Automobile Hoses

Automotive Hoses 




The hoses used in automobiles are  coolant hoses, power steering hoses , fuel hoses. air conditioning hoses,oil cooler hoses 

Coolant Hoses

The Coolant hose is the critical and important part of the automotive engine.As the IC engine runs so hot a fluid called coolant is needed to circulate throughout the engine.

The coolant basically picks up and carries the heat  with it into the radiator, where cooler outside air dissipated the heat. The hose is therefore required in larger size to carry coolant into and out of the radiator, as well as in smaller sizes along the intake manifold.

Coolant Hose

The Coolant hose is the critical and important part of the automotive engine.As the IC engine runs so hot a fluid called coolant is needed to circulate throughout the engine.

The coolant basically picks up and carries the heat  with it into the radiator, where cooler outside air dissipated the heat. The hose is therefore required in larger size to carry coolant into and out of the radiator, as well as in smaller sizes along the intake manifold.

Major polymer – EPDM Rubber

Silicone - For heavy vehicle 

Reason – EPDM has outstanding  resistance to heat  and hot water as well as ethylene glycol, which is the most widely used antifreeze

The technique for manufacturing coolant hoses ranges from fiber reinforcement of the rubber to textile knitting, braiding and spiraling.

Fiber reinforcement of rubber  can be achieved by a process patented and licensed by Monsanto. The fibre santoweb is composed of short cellulose fibers treated to bond  to the hose polymer during vulcanization.

         

Extrusion of  the fiber reinforced compound takes place through a conventional cold feed extruder, but in the region of the die the extrudate is expanded diametrically very rapidly to give a significant amount of radial orientation of the  fiber  reinforcement as well as an element of axial fiber orientation. This leads to a reasonable balance radial and axial reinforcemen, and adequate  working pressure capability is achieved in the product.

Hoses can be produced straight or by a more recent innovation the production of curved hoses is effected by moving the die in the head of the extruder.

Most coolant hoses are at present still produced by the older techniques of extruding an inner liner passing this through a textile kinitting machine, then extruding a cover over this knitted reinforcement. The unvulcnized  hose is chopped to length then pushed onto lubricated shape mandrels, vulcanized in high pressure steam, stripped, and trimmed. Any branches  or T- pieces required in the coolant hoses can be built in vulcanization.

Smaller bore coolant hoses, such as from radiator to header tank, are usually  produced on a flexible mandrel in very long lengths, which are vulcanized by continuous vulcanization techniques in steam, salt or fluidized  bed or pan cured in steam. If the hose is not shaped, vulcanization is completed , if the hose is to be shaped, the hose is partially vulcanized the mandrel removed, and the hose put onto a lubricated shaped  mandrel, where vulcanization is completed and the desired shape achieve.

For heavy vehicles in which the coolant hose is expected to last for several hundred thousand kilometers the hoses can be made of  silicone rubber reinforced by aramid textile. This combination very good service life.

Aramid textile reinforcement of coolant hoses for cars has  increased steadily, 50 % of all coolant hoses are aramid reinforced.

Power Steering Hoses:

Power steering hoses are composed of three main types  

1.     H igh volumetric expansion textile reinforced hoses

2        A low volumetric expansion textile braid hose

3.     A return hose that is textile reinforced .

The main types of high volumetric expansion hose are based on SAE J 188 types 1 and 2. These textile reinforced rubber hoses have high volumetric expansion characteristics  that dump pump pressure pulsations.

Type 1 requires a volumetric expansion of 9.826.2 cm3/m and type 2 a volumetric expansion of 26.255.8 cm 3/m, both at a working pressure of 90 bars (130 psi). Both type 1 and type 2 have a maximum working pressure of  103 bars( 1500 psi) and minimum  burst pressure of 414 bars(6000 psi).

These hoses are mandrel built normally on a flexible rubber or thermoplastic mandrel by the process used to make wire reinforced hydraulic hose. 

They consist of an inner line of Polychloroprene, NBR, HNBR.

The reinforcement for type 2 is usually polyamide or polyester , the yarn of a tire cord type construction  with high levels of twist giving high extension characteristics to permit the high volumetric expansion required.

Type 1 reinforcement is alos polyester or polyamide but nor twisted to the same degree. In both types of hose the yarns are treated to give strong dynamic bonding levels to the rubber. The outer cover is usually Polychloroprene, CSM . A low expansion power steering hose based on SAE J 191 which has a maximum working pressure of 90 bars is sometimes used where pressure pulsations created by the pump do not require to be damped.

Power steering return hose is usually based on SAE J 189, Both SAE J 189 and J 191 are usually manufactured with NBR inner liner and Polychloroprene outer cover, the reinforcement is usually rayon or polyvinyl alcohol which is braided.

Fuel Hoses:

Fuel hose can range form a section of polyurethane tube with no reinforcement to a quite sophisticated reinforced hose with an inner liner composed a veneer of fluoroelastomer inside another fuel resistant polymer, a textile reinforcement layer and an outer cover. Some fuel hoses are completely in the fuel inside the fuel tank all the time and therefore the outer cover  must  exhibit as much resistance to fuel as the innerlliner. Many fuel hoses have no outer cover and consist of an inner liner and a braided reinforcement only. There is an increasing trend  for fuel hoses to be shaped. Fuel hoses  have traditionally been manufactured with an NBR or NBR/ PVC   innerline, reinforced by cotton, rayon, polyamide or polyester. If a cover was required it was usually polychloroprene or CSM.

Fuel hose for the more difficult conditions may have an inner liner of NBR, HNBR, CO or ECO or have a veneer of fluroelastomer with NBR or ECO as the second polymer specially compounded  bond to the  fluroelastomer  compound and the textile reinforcement layer.  Mostfuel hoses are produced on mandrels although significant amounts are made without mandrels. Mandrels made hose processes usually utilize flexible rubber or plastic mandrels and are  continuously vulcanized.

Air Conditioning Hoses:

SAE J 51 is the normal standard used for air conditioning hoses. The standard four types of hose designed to be used with dichlorofluromethane. Refrigerant  12 has been identified as a material that is alleged to be capable of damaging the ozone layer .

SAE J 51 type A is a textile reinforced rubber hose having a thick innerliner, usually of NBR although CSM is also used. Type A 1 has a single braided reinforcement layer of rayon or similar textile

Type 2 has two textile braided layers, separated from each other by a layer of bonding rubber compound. Both types of an outer cover of CSM or Polychloroprene. The outercover is pricked to allow any refrigerant gas that has permeated through to the reinforcement layer to escape without causing the hose  to blister. CSM has been found to be particularly useful in preventing ingress of water from the atmosphere into the refrigerants system. 

SAE J51 type B is a wire reinforced hose comprised of an innerliner  usually NBR, a wire reinforcement layer, and an outer layer of heat resistant textile reinforcement. The hose is manufactured by the same method as SAE 100 R5 .

SAE J51 type C is a  textile reinforced thermoplastic  hose  usually polyamide inner liner and outer cover. This type of hose has a lower permeation rate for the refrigerant gases than does the rubber hose and is significantly lighter in weight  but noise transmission is higher and this disadvantage  has tended to  limit the use of the type C hose. 

SAE J 51 type D is designed to give the lower permeation rates associated with type C but also to have the noise transmission rate of type B. A thermoplastic ( usually polyamide ) inner liner is bonded to a layer of rubber over which the reinforcement is applied, followed by a rubber outer cover usually CSM or polychloroprene.

Air brake and Vacuum Brake Hose:

Normally hoses for air and vacuum brakes are made to the SAE 1402 and 1403 standard respectively and consist of an inner liner of NBR, CR or NBR/ SBR blend  a textile reinforcement of polyester, polyamide, rayon, or polyvinyl alcohol and an outer cover of CR or CSM. Continuous  vulcanization or pan curing is the usual method of manufacture.

Brake Hoses:

Brake hoses were traditionally manufactured on steel mandrels to meet the requirements of SAE J1401.A more modern technique for producing this type of hose is  by flexible mandrel and continuous vulcanization either steam or pressurized liquid salt.

Turbocharger         Hose:

Turbocharging of cars to give extra performance has grown quite markedly.  Hose connected to the turbocharge must withstand high temperature are usually made with silicone rubber, polyacrylates or ethylene acrylic rubbers and reinforced with aramid yarn such hoses are capable of operating at  150°C for a substantial length of excursions up tp 170 pr  180°C. The hoses must be resistant to oil as well as hot air.

Oil cooler hoses:

Oil coolers are frequently used on heavy vehicles and also on some larger cars, particularly those with automatic transmissions where temperature of around  150° C  are encountered.  Oil cooler hoses for cars are usually textile reinforced with end fittings attached. Chlorinated polyethylene or ethylene acrylic is the usual choice of polymer but if  oil temperature will frequently rise to 150 degree Celsius or more a fluroelastomer must be used as the inner liner.