Corrosion Resistant Finish Compound Cure Time 502
28-11-0 Figure 702 May 1/98
Page 710
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
T52591 T52592 T52593
501 DeSoto (MIL-C-27725) Compound Cure Time
Nov 15/78 as Affected By Temperature and Relative Humidity 28-11-0
Figure 704 Page 711
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
DeSoto (MIL-C-27725) Compound Cure Time 501
28-11-0 as Affected by Temperature and Relative Humidity Nov 15/78
Page 712 Figure 705
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
501 Products Research (C-27725) Compound Cure Time as Affected by
Nov 15/78 Temperature and Relative Humidity 28-11-0
Figure 706 Page 713
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
INTEGRAL FUEL TANKS - APPROVED REPAIRS
1. General
A. This section contains information on the following subjects:
(1)
Causes of leaks
(2)
Leak evaluation and repair requirements
(3)
Repair of sealant leaks in tank structure
(4)
Non sealant leaks approved repairs
(5)
Examination and closure of repaired fuel tanks
(6)
Fueling repaired integral fuel tanks
(7)
Secondary fuel barrier sealant approved repairs
B. These procedures include the preparation, handling and curing of sealant and finish materials, and the application of corrosion resistant finishes in the tank interior. The sealant and preferred finish materials listed for use in this section are mutually compatible, i.e., the fully cured corrosion resistant finish may be used as a primer coating, prior to application of the sealant, or it can be used as a top coat to be sprayed or brushed over the sealant. Previously applied top coatings should be stripped down to bare metal in sealant repair area unless old coating is known to be compatible with new sealant.
CAUTION: DO NOT APPLY SEALANT OVER EXISTING TANK SURFACE FINISH UNLESS COMPATIBILITY IS KNOWN.
C. For repair of corrosion resistant finish where sealant repair is not required, refer to 28-11-0, integral fuel tanks CP.
2. Cause of Leaks
A. Most leaks in integral tank structure can usually be traced to one or more of the following:
(1)
Improper Preparation of Surface
(a) All surfaces must be free of foreign material such as grease, metal chips, hair, loose paint, or wax which can affect bonds sufficiently to cause failure. Since jet fuel has low surface tension and viscosity, it can penetrate small openings and seep considerable distances.
(2)
Improper Mixing or Storage of Sealant
(a)
Synthetic rubber forms the base for most sealing compounds. The manufacturer adds ingredients to control strength, cure time, plasticity, work life, and fuel resistance.
(b)
Sealants are supplied in two parts; base material and accelerator. Extreme care must be taken to ensure that only the proper portions and the accelerator recommended by the manufacturer are used. Variation from the manufacturer's instructions will change physical properties of the mixture which may produce a seal failure and tank leak.
(c)
Sealing compounds have a specified shelf life. After a specified period of time, it must be tested for curing capacilities before use. Some sealants can be stored under refrigeration for short times after being mixed with accelerator, but must be discarded after the storage time is elapsed. Old sealant will not flow or stick properly, thereby producing an unsatisfactory seal and a leak.
(3)
Improper Application of Sealants
(a) Sealant application is important. Follow all manufacturer's instructions. A brush precoat must be applied when recommended. Proper sealing will be impaired if any steps in sealant application are eliminated. Air bubbles in sealant cause voids or pin holes and possible fuel leaks. If structure gaps are bridged instead of filled it will leave a void in sealant. Overlapping sealant and lack of faired contact with all surfaces will be cause for leak.
(4)
Loose Fasteners
(a) Loose fasteners may initiate a fuel leak by allowing movement in a fabricated assembly. Excess movement may crack faying surface seals and provide a fuel path through the seal plane. Loose rivets will not maintain a self-sealing status. Sealant or a seal cup will not adhere to a loose bolt or lockbolt. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737 AMM 飞机维护手册 燃油 FUEL(51)
