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RISK ANALYSIS OF INTERNAL COMBUSTION ENGINE 37
VALVE PRODUCTION USING FMEA METHOD

3. 1. Basic Valve Characteristics
There are some main specifications for valves we need to know while doing our P-FMEA for
them. If we subgroup them briefly;

 One-piece valves: They are made from one piece as whole, from martensitic/austenitic
or nimonic materials.

 Two-piece valves: They are made from two pieces differently, one part (stem) is from
martensitic material always, and the other half is made from austenitic or nimonic
material.

 Seat-hardened valve: For only martensitic valves, seat part may be hardened with high
temperatures.

 Stellite-welded valves: In order to hardening, seat part may be welded with a material
called stellite.

These are some main characteristics that we shall keep in mind while making our FMEA sheet.
Also we can keep in mind that the working temperatures for a valve in an engine, changes like
the figure below:

Figure 5. Working temperatures for exhaust (left-side) and intake (right-side) valves.

4. FMEA
As we defined FMEA at the introduction section above; there are numerous variations of such
worksheets. A FMEA can be a qualitative analysis, [7] but may be put on a quantitative basis
when mathematical failure rate models are combined with a statistical failure mode ratio
database.

Sayı 5, 2016 GiDB|DERGi