Pumps, Pipes, and Pads
As much as we all love pumps, we have to admit they’re pretty useless unless they’re connected to pipes on the suction and discharge sides. And, of course, pumps need to be properly anchored if you want to avoid noise, vibration, leaks, and lawsuits. So, without further adieu, here are some tips for connecting pumps to pipes and pads.
It should go without mentioning that it’s not a conventional practice to weld a pump into a piping system. Pumps are joined to pipes with removable couplings so they can easily be removed for service, reconfiguration, and replacement. Despite their simplicity, engineers need consider a lot of parameters when electing couplings, such as:
- Simple and reliable installation
- Accommodation of thermal expansion and contraction of piping
- Noise and vibration abatement
- Retain integrity under seismic loads
- Galvanic (metals) and chemical (seals) compatibility
- Accommodation of anticipated fluid temperatures and pressures
- Seismic codes and standards
One design tip worth mentioning is that inlet (suction-side) connections should have 10 diameters of straight pipe heading into the pump. Otherwise, turbulence is introduced and water strikes the impeller unevenly, resulting in cavitation and the associated problems such as premature wear-and-tear, noise, and wasted energy as described in an earlier ITTH2OPros blog post.
A couple of good articles cover housekeeping pads and intertia bases are:
- Great read on how to “Prime The Pump”
- Some very useful information on “Seismic Design for Mechanical Systems”
Pumps are usually not anchored directly to floors, whether the floor is the slab-on-grade concrete floor, or an above-grade floor or the building roof. If installing a pump on the slab, housekeeping pads are used to elevate the pump and faciliate anchoring bolts. When mounted above the slab, or, when extra vibration control is needed, pumps are mounted on inertia bases.
Concrete pads, also called housekeeping pads, are typically 4-in. high, but the height depends on the size of the anchor bolts. Housekeeping pads provide a solid anchor, protect the pump and motor from shallow floods and floor cleaners, and help keep feet away from moving machinery. Housekeeping pads usually extend past the pump 6-in. on all sides, which provides room for service.
Inertia bases are used when floor-mounted pumps are on floors above grade – such as rooftops and mid-floor equipment rooms. They may also be used in noise/vibration-sensitive environments, such as performing arts centers and research laboratories. Inertia bases consist of heavy-duty metal frames and vibration isolators, and they form a cavity that is filled with concrete or non-shrinking grout for additional stability. Because they cost more than concrete pads, engineers should only specify them when they’re really needed.
For more information about suction-side piping design and couplings, read: