Section Six Offsets

Question 1

What is an offset and why is it used?

Answer 1

An offset is a change in direction of pipe to get around obstacles such as equipment or other pipe.

Question 2

In most piping systems, it is impossible to run pipe in a straight line without making offsets. Offsets can be made easily with 90° elbow‘s. Explain why this isn’t always the best solution.

Answer 2

High friction loss and installation costs.

Question 3

What are the common elbows used for offsets?

Answer 3

90°. 45°. 22 1/2°. 11 1/4°.

Question 4

What is the rise of an offset?

Answer 4

The vertical distance between the centers of bend of two parallel vertical running pipes.

Question 5

What is the run of an offset?

Answer 5

The horizontal distance between the centres of bend of two parallel horizontal running pipes.

Question 6

What is the travel of an offset, what is another name for the travel?

Answer 6

The diagonal distance between the centre lines of two parallel running pipes. The technical name for a travel in all cases except 90° offsets could also be called the hypotenuse.

Question 7

There are three offset calculation methods what are they?

Answer 7

Pythagorean theorem. Trigonometry. Constant multiplier.

Question 8

What is the most common method used to calculate the travel of an offset?

Answer 8

By use of Constants for the respective elbows being used.

Question 9

With the exception of the 90° elbow offset, what are the common Constants used for the remaining elbows?

Answer 9

45° equals 1.414.
22 1/2° equals 2.613.
11 1/4° equals 5.126.

Question 10

What are equal spread offsets?

Answer 10

Two or more offsets parallel to each other.

Question 11

For equal spread offsets what are the more common Constants used for finding the starting and ending length differences?

Answer 11

45° equals 0.414
22 1/2° equals 0.199
11 1/4° equals 0.098

Question 12

What is a rolling offset?

Answer 12

A normal offset where the bottom acts like a fixed point and the top is rotated either in distance of measurement or degrees.

Question 13

What is the mathematical formula for a rolling offset?

Answer 13

Offset = ,———————

/ Roll(2) + rise(2)

Question 14

Find the travel and run for 45° rolling offset with the role of 11.5 inches and a rise of 15.5 inches.

Answer 14

Offset = ,———————
              / 11.5(2) + 15.5(2)
               ,———————
          =  / 132.25 + 240.25
          = ,———
            / 372.5 = 19.3 inches