TM 5-4220-225-14
1-9. Equipment Data.
Helmet Assembly
Weight ..............................................................................................
40 lb (18 kg)
Flow..................................................................................................
6 ACFM
Breathing Medium ............................................................................
Air
Operating Temperature Range (Air) .................................................
29-129°F (-2-49C)
Operating Temperature Maximum (Water) ......................................
92°F (33C)
Normal Working Dive Limit ..............................................................
190 FSW
Exceptional Exposure Dive Limit .....................................................
285 FSW
Maximum Water Current...................................................................
2.5 kn
Drysuit
Weight ..............................................................................................
8 lb (3.6 kg)
Outer Garment
Weight ..............................................................................................
4 lb (1.8 kg)
Jocking Harness
Weight ..............................................................................................
3 lb (1.3 kg)
Leg Weights ...........................................................................................
40 lb (18.2 kg)
Boots (lightweight)
Weight ..............................................................................................
10 lb (4.5 kg)
Hip Weights (optional) ............................................................................
20 lb (9 kg)
1-10. Safety, Care, and Handling. When operating or performing maintenance on MK12 SSDS observe all
WARNING's, CAUTION's and NOTE's in this manual. Avoid careless operating or maintenance habits which cause
accidents to personnel and damage to the equipment. The equipment can be extremely hazardous to diving personnel if
not operated and maintained properly. If there is the slightest hint of a problem with the equipment, or the equipment
may be contaminated do not operate the equipment. Notify your supervisor.
SECTION III. TECHNICAL PRINCIPLES OF OPERATION
1-11. Theory of Operation. The MK12 SSDS consists of helmet and dress assemblies with support equipment. The
MK12 helmet is operated using air as the breathing medium. The basic helmet assembly is used in all configurations
mating with the lower breech ring affixed to either the neckpiece of the drysuit or to a neckdam. Two exhaust valve
configurations, using the same body, are available; the adjustable and the ambient. The adjustable valve permits varying
the helmet differential pressure (P). The ambient valve has an inherent fixed P. The helmet is secured to the lower
breech ring by locking devices w/safety pins. This arrangement provides quick positive alignment of the helmet to the
lower breech ring and eases removal. Diver's dress can be tailored to task requirements. A drysuit and outer garment
may be used in severe cold working conditions. For diving in warm water a neckdam may be used with or without a
wetsuit. The jocking harness is the same for all configurations. The umbilical consists of the diver's high pressure hose,
communication/strength cable, and pneumofathometer hose joined together into a single component. Two-way
communication between diver and tender or diver to diver is provided, using the communication station.
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