Butt Welded Fittings
|
Return allows pipe runs to change direction by 180 degrees. These are usually found in the construction of heating coils and vent on the top of storage tanks. Bends are constructed from straight pieces of pipe. Commonly they are bends of 3 and 5 times the NPS of the pipe. They are referred to as 3R or 5R. Only seamless pipe or ERW is suitable for bending. Reducers are used to join a larger pipe to a smaller pipe. There are two types of reducers. The concentric reducer is used where the two pipes are to have the same center line elevation. The eccentric reducer is used to keep two pipes at the same bottom of pipe elevation. The eccentric reducer has an offset equal to ½ times the larger pipe ID minus the smaller pipe ID. Swages are used to connect butt welded piping to smaller screwed or socket welded piping. There are 3 styles of swages. As with reducers two of the types are concentric and eccentric. The third type of swage is the Venturi type. This is used where a smoother flow is required through the piping. Mitered Elbows are constructed as required from pipe. They are not true fittings. The use of mitered ells to change direction is limited to low pressure lines 10" and larger where pressure drop in the flow is unimportant. In these cases a mitered ell is cheaper then the more costly ells. In a 2 piece mitered, 90 degree elbow the flow resistance is 4 to 6 times that of a regular 90 degree continuous elbow. A 3 piece mitered elbow is approximately double the resistance. Stub-in is the term used in welding a branch pipe run into the side of the main piping run. It too, is not a true fitting. This is both the most common and cheapest approach in welding a full size or a reducing branch for pipes 2" and larger. A stub in can also be reinforced with a pad made from a piece of pipe the same size as the main run. Straight Cross and Reducing Cross. Straight crosses are readily available. The cross is a 4 way branch fitting. The use of crosses is not recommended except for where there are space restrictions, as in marine piping or revamp work only. Tees are the preferred choice. Crosses do not require any reinforcement. Straight Laterial or Reducing Laterials allow for odd-angle entry into a pipe run where the low resistance to flow is desired. Straight laterials which have a branch equal to the pipe run are offered in STD and XS weights. Reducing laterials and laterials at angles other then 45 degrees are usually only available as special order components. Reinforcement may be necessary to bring the strength of the joint to match that of the pipe run it is connected to. Shaped Nipples are rarely used today. They are offered in 90 degree and 45 degree angles. The nipple is field installed and the joint must be reinforced to match the strength of the pipe run. Caps are used to seal off the open end of a pipe run. They are commonly used to make headers and manifolds. |
| Back to Main Site Page | Comments? | Back to the Pipe Fittings Page |
