Hand-built hose

A solid or hollow metal pole used in the assembly or vulcanising of rubber products, e.g., the assembly of hand-built hose. 

The rubber hose industry is one of the two largest segments of nontire rubber fabricators. Worldwide, the hose industry had about 6 billion dollars in total sales in 2010. Automotive and industrial are two very large market areas for hose. Some hose processes, for machine-made and hand-built hose, are very labor intensive. Processes for braided and spiral hose are less labor intensive. Hoses constructed in the factory are commonly cured in autoclaves. 

A large variety of hose constructions are produced by the rubber industry for a wide range of applications. To contain transported liquids, usually under pressure, it is necessary to reinforce the hose construction with fabric, yam or short fibres to constrain expansion of the rubber. Although hand-built construction using fabric still represents a proportion of the production, it is also very common to use yams either braided or knitted directly onto the hose liner. For heavy duty purposes it is also necessary to use wire, in a braided form, to either reinforce or protect the hose from external damage. Use of short fibres as reinforcement represents a small proportion of hose production and requires specialised dies for extrusion to orientate the fibres circumferentially. 

These fabrics can be applied in the hand-built construction of hoses in a spiral form at an angle to the axis of the hose. The knitted fabric can also be produced directly onto the surface of the inner liner of a hose and subsequently be covered with the outer cover compound by a cross-head extruder. 

Hose may be hand built using a three roll wrapping machine. The centres of the three rolls form an equilateral triangle. The hose during construction sits on the junction between the two lower rollers and pressure is exerted to consolidate the composite by the upper movable roller. An extruded inner liner, after fitting to a solid inner mandrel, is placed into the machine between the rollers and then the various layers of rubber coated or resorcinol-formaldehyde-latex treated, fabric are applied in a spiral form, with overlap. Once the reinforcement layers have been added the cover rubber is applied and a cloth, usually nylon, is spirally wrapped around the constructed hose using the roller system. The hose is now ready for vulcanisation. 

While it is important to take proper precautions (see Appendix 2), properly built equipment offers few hazards if relatively small quantities of liquids are used under pressure. The energy stored in a compressed liquid is of the order of 0.2-0.5 kJ mor kbar" this is much less than in a gas. In the event of the catastrophic failure of a vessel, only around 10 per cent of the liquid would need to escape to reduce the pressure to the atmospheric value, and double-walled vessels are unlikely to suffer a failure of both cylinders. The author has experienced the failure of a piston-cylinder apparatus which led to nothing more than a sudden depressurization. On the other hand, hazards may arise from the low-pressure side, which is likely to be carrying oil at 500 bar or more a pin-hole jet at this pressure can penetrate the human body. The valve threads may become worn and the stems may then be forcibly ejected. So hose connections should be inspected and renewed regularly and, where possible, they should be shielded from personnel, the valves should be mounted with the stems pointing away from the operator, and the guidelines set out in the code of practice (see Appendix 2) should be followed. 

---