Why supports are part of the design
A riser is held by supports at intervals along its height. Where they are placed, and what kind they are, decides how the pipe moves and where the force goes when it warms, cools or is carried by a swaying building.
Three jobs
Some supports carry the weight of the pipe. Some guides let the pipe slide along its length while stopping it from moving sideways. Anchors fix the pipe at a point, so that the growth is directed towards the loops or bellows instead of building up in the wrong place.
Spacing
The PNGRB T4S regulations (2008) give a guide figure of about 2 m for support spacing on pipework of this kind. The actual spacing for a riser depends on the pipe size and the loads, and is set in the stress analysis.
Distance from the wall
The regulations ask for a 25 mm clearance between a welded riser in a confined space and the wall. That clearance leaves room for inspection and for the pipe to move.
Loads on the structure
Every support passes a load into the building. A heavy anchor load on a thin shaft wall or slab can be a problem for the structural designer, so these loads should be shared with the structural team early.
Check after installation
Supports that are placed in a different position from the drawing, or that grip when they should slide, change how the riser behaves. A walk-through against the drawing before commissioning catches this.
If you would like the supports and guides checked for a tower, send us the riser layout. See our PNG riser stress analysis service.