UFC 4-390-01
23 July 2003
B.7.1 Welding and Brazing. All welded and brazed pressure-
retaining construction should be performed in accordance with
written and approved procedures, as discussed in Section 3,
Sections 3.3.3 and 3.3.4. Welding and brazing of structural
members may require the use of approved procedures depending on
the application. The applicant is responsible for the integrity
of the joint design and the proper choice of filler material.
B.7.2 Threaded Fasteners. The design of all critical threaded
fasteners, including bolts, studs and nuts, should meet the
requirements of the Screw-Thread Standards for Federal Services,
FED-STD-H28, Screw-Thread Standards for Federal Service. Studs
and bolts should be of sufficient length so that, when nuts are
tightened to their appropriate torque values, at least 1 thread
is exposed. Where practicable, the number of threads exposed
should not exceed 5; however, in no case should the thread
exposure exceed 10 threads. Any fastener design not covered in
FED-STD-H28 or ASTM A325, Standard Specification for Structural
Bolts, Steel, Heat-Treated, 120/105 ksi Minimum Tensile Strength
must be brought to the attention of the SCA for approval.
B.7.3 Locking Devices for Critical Mechanical Fasteners. The
need for locking devices on mechanical fasteners should be
evaluated by the applicant. In cases where the loss of a
fastener would cause a critical failure, locking devices should
be used. Generally, a locking device should provide a positive
locking action, be simple to install and should lend itself to
easy inspection without disturbing the locking feature.
If the locking device does not meet the above guidance, or is
unique in design, the applicant should bring this device to the
attention of the SCA, with sufficient information to justify the
safety and integrity of the device. The justification should
include recommended inspection procedures and acceptance
standards.
If locking devices are not practical, critical fasteners should
be marked with a "torque stripe" which identifies the relative
locations of parts when properly torqued.
B.8
DESIGN OF PIPING SYSTEMS
When designing piping systems, the applicant should employ the
design requirements of established military or commercial
standards where a substantial body of service experience exists
in similar applications.
Maximum System Pressure (MSP) is the highest pressure that can
exist anywhere in a system or subsystem during any condition
(i.e., uncontrolled pressure excursion). MSP is generally
understood to be the relief valve set pressure and must include
the effect of static head pressure. Pressure ratings for all
piping and components should be equal to or greater than the MSP
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