The neck clamp assembly, like all other mechanical parts, will wear over time, thus requiring routine maintenance and eventual replacement. DSI® strongly recommends that all Kirby Morgan® SuperLite®-17 A/B / MK 21 Neck Clamp Assemblies be carefully inspected for signs of damage and wear at least semi-annually and checked daily for proper adjustment prior to commencement of dive operations. Worn or damaged neck clamps and especially those damaged from improper adjustment pose a potentially serious safety hazard to the user. All neck clamp assemblies will eventually become worn to a point where they must be replaced. Proper routine inspection should reveal wear and damage before it becomes a danger to the user.
In April of 1999 DSI® started embossing all new neck clamp assemblies with the date of manufacture and identification number. All newly manufactured neck clamps undergo inspection and testing in accordance with AWS Standard D1.1. Prior to this date, neck clamps were built to an engineering drawing and were not subjected to the ANSI/AWS standard. DSI® continues to use the same engineering drawings but has additionally adopted the ANSI/AWS standard to help ensure highest quality control.
DSI® recommends a maximum service life of five years for neck clamps that are used in harsh environments (i.e. welding, cutting, and burning, contaminated waters) or other practices that can degrade the metal components of the neck clamp. All neck clamps should be visually inspected at least on a semi-annual basis in detail with the neck dam fabric removed so all welds can be visually inspected for signs of cracking or damage. Neck clamps kept in service after 5 years should be inspected more frequently. Additionally, the three pins and clevis welds should be carefully inspected, as well as the adjustment stud. All metal parts should be carefully inspected for signs of wear or damage. The stainless nylon lock nut will wear out over time and will require replacement. If any other metal components appear worn or damaged, the neck clamp must be replaced. This inspection is considered the minimum. The use of other non-destructive test methods such as dye penetrant testing can be used to validate suspected damage.
Neck clamp assemblies which are bent or deformed due to mis-adjustment or accidental damage may be returned to DSI®, via your local dealer, for possible repair. Users must keep in mind that there are limits to restoring used or abused parts. DSI® uses a fixture that resembles the bottom of a SL 17A/B to adjust all new neck clamps and this same fixture can often be used to reshape bent or deformed neck clamps. If there is any question regarding the condition of the neck clamp, don't use it. Suspected worn or damaged neck clamp assemblies should be taken to a DSI® dealer to be sent on to DSI® for a factory inspection.
Neck clamp/Yoke assemblies should be visually inspected prior to each dive as part of the pre-dive check of the helmet. This pre-dive inspection is done with the neck dam fabric/rubber in place.The following procedure is designed to help identify degradation of neck clamp components before the degradation poses a threat to the user. It should be preformed daily before the start of dive operations. Diving Systems highly recommends that a neck dam/yoke assembly for each diver or at least of each neck dam size be available during dive operations with multiple divers using the same helmet. An ill fitting, wrong size neck dam can pose a serious hazard to the diver.
Neck Clamp and Yoke Assembly Pre-Dive Inspection:
(Refer to the illustrations for reference).
Visually inspect the moving parts of the clamp assembly including the three pins (A) in the over-center lever assembly, and the three clevis blocks. Visually inspect for bent or broken pins or a bent or broken handle and locking bail (B).
Visually inspect the welded area (E) on the long & short track for signs of stress or weld cracking.
Check to ensure the adjustment stud (C) is not bent or damaged. Visually inspect the welded area (D) around the base of the stud for signs of stress or weld cracking. (See Safety bulletin 1 of 2000)
Check to ensure the pull pin latch catch mechanism (1) functions smoothly. Ensure the safety pin is present and attached by a lanyard.
Check to make sure the rear hinge tab is secured tightly to the clamp foundation. This can be checked by wiggling the yoke back and forth sideways (M) to ensure it and the hinge are securely tightened to the hinge tab and the hinge tab is secured to the clamp. If there is a slop in this movement, the neck clamp/yoke assembly should be serviced per the operations/maintenance manual.
Check the condition of the neoprene or rubber neck dam for wear and deterioration, replace if necessary.
Check fit and adjustment of the neck clamp by installing the clamp on the helmet, ensuring that the clamp is seated properly over the o-ring area of the helmet. When closing the lever, the lever should get tight at the mid-point of travel, and once the lever is past the mid-point of travel, the clamp should close easily. DO NOT FORCE THE CLAMP SHUT! If it does not close as described, you MUST adjust the clamp by loosening the adjustment locking nut (F). From the closed position, if you pull out on the lever approximately 1-2 inches, the lever should snap closed when released.
As the neck dam ages it compresses. The clamp must be adjusted by tightening the adjustment locking nut (F) so that the clamp operates as described above.
The stainless steel nylon lock nut (F) will require periodic replacement as the nylon insert wears out due to the periodic adjustments to the clamp that MUST be made as the neck dam ages or you change to a dry suit mount. YOU SHOULD NEVER HAVE TO FORCE THE CLAMP SHUT!
Proper adjustment of the neck clamp should place the bail squarely in the groove of the latch catch body when the clamp is closed.
The following service procedure is to be followed when doing the pre-dive inspection described above and a "slop" or looseness is observed in the yoke mounting. This procedure is not in many of the older Operations and Maintenance Manuals and should be printed out and added to your manual. Diving Systems recommends that if your Operations and Maintenance manual is not ©1997 or newer (on the bottom of the title page), you should upgrade your manual. There have been several maintenance and safety issues addressed in the newest version that every end user of the SL-17 and MK 21 should be aware of.
Neck Clamp/Yoke Assembly Maintenance
After inspecting the pins and welds of the neck clamp, check to make sure the rear hinge tab is secured tightly to the clamp foundation. This can be checked by wiggling the yoke back and forth sideways (M) to ensure it and the hinge are securely tightened to the hinge tab and the hinge tab is secured to the clamp. If there is a slop in this movement, first check to ensure the brass hinge is firmly attached to the yoke assembly (2). If these are loose, they should be removed, cleaned and reinstalled using Locktite® 222 on the screws and torquing them to 20 inch pounds. The purple colored Locktite® 222 is service removable. Do not use Locktite® 262, or any permanent thread locker!
Insure that the two bolts (3) are installed securely to the brass hinge. If these are loose, they must be removed, cleaned and reinstalled. They should be retorqued to 70 inch pounds. You must use Locktite® 222 on the bolts (3).
If these are tight, the hinge tab to clamp screws may be loose. To tighten these screws you must remove the two bolts (3) holding the brass hinge to the clamp and remove the yoke & hinge from the clamp. The screws may then be accessed by pushing the neck dam neoprene (4) to the side. Retorque the screws to 60 inch pounds. No Loctite is used on these screws as the star washers provide the locking mechanism. If these screws tend to work loose, the star washers should be replaced.
Remount the yoke & hinge using the two bolts as described above. You must use Locktite® 222 on the bolts (3) when reinstalling them.