Some common goals clients report to me include having a pump that operates reliably for a long time combined with an inexpensive installation. I would argue that it is rare to accomplish both on the same job. Manufacturers often encourage their customers to have a foundation with a mass three to five times the mass of the pump, driver and baseplate combined—even more if the pump is a positive displacement design, especially reciprocating pumps. Additionally, recommendations and specifications focus on ensuring that the baseplate is properly grouted (grouting bonds the base to the foundation).
The purpose of any baseplate is to provide level, coplanar surfaces to mount the pump and driver, allowing for a proper and precise alignment between the two. More importantly, the base provides a path for the transmission of vibrations, nozzle loads and piping forces to the foundation and into the ground. If the base is not designed or installed properly, the investment in the alignment process will be lost in the first moments the pump operates. A proper baseplate installation will maintain that crucial alignment—and pay off for decades with reduced maintenance costs.
I acquiesce that the smaller the pump and consequential horsepower, the need for the expensive installation (foundation, baseplate and grouting) is diminished.
Some companies will buy the least expensive baseplate and then lay it on the floor/ground with no further action other than to pipe up the pump and connect the electricity to the motor. Anyone with pumps that operate in this manner for more than three years with no downtime for bearings, mechanical seals or couplings also has luck on their side. Chances are the pump is lower horsepower, and the service is ambient temperature and at low-duty hours.
Many end users shy away from pre-grouted bases or poly bases because of their higher initial cost, but anyone wanting a proper installation at an overall and long-term value should consider these alternative choices, especially in the National Electrical Manufacturers Association (NEMA) motor size ranges of 250 horsepower (hp) and below.
This article does not address stilted bases.
As an example, a 100-hp pump/driver set is purchased and the next step is installation. A cast iron, Process Industry Practices (PIP) or structural steel base also has been purchased. A good foundation has been designed and it is time to grout the base to the foundation. Here are some tips for the grouting process.
To start, do not assume the mechanical contractor may be the best at the pump installation process. Effectively communicating the specifications and procedures to the contractor increases the chance for success.
1. Prepare the Underside
With no other actions or specifications, almost no pump or base manufacturer will have the baseplate’s underside properly prepared for the grouting procedure. They will have prepared the surface solely to prevent corrosion in the transit and storage stages. Consider these questions: When was the last time you turned the baseplate over and prepared the surface to be grouted? Did you remove the pump and driver?
You can sandblast the underside and then install the base immediately before corrosion occurs (less than eight hours in an ideal ambient). Another approach is applying the proper epoxy paint to the underside as a surface to which the grout can bond. Grout manufacturers will advise the proper surface preparations and paint for their grout.
Many people do not properly prepare the base’s underside surface or they apply too much epoxy paint. Check with the manufacturer, but in most cases 4 mils (dry) is the proper amount. If the paint is too thick, the epoxy grout will pull the paint off of the metal, a process known as delamination. It may be necessary to remove the protective paint supplied by the manufacturer.
In the past, many installations used cementatious grout, but most companies in the last 20 to 30 years have elected to use epoxy grouts. Epoxy grouts yield superior results in most cases, while cementatious grout is less expensive.
2. Remove Equipment from the Baseplate
The equipment (pump and driver) should be removed from the baseplate during the grouting process. Before removing the equipment, make sure it can be aligned and the base is flat and coplanar.
Field machining of the base after completing the critical grouting process is difficult and expensive.
The concrete foundation must be adequately cured before installing and grouting the base. In the case of a new foundation, this depends on ambient conditions and on the concrete mix that was used (a five-bag mix can take as long as 28 days while a seven-bag mix may cure in a week).
Test for moisture by using duct tape to secure a 2- or 3-foot-square piece of plastic over the foundation overnight. Wait longer if moisture is visible on the underside of the plastic the next day.
If installing a base on a new or existing concrete foundation, be sure to chip away the laitance at least one-half inch or, in the case of working an old foundation, until reaching stable concrete or aggregate.
Laitance refers to the thin, flaky layer of hardened yet weak hydrated cement and fine sand on the top surface of concrete, usually from too much water or overworking the surface (for example, resulting from excess trowel work).
When removing the laitance, do not use a jackhammer, which may crack the concrete. Instead, use a small, light-duty pneumatic hammer with a sharp point tip, sometimes referred to as “bush hammering.”