4.1.7 Valve Spring
4.1.7.1 This part is highly stressed. The exterior surface must be free of pitting, cracks and
corrosion. If any corrosion is observed on the spring, use magnetic-particle or dye-
penetration inspection (performed by certified trained personnel) to evaluate the exterior
surface and ensure that it is free of cracks and corrosion pits.
Figure 4-9 Valve Spring
WARNING: Valve-Spring Failure. Defects in coil springs, such as cracks and
corrosion pits, can act as stress concentrators. Failure to detect these defects can
result in coil-spring breakage and uncontrolled valve venting.
4.1.7.2 Test the springs by pressing them to 80% of maximum deflection in a press for two (2)
minutes. Remove from the press and then measure the spring free-height. If free-height is
less than the minimum indicated in Table 4-1, replace the spring.
WARNING: Deficient Valve Travel. Coil springs that have taken a “set,” resulting in
an undersize free-height, will not allow the valve to open fully. The spring should not
be bowed more than 1/4" when in the assembled position. Bowing in excess of this
amount can cause the spring to rub against the inside wall of the nozzle or guide
tube and adversely affect the pressure settings. If any of the defects mentioned
above are observed, the spring cannot be repaired and must be replaced.
Height at 80% of Max.
Deflection (Inches)
Minimum Free-Height
(Inches)
Table 4-1 Minimum Free-Heights for Spring After Pressing 80% of the Maximum Deflection for Two Minutes
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