Viking Johnson couplings give their optimum performance when they are a close fit on the pipe. Seal effectiveness depends on the pressure which the gasket applies to the pipe surface. Undersized pipes may mean a loss in pressure rating.
\n\n\n\nMany pipe standards quote the main pipe barrel tolerance separately from the tolerance on the pipe ends.
\n\n\n\nUnless otherwise informed, Viking Johnson products are designed to accommodate the pipe end outside diameter and associated tolerance from the relevant industry specification for the pipe material concerned. If the pipe outside diameter and tolerances are not in accordance with the standard then guidance should be sought from Viking Johnson on how these can be accommodated in our products
\n\n\n\nSince all Viking Johnson products work on the outside of a pipe this dimension is critical in ensuring the products will fit correctly. The most reliable method of measuring the outside diameter (OD) is by circumference measurement, which eliminates the effects of ovality and, provided that ovality is moderate, it is almost always possible to correct during assembly. Circumference measurement may be carried out using either a purpose-made circumference tape, which reads out directly as an effective diameter, or it is possible to use an ordinary tape wrapped around the pipe and the resulting circumference value converted to effective diameter by dividing the result by π (= 3.142).
\n\n\n\nIf pipe callipers are available, these can give a useful further indication of pipe shape and the possible need for special sizing of the coupling. If in doubt, contact Viking Johnson for further advice.
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