Pinholes repair

The tank had contained a light naphtha and had not been thoroughly cleaned before repairs started. It had been filled with water and then emptied, but some naphtha remained in various nooks and crannies. (It might, for example, have gotten into the hollow roof supports through pinholes or cracks and then drained out when the tank was emptied.) No tests were carried out with combustible gas detectors. 

Internal seals require more thorough annealing than the more simple joints, and if any pinholes require subsequent repair great care should be taken in reheating the joint. 

If a pinhole appears whilst the vacuum line is in use and cannot be opened, a temporary repair can be made with black wax (Apiezon or similar) as follows The wax is warmed and worked into a short rod about the diameter of a match-stick and about 1 cm long. The region of the pinhole is warmed with a very small flame, the black wax is applied to the pinhole as a spot not more than 2 mm in diameter, and then warmed with a very small flame just sufficiently to flow and wet the glass. Before a pinhole patched up in this way is repaired properly, all traces of the wax must be removed with a solvent, otherwise the charred remains and ash from the wax will spoil the glass and make a proper fusion repair that much more difficult. 

Major causes for coating failure are surface cracking and undetected pinholes or voids. These can be repaired and serious problems avoided. Coatings generally fail in different modes, these are chemical failure, abrasion failure, adhesive failure, cohesive failure and undercoat corrosion. For performance evaluation of coatings on experimental basis on these parameters various ASTM and BS specifications are presently being used. 

Repair pinholes in glass or poorly welded or brazed metal parts. 

Application of the hot asphalt on a floor (or other horizontal flat surface) is by pouring the material on the surface and spreading it with a squeegee-usually wood, and approximately 18 in. long. Observe workmanship carefully to be certain the mechanic is providing a glassy, smooth and pinhole and bubble (or blister) free surface. If there are bubbles or blisters in the membrane, the job must be stopped until they have been removed and the membrane repaired. (See the section on Asphalt for procedure.)... 

The formation of second or more layers is helpful in repairing defects like pinholes or small cracks which are present in the first layer. 

Necessity for Reinforcement. Handling of the membranes may tend to cause pinholes or tears. Adequate reinforcement of the membrane is therefore necessary to ensure long service life. It is also important to establish methods for repair of the damaged membranes. 

The loth set to work to clear up as many of these defects as possible. There was no quick solution for the problem of pinholes in the cylinders. All that could be done was to repair those cylinders which were not excessively corroded and replace the rest, insofar as supplies permitted. In order to make it possible for troops to spot flame throwers with defective cylinders before attempting to use them in combat, pressure gages and adapters to fit all types of commercial pressure... 

Twenty-nine percent of respondents with leaks reported that the expense of repairing pinhole leaks was less than 100 while 30% reported expenses between 100 and 500 and 37% reported more than 500 in expenses for pinhole leak repairs (Table 5). Seven respondents reported more than 10,000 in costs of repairs. 

Numbers do not sum to 100 due to rounding. Table 5. Costs of repairing pinhole leaks. 

Total cost of repairing pinhole leak damage includes the financial and time costs. 

Epoxy coated rolls (450-500 inVkW) offer a more durable covering than silicone or Hypalon and are also a logical choice for basic corona treating applications. Epoxy coatings have harder surfaces than silicones or rubbers and offer added insurance against unexpected roll failure from exposure to excessive corona discharges, heat build-up, or accidental operator-inflicted damage from an operator s knife. A pinhole in an epoxy roll can usually be repaired on the production site. Life expectancy of an epoxy covered roll is approximately one year. 

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