Dow Dowsil Q4-2805 Fluorosilicone Channel Sealant

Application

Dispensing: Although any high pressure sealant gun may be used, the No. 223 Grover air operated aircraft sealant gun is recommended by the U.S. Navy and Air Force, and is covered by a national stock number for both branches. The gun is made by Grover Manufacturing Corporation. To utilize the cartridge, the sealant container supplied with the Grover gun must be replaced with a special Semco Cartridge Adapter Kit. The adapter is easily attached and has been assigned national stock numbers.

Injecting The Sealant: DOWSIL™ Q4-2805 Fluorosilicone Channel Sealant is injected from the gun directly into the channel, port by port, so the channel is filled sectionally. Starting at either end of the wing, the first two ports are opened. The sealant is injected in the first port, travels the length of the channel between the ports (usually 10–15 cm), and exits from the second port. The first port is then closed and the third opened. The sealant is then gunned into the second port until it exits from the third port.

The procedure is followed until the entire wing channel has been sealed, section by section. With the exit ports opened, the sealant will not be forced to the faying surface or into the fuel tank, the exiting sealant indicates a fully sealed, leak free channel section.

When injecting DOWSIL Q4-2805 Fluorosilicone Channel Sealant, the gun nozzle should be in direct contact with the port. The use of a hose connection between the gun and injection port should be avoided, as it considerably reduces outlet pressure. If it is impossible to place the gun nozzle directly into the port, and a hose must be attached, the following suggestions should be followed: 1. Use as short a hose as possible.

2. Increase the input pressure to permit the maximum allowable output pressure at the nozzle if it can be done safely and is permitted by the aircraft manufacturer.

3. Inject over as short a distance as possible.

Usually the port diameter is smaller than the channel is wide. This diminishes the sealants flow rate from the port. The size of the grease fitting used to inject the sealant and the exit port diameter may contribute to a slower flow rate. For example, if the exit port is 6 mm in diameter and the I.D. of the grease fitting is 1.5 mm, the exit bead will be very large compared with the injected bead. The operator should consider a reduced rate of exit normal.

Air Pressure: No specific recommendation can be made pertaining to the amount of inlet pressure required to move the sealant down the channel. Because the Grover gun multiplies the inlet pressure by 70, it is necessary to know the maximum pressure the wing structure can safely take. Too much pressure can separate wing skins, damaging the plane structure. It can also blow off the cartridge adapter, creating a projectile danger. As examples of inlet pressure variance, 0.42MPa is recommended for injecting the McDonnell Douglas F-4, 0.28MPa for the Grumman A-6A.