Figure 4-4。  MK-46 workbench hood。

Figure 4-5。  MK-46 parts washer hood。

4-3。2 Exhaust Air for MK-48 Ventilated Spaces。  The floor plan shown in Figure 4-6 optimizes the work path while allowing the ventilation system to control airborne contaminants。 Obtain detailed MK-48 exhaust hood drawings from Naval Underwater Systems Center, Code 8113。

Figure 4-6。  Typical MK-48 ventilated space layout。

4-3。2。1 MK-48 Afterbody Teardown Hood。  Workers uncouple the fuel section and the engine section of the torpedo in the teardown operations。 During these operations, Otto Fuel II remains in the lines and the components of the engine section, and in the fuel tank。 The residual fuel releases vapor into the air。 Design the afterbody teardown hood as shown in Figure 4-7 to capture Otto Fuel II vapor。 Design the hood using the following criteria。

a。 Install baffles on the top and side of the hood forming a booth。

b。 Install a 7-mm (3-in) airfoil on the outer edge of the hood。 The airfoil, bent inward from the baffle, must provide an airfoil effect and prevent turbulence and backflow。

c。 Install lighting that is vented and flush mounted in the overhead baffle as shown on Figure 4-7。

d。 Bolt the hood to the floor, using a continuous natural rubber gasket on hood bottom to create a seal between the hood and the floor。

Figure 4-7。  MK-48 afterbody teardown hood。

4-3。2。2 MK-48 Workbench Hood。 After defueling and decoupling, personnel dismantle and inspect the fuel tank and the engine section。 They then load components of the fuel tank and the engine section into the parts washer。  Design a backdraft exhaust hood as illustrated in Figure 4-8 to control contaminants generated by these workbench operations。  Specify the following criteria for workbench hoods:

a。 A 1850- x 600-mm (72- by 24-in) stainless steel workbench top to support the whole exhaust hood。 See Figure 4-8 for dimensions of the hoods。

b。 A 76-mm (3-in) airfoil rotated inward to prevent turbulence and backflow。

c。 Lighting that is vented and flush mounted in the top of the exhaust hood。

4-3。2。3 MK-48 Parts Washer Hood。  Design or modify the parts washers as shown on Figure 4-9。  Specify the following criteria for the parts washers:

a。 Fabricate a new enclosure to mount on top of the parts washer。

b。 Relocate the cover with a pneumatic plunger and a fusible link assembly。

c。 Install an automatic switch to turn on the exhaust fan when the cover is opened and to turn off the exhaust fan when the cover is closed。

Figure 4-8。  MK-48 workbench hood。

Figure 4-9。  MK-48 parts washer hood。

4-3。2。4 Workflow in Afterbody Teardown Room and Accessories Room。 Figure 4-10 illustrates the workflow in both the afterbody teardown room and the accessories room with the proper sequence of hoods。

Figure 4-10。 MK-48 hood sequence afterbody teardown and accessories rooms。

4-3。2。5     MK-48 Refueling Hood。  Before refueling, personnel connect the hoses from the fueling equipment to the fuel tank。 Once the fueling operation has begun, the operator does not need access to the fuel tank, except to see the hose connections。