In 1979, and until the early 1980s, the first ‘Deseal/Reseal’ (DSRS) Program started using a chemical and mechanical desealing process at Amberley. Over a six month period each aircraft was subject to RAAF maintenance workers entering the fuel tanks, setting up apparatus to spray a softening agent (SR51), laboriously removing the sealant by hand and then preparing the surface for new sealant. This sealant consisted of two coats of a putty-like substance that had to be applied by hand. In all of this, RAAF staff had to wear protective clothing, as the chemicals and sealant were known to be toxic.
The work was dirty, stressful and workers were exposed to foul smelling chemicals that led to them being ostracised by their colleagues in recreational areas. Families complained of the residual stench emanating from the workers’ bodies which even stained their bedsheets.
The second DSRS program occurred in the late 1980s after it was found that the fuel tanks had begun to leak again. This time the DSRS process was undertaken by contractors under the supervision of RAAF staff, and did not involve the chemical SR51 given the previous problems.
By 1992 the USAF had developed a ‘respray’ process which involved cleaning the fuel tanks and spraying new sealant over the residual and cracking sealant. This process involved RAAF staff entering the fuel tanks, and while wearing protective clothing, cleaning and spraying new sealant.
In a bit more detail the prcess involved workers firstly stripping all of the fuel tank plumbing from the tanks. A spraying apparatus was then assembled inside the tank (resembling a very large and complicated water reticulation system) and this was hooked up to a large heater assembly containing the SR51 chemical. The chemical was heated and pumped through the spraying apparatus and was returned to the heater tank and recycled. Eventually the chemical was too contaminated with old sealant and had to be discarded.
After this phase most of the remaining sealant was removed with hydro lasers which are a very high pressure (3000 psi) water jet. These lasers were very dangerous as they could easily remove a limb if an operator accidently put part of his body in the stream.
Maintenance workers would then enter the tanks and hand remove the remainder of the sealant - this included bits of sealant attached to bolts and rivets and stains of sealant left behind on flat surfaces. This was accomplished with dental picks, brushes and plastic scrapers and to soften the sealant various chemicals were used.
Once the tanks were perfectly cleaned the resealing of the tanks would commence. Utilising the 2 part sealant and air pressure sealant guns the sealant was applied after a primer compound was first brused on to all surfaces. Sealent was applied in at least two layers. A first, thin, layer of a thinner sealant was applied then a second, heavier, sealant was laid on.
Once this was done the tank plumbing was reinstalled and tested then the aircraft was released. The time taken to accomplish all this varied but officially it was about 6 months in duration.
Note: Through most of these processes there were dangerous chemicals present and even though it was a requirement to utilise PPE (personal protective equipment) it was rarely worn due to the heat, innefectiveness and close quarters of the tanks.