(1) Insert pressure tank (with pressure-tank valve and check valve mounted on the tank) through the pressure-tank clamp. Be sure to aline the regulator tube, elbow, and pressure-tank valve threads carefully so that they cannot be damaged when connecting. (2) Close the pressure-tank clamp. (3) Start the threaded connections by hand to be sure they are well alined. Do not force. Use wrench for final tightening, but do not apply great torque to the wrench. (4) Insert the valve flexible shaft through small clamp into the pressure-tank valve. Using wrench, tighten the large hex nut located between shaft and valve. (5) Tighten the clamp on the valve flexible shaft. (6) Place pressure-valve handle on threaded end of the shaft. Place nut on threaded end and tighten with adjustable-end wrench. _d. Adjustment._ If valve handle cannot be turned by hand: (1) Remove flexible shaft and handle. Never apply a wrench to these parts. (2) Turn end of pressure-valve stem with wrench to open valve. (3) If stem will not turn, replace the tank and valve. (4) If stem turns, work it back and forth with wrench. (5) Reconnect flexible shaft and handle. (6) If handle does not turn easily, repeat the process until handle turns, or replace tank and valve. (7) Close valve before charging tank. _e. Maintenance._ (1) If either pressure tank, pressure-tank valve, or check valve are damaged or defective, all three must be replaced as a unit. No attempt may be made to repair any of these parts or their connections. If makeshift repairs or improvised parts are devised, serious accidents can result because of the extremely high pressures to which the equipment is subjected. (2) Keep all threaded connections tightened. If a leak is suspected at any threaded connection, follow procedure in Paragraph 53 _d_. 67. PRESSURE REGULATOR. _a. Description and functioning._ The regulator automatically reduces the variable pressure of air or nitrogen in the pressure tank to a constant operating pressure of approximately 350 pounds per square inch in the fuel tanks. The regulator is located at a protected position in the tank group of the M2-2 portable flame thrower, where it is not readily subject to tampering or damage from the outside. The regulator tube with fittings connects the pressure-tank valve and pressure regulator. (Fig 33) Its outlet is connected to the fuel tanks by the diffusion-pipe assembly. (Par 68 _a_) Either of two interchangeable types of regulators is furnished: the spring type (Figs 33, 36, and 37), and the dome type (Fig 38). [Illustration: Fig 36. Rear of tank group, with carrier removed to show pressure regulator (spring-type) and connections.] _b. Removal of pressure regulator._ After release of all pressure: (1) Remove carrier (Par 71 _b_), if necessary. (2) Using wrench, unscrew the flared tube nuts and other fittings. (3) Lift out the pressure regulator.