Technical limitations and technological barriers

Within each stage, we have found several technical limitations to be overcome with the knowledge generated in the designed work programme for this FOIRCEV project.

Rubber Compounding and Processing

The unknown detailed composition of the rubber compound, the unknown effect of the mixing procedure and the lack of knowledge on the effects of the extrusion process are technical limitations encountered that prevent us to improve the manufacturing method. The lack of control on the compound design and production and the current manufacturing process produce a very high reject rate of the order of 15 to 30% (depending on size and the diameter of the hose) of the total production, which accounts, for the 25 mm diameter hose, for approximately a 12% of the final manufacturing costs. For example, a reduction of 80% reject rate would allow for a 10% direct cost reduction. For higher diameter hoses, the saving will be higher.

Vulcanization

Ideally, vulcanization should be done with pressure applied on both sides, but process economy has led to inject steam pressure on the manufactured hose without pressure on the external surface. Pressurization of the very long tables currently used on manufacturing would be very expensive and would complicate the handling reducing the production rate.

Solutions developed for the wire and cable industry for the vulcanization of very long items, either continuously or discontinuously, are designed for solid items. Some solutions developed for hoses, either are not suitable (wrapping is for not patterned surfaces and almost all rubber hoses have ribs), or are too expensive (lead- or resin moulding), or both.

Continuous vulcanization

Keeping the round shape of the relatively thin rubber hose while vulcanization takes place, in continuous can only be achieved by increasing heavily the equipment needed and enormously complicating the process.

No simple and economically sound technological solution for vulcanizing the rubber hose without applying internal pressure has been implemented yet, and this is another technical limitation encountered that prevent us to improve the manufacturing method

Limitations on hose length

The curing cycle limits the maximum rate of production of the hose and the achievable maximum length of the hose, in practice limited to approximately 150-200 meters (200 m is traditionally the base unit for agricultural land in the USA). Implementation of a continuous vulcanization system would allow for longer hoses, demanded by some areas of the market, and higher production rate. The development of an alternative continuous method will mean no practical limit length, and it is of paramount importance.