JFD B44771, Руководство по эксплуатации и обслуживанию

Страница: 35 / 136

OM131 23
P1939-OM-131 R11 Chapter 2
Fig 2.8 Demand regulator
The purpose of the demand regulator is to supply cylinder gas to the SLS System when inhaling
from deflated counterlungs and to compensate in gas volume during any descent whilst the SLS
System is activated.
Normally, this regulator will function only during the first inhalation when using the SLS System. To
prevent it from passing gas when not required, it is biased such that it will flow gas only when
subjected to a negative pressure of 26 to 27 cm WG. The regulator is similar in principle to a
conventional demand regulator but differs in that it is designed to function with gas supply pressures
ranging up to 300 bar so that it does not require first stage pressure regulation.
Additionally there is an indicator pin fitted to the lid which uses the diaphragm movement to indicate
to the diver’s attendant that the positive pressure system is functioning whilst in the stand-by mode
(this is an additional confirmation to the overpressure indicator).
H.P. gas enters the demand regulator through the banjo fitting (Fig 2.8, Item 6). The valve pin (Fig
2.8, Item 19) is pressure balanced since gas supply pressure acts on the pin at the O-ring (Fig 2.8,
Item 15) and (over the same area) at the valve seat (Fig 2.8, Item 18). This means that the regulator
supplies gas at the same negative pressure setting over a wide range of gas supply pressures. The
valve is normally held closed by means of the spring (Fig 2.8, Item 12). When the pressure
difference sensed by the diaphragm (Fig 2.8, Item 20) is sufficiently great for the lever fork (Fig 2.8,
Item 21) to overcome the spring (Fig 2.8, Item 12) the lever fork pushes the valve pin allowing gas to
flow into the SLS System.
The overpressure valve (Fig 5.11, Item 19 - not shown above) ensures that in the stand-by mode,
the internal pressure in the SLS System, never exceeds 172 mbar (2.5 psi). This valve is factory set
and should not require adjustment.