The questions our engineers answer most often. Where an answer quotes a figure, the full table it comes from is linked from technical resources.
Questions and answers
What is the difference between corrugated hose and interlock hose?
A corrugated hose is a continuous pressure-tight membrane whose flexibility comes from elastic deformation of the corrugation flanks. An interlock hose is helically wound profiled strip whose flexibility comes from coils sliding against each other; it is not pressure-tight. Use corrugated for anything holding pressure, interlock for heat, abrasion, vibration damping and mechanical protection.
What pressure can a stainless steel braided hose take?
It falls as the bore grows. Single braid runs from 100 kg/cm² at DN6 to 28 kg/cm² at DN50, 18 kg/cm² at DN80, 10 kg/cm² at DN150 and 2 kg/cm² at DN350. Double braid raises those to 160, 44, 28, 16 and 4 kg/cm² respectively. The full table, size by size, is on the braided corrugated hose page. Every figure is at ambient temperature and must be derated for service temperature. Burst pressure is at least four times working pressure and test pressure is 1.5 times.
What temperature can the hose handle?
Stocked grades 304L and 316L are rated −196 °C to +450 °C. SS 321 extends to +550 °C for pressure-retaining service. Unpressurised interlock conduit goes to 700 °C in SS 304 and 800 °C in SS 321. Above 450 °C in 304L or 316L we assess case by case because of sensitisation risk.
Can a metal hose absorb pipe expansion?
Only if it is installed as a loop, so that growth becomes a change in loop geometry rather than a stretch along the hose axis. A braided hose resists axial extension by design — that is what the braid is for. Where a line grows axially, the correct component is an axial expansion joint.
Can I twist a metal hose to line up flange holes?
No. Torsion produces very high stress at very small angles and causes sudden failure. Rotate the pipe instead, or specify a swivel flange at one end. On interlock hose, twisting unwinds the helix.
What is the difference between static and dynamic bend radius?
Static is the tightest fixed radius for a hose that will not move again. Dynamic is the radius to design to where the hose flexes in service, and it runs roughly 2.9 to 5.6 times the static figure, depending on size. Installing to the static radius and then flexing the hose is a common cause of early failure.
When do I need an internal liner?
When flow velocity exceeds 45 m/s for gas or 22 m/s for liquid in a straight run on a braided hose, or 30.5 and 15.2 unbraided. Take a quarter off those figures if the hose is installed in a 45 degree bend and half off for a 90 degree bend. A liner is also needed whenever the medium carries abrasive solids, whatever the velocity. Above the limit the corrugations resonate and fatigue at the crest. Braid makes no difference to this — it carries pressure, not flow.
Is your ISO 9001 certificate valid for bellows?
We hold three certificates from TÜV Rheinland: ISO 9001:2015 (01 100 2437759), ISO 14001:2015 (01 104 2537285) and ISO 45001:2018 (01 213 2537285). Each carries its own scope statement, printed on the certificate. Ask at enquiry and copies come with the quotation, so you can read the scope against your own requirement rather than take our summary of it.
Do you supply material certificates?
Yes. Every pressure-retaining component is traceable to a mill test certificate and we issue EN 10204 3.1 documentation on request. Ask at enquiry so it is planned into the order.
What information do you need to quote?
Seven things: bore size, temperature of medium and ambient, application, media and concentration, working pressure, end connections at both ends, and dynamics — how far and how often the assembly moves. Also tell us the governing code and any certification required.
Can you make assemblies to our drawing?
Yes. Custom fabrication to customer drawing is a substantial part of what we do, in any of the materials we work with.
Do you appoint distributors or channel partners outside India?
Yes, and we are actively looking for them — in the Gulf, Europe, Africa, the United States and Asia Pacific. What we bring is manufacturing: stainless steel corrugated hose, interlock hose and bellows expansion joints built to drawing at our own works in Ahmedabad, with hydrostatic testing and mill traceability on every pressure assembly and EN 10204 3.1 documentation on request. What we look for is a partner who knows the specifying engineers in their market and can hold stock or fabricate assemblies locally. Write to info@essemworks.com with your territory, the industries you sell into and the lines you already carry, and mark it a partnership enquiry.