Common Pumping Mistakes
09/12/2017
Horizontal end suction centrifugal pumps are undoubtedly the most common pumps in use in the world today, yet I witness basic misunderstanding of the pump specification almost every day. I thought it might make for an informative and fun quiz to go over some of the more misunderstood sections of ASME/ANSI specification B73.1 (2012).
Figure 1. Example of a pump designed to fit the ASME/ANSI B73.1 (2012) specification. (Courtesy of the author.)1. The modern version of the ANSI B73.1 specification has its roots in the AVS (American Voluntary Standards) from the 1950s. A) True B) False 2. Flanges: Bolt holes may be drilled and tapped when there is inadequate space for nuts behind the flange. A) True B) False 3. When a heating jacket is used the steam inlet shall be: A) On the top and the drain on the bottom B) On the bottom with the drain/vent on the top C) Inlet and outlets should be on the sides to allow for ease of piping. D) None of the above. 4. Impellers shall be balanced to this standard at a minimum: A) NASA standard CFR 1928:WWYATQ -2 B) ISO 1940-1 Grade 6.3 C) ANSI standard B20-22A (balance of metallic impellers) D) ASME B638.637 5. If the method of impeller attachment is threaded, the pump rotation shall have the shaft (design) function to tighten the impeller: A) True B) False 6. The casing drain connection shall be drilled and tapped only when specified by the purchaser. Otherwise, there will be no drain penetration. Further, the manufacturer shall always provide a casting “boss” at the lowest point on the casing to accommodate at a minimum a ½ in NPT penetration when specified. A) True B) False 7. Pump operating clearances shall be adequate to prevent internal rubbing when the pump is subjected to the maximum allowable flange loads (pipe strain) when operating in the allowable operating region (AOR). A) True B) False 8. Pump shaft “runout” on new pumps shall be no more than 0.001 inches when measuring the shaft on centers, and 0.002 inches when the shaft is installed in the pump. A) True B) False 9. Bearing life (L10) shall be a minimum 37,500 hours if the pump is operated in the allowable operating range. A) True B) False 10. Standard lubrication design for the bearing frame is set for: A) Oil mist lubrication B) Sealed for life bearings C) Greased bearings D) Oil bath 11. The bearing frame shall include a drain plug that is: A) Non magnetic B) Manufactured from either aluminum, kryptonite or nonobtainium C) Easily removed and reinstalled using a Phillips screwdriver D) Magnetic 12. The bearing frame when set up for oil bath lubrication shall have: A) A bull’s eye level indicator B) The option for the bull’s eye indicator to be mounted on either side of the pump C) The bull’s eye level indicator will be 1 inch in diameter. D) All of the above are true. 13. Gland bolt stud and nut materials can be made from grade B7 and 2H carbon steel. A) True B) False 14. The minimum casing corrosion allowance is: A) 0.125 inches B) 0.250 inches C) 0.500 inches D) 0.120 inches 15. The direction of rotation when viewed from the driver perspective shall always be: A) Clockwise B) Counterclockwise C) Doesn’t matter as long as the customer specifies which one D) Clockwise, but only if using a variable frequency drive or if pump shaft is oriented in the vertical plane. Otherwise, it must be counterclockwise. 16. A lifting eye is to be provided on the motor and shall be capable of lifting the entire weight of the motor, baseplate and pump. A) True B) False 17. The bearing frame adaptor shall: A) Be designed to resist any amount of torque that the shaft design can handle B) Be manufactured from any material the manufacturer has left over in an effort to hold down costs. C) Be painted yellow (spec USCG 637) or orange (spec USCG 638 International) in accordance with OSHA CFR 1929-638 D) None of the above 18. When testing the pump for noise: A) The driver noise data must be determined separately. B) The test shall be conducted in accordance with ANSI /HI 9.1- 9.5). C) Must be conducted in an ultra-quiet test room per OHSA CFR 1929-4256 D) Answers A and B above E) None of these answers 19. Vibration limits for the pump as measured on the bearing frame must meet ANSI /HI 9.6.4 limits no matter where the pump is operated on the curve. A) True B) False 20. The pump allowable operating range (AOR): A) Can be anywhere on the published curve the operator forces the pump to operate B) Must be within 20 percent of the best efficiency point (BEP) C) Must be no greater than 120 percent of BEP D) Cannot be less than minimum flow, where min flow is per table 7.1.6-1 in the standard E) None of the above F) Answers C and D above 21. With the pump operating in the AOR: A) There is no consideration for minimum thermal flow considerations B) The pump expected life range will be the same no matter where the pump is on the curve. C) Vibration levels will be near zero D) You never need to calculate NPSHR or critical submergence. 22. Pursuant to the ANSI specification B73.1, it is perfectly acceptable for any portion of the motor to hang over the base plate on the sides and back (non-coupling end) by any amount. A) True B) False 23. There are circumstances where the NPSHR for the pump may be less than the NPSH3. A) True B) False 24. Published performance curves shall be based on tests conducted in accordance with ANSI/HI 14.6. A) The accuracy of the curves shall be that 90 percent of pumps purchased untested when operated between minimum flow and BEP will meet published head points within plus or minus 5 percent and efficiency within plus zero percent and minus 5 percent. B) The accuracy of the head and efficiency curves shall be within 10 percent if operating within 10 percent of BEP. C) The accuracy of the published curves shall be 100 percent, with no deviations 100 percent of the time regardless of owners’ instrumentation accuracy or the product being pumped and at any temperature below 450 F. D) The accuracy of the published curves is governed and regulated by ANSI P&J-S 8717. E) None of the above are true. 25. When NPSHR tests are required and conducted: A) The temperature of the water does not need to be factored into the test criteria. B) The vapor pressure of the water is not to be considered and is irrelevant. C) The absolute pressure on the suction side of the system does not need to be added to the calculation if the test is being conducted at elevations 5000 feet above sea level or higher. D) Answers A, B and C E) Unless otherwise agreed to by the purchaser and supplier, the test shall be a type II test, which is solely for determination of NPSH3 at the rated flow point only. Bonus Question For metallic pumps. All casings, seal chambers (stuffing boxes) and jackets MUST be hydrostatically tested: (This test should be a witnessed and documented test.) A) For 5 minutes at 100 PSIG, except if the material is cast iron then it is 10 minutes B) For 10 minutes at 100 PSIG regardless of material or expected temperatures C) For 10 minutes at 150 percent of the maximum design pressure for that material and expected operating temperature maximum D) For 10 minutes at 150 percent of the maximum design pressure for that material rating at 100 F (38 C). Click here for the answer key to see how you did.
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