in figure 3-23. Units of this type normally consist of a receiver or condensate tank and pump independently controlled by float switches. A check valve and a vent on the receiver allow the receiver to fill and empty as the need arises.
Condensate return pumps are maintained as prescribed by the manufacturer of the unit. Usually, the motor should be oiled, the check valves and vents cleaned, the float switches adjusted, the pump repacked, and the tank cleaned at least once each year.
Expansion joints and expansion loops in long heating lines are convenient devices for handling the pipe elongation caused by expansion. The five major types of expansion joints are as follows: slip joint, bellows joint, swing joint, expansion loop, and ball joint.
The slip joint is shown in figure 3-24. The female part of the joint is placed over the male part and the joint is held tight by the packing that permits expansion. The kind of packing used determines the temperature to which the joint can be subjected.
The bellows joint, as shown in figure 3-25, has a metal bellows that flexes as expansion occurs. The joint
Figure 3-23. - A typical condensate return pump.
Figure 3-24. - A typical slip-type expansion joint.
consists of a thin-walled corrugated copper stainless steel tube clamped between flanges. Rings help to keep
Figure 3-25. - A typical bellows-type expansion joint.
the corrugations under relatively high pressure. The steam pipe and joint should be supported and guided to keep misalignment to a minimum.
The swing, or swivel, joint is most often used to allow expansion to occur naturally in a system that has screwed joints. When it is used with welded elbows, the swing joint introduces torsional strains in the elbows and in the swing piece.
The expansion loop absorbs expansion through the formation of U- or Z-loops in the pipeline.
The ball joint is often used instead of the expansion loop, because it requires less space and material. A ball joint consists of four basic parts. The joint has a casing or body to hold the gaskets and a ball. The ball is a hollow fitting shaped externally like a ball at one end (inside the casing) and is threaded, flanged, or adapted for welding to the pipe at the other end. There are two gaskets that hold the ball and provide the seat. There is also a retaining nut or flange that holds the ball and gaskets in the casing. The end of the two pipes being coupled is connected to the joint casing; the end of the other pipe is connected to the ball. In operation, the ball joint allows the movement of the pipe with 30 to 40 of flexibility, plus a rotating or swivel motion of 360.
The slip-type joint must be kept properly aligned, adequately packed, within the proper limit of travel, and thoroughly cleaned and lubricated. You should adjust or replace the packing, as required, to prevent leaks andContinue Reading