Oil hoses venture into new temperature territory

Paul Boughton

Christof Kirsch reports on high-temperature hoses for turbochargers, extremely pressure-resistant lines for part-time front-wheel drives and fuel lines for modern truck engines.

High-temperature hoses for turbochargers and extremely pressure-resistant lines for part-time front-wheel drives are creating new engineering solutions. And today's fuel lines for modern truck engines meet most stringent cleanliness requirements.

"The new generation of high-temperature oil hoses for turbochargers are enabling us to venture into 250°C temperature territory," states ContiTech's Product Developer, Klaus Brühne. In addition, the hose design features numerous advantages over Teflon corrugated tubing and flat hoses used to date.

For example, the hoses have significantly greater flexibility, thus enabling tight bending radii, downsized weight and can accommodate smaller package spaces. This benefit is further amplified by lighter system integration when combined with aluminium tubes.

Sheathed hoses

The new sheathed hoses are used on the supply and return sides of the turbocharger. The key to withstanding such high temperatures is based on a braided sheath made of a plastic exhibiting high temperature and chemical resistance which encloses the FKM rubber inner lining having excellent stretch ability. The hoses have a very tight bending radii using a molding process, and can withstand operating pressures of up to 15bar (218psi).

The hose is part of a kit which the customer selects for the particular application, resulting in cost benefits. The new product can be used for lubricating turbochargers and further applications.

Another innovation are lines developed for part-time front-wheel drives. These lines are designed for trucks which spend a large proportion of their operating time on the road but also occasionally need off-road capability.

The lines carry hydraulic oil which is pumped to motors and drive the vehicles' front wheels under extreme pressures. ContiTech supplies between 15 and 30 such lines per vehicle. Ultimately, they represent an inexpensive alternative to a permanent all-wheel drive system and fuel savings.

The new lines must withstand pressure up to 450bar (6527psi). This is ensured by a spiral steel sheath which forms the strength member. ContiTech offers these lines up to a nominal diameter of 25mm and can also fit them with snap-on connectors. This not only simplifies installation in the customer's plant, but also prevents torsion on the line which is unavoidable with screw unions and detrimental to the component's pressure resistance.

"To ensure that the lines remain permanently leakproof, they are subjected to rigorous impulse and movement testing before leaving our plant," emphasises Brühne. This also includes vehicle-related tests in which the applications are simulated.

Fuel line cleanliness

Other challenges are the increasing demands placed on cleanliness of fuel lines for modern engines. Even the smallest particles could damage or even destroy the extremely fine injector nozzles. ContiTech has invested some 400,000EUR in rinsing unit at its Karben site. A special cleaning medium and filter with exceptionally fine diaphragms ensure that no solid particles larger than 200µm are in the fuel lines.

"This means that we satisfy the requirements for the latest generation of engines and are also ideally equipped for future developments," says Brühne.

With its extremely resilient fuel lines for heavy-duty truck engines, ContiTech made a crucial contribution to this engine generation which is both heavy-duty and environment-friendly. The Karben site currently produces tens of thousands of these high-tech lines every week. But the issue of cleanliness is playing an increasing role not just in relation to trucks, but also construction, agricultural machinery, compressors and machines for materials transport. The same applies to hydraulic lines for industrial applications which are manufactured on the Hoppegarten site.

ContiTech is able to supply its commercial vehicle and industry customers worldwide using local production operations - working with the same processes and high standards as in Europe.

For example, ContiTech supplies truck manufacturer Paccar with coolant lines which withstand temperatures up to 210°C and with high-temperature oil hoses for the turbocharger from Germany, and Brazil. ContiTech also, produces a variety of lines for Volvo from its plants in Germany, France, Brazil and China. This year, ContiTech began production in Mexico, producing a range of applications from power-steering lines to heated urea lines for SCR systems and air-conditioning lines.

For more information at www.engineerlive.com/ede

Christof Kirsch is with ContiTech AG, Hanover, Germany. www.contitech.de