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Section II. REPAIR PARTS, TOOLS, TMDE AND SUPPORT EQUIPMENT
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TM-5-5420-279-23 Dry Support Bridge (DSB) (NSN
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Fig 5.1 Stress Corrosion Cracking
TM 5-5420-279-23
Section III. PREVENTATIVE MAINTENANCE CHECKS AND SERVICES (PMCS)
This section details the preventative maintenance checks and services (PMCS) which are carried
out at unit level to prevent failure of components.
WARNING
DEATH OR SERIOUS INJURY CAN OCCUR IF PMCS ARE NOT CARRIED OUT BY
AUTHORIZED PERSONNEL, AT THE FREQUENCIES STATED IN THIS SECTION.
NOTE
Before any inspection is carried out, all components must be cleaned using a high-
pressure water hose.
Prior to the use of lifting equipment, the operator must ensure that all lifting equipment
(crane, jacks, tail lift, shackles, lifting beams, lifting slings, etc.) is serviceable.
CORROSION AND CRACKING
a. Early detection of cracks in highly stressed components is essential. Any delay may result in
the complete failure of a component. Visual inspection of dismantled components is therefore to
be carried out thoroughly and the inspector should in particular, look for stress corrosion cracks.
b. Stress corrosion cracks are a form of inter-crystalline corrosion, which occur under the
influence of static stress and which may also occur within heat affected zones of welded
components. Stress corrosion cracks lead to mechanical failure.
c.  Any cracks less than 3/8in (10mm) long must be clearly marked and observed. Cracks over
3/8in (10mm) long must be repaired. Any cracks or damage to the paint and/or aluminum
protective coating must be reported immediately and the necessary repair action taken.
d. If bituminous black material is oozing from a component, with the exception of around seal
plates, the component must be closely examined. This may indicate a serious crack, which would
require repair at Depot Maintenance.
e. The inspection of dismantled components should be carried out visually in great detail and
the designated inspector should, in particular, look for the following defects:
(1) Stress Corrosion Cracks. This form of corrosion, inter-crystalline in nature, occurs under
the influence of static stress and may occur within the heat-affected zones of welded
components. It leads to mechanical failure generally in the form of cracking (Fig 5.1).

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