What is the difference between the burst pressure and the working pressure of a hose?

You determine the right hose based on the full application: the size, the medium, the temperature, the pressure, the length of the hose and the couplings to be fitted. There is no fixed formula; just like choosing a car, it depends on what you are going to use it for.

When specifying the size, pay close attention to the difference between inside and outside diameter. Pipes are specified by their outside diameter: a 50 x 5 mm pipe has an outside diameter of 50 mm and a wall thickness of 5 mm, and therefore an inside diameter of 40 mm. Hoses are always specified by their inside diameter, often in inches:

• 1/2" = 12.7 mm
• 1" = 25.4 mm
• 1 1/4" = 32 mm
• 1 1/2" = 38 mm
• 2" = 51 mm

The required working pressure follows from the maximum pressure in your installation, combined with the temperature and the medium. When making an enquiry, provide the full application details so that SCHIEMA can recommend the right combination of hose and couplings. You can request a quote directly.

As a rule of thumb, plastic hoses have a maximum temperature of 60 °C. Depending on the rubber compound and construction, rubber hoses can handle considerably higher temperatures. An EPDM steam hose such as the FLOWINTUBE® VAPORTOR-18-D, for example, is suitable for saturated steam at up to 210 °C continuous.

Take into account not only the temperature of the medium, but also the ambient temperature and direct sunlight. Experience has shown that with plastic hoses exposed to extreme heat and full sun for long periods, such as in the Middle East, the inner and outer layers could separate due to overheating. Such effects are difficult to predict in advance. At high ambient temperatures, rubber is therefore the better choice.

That depends on the type of reinforcement. You need a helix as soon as the hose must be suitable for suction or may be exposed to vacuum: without a helix, the hose collapses. For discharge only, a helix is not necessary. Textile or steel plies determine the pressure resistance of the hose; without plies, a hose would expand under pressure.

This is how a rubber hose is built up: unvulcanised rubber is first wrapped around a mandrel to form the inner lining. This is followed by the plies, then the helix, and then another layer of unvulcanised rubber for the outer cover. The complete mandrel, often with a hose length of 40 metres, then goes into a vulcanising autoclave, where heat bonds all layers into a single unit.