Technologies for Increased Valvetrain Lifetime
Tenneco develops and manufactures engine valves and valvetrain components, such as valve cotters, valve rotators and spring retainers for 4-stroke engines for use in ships – propulsion and auxiliary – as well as for power plants and off-road applications, e.g. railway or mining.
Basic valve designs are monometallic, bimetallic and hollow valve type with dimensions up to a maximum length of 1,000 mm, a stem diameter of 38 mm and a head diameter of 180 mm. They are made of high-alloy materials that can meet working conditions of modern engines and which are resisting against high combustion pressures, temperatures, corrosion attack and mechanical loads.
Valve rotators are designed to provide a defined rotation of the valve to create homogeneous surface contact and to prevent the forming of deposits on the valve seat and seat ring. The rotation results in optimized sealing and increased valve lifetime. Current challenges for rotators result in new creative designs based on reduced packaging space but increased valve spring forces within the valvetrain; a consequence of increased operating temperatures and combustion pressures of modern engine designs.
Powder Metal Technology for Superior Wear Resistance
Tenneco’s Valve Seats and Guides (VSG) product line develops valve seat inserts (VSI) as well as valve guides (VG). Parts are manufactured utilizing Powder Metal technology for applications up to 65 mm VSI outer diameter and 125mm VG length.
Powder Metal (PM) is a near-net shape primary shaping technology with efficiency advantages compared to casting. With superior wear resistance based on tailored mechanical and tribological properties, valve seat insert and valve temperature reduction by high thermal conductivity and the oil-impregnated Powder Metal intrinsic porosities providing liquid lubrication under all running conditions, PM valve seats and guides are already in use with several LBE customers.
Tenneco’s material portfolio for VSI and VG covers a wide range from cost-efficient, lower-alloyed materials up to highly alloyed grades including copper infiltration, machinability enhancers, solid lubricants, hard phases and hard particles. The portfolio also includes densified materials for outstanding mechanical properties and highly corrosion-resistant alloys.
PM production technology enables for a so-called dual layer VSI design for the purpose of cost reduction, which consists of an optimized back layer material with high mechanical strength against plastic deformation under high thermal and mechanical load, and relaxation properties on par with or above cast materials. The top layer material is optimized for low wear and tailored tribological properties in combination with the mating valve head material.