Document 9913
Rev. V
Instruction Manual
Style 3
Runway Centerline Light L-850A & Touchdown Zone Light L-850B
7
9.4
Gasket Replacement
Everytime the Optical Assembly is opened the gasket must be closely examined and replaced if necessary. Any
gasket that is stretched, torn, has a permanent set or some other defect, which would prevent it from forming a
watertight seal must be replaced with a new gasket. Remove the old gasket from the groove in the inner cover.
Carefully clean the flange mating surfaces and the inner cover groove. This can be done by carefully scraping.
Take care not to damage the mating surface and the bottom and sides of the groove. Coat the gasket (P/N
21124) with a thin layer of Dow Corning FS 1292 Lubricating grease. Position the new gasket in the center of
the groove and press it into place. The grease will hold the gasket in place while the inner cover is positioned on
the light housing. Torque the inner cover screws to 30 in-lbs. Perform a pressure test as described in paragraph
9.8. Clean the mounting flange area of the support ring. Place the Optical Assembly into the support ring.
Secure per section 8.2
9.5
O-Ring Replacement
Every time the Optical Assembly is opened the o-ring must be closely examined and replaced if necessary. Any
o-ring that is stretched, torn, has a permanent set or some other defect, which would prevent it from forming a
watertight seal must be replaced with a new o-ring. Remove the old o-ring from the groove in the optical
housing. Carefully clean the o-ring groove and flange mating surface on the inner cover. Take care not to
damage the mating surface or o-ring groove. Coat the o-ring (P/N 10035-62) with a thin layer of Dow Corning
FS 1292 Lubricating grease. Position the new o-ring in the groove and press it into place. Torque the inner
cover screws to 30 in-lbs. Perform a pressure test as described in paragraph 9.8. Clean the mounting flange
area of the support ring. Place the Optical Assembly into the support ring. Secure per section 8.2
IMPORTANT
IMPORTANT
NOTE – A bad gasket seal is the most common cause of inset fixture leaks. It is
strongly recommended that a new gasket be installed every time the Optical Assembly
is opened.
NOTE – The groove is designed to be wider than the gasket. This provides room for
displacement of the gasket when compressed between the housing and mating surface.
Properly tightened screws are important in obtaining a complete seal.
