These fittings have become standard with nearly all manufacturers and are illustrated in [Fig. 55], which shows the right and wrong way to install same.
Trouble was experienced on some of the earlier systems using high vacuum with the fittings cutting out on the side subjected to the impact of the dust-laden air. To overcome this trouble one manufacturer re-inforced the fittings by increasing the thickness of metal at the point affected. The trouble was undoubtedly caused by too high a velocity in the pipe line, as in the case of the small brass stems, explained in [Chapter V]. With the introduction of vacuum control and larger pipes, this trouble disappeared and the special fittings never came into general use.
RIGHT WAY.
WRONG WAY.
Use two Y-branches instead of straight or cleanout tees. In case the latter are used the dirt will shoot by into the other branch.
Always place Y-branches so they will turn in the direction of the flow.
Place the clean-out at right angles to the direction of flow entering the fitting. Otherwise it serves as a pocket to catch passing dirt.