A hose fitted at a pump is not there to carry the fluid — the pipe was doing that perfectly well. It is there to stop the pump shaking the pipework apart. Whether it succeeds is decided almost entirely by how it is installed.
What this service does to a hose
Vibration is low amplitude and high frequency, which means cycles accumulate at a rate nothing else on a plant matches. A hose on a machine running at 25 Hz sees over two million cycles a day. A thermal expansion duty might see two hundred in the same period. The two are not comparable and should not be specified the same way.
Two failure modes dominate. The first is fatigue just behind the braid collar, where the hose is stiffest and the bending concentrates — a clean circumferential crack with no deformation around it. The second is flow resonance, where the velocity through an unlined corrugated bore sets up vortices in every valley and the hose is excited from the inside as well as the outside.
What we would fit
| Element | What we would supply | Why |
|---|---|---|
| Hose | 304L or 316L annular corrugated, braided | The braid carries the thrust so the corrugations only have to flex |
| Length | Sized on the flexing bend radius, not the static one | The flexing figure is 2.9 to 5.6 times the static, depending on size |
| Liner | Considered wherever the velocity is high | It keeps the flow off the convolutions and stops resonance |
| Orientation | Installed across the direction of movement | In line with the movement the hose is being stretched, not flexed |
| Support | Rigid pipework clamped; hose and braid never clamped | A clamp on the braid creates the stress riser you were trying to avoid |
What we would not fit, and what happens
A hose sized on the static bend radius. It will fail at the collar, usually within months, and it will look like a manufacturing defect when it is a specification one.
A hose installed in line with the movement. A braided hose resists axial extension by design — that is what the braid is for. Asking it to stretch is asking the braid to fail.
A hose pulled taut to reach. It needs slack to work. The movement types page shows the installation geometries that survive and the ones that do not.
What we need to size it
| We need | Because |
|---|---|
| Frequency and amplitude of the movement | This is the duty; without it we are guessing |
| Direction of the movement relative to the pipe | It decides the orientation and therefore the length |
| Medium, pressure and temperature | The ordinary three, still required |
| Flow velocity, or enough to calculate it | High velocity in an unlined bore is a resonance risk |
| Whether the hose is accessible for inspection | It changes what we would recommend for a liner |
Check it yourself
The calculators will give you the flexing bend radius and the live length for the size you are using, from the same tables we quote from.