(b)  
Tighten the conduit captive nut to a torque of 266-294 inch-pounds (30-33.2 Nm).

(c)  
Loosen the conduit captive nut again to relax the torque.

(d)  
The subsequent step must be witnessed and written in the maintenance
documentation for the airplane.

(e)  
Tighten the conduit captive nut again to a final torque of 266-294 inch-pounds (30-33.2 Nm).

(f)  
Make sure the final torque is written in the maintanence records.

(5)  
Do these steps to complete the installation of the float switch:

(a)  
Clean the bonding surface on the float switch ground lug with cleaning method 1 (SOPM 20-11-03),

(b)  
Clean the bonding surface on the float switch bracket (integral tank) or conduit clamp (bladder cell tank) with cleaning method 1 (SOPM 20-11-03).

(c)  
Install the bonding jumper (44) on the float switch ground lug with the screw, nut and washers.

(d)  
Install the other end of the bonding jumper on the float switch bracket (integral tank) or conduit clamp (bladder cell tank) with screw, nut, and washers.

NOTE:  AIRPLANES WITH BLADDER CELL TANK; Position the conduit clamp to remove excess slack from the bonding jumper.
28-21-71  May 01/03
Page 424
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

(6)  
Measure the resistance from the float switch lug to the wing primary structure (integral tank) or the conduit (bladder cell tank) (SWPM 20-20-00).

(a)  Make sure the resistance is less than 0.010 ohms.

(7)  
AIRPLANES WITH INTEGRAL TANKS; Measure the resistance from the float switch conduit to the wing primary structure  (SWPM 20-20-00).

(a)  Make sure the resistance is less than 0.010 ohm.

(8)  
Install lockwire in these locations:

(a)  
Install lockwire from the bracket to the float switch mounting nut (42).

(b)  
Install lockwire from the float switch mounting nut (42) to the conduit captive nut (43).

(9)  
Out of the tank, remove the lockwire that attaches the conduit mounting nut (36) at the front spar to the bolt (33) for the retainer.

(10)
Make sure the conduit mounting nut (36) at the front spar is tightened to a torque of 342-388 inch-pounds (38.6-43.8 Nm).

(11)
Measure the resistance between the two terminals of the bonding jumper (45) and the float switch conduit (View D).

(a)  Make sure the resistance is less than 0.010 ohm.

(12)
Measure the resistance between the float switch conduit and the two sides of the web (View F).

(a)  Make sure the resistance is less than 0.010 ohm.

(13)
Measure the resistance between the float switch conduit and the wing rib (View E).

(a)  Make sure the resistance is less than 0.010 ohm.

(14)
Measure the resistance between the float switch conduit and the front spar (View A-A).

(a)  Make sure the resistance is less than 0.010 ohm.

(15)
Do these steps to do a pressure test of the conduit and float switch:

(a)  
Install a fitting into the center tank float switch conduit at the front spar to let you do the pressure test.

NOTE:  The float switch cable and the end of the convoluted tube that comes out of the union must be inserted into the test fitting to let the conduit be pressurized.

(b)  
Attach a pressure source to the fitting.

NOTE:  The pressure source must be able to supply and control pressures from 0 to 6 psig.  It must have an absolute accuracy of ± 1 psig and be capable of showing change in pressure of 0.005 psig.

(c)  
Pressurize the float switch conduit to 5 psig ± 1 psig.

(d)  
Close the test bench shutoff valve to hold the pressure in the conduit.

(e)  
Permit the pressure to become stable for 1-2 minutes.

(f)  
Make a record of the pressure in the conduit.

(g)  
Make sure the pressure in the conduit is 5 psig ± 1 psig.

(h)  
Permit the conduit to hold pressure for 1-2 minutes.

(i)  
Make a record of the pressure in the conduit.

(j)  
Make sure the pressure is ± 0.05 psig of the pressure at the start of the test.

(k)  
Slowly reduce the pressure from the float switch conduit.

(l)  
Remove the test fitting from the center tank float switch conduit.

(16)
Before you install the drain port assembly, make sure it is witnessed that the liner is installed in the conduit.

505 
May 01/03  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  28-21-71 Page 425 
　
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