How do you inspect hangers?
We’re continuing on our series covering inspections from an insurer’s point of view. Today we’re covering hangers for fire suppression systems.
The position of hangers should be checked during the field inspection. Here, we’re looking for obvious deviation from the standards.
HANGER POSITION CONT
Normally, there should be a minimum of one hanger for each section of pipe, though there might be some exceptions. This comes up commonly when sprinklers are close together, or there are a sequence of small pipe jogs that aren’t particularly long.
Missing hangers or hangers that are detached should be reported for corrective action.
Hangers should not be located too close to upright oriented sprinklers. We don’t want the hanger itself to create an obstruction to the water discharge from the sprinkler. For upright sprinklers, a minimum of 3-inches should be maintained to avoid affecting the distribution pattern. This doesn’t apply to pendent or sidewalls, since the hangers don’t obstruct the spray.
PIPE END SECTIONS
The end section of pipes is also an area of concern. These can be missed frequently in the field.
To avoid a long run of pipe cantilevered at the end, hangers need to be within a certain distance to the end of a pipe. NFPA 13 addresses these as the “maximum unsupported horizontal lengths of pipe”. It details the maximum distance between the last hanger and the end of the horizontal pipe. These limits are:
There are also requirements for preventing pipe moving vertically upward. If a sudden surge in pressure occurs, either from a pendent sprinkler spray under a lot of pressure, or from a fire pump kicking on, we don’t want the system to move significantly and potentially risk not getting water where it needs to go.
For systems subject to pressures over 100 psi (or 6.9 Bar), we use surge restrainers to limit the upward movement of pipe. Another method is to deliberately cut the hanger rod so that the rod prevents upward pipe movement. This takes a little more field effort, but works just as well.
Suppression systems need adequate support to avoid movement during the dynamic course of a fire, but we also need to be kind to the building structure. We don’t want to create too much load or strain that a facility cannot handle structurally.
EARTHQUAKES & SWAY BRACINGS
Many additional provisions come in with bracing and restraint in areas subject to earthquakes. We’ll spend plenty of time on this in the future, but know that if a building is required to be protected against seismic activity then we would also be looking to review seismic bracing and restraint throughout the system.
For a quick overview of hangers from an insurance perspective, we’re generally concerned with the frequency of hangers, adequate support and attachment to the building, and guards against upward movement on the end of lines.
I’m Franck Orset, this is MeyerFire University
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