The valves are made of very high quality steel because they get very hot during combustion. The cool intake mixture cools the intake valve. The materials and surface coatings used on valves depend on expected temperatures. The exhaust valve is usually made of austenitic stainless steel alloy. The valve face may be hardened with a hard alloy. This is called valve hardfacing. Hard facing is applied to the teeth and gage surface by welding with a rod in the form of a uniform mixture of particles of tungsten carbide and particles of matrix metal sintered together enough to form a rigid rod with some strength, but not completely sintered; that is, the rod has some remaining porosity.
Valve housing is made from steel, especially for gate valves. It has a central housing part provided in opposite walls with frustoconical openings tapering in outward direction and being aligned along a common axis and a pair of connecting sockets having inner chamfered end faces of the same cone angle as the aforementioned openings and aligned along the common axis with the latter. The connecting sockets are connected at the aforementioned openings to the opposite side walls of the central housing part by a pair of annular connecting members. The connecting members have each a cross-section in the form of a substantially right-angled triangle along frustoconical outer surfaces of the connecting members in which this frustoconical surface has a generatrix which is formed by the hypotenuse of the triangle, in such a manner that the cylindrical inner surfaces of the connecting members form continuations of the inner cylindrical surface of said connecting sockets and the inner annular surfaces of the connecting members facing a central plane of symmetry of the valve housing form directly or indirectly seating faces for a closer member to be mounted in the valve housing.
Valve Insertion is a method of inserting a specialty gate or ball valve directly into an existing main, while the existing pipeline is under working pressure without interruption of flow or service. Valve Insertions are performed on the types of pipe such as carbon steel, galvanized steel, stainless steel, copper and brass.