardness | Abrasiveness varies enormously between powders |
| Conveying velocity and whether the system is dilute or dense phase | Dense phase pressure decides whether interlock is possible at all |
| Conveying pressure | This is the constraint that rules interlock in or out |
| Whether the powder is combustible | It makes bonding and earthing a design requirement |
| The bend radius available in the installed position | It is the single biggest influence on the life of the part |
| Expected replacement interval and access | We can design for easy replacement if we know it is a wear part |