Elbows

 Elbows

• Elbows are used for change in direction at a particular angle .The most widely used are 90 and 45 elbows. 30 & 60  elbows also used where required.

• For large diameter piping, bends are fabricated by profile cutting of pipes. These are called Mitre bends.

1) 90° Elbow :

Elbows can turn up, turn down, turn left, right, or any angle in between. Ninety degree ells can be classified as one of the following:

• Long Radius Elbow
• Short Radius Elbow
• Reducing Elbow
• Mitered Elbow

When determining the length of an elbow, one must establish the centre to end dimension, It is the measurement from the centerline of the fitting to the end of the fitting.

Long Radius Elbow :

Long radius elbow is the most often used elbow. It provide smooth flow characteristics and has less sharper turn.

The center to end dimension will be used as radius for elbow's centreline. To find the dimensions use Welded fittings-flanges chart.

Drawing the Long Radius Elbow

Short Radius Elbow :

The 90° short radius elbow makes a much sharper turn than the 90° long radius elbow. This elbow creates a large pressure drop inside the line and does not have smooth flow characteristics. For this reason the short radius is seldom used.

Drawing of Short radius elbow:

Whenever S.R.H elbow is used , The abbreviated note S.R must be placed adjacent to the drawing symbol.

Mitered Elbow:

• The mitered elbow is not an actual fitting, but instead is a manufactured turn in the piping system. This elbow is made by making angular cuts in a straight run of pipe and then welding the cuts together after they have been rolled to a different angle. 
• The mitered ell may be classified as one, two, three, or four weld miters. The number of welds used depends on the smoothness of flow required through the turn. A two weld miter will create more turbulence within the pipe than will a four-weld miter.

Drawing of Mitered elbow

2) 45° Elbow:

This elbow is also used to make changes in direction within the pipe.

The obvious difference between the 90° and 45° elbows is the angle formed by the turn. It is one-half of a 90° elbow. The dimensions of fittings are found in welded fitting-flange chart.

It is logical to assume a design using two 45° elbows to make a directional change instead of two 90° elbows would result in considerable savings in cost and space.