FAQ's

• Why should I specify a silicone hose?

Silicone possesses many advantageous properties: resistance to extremes of temperature, to heat-induced compression set, UV light corona, ozone and even saltwater in marine engines. Silicone retains its flexibility, has a long life and is reliable.


• What are the maximum and minimum operating temperatures for silicone?

Depending on the specific silicone compounds, silicone remains serviceable between minus 50ºC and 250ºC. Short periods above 250ºC are possible, depending on the application.


• How can I protect a hose, which is close to a radiant heat source?

A hose with a reflective heat shield can withstand temperatures of up to 550º C at a distance of 5 - 6mm from the radiant heat source.


• How much movement can silicone hose absorb?

Hoses can be designed with features to accommodate engine movements. Typical charge air hoses are exposed to +/- 15mm, whereas crossover hoses tend to handle smaller high frequency vibrations without special design. Hose reinforcing materials can also be influenced by movement requirements.


• What types of reinforcing fabric are available and what are the selection criteria?

Three yarn types are used: Polyester, Nomex and glass.


• What is the purpose of the steel reinforcing rings?

Under pressure, the convolutes of the hose would tend to blow outwards and flatten. The steel rings maintain the convoluted shape and control the dilation of the hose. They also maintain the shape of the hose when it is flexed, preventing it from kinking or buckling. Internal reinforcing rings may be incorporated if the hose is to be used under vacuum, thus preventing it from collapsing.


• Can silicone hoses be used for handling gases?

Silicone is permeable to many gases, so hoses require an impermeable liner such as fluorocarbon in order to be suitable for gas handling.


• Because of increasingly tough legislation on emissions, our engine incorporates an Enclosed Breather System. What type of hose is suitable for these conditions?

Because of the oil particulates present in the emissions, the hose will require a fluorosilicone or fluorocarbon oil-resistant liner. Please consult us for further advice.


• Are silicone hoses compatible with extended life coolant fluids? (OATs)

Yes. Extensive testing has shown that our silicone compounds, used for water coolant hoses, are unaffected by OATs.


• To what specification do silicone hoses perform?

Many customers have their own specific requirements. Water coolant hoses can be classified against SAE J 20 types R1 or R4 for Class A materials. James Dawson Global Hose can help you formulate specifications to suit your own requirements.


• Is it possible to make branched hoses?

Yes, but careful design considerations must be taken into account, as the hoses have to be fabricated by hand and are generally unsuitable for water coolant applications.


• How can I design an engine for maximum cost efficiency in the silicone hose?

Try to design the engine so that hoses are straight and of minimum length. Take up as much distance as possible and compensate for inle / outlet differentials with pipe work / metalwork so that the hose bore size is the same at both ends. Special shapes and reducer hoses are more labour intensive and take longer to produce, and are therefore less cost effective.


• What colours of hose are available?

Blue is the standard colour for James Dawson Global Hose and is usually associated with the "Cold Side" of an engine and with water coolants.


• What methods are available for fitting silicone hoses to engines?

Commonly used methods involve worm drive band clamps, with or without spring tensioning mechanisms to offset the effects of thermal expansion and compression set. We recommend non-perforated clips with a smooth inner band 13mm wide for bore sizes over 12.7mm and 9.5mm wide for bore sizes smaller than 12.7mm. Custom design metal fittings can be swaged onto hose ends, as requested. We can also offer cuff-less designs for CAC hoses to maximise design opportunities for flexibility.


• My hoses are leaking. Why?

This problem would require further investigation as there are many potential causes: the hose bore is oversized for the metal spigot, the bead on the end of the spigot is too large, the hose clips have been over-tightened or the hose construction has insufficient reinforcing plies.


• How quickly can I obtain hoses from James Dawson?

Our standard lead-time from receipt of order to despatch is 4 - 6 weeks. Please allow additional time if your hose is of special design and a new production tool is required.


• How quickly can James Dawson Global Hose deliver the hoses?

Delivery by road haulage takes up to 2 days within the UK and up to 6 days within Europe.