Airflow rate:
The air train of the DESCO Air hat will deliver a minimum of 12cfm at 100psi. Each new and rebuilt Air hat is
tested at the factory to assure this flow rate. Factors such hose diameter, delivery pressure, and condition of the
Lambswool will effect this flow rate. The 6000 PSI Stainless Steel Hoke Valve (p/n 2112G6Y) is capable of
delivering in excess of 50 SCFM at 100 PSI. It will reach approximately 75% of its maximum flow at one turn
of the valve handle. DESCO recommends a minimum of 6CFM at 100 PSI to properly ventilate the Air Hat.
This figure is based on U.S. Navy Diving Manual recommendationsfor open circuit diving, and DESCO testing
of the Air Hat. For light work setting the Air Control Valve between ¾ and one turn will provide sufficient air
flow while reducing air flow noise. If the workload becomes more strenuous the flow rate should be increased.
How to Minimize Air Intake Noise:
The air train of the DESCO Air Hat will deliver a minimum of 12 cfm at 100 psi. Each new and rebuilt Air Hat
is tested at the factory to assure this flow rate.Factors such as hose diameter, delivery pressure, and condition of
the Lambswool will affect this flow rate. The 6000-PSI Stainless Steel Hoke Valve (Hoke P/N 2112G6Y) is
capable of delivering in excess of 50 SCFM at 100 PSI. It will reach approximately 75% of maximum flow at
one turn of the valve handle. DESCO recommends a minimum airflow deliveryof 6cfm to properly ventilate
the Air Hat. This figure is based upon U.S. Navy Diving manual recommendations for the Mark 12 helmet,
which has a higher interior volume than the Air Hat. For light work setting the Air Control Valve between ¾
and one turn will provide sufficient airflow while reducing airflow noise. If the workload becomes more
strenuous the flow rate should be increased.
The Polyethylene air distributor directs air across the inside surface of the window and helps to prevent fogging.
As delivered from the factory, the interior of this air distributor is tightly packed full of Lambs wool, which
greatly reduces air intake noise. If a new air distributor is installed be sure new Lambs wool is inserted and
packed. Lambs wool is a coarse fiber material that does not compress to the point where it would choke airflow.
THERE IS NO SUBSITIUTE FOR LAMBSWOOL. Cotton and other similar materials will compress to a point
where it can impede airflow. Never substitute another material in the air distributor. Lambs wool is available in
Drug Stores, and the health products aisle in most department and grocery stores. The Lambs wool will also act
as a filter in the incoming air.
Particulate matter coming down the air system can accumulate in the Lambs wool gradually reducing the
airflow capability. Periodically inspect the Lambs wool and replace if it is dirty, shows signs of compacting, or
is contaminated with oil. If the air distributor shows signs of a color change this may indicate oil contamination
and it should be checked.
IMPORTANT NOTE:
The flat neck ring gasket can take a set, which will reduce its effectiveness as a seal, if the neck ring insert
assembly is left clamped in the Air Hat while it is not in use. When the Air Hat is not going to be used the neck
ring insert assembly should be separated from the Air Hat.
Non-Return and Bail-out Non-Return Valves:
The Non-Return valve on the Air Hat is standard 9/16”- 18 Oxygen thread. The Bail-out Non-Return (marked
with a letter ”B”) is drilled to accept a SCUBA whip from a Bail-out Bottle. A dust cap is provided on the Bail-
out Non-Return to protect the threads when not in use. The dust cap will provide some sealing but a complete
airtight seal is not guaranteed. The integrity of the Non-returns can be tested by applying air pressure to the Air
Hat with the control valve fully closed, then removing the air supply hose, and applying a solution of
dishwashing detergent and water to the inlets. No air should leak back through the Non-Returns. If a leak is
found the Non-Return disk may require replacement. This test method can be used on all connections in the air
supply train.
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