Chapter XVI: Section XVI: Tank Group

65. GENERAL.

The tank group stores fuel and pressure. The fuel is placed under pressure when the pressure-tank valve is opened. The tank group is supported upon the firer’s back and shoulders by the carrier.

66. PRESSURE TANK AND VALVE ASSEMBLY.

_a. Description and functioning._ The pressure tank and valve assembly (Fig 33) includes:

(1) _Pressure tank._ The pressure tank is a lightweight, airplane-type cylinder, able to withstand the great pressure which it contains. The tank is charged with air or nitrogen at 1,700 to 2,100 pounds per square inch pressure by use of auxiliary equipment as described in Paragraphs 31 and 32. This pressure stays in the pressure tank until the weapon is ready to be fired. Opening of the pressure-tank valve releases air or nitrogen through the pressure regulator to the fuel tanks. Oxygen or combustible gases are never used in the tank because a violent explosion may result. The tank is large in capacity to assure ample pressure, and hence full range, for the entire load of fuel. The pressure-tank clamp (Fig 39), a steel-strap device with hinge and toggle-type latch, holds the pressure tank in place on the fuel tanks.

(2) _Pressure-tank valve._ (Figs 33 and 34) This valve is screwed into the bottom of the pressure tank. The valve stem slides into the valve end of the valve flexible shaft. When opened by means of the valve handle and valve flexible shaft, the valve permits passage of compressed air or nitrogen through tubes and the pressure regulator to the fuel tanks. The valve is of the quick-opening, packless, diaphragm type.

(3) _Pressure-valve handle and valve flexible shaft._ (Figs 33 and 34) The pressure-valve handle is held by a small nut on the end of the valve flexible shaft, which in turn is connected to the pressure-tank valve by means of the valve stem and a large hex nut. The handle and shaft extend to the right of the tank group, enabling the firer to open and close the valve without assistance when carrying the weapon. The handle slips over the end of the shaft and is held to it by a nut. The shaft is held to one of the fuel tanks by a clamp, nut, and bolt welded to the tank.

(4) _Check valve._ (Figs 33 through 35) The check valve has the same function as the valve on a vehicular tire tube, but it is much heavier in construction and different in design because the pressure in the flame thrower is 50 times greater than that in an automobile tire tube. Connected by threads to the pressure valve, the check valve permits compressed air or nitrogen to enter the pressure tank during charging (Pars 31 and 32) but prevents its escape when the outside source of pressure is removed. The cap is removed from the check valve only for charging or testing.

_b. Removal._ (Fig 33) To prevent damage to threads, leaks, and loss of pressure and range, remove pressure tank and valve assembly only when necessary.

(1) _Release of pressure._ Be sure all pressure has been released from the pressure system before disassembling or removing any part or assembly of the pressure system. To release pressure, operate fuel valve (Par 26) and hold open until pressure is exhausted. As an added precaution, personnel should avoid facing the connections when disconnecting parts or assemblies.

(2) _Removal procedure._ After release of all pressure:

(_a_) Loosen the clamp from the valve flexible shaft.

(_b_) Using wrench, unscrew the large hex nut which holds the
flexible shaft on the pressure-tank valve.

(_c_) Pull the valve flexible shaft and handle free of the valve.

(_d_) Using wrench, unscrew the flared tube nut on the regulator tube
adjacent to the pressure-tank valve.

(_e_) Open pressure-tank clamp (Fig 39) and swing clamp strap outward.

(_f_) Remove the pressure tank together with the pressure-tank valve
and check valve.

(_g_) To remove valve handle, use the adjustable-end wrench to loosen
and remove nut from threaded outer end of valve flexible shaft. Slide
out the valve handle.

_c. Installation._ (Figs 33 and 39) To install:

(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).

_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.

_c. Installation of pressure regulator._ Line up pressure regulator, regulator tube, diffusion-pipe assembly, and fittings carefully so they will not be damaged when threads are tightened. Start threads with the hands. Apply only moderate wrench pressure to complete tightening. Replace carrier or carrier pack if either has been removed.

_d. Adjustment of pressure regulator._ The pressure regulator ordinarily requires no attention other than checking and tightening connections with the regulator tube and the diffusion-pipe assembly. If a defect in the regulator is indicated by falling off of the range of the weapon or by frequent breakage of the safety-head diaphragm (Par 56 _b_), the following procedure should be carried out. (When using wrenches, do not apply excessive force.)

(1) Remove the filling plug (Par 69 _b_) and ignition cylinder. (Par
30 _a_)

(2) Fill the fuel tanks with 4 gallons of water (or fuel).

(3) Connect the 0-to 500-pound fuel-tank testing gage, found in the
service kit, to the filling-plug hole. Tighten plug of gage with
wrench.

(4) Charge the pressure tank to a pressure of 1,800 pounds per square
inch. (Pars 32 and 33)

(5) Open the pressure-tank valve.

(6) Read the pressure on the gage. If 350 to 390 pounds is indicated,
omit steps (7) through (10).

(7) _To increase the pressure of a spring-type regulator_:

(_a_) Pry off the protective cap.

(_b_) Turn a set-screw wrench clockwise in the adjusting screw and
read pressure on gage.

(8) _To decrease the pressure of a spring-type regulator_:

(_a_) Turn the set-screw wrench counterclockwise more than is
considered sufficient to effect the desired reduction.

(_b_) Turn the pressure-tank valve off.

(_c_) Relieve pressure in the fuel tanks by compressing the fuel
valve until the pressure is below that desired.

(_d_) Release the fuel valve.

(_e_) Open the pressure-tank valve and allow the system to reach a
state of equilibrium, which occurs when the hissing sound ceases.

(_f_) Repeat the steps described above in (6) and (7).

(9) _To increase the pressure of a dome-type regulator_:

(_a_) Open needle valve No. 1 one full turn. (Fig 38)

(_b_) Open needle valve No. 2 one full turn. (There will be slight
leakage around the needle-valve thread.)

(_c_) Open needle valve No. 3 very slowly, watching pressure gage
closely. (As pressure builds up in fuel tanks there will be slight
leakage through needle valve No. 1.)

(_d_) When the pressure gage indicates 350 pounds, close needle
valve No. 3 tight.

(_e_) Close needle valve No. 2 tight.

(_f_) Close pressure-tank valve.

(_g_) When gage indicates zero, close needle valve No. 1 tight.

(10) _To decrease the pressure of a dome-type regulator_:

(_a_) Open needle valve No. 1 one full turn. (Fig 38)

(_b_) Open needle valve No. 3 very slightly, which will lower the
pressure.

(_c_) When 350 pounds is reached, close valve No. 3 tight.

(_d_) Close pressure-tank valve.

(_e_) When gage indicates zero, close needle valve No. 1 tight.

(11) Open pressure-tank valve and press the fuel valve to observe the
pressure with the weapon operating.

(12) After final adjustment:

(_a_) Close the pressure-tank valve.

(_b_) Open the fuel valve and release the pressure from the fuel
tanks.

(_c_) Remove the pressure gage and plug from the fuel tank.

(_d_) Install filling plug.

(_e_) Tighten filling plug with wrench.

(_f_) If regulator is spring-type, replace its protective cap.

68. FUEL-TANK ASSEMBLY.

_a. Description and functioning._ (Figs 4, 5, and 39) The fuel-tank assembly includes:

(1) _Fuel tanks._ Two alloy steel fuel tanks hold the fuel before it
is propelled to the target. They have a combined capacity, including
void, of 4-1/2 gallons. A void of approximately 1/2 gallon is left
in tanks when filling to allow for expansion and to permit entry of
the compressed nitrogen or air. To speed filling and cleaning of
the tanks, two openings are provided on top of the fuel tanks. The
openings are threaded to receive the filling-plug assembly and the
safety-head plug assembly, which are interchangeable in the openings.
Filling operations involve the use of auxiliary equipment and are
described in Paragraphs 34 through 40. The carrier and the pressure
system are supported on the fuel tanks.

(2) _Tank connector._ This open passageway between the fuel tanks
makes them, in effect, a single container. The location of the
tank connector and its large diameter permit easy flow of fuel and
pressure between the two tanks.

(3) _Hose connector._ The hose connector is the outlet for fuel
from the fuel tanks. It is located so that nearly all the fuel is
propelled from the weapon if firing positions are correct. (Par 24)
One end is welded to an opening in the tank connector. The other end
is threaded into the tank coupling.

(4) _Frame clamp._ This small metal clamp, with bolt, nut, and
washer, holds the hose connector to the carrier frame.

(5) _Diffusion-pipe assembly._ This T-shaped tubing carries
compressed air or nitrogen from the pressure regulator to each of the
fuel tanks. A flared tube connection and elbow connect the stem of
the T to the pressure regulator. The horizontal tubes of the T extend
into the fuel tanks and are welded to the fuel tank walls. Within the
fuel tanks these tubes are perforated with holes which permit ready
escape of the compressed nitrogen or air into the fuel tanks when the
pressure-tank valve is open.

_b. Removal and installation._ The tank connector, hose connector, diffusion-pipe assembly, and the two fuel tanks are welded together and cannot be disassembled from each other. No attempt should be made to remove any of these parts or assemblies.

_c. Maintenance._ Other than cleaning (Pars 51 _d_ and 55 _e_), repainting, and tightening of threaded joints, no repairs will be attempted by the first or second echelon on the fuel tanks, tank and hose connectors, or diffusion-pipe assembly. Emergency repairs may be made only by the third or fourth echelon. No attempt should be made to weld or patch any part of the fuel tanks.

69. FILLING AND SAFETY-HEAD PLUG ASSEMBLIES.

_a. Description and functioning._

(1) _Filling-plug assembly._ (Fig 39) This assembly fits into the
1-3/8-inch threaded opening at the top of either one of the fuel
tanks. It permits filling and cleaning of the tanks, and seals the
opening when the tank is not being filled or cleaned. The assembly
includes the filling plug proper and a plug-retainer assembly. The
latter is a metal rod which hangs from the plug on a metal chain. The
rod and chain prevent accidental loss of the plug.

(2) _Safety-head plug assembly._ (Figs 39 and 40) This assembly is
screwed into the threaded opening on top of either fuel tank. It
serves the same functions as the filling-plug assembly and moreover
protects the firer and other personnel. It includes:

(_a_) _Safety-head plug._ This plug is similar to the filling plug
except for the threaded hole which receives the safety head.

(_b_) _Safety head._ This metal head screws into the safety-head
plug. It includes a soft metal diaphragm which bursts when the
pressure in the fuel tanks exceeds 500 pounds per square inch. It
prevents the building up of dangerous pressures in the fuel tanks.

(_c_) _Deflector tube._ This short, curved piece of 1/8-inch pipe
deflects fuel and pressure away from the firer if the safety head
bursts. A lock nut holds the tube in position. (Par 12 _j_)

(_d_) _Plug-retainer assembly._ This assembly consists of a metal
rod and chain which hang from the plug and prevent accidental loss
of the plug when filling or inspecting.

_b. Removal of plugs._

(1) Before removing the filling plug, the safety-head plug, or an
unbroken safety head, operate the fuel valve until any pressure which
may have accumulated in the fuel tanks is eliminated. If the coupling
plug is in the tank coupling, very slightly loosen the threads of
either the filling plug or the safety-head plug, using the 1-3/4-inch
wrench, to eliminate pressure in the fuel tanks. Keep face and eyes
away from the threads.

(2) The plug-retainer assemblies should not be lifted completely out
of the tanks unless required.

(3) If either the rod or the rod and chain breaks from one of the
plugs and falls into the tank, upend the tank group to permit removal
of the parts.

(4) To replace burst safety head, unscrew lock nut and deflector
tube. (Fig 11) Using wrench (Fig 41), unscrew safety head. Never
disassemble the safety head.

_c. Installation of plugs._ The filling plug, safety-head plug, and safety head are screwed in by hand and then tightened with wrenches. No substitution will be made for the safety head, which is manufactured to burst at the safe limit of pressure. The plug threads and seats should be cleaned with a cloth (Fig 29) before installing plugs. Screw in deflector tube, using hand pressure. The tube outlet should face to the rear and at a 45-degree angle to operator’s left shoulder. (Fig 18) Replace lock nut and tighten with wrench. (Use wrench on lock nut, not on deflector tube.)

_d. Maintenance of plugs._ Replace safety head if damaged or blown. Never repair safety head or use an improvised head.

70. TANK COUPLING.

_a. Description and functioning._ This quick-connecting coupling (Fig 42) connects and locks the fuel hose or the coupling plug to the tank group. The coupling cams, lock, and washer provide a secure and tight joint. The tank coupling makes possible rapid replacement of emptied tank groups with filled and charged tank groups in the field. No tools are needed for this operation.

_b. Removal._

(1) To remove the tank coupling from the hose connector, apply a
wrench and unscrew.

(2) To disconnect the tank coupling from the fuel hose or the
coupling plug:

(_a_) Release pressure from fuel tanks by operating the fuel valve
or by opening very slightly the filling plug.

(_b_) Using hands, pivot the coupling lock back on the coupling
body.

(_c_) Using hands, pivot the two coupling cams back on the coupling.

(_d_) Slide out the fuel hose or the tank coupling.

(_e_) If coupling washer is to be removed, pry out with a screw
driver.

_c. Installation of tank coupling._ Proceed as follows:

(1) If coupling washer has been removed, replace.

(2) Insert coupling plug or hose nipple, tank end, in the coupling as
far as it will reach. Close the two cams. (Fig 43)

(3) Close the coupling lock (Fig 44), being sure to push it all the
way, until it covers the ends of both cams. (Figure 45 shows coupling
lock correctly locked on coupling plug.)

(4) If the tank coupling has been removed from the hose connector,
screw it on hand tight. Anti-seize compound should be applied lightly
to the threads to assure a tight joint. Use wrench to tighten the
coupling until it is in the position shown in Figure 34.

_d. Maintenance of tank coupling._ The coupling washer, made of synthetic rubber, should be inspected frequently. If it is damaged or swollen, remove it and replace. If the coupling leaks, inspect, and if necessary, remove and replace the washer.

71. CARRIER.

_a. Description and functioning._ (Fig 46) The tank group is securely carried on the firer’s back and chest by the carrier, which includes the metal carrier frame, the canvas carrier pack, webbing straps, and cord, all of which are parts of the tank group.

(1) _Carrier frame._ This lightweight, tubular-metal frame is bolted
to two pairs of brackets (upper and lower) on the fuel tanks. It is
also bolted to the hose connector by the frame clamp, which helps
support the connector. The frame is pierced by two parallel series of
holes, through which the cord (lashing) of the carrier is laced.

(2) _Carrier pack._ This is a sheet of heavy canvas, reinforced on
the tank side with strips of webbing. The smooth side of the carrier
pack rests against the firer’s back and cushions the back from
contact with the metal tanks. A series of eyelets is located on each
side of the pack.

(3) _Seine cord (lashing)._ The carrier pack is fastened to the
carrier frame by means of hard-braided cord which is laced through
the eyelets in the pack and the holes in the frame. The cord that
comes on the flame thrower stretches very little under load.

(4) _Straps._ The straps, made of wide cotton webbing, are
adjustable to fit the wearer. (Fig 18) They are provided with snap
release, hook-and-eye, and snap fasteners. The shoulder straps have
quick-release fasteners for rapid removal, if necessary, of the tank
group from the firer. The upper ends (steel loops) of the shoulder
straps are secured by pins to the steel support which connects the
two fuel tanks. Each of the pins is held in position by a split
cotter pin, which is inserted through a hole in the pin and is
then spread. The lower ends of the shoulder straps snap onto metal
loops at the bottom of the carrier frame. The upper body straps are
attached to metal loops on each side of the carrier frame. The lower
body straps are fastened to one of the lower two pairs of eyelets of
the carrier pack.

_b. Removal of carrier._

(1) To remove carrier or carrier frame, use screw driver and
adjustable-end wrench to take off frame clamp, bolt, nut, and lock
washer. (Fig 34) Then remove two pairs of bolts, nuts, and lock
washers which hold the carrier frame to bottom and top of the fuel
tanks. Lift off the carrier.

(2) To remove body straps, unsnap ends and lift out of holes. To
remove shoulder straps, unsnap lower ends and remove from holes. Pull
out cotter pins, then pins, from upper ends of shoulder straps, and
lift out straps.

(3) To remove carrier pack, unknot and unlace cord.

_c. Installation of carrier._

(1) To install carrier frame (or a complete carrier) place frame in
position adjacent to fuel tanks (Fig 46), insert bolts in holes,
place lock washers and nuts on bolts, and tighten with screw driver
and wrench. Replace frame clamp on fuel connector and frame. Insert
bolt in holes, place lock washer and nut on bolt. Tighten with screw
driver and wrench.

(2) If carrier pack has been removed, use cord to relash. Lace tight
and use slip-proof knots. (Fig 46)

(3) To install straps, snap ends of body straps and lower ends of
shoulder straps into positions shown in Figure 46. Place upper ends
(steel loops) of shoulder straps in steel support between fuel tanks.
Insert two pins through any two of the holes in the support and
through the shoulder strap loops. Insert cotter pins in holes in pins
and spread cotter pins to lock pins in place.

_d. Adjustment of carrier._ Carrier must be carefully adjusted to fit the individual firer so the load will not shift during sudden, rapid changes of firer’s position. Adjustments are as follows:

(1) _Cord and carrier pack._ Cord must be tight at all times. The
cord furnished with the equipment has very little tendency to
stretch. However, pull cord tight when lacing and use slip-proof
knots at ends. Tighten cord periodically.

(2) _Straps._ Adjust straps to fit each firer, moving slides on
straps as necessary. Straps must fit snugly to prevent shifting of
load and to keep tank group high on firer’s back. Lower body straps
may be fastened in second pair from the bottom of carrier eyelets to
conform to firer’s physique. Pins, which hold top ends of shoulder
straps to steel support between the fuel tanks, may be moved to any
two of the three holes so as to provide the best balance in the load.

_e. Maintenance of carrier._ Keep carrier dry and clean. If flame thrower becomes wet or muddy, clean and dry carrier thoroughly. Store in a dry place. If rotted, mildewed, or damaged, replace affected parts. If cord frays or breaks, use special seine cord from service kit as replacement.