19
External-Style Pressure Relief Valve A-1402C Series
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.
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.
4.1.8 SPRING GUIDE
4.1.8.1
This structural part has guides on its outer edges (Figure 4-8). Move it up and down the length of the top guide as
indicated below. If it binds, look for dents or gouged surfaces on the inside of the top guide. Repair the damage to
allow free movement of the spring guide.
WARNING: Valve Sticking.
If the spring guide binds in the top guide bore, the valve may stick in the open
position or be prevented from opening. Always ensure free travel of the spring guide before reassembling the valve.
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.
WARNING
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.
WARNING
WARNING
Spring Part Number
Wire Size (REF)
(Inches)
Height at 80% of
Max. Deflection (Inches)
Minimum Free-Height
(Inches)
14-13-SS
0.19
3.12
4.63
15-375-SS
0.34
3.61
5.00
15-150-MO
0.28
2.80
4.00
Table 4-1 Minimum Free-Heights for Springs After Pressing 80% of the Maximum Deflection for 2 Minutes
