Pump general

How wide is your vision?

When you fly as often as I do you sometimes find yourself sitting next to a celebrity. Some years ago back, I had an occasion to fly with the playwright Arthur Miller, and because of my Navy background the conversation came around to submarines and nuclear power, when Mr. Miller told me the following story.

He once had an occasion to fly cross country seated beside a nuclear physicist. As they flew over the western part of the United States, Miller noted that much of the scenery below was desert, unable to support a very large population because of the lack of drinking water. The physicist pointed out that some of the largest fresh water reserves on the earth were located close by in the Rocky Mountains, but they were deep below the ground and hard to get at. He said there was enough water below the Rockies to sustain a population of two hundred million people with no problem at all. He further stated that three atomic explosions carefully placed could release this water.

Miller was impressed, but asked the nuclear physicist if the explosions would not in fact contaminate the very water they were releasing? The physicist thought about it for a couple of seconds and then pointed out that contaminated water was not his field.

This is the same problem that we see through out our industry. People with tunnel vision prepared to take action, with no thought about the consequences of their actions, an example:

1. A group or committee puts together a specification for centrifugal pumps with no thought about what happens when the pump is converted from conventional packing to a mechanical seal and you lose the shaft support that the packing was providing.

2. The polymer salesman (similar to Devcon or Belzona) tells the customer to turn down his shaft and build it up with the product he is selling. Not being a pump professional he does not realize that the shaft is being weakened by this procedure. We see this same problem when the salesman tries to rebuild the pump discharge cut-water and neither he nor the maintenance man knows the correct length. The result is that the pump begins to cavitate following the repair.

3. The salesman sells the customer a mechanical or lip seal that will frett and damage his expensive shaft and then tells the consumer to use a sleeve under the seal with out understanding that he is weakening the shaft because of the “fretting corrosion”.

4. The seal salesman tells the customer that he does not need cooling with his bellows seal. The customer then learns that the stuffing box cooling jacket he did not hook up, or that he shut off, was also supplying cooling to the shaft, to prevent heat from traveling back to the bearings that are very sensitive to heat.

5. The oil salesman tells the customer that synthetic oil is better in his pump power end, but doesn’t realize that the bearing case is coated with an epoxy or some other type of coating that can be removed by the high detergent, synthetic oil. The result is contaminated bearings and premature pump failure.

6. The maintenance man, in an attempt to get a higher head at low cost, installs an over size impeller and larger motor on the pump. This causes the impeller to run too close to the cut water, causing “Vane Passing Syndrome Cavitation”.

7. The well meaning maintenance man that re-laps his seal carbon faces with lapping powder that imbeds its self into the carbon, causing it to act as a grinding wheel that will damage the expensive hard seal face.

8. The operator that throttles the discharge of the centrifugal pump and breaks the shaft because he is operating too far off of the best efficiency point and doesn’t realize that the B.E.P. relates to shaft deflection and breakage.

9. The maintenance man that repaints the pump room including the equipment, and doesn’t realize that he has painted the exposed springs on the outside seal of a double seal application.

10. The operator that flushes a solvent, caustic or steam through the lines and doesn’t realize that the elastomer in the mechanical seal is not compatible with the flush.

11. The mechanic that replaces carbon steel bolts with stainless steel bolts because they are rusting and doesn’t realize that he is now sensitive to chloride stress corrosion that can cause a catastrophic failure of the part. We often see the same type of problem when people insulate stainless steel pipe and tanks.

12. The seal salesman that concerns him self with problems of clogging the seal in abrasive slurry applications and does not realize that the abrasive slurry will cause the equipment to go out of dynamic balance. The faster moving impeller will cause frequent impeller adjustments that will eventually unload the seal and open the lapped seal faces.

13. The pump salesman that opens the eye of the impeller to get a lower net positive suction head (NPSH) and causes a “Suction Specific Speed” cavitation problem.

14. The seal salesman that installs a quench line behind the seal causing steam to enter into the bearing case through the inexpensive grease or lip seal.

15. The pump company that installs a discharge recirculation line from the discharge side of the pump to the stuffing box that causes the entrained solids to act like a sand blaster that cuts the thin seal bellows plates.

16. The chemical manufacturer that blends chlorine with his cleaning chemical or coating so that it will act as an antiseptic in the event the customer has an open cut on his hands. He does not realize that the chlorine he added will cause problems with the stainless steel that the worker is cleaning or coating. Chloride stress corrosion problems are very common in the process industry.

These types of problems, and a thousand more, will increase as we see more companies going to the “multi craft” concept or contract maintenance. Your knowledge of seals, metal repair, and rotating equipment will be invaluable to your company in the above and similar situations.



  • On February 17, 2018