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Typical Pressure Seals 500
52-09-100 Figure 801 May 15/69
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
C. There are three types of adhesives used for repairs.
(1)
Type I is a high tack (two part system) adhesive. This type of adhesive, air cured, is relatively hard and inflexible. The adhesive may be handled after 8 hours and requires 24 hours before stressing. This type of adhesive may be used for the repair of delaminated areas away from the seal edge, on the flange or channel. Two of the Type I adhesives are:
(a)
Dow Corning A-4000 with catalyst.
(b)
General Electric PSA-529 adhesive base with SRC-18 catalyst.
(2)
Type II is a high flexibility (one part clear) adhesive. The Type II air cured rubbery type adhesive retains flexibility after curing and has good low temperature flexibility. The adhesive may be handled after 24 hours and requires 48 hours before stressing. This type of adhesive, or the Type III adhesive described in a following paragraph may be used for repairs on the sealing lip or flat side of a seal where flexibility is necessary to make an airtight seal. Two of the Type II adhesives are:
(a)
Clear - Dow Corning Silastic 140 RTV
(b)
White - Dow Corning Silastic 731 RTV (formerly DC 30-121) or General Electric RTV 174 1) Due to a low pot life of 10 minutes General Electric RTV 174 adhesive surfaces
must be joined immediately after application.
(3) Type III is a two-part aerospace sealant. Type III adhesive is air cured or cured under polyethylene and has high flexibility. Two Type III adhesives are Dow Corning 93-076-1/2 and 93-076-2.
(a)
It is necessary to cure Type III adhesive for 24 hours before stressing.
(b)
Type III adhesive can be used for all door seal locations.
(c)
Accelerated cure times for Type III adhesive may be obtained using contact pressure.
NOTE: Cure under contact pressure at approximately 1800F for 4 hours minimum or at approximately 2000F for 2 hours minimum before handling parts.
For small areas, a heat lamp is recommended to accelerate adhesive cure times.
The cure times for the foregoing Types I, II and III adhesives are based on standard conditions of 75 士50F and 50士5% relative humidity. Lesser temperatures and humidities will cause longer adhesive cure times.
D. All repairs should be made with the seal readily accessible and under as little stress as possible. On installed seals it may be necessary to remove one or more sections of retaining strip to work on the damaged area. For repairs in the joint area of the entry door seal the gate should be disengaged to release tension in the seal.
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E. In the application of adhesives in seal repair, apply adhesive to both surfaces, which have been cleaned and abraded, and join together in the proper position within the pot life limit of the adhesive. Use fabric when a stronger bond is necessary. When a fabric patch is required, cut Dacron Tricot D-117 or D-118 to fit the area and press into the wet adhesive. Then apply more adhesive over the fabric. Smooth surface of excess adhesive and allow to cure the minimum time required (par. 1.C.(1), (2) and (3)) prior to stressing.
F. In determining the type of repair required and the procedure to be used consideration should be given to replacement of the seal if warranted.
2. Equipment and Materials
A. Adhesive - Dow Corning A-4000, with Catalyst (Ref 20-30-11)
B. Adhesive - General Electric PSA-529, with Catalyst SRC-18 (Ref 20-30-11)
C. Adhesive - Dow Corning Silastic 140 (Ref 20-30-11)
D. Adhesive - Dow Corning Silastic 731 RTV (Ref 20-30-11)
E. Adhesive - General Electric RTV 174 (Ref 20-30-11)
F. Adhesive - Dow Corning 93-076-1/2 or 93-076-2 (Ref 20-30-11)
G. Primer - Dow Corning 1200 RTV or S-2260 (Ref 20-30-11)
H. Primer - Dow Corning 1204 (Ref 20-30-11)
I. Primer - Dow Corning 92-035 (Ref 20-30-11)
J. Dacron Tricot Reinforcing Fabric - D-117 or D-118 (Ref 20-30-51)
K. Solvent - Final Cleaning of Metal Prior to Non-structural Bonding (Series 88) (Ref AMM/SOPM 20-30-88)
L. Gauze or new cheesecloth (Ref 20-30-51)
M. Abrasive -100 grit
3. Storage of Adhesives
A. Adhesives may be stored for 14 months at 35 to 900F.
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