Appendix IAddenda

GARR M. JONES

CONTRIBUTORSRoberts. BenfellArnold R. Sdano

1-1. Fire Safety in Pumping Stations

Several codes (NFPA 820, NFPA 70, NFPA 101, to name a few) provide guidance for fire protection for instal-lations such as pumping stations. In addition to these documents, the designer should consider the following:

Choice of Materials

Be careful in the choice of materials that could add to the fuel load (the amount of burnable material present) in astructure. Plastic, although useful for corrosion protection and resistance, will burn if ignition occurs. The productsof combustion from plastics are often toxic and corrosive and become more so when they contain fire retardants.

Be suspicious of materials that could auto combust, such as some forms of activated carbon. If these materialsare used, make certain that they are isolated from other combustible materials.

Fire Suppression Systems

Storage areas, such as those for records, lubricants, and fuels, should be separated from other areas of thestructure by two-hour rated fire walls and should be served by independent ventilation systems. Appropriatefire suppression systems should be considered for these areas.

Cable trays and other locations where electrical conductors are not protected by conduit should be monitoredby rate of temperature rise, particle ion, and smoke detection systems.

In large installations, consider dividing the electrical systems into identical halves and placing the switchgearin separate fire-rated rooms to avoid the prospect that an electrical fire will disable the entire facility.

In critical facilities, install sprinklers over cable trays.

1-2. Application-Engineered Equipment

Consider specifying application-engineered equipment for those facilities considered to be critical to the overallfunction of the installation. Included in this category are the main pumps and motors, engine-generators, andengine drives for pumps. The hallmark of application-engineered equipment is the design of machines for thespecific installation and application. Generally, a greater level of conservatism is employed to provide equip-ment more robust (and therefore more reliable with longer life) than that obtainable from standard machines.The following are suggestions for improving the performance of typical machines.

Pumps

A maximum permissible pump shaft deflection of 0.05 mm (0.002 in.) at the pump seal is suggested for anyoperating condition specified. Pumps can usually be modified to accept larger bearings and shafts.

Specify bearings with L-IO ratings of 100,000 hours for any loads imposed by any specified operating condi-tion. Some engineers insist that life is actually increased by specifying an L-IO rating of 50,000 hoursbecause of the reduced tendency for skidding in the more heavily loaded bearing. Others maintain that skid-ding is not a problem (or at least unlikely) in bearings turning at 1725 rev/min or less.

Specify either austenitic cast iron (ASTM A439) or that nickel be included in iron castings (2-3% is sug-gested) for improved resistance to corrosion and erosion. Alternatively, consider applying ceramic coatingssuch as Thortex Cerami-Tech [1] to internal pump surfaces to reduce wear and erosion (see page 758).

Specify cast stainless steel or aluminum bronze for impellers where NPSHA margins are borderline to reduceerosion due to cavitation. The more flexible ceramic coatings (such as Thortex Cerami-Flex [I]) on ordinaryimpellers might also serve at less cost.

Require the pump rotor unbalance to be no greater than grade G2.5 per ISO Standard 1940/1. Require the pump and driver supplier to perform a torsional analysis for systems with engine drivers of

250 kW (335 hp) or larger or for synchronous motors of 500 kW (670 hp) or larger.

Motors

Specify NEMA Class H insulation, but require the motor be designed for a Class B temperature rise. Note, how-ever, that the thicker insulation requires wider slots and thereby reduces the amount of iron and the efficiency.

Require a 1.15 service factor over nameplate rating, but prohibit the use of the service factor for driving themachine at any specified operating condition.

Specify inverter duty motors for all variable speed applications. Specify IEEE efficiency compliant motors for cooler operation. Consult the vendor for derating motors at altitudes above 1000 m (3000 ft).

Engines

Derate engines to allow no more than 85% of the manufacturers continuous duty rating. Pay attention to elevation and temperature conditions to make certain engines are selected properly. Insist upon a thorough mass elastic system analysis. Do not allow controls to be mounted on the engine.

Generators

Specify the same construction as detailed above for motors. Require solid state field-forcing regulators. Specify generator loading criteria specific to the applicationthat is, if the generator is to start 75 kW

(100 hp) motors in sequence, so state. Require the manufacturer to produce a voltage transient study to dem-onstrate that the generator and engine have been selected for the actual starting duty.

1-3. Air-Vacuum Valves for Wastewater Service

Historically, air release and vacuum relief valves for wastewater service have been expensive to maintain andare prone to jamming either open or closed due to grease and debris. In side-by-side tests in a system known forconsiderable difficulty with traditional air-vacuum valves, a new design, Vent-O-Mat series RGX [2], wasfound to be much more reliable and easier to maintain. After testing, a large number of these valves were pur-chased for installation in the system tested. Note that the period between cleanings of conventional air-vacuumvalves is typically one to three months whereas the permissible period between cleanings of the RGX valve issaid to be at least six times longer. A somewhat different style, Series RBX, is intended for water service. Prod-uct information comes with software to help the engineer select the proper size valve for a specific application.

1-4. Machine Foundations and Installation

Experience has shown that commonly accepted practices for preparation of machine foundations and formachine alignment have not been adequate in many instances. Lack of adequate care in preparation of the foun-dation has resulted in poor support of the equipment, progressive misalignment of the machines, and high main-

tenance costs. Excessive equipment vibration can often be traced directly to an inadequate foundation. Often,equipment manufacturers are not fully aware of the need for the care required to construct a proper machinefoundation and thus their own recommendations for equipment supports are found wanting. API standard 610provides an excellent specification for baseplate construction details. Although a rigid baseplate or soleplate isimportant, it must be installed level and with sufficient care to ensure that it is fully supported by a long-lastinggrout base. Key elements required to achieve this objective include: Anchor bolt sleeves are filled with wax or similar compounds to prevent grout from bonding to the anchor bolts.

The wax filling assures that the full clamping force required to anchor the machine is transmitted to the struc-tural foundation and not to the grout.

The concrete foundation pad is roughened by chipping the concrete to a depth of 50 to 100 mm (2 to 4 in.) toreach solid aggregate. The baseplate or soleplate is roughened by abrasive blasting. Both concrete and base-plate are primed with an epoxy bonding compound prior to grouting.

Soleplates or baseplates are leveled on shims and steel blocks or jackscrews (not leveling nuts) against theanchor bolt nuts to a tolerance of 0.17 mm/m (0.002 inches/ft) prior to grouting.

Epoxy grout, poured under a head of not less than 150 mm (6 in.) is used rather than cementitious grout. Careis taken to ensure complete contact with baseplate or soleplate.

Once the grout has fully cured and reached its design strength, the leveling devices are removed and theanchor bolts are torqued sequentially by increments to develop the required clamping force and ensure com-plete contact with the grouted foundation.

Pockets left for the removal of shimming devices are filled with grout and pointed.

Although the cost of the procedures outlined above is somewhat greater than that with commonly acceptedpractices, the results can be startling in terms of reduced vibration and lengthened equipment service life. Onecompany was able to reduce the magnitude of equipment vibration by more than half by using these procedures[3]. Another company credits the major portion of an increase in mean time between failures of 950 percent (from6 months to 57 months) in pumping equipment in their plant to improved equipment support requirements [4].

In addition to improved equipment support design, owners have found that advanced alignment techniques,using laser- and computer-based equipment, have resulted in improved power train alignment. This equipmentis also capable of detecting support imperfections on both driving and driven machines. A study reported by theUniversity of Tennessee demonstrated that even small amounts of misalignment result in significant increases inthe loads applied to bearings, shafts and seals [5]. Machine alignment should be the responsibility of specialistsusing a variety of tools to align all elements of the power train accurately.

1-5. References

1. Maintenance Protection Systems, 43317 Moody Dixon Road, Prairieville, LA 70769, or Thortex America, 420 BabylonRoad, Horsham, PA 19044, or Thortex America West, 600 S.E. Maritime Ave., Ste. 250, Vancouver, WA 98661, or MountainWest Thortex, 6969 N. 16th., Coeur d'Alene, ID 83814.

2. International Valve Marketing, Inc., P.O. Box 56, Plainfield, IL 60544. Phone (815) 439-0588; Web www.ventomat.com.3. Monroe, PC. "Pump baseplate installation and grouting." Proceedings of the Fifth International Pump Users Symposium,

Turbomachinery Laboratory, Texas A & M University, College Station, TX, pp 117-128 (1988).4. Hrivnak, SJ. "In-plant perspective: Eastman Kodak Company." Pumps and Systems (January 2000).5. Piotrowski, J. "Understanding and using shaft-to-shaft alignment measurement systems." Pumps and Systems (April

1999).

Front MatterTable of ContentsAppendicesAppendix A: Physical DataAppendix B: Data for Flow in Pipes, Fittings, and ValvesAppendix C: Typical Specifications for Pumps and DriversAppendix D: Common BlundersAppendix E: Codes, Specifications, and StandardsAppendix F: PublishersAppendix G: Checklist for Project ReviewsAppendix H: Start-UpAppendix I: AddendaI.1 Fire Safety in Pumping StationsI.2 Application-Engineered EquipmentI.3 Air-Vacuum Valves for Wastewater ServiceI.4 Machine Foundations and InstallationI.5 References

Index