Chapter 2 OPERATING INSTRUCTIONS

TB 5-4220-200-12-1

Chapter 2 OPERATING INSTRUCTIONS

Section I. THEORY OF OPERATIONS

2-1 GENERAL.

This section describes, locates, illustrates, and furnishes the diver with sufficient information for the proper opera-

tion of the components of the open circuit SCUBA system.

2-2

AIR-DEMAND REGULATOR (FIG. 2-1).

a. The Conshelf Arctic Explorer Regulator reduces high pressure cylinder air to ambient pressure using two

separate stages that are joined together with an Intermediate pressure hose. The 1st stage regulator has

a diaphragm operated, balanced high pressure valve to reduce cylinder pressure to 130 psig intermediate

pressure. The 2nd stage regulator reduces the intermediate pressure to ambient breathing pressure with

a downstream, diaphragm and lever operated demand valve.

When the diver inhales, a negative pressure is created inside the 2nd stage regulator, drawing diaphragm

(47) inward, opening demand valve (36). This results in a drop in the intermediate pressure acting on dia-

phragm (20) inside the L. P. chamber. allowing mainspring (23) and pin (18) to push the 1st stage valve

(14) open.

At the end of the inhalation cycle, the pressure on both sides of diaphragm (47) equalizes, and the dia-

phragm is outward allowing the 2nd stage valve (36) to close. Intermediate pressure acting on diaphragm

(20) then increases to 130 psig, overriding the force of mainspring (23), allowing the 1st stage valve (14)

to close.

The 1st stage valve (14) is "Balanced," meaning that the high pressure air surrounding it exerts no open-

ing or closing force against the valve itself. The only forces acting on the valve are: the valve seating force

of spring (13); and an intermittent opening force from mainspring (23) acting through pin (18). These are

forces required for the normal operation of the valve. The purpose of the "balanced" valve is to maintain

a constant, steady Intermediate pressure setting regardless of the drop in cylinder pressure from a full

to an empty cylinder. This permits sensitive adjustment of the regulator for easy breathing at all cylinder

pressures.

Figure 2-1. Air Demand Regulator

2-1