and the poslIlon of the axle should be sucb that rhe pawl, when resting on the horizont.aJ
chain link. foms an a ngle of approxjmately 40 ° with rbl:: ct.'ntrtliDl· or the chain. The
surface of the pawl which rests against the chain should be concave to essentiaUy con form
with the external contour of the chain link. If tbe pawl is to be lifted and lowered by a
lever, the lever should be easily operated by a force of not more tban 245 N (55 Ib) exerted
on its end. The pawl should be provided with a counterweight ij necessary to meet this
criteria.
- The bar in a bar·type chain stopper should be pivoted on brackets off one of the fiide plate-s
such that it falls into slots cut in the side plates, as shown i.o Figure Al. The arrangement
and orientation of the slots and the position of the pivot should be such that the side of the
bar which reSLS against the upright chain link makes an angle of approximately 50° with the
chain centreline and that the lon!.',irudinal axis of the bar is horizontal in the close d position
Tbe surface of the bar which rests against the chain sbould be concaved to essentially conform
with the external surface of the chain link. The bar should be lifted and lowered by a man
standing on the deck and be capable of being lifted by a force of not more than 245 N (55 Ib)
exerted on the handle. Tne bar should be provided with a counterweight having a striking
surface for raising the bar with the blow of a hammer.
- TIte pawl axle bearing surfaces, the crank mechanism, and t.he bar pivot surfaces should be
designed to resist corrosion and be provided with suitable lubrication points.
- A latching pin(s) or mechanisro(s) should be provided to hold the pawl or bar in the
closed position such tbat the chain cannot release and to hold the pawl or bar i.n the opeo
position such that the chain can run freely. The latching pin or mechanism should be
attached to the frame of the stopper by a shon chain if it might ot.herwise be separated from
the stopper.
- The chain stopper should be constructed of rolled, cast, or forged steel. Cast iron is not
acceptable. If the chain stopper is to be welded to the deck, the sleel used in the chain stopper
base should be either ordinary-strength or high-stTength steel as defined by the Classification
Societies.
A.2 WELDING PROCEDURES FOR CHAIN STOPPERS
- Welding in the construction and fabrication of chain stoppers should comply witb the
requirements of this section. unless approved otherwise by owner. In all instances welding
procedures and filler metals shou.ld be applied which produce sound welds that have strength
and toughness comparable to that of tbe base material.
- The plans submitted for construction and installalion should indicate clearly all welds. The
welding process, filler metal, and joint design sbould be shown on the detajJ drawings.
- Only qualified welders should be used for tbe construction and installation. On owner's
request, the manufacturer and installer should submit up-to-daLe records of the qualification
papers for each of the welders to be used.
- Procedures for the welding of all joints should be established before construction or
installation of the chain stopper. Upon owner's request the manufactuler and installer should
submit the proposed welding procedures [Q be used. The procedures shouJd include the
welding processes, types of electrodes, edge preparations, welding techniques. and pOSitions
proposed. The procedures should be in accordance wjth the appropriate parts of Section 30
of Lhe Rules for Building and Classing Steel Vessels by the American Bureau of Shipping or
in accordance with appropriate specifications by other Classification Societies.
- All welded joints should be inspected to t he satisfaction of the owner's representative by
established non-destructive test methods such as radiographic, ultrasonic. magnetic. particle,
or dye-penetrant inspection.
