Hose pressure testing: which standards apply and what matters to the customer
Working, proof and burst pressure; ISO 1402, EN 853/856, GOST; type and acceptance tests; the report customers require — and how all of this is done on the LT-S/Z bench.
An assembled high-pressure hose is outwardly indistinguishable from a rejected one: the joint looks the same with a correct and with an insufficient crimp. The only way to confirm that the assembly will withstand its working pressure is to load it above working pressure and see what happens. That is what the test required by the standards — and increasingly by customers themselves — consists of. In this article we look at which tests exist, what international and Russian standards say about them, and what matters in practice.
Three pressure levels
Any hose standard operates with three values tied to the working pressure:
- Working pressure — the maximum pressure the hose is designed to operate at; it is given in the marking.
- Proof (test) pressure — the pressure the assembly must withstand without leaking, weeping or fitting movement. For hoses, ISO 1402 and the standards harmonised with it set it at twice the working pressure; at outgoing inspection of finished assemblies, manufacturers often apply 1.5 times working pressure so as not to load the joint excessively before service, and fix the value in the technical specification or the customer contract.
- Burst pressure — at which the hose bursts or the fitting slips off. For hydraulic hoses the standards require a margin of at least four times working pressure.
Which standards apply
Requirements for hoses and test methods are described in several groups of documents:
| Document | Subject |
|---|---|
| ISO 1402 | hydrostatic test methods for hoses and assemblies: proof pressure, hold, assessment criteria |
| ISO 7751 | ratios of proof and burst pressure to working pressure for hoses |
| EN 853, EN 856, EN 857 / ISO 1436, ISO 3862 | requirements for hose types (1SN, 2SN, 4SP, 4SH etc.), including impulse tests — hundreds of thousands of cycles above working pressure |
| SAE J517 | the American hose type system (R1–R17) with similar requirements |
| GOST 6286, GOST 25452 | Russian standards for hoses with metal braids and spirals |
| GOST ISO 1436, GOST ISO 3862 | interstate standards harmonised with ISO — applied in their current editions |
It is important to distinguish two kinds of tests. Type tests — burst and impulse — are carried out by the hose manufacturer at type certification; they are not repeated in the assembly shop. Acceptance tests — a static proof pressure test — are performed by the assembly maker, and it is these that confirm the quality of the specific crimp.
What matters to customers in Russia
In practice, Russian customers — especially in mining, oil and gas, shipbuilding and defence — state their requirements as follows:
- A test report per batch or per assembly. Stating the assembly number, hose and fitting types, proof pressure, hold time, result and date. A bench with automatic logging removes manual form-filling.
- Assembly marking linked to the report: date, working pressure, manufacturer. This is the subject of a separate article on marking.
- Documents for components: a declaration or certificate of conformity for the hose, passports for the fittings. The assembly maker collects them into a package with the shipment.
- Frequency. Individual tests for critical machinery, sampling under an agreed plan for serial batches. The scope is fixed in the contract or technical specification.
For many customers, having an own bench with logging is a condition of getting onto the supplier list: without it, assemblies for critical machinery are not accepted.
How the LT-S/Z bench is built
LT-S/Z benches are air-driven hydraulic units: compressed air at 1–8 bar drives an intensifier pump that generates the test pressure. This arrangement needs no high-pressure electro-hydraulics and is safe: there is no stored energy in the system, and when the air is shut off the pressure stops rising.
- Pressure range. Model range from 35 to 300 MPa; a special version up to 400 MPa. This is enough both for acceptance testing of assemblies and for burst testing of hoses, valves, pressure vessels and tubes.
- Adjustable pressurising rate — stepless, set by the operator: the standards require a smooth pressure rise.
- Working medium — water, oil or emulsion; pumps, valves and piping in AISI 316 stainless steel, Parker high-pressure fittings.
- Control and reporting. 15-inch touch screen, manual and automatic modes, pressure-versus-time curve, report output to USB.
- Safety. Burst tests are carried out in a safety enclosure; when a specimen fails, the energy of compressed liquid is small compared with gas.
| Model | Pressure, MPa | Flow, l/min |
|---|---|---|
| LT-S/Z-S-35 | 3–35 | up to 3.5 |
| LT-S/Z-S-80 | 7–80 | up to 1.8 |
| LT-S/Z-S-120 | 13–120 | up to 1.1 |
| LT-S/Z-S-200 | 19–200 | up to 0.7 |
| LT-S/Z-S-300 | 30–300 | up to 0.4 |
Acceptance test procedure
- The assembly is connected to the bench and filled with the medium, removing air from the bore.
- The pressure is raised at a set rate to the proof value.
- It is held for the established time — as a rule from 30 seconds to several minutes according to the method — and inspected: no leaks, weeping through the braid, bulging or fitting movement relative to the hose are permitted.
- The pressure is released, the assembly is inspected again and the result is recorded in the report.
An assembly showing any sign of rejection (see the article on crimping defects) is rejected — re-testing after "tightening up" is not permitted.