Exhaust Valve Spindles & Seats

In order to withstand the extreme combustion temperatures generated in high performance two-stroke diesel engines, the exhaust valves must be manufactured from special alloys. The traditional material used in the manufacture of 2-stroke exhaust valves is stainless steel with a stellite layer inserted into the seating face. Later generation engines are fitted with exhaust valves manufactured from solid nimonic material. The high material cost of exhaust valve spindles and seats makes reconditioning a very attractive commercial proposition provided that it is carried out in a controlled manner.

Exhaust Valve Spindles

The process for reconditioning exhaust valve spindles involves the following steps:

• Complete pre-inspection.
• Pre-machining of valve disc and seating area. Crack repair is done at this stage if required.
• Welding of the valve disc (upper and lower side) with suitable material using MIG welding equipment.
• Stelliting of seating area using plasma transferred arc process which ensures a high quality weld with minimum dilution of base material.
• Final machining and grinding to the OEM specifications.
• Stem treatment, if needed, by chrome plating or HVOF spray.
• Final inspection by certified QC department.

Exhaust Valve Seats

DMI is also able to recondition exhaust valve seats for all types of engines. This is done by removing the existing stellite layer, building up seating area followed by re-stelliting, machining and grinding to original profiles.