A Pipe Spacing Chart provides the minimum distance between two adjacent pipes or pipelines. Whenever two pipes run parallel to each other, piping designers or engineers must maintain a minimum gap between the two pipes or pipelines. Placing the pipes in proper order following a pipe spacing chart provides various benefits like:
- Proper pipeline spacing prevents the clash between pipes/pipelines during construction and erection.
- Sufficient Spacing accommodates sideways thermal movement of pipes generated due to thermal or occasional movements.
- Pipe spacing accommodates pipe supports, specifically guide plates.
So, to fulfill the above requirements and help pipeline and piping engineers during their pipe-laying activities, organizations prepare a standard pipe spacing chart. Following those standardized pipe spacing charts, the activities become quicker, and the chances of error during pipe and pipeline placement are reduced a lot. So, in a sentence, we can define a pipe spacing chart as a tabular representation of minimum pipe-to-pipe distances of various sizes.
Pipe spacing charts are very useful while routing pipes over a pipe rack or sleepers where lines of various sizes run parallel to each other.
Pipe Spacing Criteria
Various factors need to be taken one while piping or pipeline spacing. Some of those factors are:
- Adequate space for maintenance, inspection, and component repair must be provided during the layout.
- Spacing should be considered the worst free thermal movement between pipes. When the thermal movement is large, additional pipe spacing must be considered so that pipe thermal displacement is accommodated.
The usual practice to develop a pipe spacing chart is to consider a 25 mm gap between the outermost periphery of the piping components. So for example, if there are two pipes running parallel to each other, one having insulation and the other having a flange connection, a minimum of 25 mm gas has to be maintained in between the Insulation surface and flange surface. If both lines have a flanged connection, the flanges must be staggered to reduce pipe spacing between the two.
The formula for pipeline spacing:
The basic formula that is generally used to develop a pipe spacing chart is:
Centre to center distance between two adjacent pipes (mm)=half outer diameters of the bigger size pipe flange (OD/2)+half outside diameter of smaller size pipe (od/2)+ insulation thickness of both the smaller and bigger size pipe as applicable (T+t)+ 25 mm +Thermal displacement=(OD+id)/2 + (T+t) + 25 +Thermal displacement
The Pipe Flange Outer diameter is available in the flange standard. For example, ASME B16.5 for flanges up to 24″ size and ASME B16.47 for flanges above 24″ size. For custom flanges or flanges designed with other standards, you have to refer to that standard.
Pipe outside diameter you will get in ASME B36.10/B36.19 standard.
Pipe insulation thicknesses you will get in the project-specific insulation specifications. That will be a project-specific in-house document and can vary from project to project depending on the design criteria.
Thermal displacement needs to be calculated based on the worst situation consideration. For example, if two lines are running parallel to each other. One is having a design temperature of 2500C (hotline) and the other has a design temperature of -460C (cold line). So the hotline will expand and the cold line will compress. So, while calculating the pipe span both this displacement needs to be added. This means if the hot-line expands by 30 mm and the cold line compresses by 15 mm then the thermal displacement that needs to be added in the pipe spacing calculation is 30+15=45 mm. However, if both lines are hotlines, then while thermal displacement calculation, consider a situation when one pipe is operating and the other is in ambient condition (preferably consider winter’s lowest ambient temperature).
So, using the above parameters in the above equation, you can easily calculate the pipe to pipe distance requirement for pipes of any size.
Pipe Spacing Chart
Standard pipe spacing charts are developed by organizations that provide center-to-center distance between two pipes. If there is a considerable amount of lateral thermal displacement (usually >15 mm) then the same need to be added with the spacing values given in the standard pipe spacing charts. Typical pipe spacing charts are provided below to get an idea of the pipeline spacing charts used in the piping industry. However, these values may vary depending on the component design codes. So, it is always better to practice calculating using the above formula.