Quality Assurance

Assemblies are tested (air pressure under water) or hydraulically. Test certificates can be issued upon customer request also material certification to DIN 50049.3.1.
To avoid distortion of the convoluted form, the maximum test pressure quoted in this literature must not be exceeded.

Assemblies will be tested at 1.5 times customer's stated working pressure providing that this does not exceed the stated maximum pressure. Where working pressure is not stated, Hamer Stevenson's standard test procedure will apply.

Standard Flexibility
is a standard 'B' class flexibility, medium pressure hose used in vibration and flexing applications NB Excessive vibration can cause metal fatigue and premature failure. This applies to all grades of hose. Materials are Tube BS1499 Part 2 (1983) 321S31 or 316S11. Braid BS1554 (1990) S304 S31 or 316S19 Flexibilty; Type B Assembly to BS6501 Part 1: 1991 [Table]

Pressure Loss
As a rough estimate, it can be assumed that the pressure loss in corrugated hoses is 100% higher than in new welded steel pipes and in stripwound hoses it is 20% higher. This means that in the case of corrugated hoses an increase in diameter of 15% and in the case stripwound hoses of only 4% is sufficient to reduce the pressure loss to the value of the pressure loss in steel pipes.

Pressure Derating Factors
The listed pressure ratings are for unbraided and braided hose with factory fitted welded end connections at room temperature. The following derating factors must be applied to assemblies with welded end connections at higher temperatures. [Table]

Flow Velocity
High velocities in corrugated hose should be avoided as the corrugations could be forced into resonant vibrations resulting in premature fatigue failure. Where the flow velocity exceeds 100 ft/sec for gas or 50 ft/sec for liquid in unbraided hose and 150 ft/sec for gas or 75 ft/sec for liquid in braided hose, an interlock hose may be used as a liner. When the hose is installed in a bent condition, these flow values should be reduced by 50% for a 90bend, 25% for a 45° bend and so on, proportionally to the angle of bend. Where velocity exceeds the above values, the next larger size of hose with liner should be used.