Pump Wisdom. Robert X. PerezЧитать онлайн книгу.
3.5) must have a diameter‐to‐length ratio somewhere between 1 : 10 and 1 : 12. The anchor bolts are provided with steel sleeves and soft filler. The sleeves prevent entry of grout and accommodate the differing amounts of thermal growth of a concrete foundation relative to that of a steel baseplate.
Figure 3.5 Foundation anchor bolts and sleeves encased in pump foundation.
Source: Based on Barringer and Monroe [2].
Conventional vs. Prefilled Baseplate Installations
In general, horizontal process pumps and drivers are shipped and received as a “set” or package, i.e. already premounted on a baseplate. Seeing a conveniently mounted‐for‐shipping pump set very often leads to the erroneous assumption that the entire package can simply be hoisted up and placed on a suitable foundation. However, that's certainly not best practice and best‐in‐class (BiC) plants will not allow it.
Shipping method has little to do with how pumps should best be installed in the field, and pump installation issues merit considerable attention. Again, before installing a conventional baseplate, the pump and its driver must be removed from the baseplate and set aside. Leveling screws (Figure 3.6) are then used in conjunction with laser‐optic tools or a machinist's precision level. With the help of these tools, the baseplate‐mounting pads are brought into flat and parallel condition side‐to‐side, end‐to‐end, and also diagonally, all within an accuracy of 0.001 in./ft (~0.08 mm/m) or better. The nuts engaging the anchor bolts are being secured next, and the hollow spaces within the baseplate as well as the space between baseplate and foundation filled with epoxy grout.
The traditional approach to joining the baseplate to the foundation has been to build a liquid‐tight wooden form around the perimeter of the foundation and fill the void between the baseplate and the foundation with either a cement‐based or epoxy grout. Both grouting approaches are considered conventional and should not be confused with the preferred epoxy prefilled method which is highlighted below.
Grouting a baseplate or skid to a foundation requires careful attention to many details. A successful grout job will provide a mounting surface for the equipment that is flat, level, very rigid, and completely bonded to the foundation system. Many times these attributes are not obtained during the first attempt at grouting, and expensive field correction techniques have to be employed. Predominant installation problems involve voids and distortion of the mounting surfaces. In fact, the most frequently overlooked foundation and pipe support problems are related to foundation settling.
Figure 3.6 Steel baseplate with anchor bolt shown on left and leveling screw on right. A chock (thick steel washer) is shown between leveling screw and foundation [2].
Source: Modern Pumping Today.
How so? Just as a residential dwelling or sidewalk will probably shift, settle, and crack over time, pump foundations and supports should be expected to do the same. It would be prudent to plan for preventive or corrective action over time or during plant shutdowns. Fortunately, there is now an even better option; it involves the use of standard baseplates prefilled with epoxy.
Epoxy Prefilled Baseplates
As of about 2000, Best Practices Companies (BPCs) have increasingly used “monolithic” (all‐in‐one, epoxy prefilled) steel baseplates in sizes approaching 1.5 m × 2.5 m (about 5 ft × 8 ft). Larger sizes become cumbersome due to heavy weight.
In the size range up to about 1.5 m × 2.5 m, conventional grouting procedures, although briefly mentioned in this text, are being phased out in favor of baseplates prefilled with an epoxy resin or grout [3]. These standard material prefilled steel baseplates then represent a solid block (the “monolith”) that will never twist and never get out‐of‐alignment.
The process includes five successive stages, all done under controlled conditions before shipment to the site:
1 Baseplate fabrication. (No pour holes are needed for prefilled baseplates)
2 Stress relieving
3 Pregrouting (primer application) in preparation for prefilling. (If there are large pour holes, the inverted baseplate must be placed on a sheet of plywood, Figure 3.7)
4 Fill with epoxy grout and allow it to bond and cure
5 Invert and machine the mounting pads to be flat; then verify flatness before shipment (Figure 3.8). Protect and ship (Figure 3.9) – possibly even with pump, coupling, and driver‐mounted and final‐aligned.
The advantage of prefilling is notable. Jobs with pumps in the 750 kW (1000 hp) category and total assemblies weighing over 12 000 kg (26,400 lbs) have been done without difficulty on many occasions. A conventionally grouted baseplate requires at least two pours, plus locating and repair‐filling of voids after the grout has cured. Prefilled or pregrouted baseplates travel better and arrive at the site flat and aligned, just as they left the factory. Their structural integrity is better because they do not require grout holes. Their installed cost is less and their long‐term reliability is greatly improved.
Figure 3.7 Underside of a baseplate after a prime coat has been applied. It is ready to be filled with epoxy. The large pour holes identify it as an old‐style “conventional” baseplate being converted to prefilled style.
Source: Stay‐Tru®, Houston, TX.
Figure 3.8 Flatness and level measurements determine if the now‐machined‐prefilled baseplate has been properly machined. It is then ready to be installed on a foundation at site.
Source: Stay‐Tru®, Houston, Texas.
Figure 3.9 Epoxy prefilled baseplate fully manufactured by a specialty company, shown ready for shipment.
Source: Stay‐Tru® Company, Houston, TX.
How to Proceed If There Is No Access to Specialist Firms
If a specialist firm is not available or if upgrading is done at a field location, ascertain that the baseplate's underside is primed