4-2 OPERATIONAL CONSIDERATIONS。 Operations in a torpedo facilities create a potential for personnel exposure to one or more of the following: (1) Otto Fuel II,

(2) Agitene - parts cleaning solvent used in MK-46 shops, (3) hydrogen cyanide - a product of combustion in torpedoes, and (4) mineral spirits - parts cleaning agent used in MK-48 shops。

4-3 DESIGN CRITERIA。 Design the facilities using general technical requirements in Chapter 2 of this handbook and the specific requirements in this Chapter。 Torpedo size differences and maintenance procedures dictate the use of different floor plans and exhaust hood designs for the two types of facilities。 Refer to NAVSEA OP5, Volume 1, Ammunition and Explosives Ashore Safety Regulations for Handling, Storing, Production, Renovation and Shipping for the specific order of operations。 In all cases, the industrial ventilation systems must remove hazardous vapor (from Otto Fuel II, and part cleaning solvent) and products of combustion。

4-3。1 Exhaust Air for MK-46 Ventilated Spaces。  The MK-46 floor plan in Figure 4-1 optimizes the workflow while allowing the ventilation system to control airborne contaminants。  Figure 4-2 shows an elevation view of this floor plan。

4-3。1。1 MK-46 Standup Backdraft Hood。  Workers uncouple the fuel section and the engine section of the torpedo in teardown operations。 During these operations, Otto Fuel II remains in the lines, in the components of the engine section, and in the fuel tank。 The residual fuel releases vapor into the air。  The defueling and refueling processes also release Otto Fuel II vapor。  Use the standup backdraft hood as shown on Figure 4-3 to capture Otto Fuel II vapor in afterbody teardown, fueling, and defueling operations。  Design criteria includes:

a。 Capture velocity of 0。762 m/s (150 fpm) at the contaminant source。

b。 Slots sized for 10。2 m/s (2,000 fpm) covered with wire mesh。 The wire mesh will prevent debris being drawn into the ventilation system。

c。 Plenum velocity less than or equal to one half of the slot velocity。

Figure 4-1。  Layout for the MK-46 fuel/defuel and afterbody breakdown room。

Figure 4-2。  Series of hood in the MK-46 shop。

Figure 4-3。  MK-46 standup backdraft hood。

d。 Hood transitions (takeoffs) with an included angle no greater than 90 degrees。 Length of the hood, served by an exhaust plenum, is not to exceed 2。44 m (8 ft)。 For example, hoods between 2。44 and 4。88 m (8 and 16 ft) in length have two exhaust takeoffs。

e。 Baffles to control airflow from the sides and top of the hood bank as shown on Figure 4-3。

4-3。1。2 MK-46 Workbench Hood。 After defueling and decoupling, workers lift the fuel and engine sections onto two different ventilated workbenches。 They remove the stabilizing baffles in the fuel section, inspect, and wipe them clean before loading the baffles into the parts washer。  Personnel also dismantle the engine section to inspect  the engine, fuel pump, and seawater pump before loading them into the parts washer。

Design a backdraft exhaust hood, as illustrated in Figure 4-4, to control contaminants generated by these workbench operations。

4-3。1。3 MK-46 Parts Washer Hood。  Design parts washer as shown on Figure 4- 5 to clean off oils and excess Otto Fuel II from torpedo components。 The parts washer cover must automatically close in case of fire in accordance with NFPA 34, Standard for Dipping and Coating Processes Using Flammable or Combustible Liquids。 Design the parts washer large enough to completely enclose the work piece。 Design the parts washer deep enough to allow a minimum clearance of 153 mm (6 in) between the liquid level and the exhaust slot when the tank is full of parts。 Position the parts washer next to the workbenches to shorten the work path and optimize ventilation control。