Dimension 'L' is the length from the ends of the pipes which must be rounded where necessary to meet the tolerance required. It is also the amount of "Clearance" to permit Coupling assembly, and applies equally for Coupling Sleeves with Centre Register, without Centre Register or with Locating Plug.
For distance 'L' the pipe must be free from any peaks, flats, depressions, roll marks, weld beads or any other such defects likely to affect the seal. See fig.1
Where it is necessary to slide the Coupling completely onto one pipe end, the wrapping must be cut back on site for minimum distance "M". For closing connections, only Coupling Sleeves without Register or with Locating Plugs may be used. See fig.2