D-8.1 GENERAL. Annual inspection of chain components of a towline system should follow the Navy practices
for anchor chain detailed in NSTM 581 After cleaning by scaling, wire-brushing or sand blasting, each link
should be checked by sounding with a hammer. Give particular attention to locating possible loose studs, bent
links, excessive corrosion and sharp gouges.
D-8.2 SPECIFIC. Proper reactions to various conditions noted in the inspection are indicated m the following
notes, most of which apply to stud link chain.
a. Missing stud: discard link
b. Out-of-plane bending of more than 3 degrees' discard link.
Average of the two measured diameters at any point less than 95 percent of nominal diameter, or a
diameter in any direction less than 90 percent of nominal diameter: discard link
d. Crack at the toe of the stud weld extending into the base material: discard link
e. Surface cracks or sharp gouges: attempt to eliminate by light grinding. If the chain diameter is reduced to
less than 90 percent of the nominal diameter after grinding' discard link.
Excessively loose stud: since it is difficult to quantify excessive looseness of chain studs, the decision to
reject or accept a link with a loose stud depends on the experience and judgment of the inspector.
Consider discarding a link if.
Stud can move more than 1/8 inch (3 mm) axially or more than 3/16 inch (5 mm) later- ally m
A gap of more than 1/8 inch exists between the stud end in a link with a stud welded only on one
g. Cracks detected by magnetic particle inspection m the internal locking area of detachable link. discard
link. External surface defects m detach- able links are not cause for rejection if they can be eliminated by
grinding to a depth of no more than 8 percent of the nominal diameter of the chain.
h. Length over six links exceeding 26.65 times nominal chain diameter or length of individual link exceeding
6 15 times nominal chain diameter. discard links.
Excessive wear or deep surface crack on shackles, open links or swivels: Attempt to eliminate by light
grinding. If the cross-section area, diameter or critical thickness in any direction is reduced more than 10
percent by wear and grind- ing: discard the chain.
If a substantial number of adjacent links m a chain section meet the discard criteria, the chain section should be
removed and the chain joined again by detachable links that have been examined and found to be in
If a large number of links meet the discard criteria and these links are distributed throughout the chain's whole
length, replace the chain with a new one.
Re-welding of loose studs in the field is undesirable for the following reasons'
a. Welding m the field may produce hard heat- affected zones that are susceptible to cold cracking.
b. Hydrogen embrittlement may occur from absorption of moisture from the atmosphere or welding
Weld repairs on loose studs should be delayed as long as possible Where a few links are found with loose
studs in a short section of a chain, it is recommended that this portion of