Pump Wisdom. Robert X. PerezЧитать онлайн книгу.
for determining bond strength, but, as a general rule, if the primer can be scraped off with a putty knife, the primer should be removed. Sand blasting to an SP‐6 finish is the preferred method for primer removal. After sand blasting, the surface should first be solvent‐washed and then pregrouted (i.e. epoxy‐filled) within eight hours.
By its very nature, pregrouting a baseplate will greatly reduce problems of entrained air‐creating voids. However, because grout materials are highly viscous, proper placement of the grout is still important to prevent air pockets from developing [4]. The baseplate must also be well supported (Figure 3.7) to prevent severe distortion of the mounting surfaces due to the weight of the grout.
Once the pregrouted baseplate has been fully cured, it is turned right‐side‐up and a complete inspection of the mounting surfaces is performed (Figure 3.8). If surface grinding of the mounting surfaces is necessary, then a postmachining inspection must also be performed. Careful inspection for flatness, coplanarity, and relative levelness (colinear) surfaces should be well documented for the facility's construction or equipment files. The methods and tolerances for inspection should conform to the following:
Flatness: A precision ground parallel bar is placed on each mounting surface. The gap between the precision ground bar and the mounting surface is measured with a feeler gauge. The critical areas for flatness are within a 2–3″ radius of the equipment hold‐down bolts. Inside of this area, the measured gap must be less than 0.001″. Outside the critical area, the measured gap must be less than 0.002″. If the baseplate flatness falls outside of these tolerances, the baseplate needs to be surface ground.
Coplanarity: A precision ground parallel bar is used to span across the pump and motor mounting pads in five different positions, three lateral and two diagonal. At each location, the gap between the precision ground bar and the mounting surfaces is measured with a feeler gauge. If the gap at any location along the ground bar is found to be more than 0.002″, then the mounting pads will be deemed noncoplanar and the baseplate will have to be surface ground (Figure 3.8). Outsourcing baseplate design, fabrication, and prefilling with epoxy grout has often been found economically attractive. Figure 3.9 shows it ready for shipment.
Relative level (Colinearity): It is important to understand the difference between relative level and absolute level. Absolute level is the relationship of the machined surfaces to the earth. The procedure for absolute leveling is done in the field and is not a part of this inspection. Relative level is an evaluation of the ability to achieve absolute level before the baseplate gets to the field.
Conventional grouting methods for nonfilled baseplates, by their very nature, are labor and time intensive [5]. Utilizing a pregrouted baseplate with conventional grouting methods helps to minimize some of the cost, but the last pour still requires a full grout crew, skilled carpentry work, and good logistics. To further minimize the costs associated with baseplate installations, a new field grouting method has been developed for pregrouted baseplates. This new method [6] utilizes a low‐viscosity, high‐strength epoxy grout system that greatly reduces foundation preparation, grout form construction, crew size, and the amount of epoxy grout used for the final pour.
What We Have Learned: Checklist of Foundation and Baseplate Topics
Use ultrastiff, epoxy‐filled formed steel baseplates (“StayTru®” method or an approved equivalent) on new projects and on optimizing existing facilitiesProceed by first inverting and preparing the baseplate; use recommended grit blasting and primer paint techniques.Fill with suitable epoxy grout to become a monolithic block. Allow to cure; after curing, turn over and machine all mounting pads flat and coplanar within 0.0005 in./ft (0.04 mm/m).Next, install complete baseplate on pump foundation. Anchor and level it within the same accuracy.At final installation, place epoxy grout between the top of the foundation and the space beneath the monolithic epoxy prefilled baseplate.
On welded baseplates, make sure that standard thickness steel is used and that the welds are continuous and free of cracks.
On pump sets with larger than 75 kW (100 hp) drivers, ascertain that baseplates are furnished with eight positioning screws per casing, i.e. two screws (“jacking bolts”) per mounting pad:These positioning screws could be located in removable tabs (i.e. tabs slipped into a welded guide bracket) or fixed tabs (i.e. tabs welded onto the baseplate).Pad heights must be such that at least 1/8 in. (3 mm) stainless steel shims can be placed under driver feet.
Conventional baseplates must be installed and grouted on foundation with pump and driver removed. Only then should pump and driver be reinstalled and leveled.
Epoxy‐prefilled baseplates can be installed and grouted on a foundation with pump and driver already aligned and bolted down on the baseplate.
References
1 1 Myers, R.; “Repair Grouting to Combat Pump Vibration”, Chemical Engineering Book Series, Volume 1, McGraw‐Hill, New York, NY, 1998.
2 2 Barringer, Paul, and Monroe, Todd; “How to Justify Machinery Improvements Using Reliability Engineering Principles”, Proceedings of the Sixteenth International Pump Users Symposium, Turbomachinery Laboratory, Texas A&M University, College Station, Texas, 1999.
3 3 Bloch, Heinz P., and Budris, A. R.; “Pump User's Handbook: Life Extension”, 3rd Edition, Fairmont Press, Lilburn, GA, 2010 (ISBN 0‐88173‐627‐9).
4 4 Bloch, Heinz P., and Geitner, F. K.; Major Process Equipment Maintenance and Repair”, 2nd Edition, Gulf Publishing Company, Houston, TX, 1990 (ISBN 0‐88415‐663‐X).
5 5 Harrison, Donald M.; “The Grouting Handbook”, Gulf Publishing Company, Houston, TX, 2000 (ISBN 0‐88415‐887‐X).
6 6 Monroe, Todd R., and Palmer, Kermit L.; “Methods for the Design and Installation of Epoxy Pre‐filled Base Plates”, Marketing Bulletin, Stay‐Tru® Services, Inc., Houston, Texas, 1997.
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