Not too long ago, I had a two-day interchange of correspondence with a machinery engineer. Located overseas, he was asking for my opinion on a situation of potential concern. The following is a lightly edited version of this round of communications.
THIS WAS THE ENGINEER’S OPENING EMAIL. . .
“I have a question regarding pumps in Booster Oil Export service. We have to select some API VS6 (Vertical Multi-stage Double-Case) pumps. One was offered with a 9.5m long shaft, one a 7m long shaft; other parameters are essentially the same, although the offers have various NSS values. The pumps are big 1,200 m^3/hr units. Some of the pumps offered have 4 stages, one has 6 stages—obviously the one with the longest shaft. I am inclined to stay away from the longer-shaft unit, preferring a shorter stiff shaft. The other pump has 6 stages; I fear that in Crude Oil service, more stages would also have potentially more reliability issues than 4 stages. With high viscosity and particulates in the oil, the flow passage with least resistance sounds best. I assume it’s better to use fewer stages, if one can get away with it. So, then, is it better to use fewer stages, whenever possible, from a reliability perspective?”
THIS WAS MY INITIAL REPLY. . .
“I tend to disagree. More stages mean lower peripheral speeds; aim for low peripheral speeds. Investigate user experience and specify rigorous testing. These checks or tests would likely corroborate my leaning toward the 6-stage pump.”
This engineer’s final email was an outpouring of utter frustration. He was critical of certain mindsets that seem to make inroads. To his way of thinking, they represented a description of future disappointments at best, and a recipe for disaster at worst.
THIS WAS WHAT HE WROTE. . .
“Thanks for the feedback. I’m sitting here on a team supporting the project engineers in the contractor’s office. My job is to keep an eye on the important items, but the engineers on the jobsite rarely like this. Our reliability assurance efforts are often perceived as interfering instead of helping. I did recommend the 6-stage pump and, as you mentioned, a main criterion was user experience. Having looked into it, the most qualified vendor is a European legacy manufacturer, Vendor “A.” The Design Contractor for our project is “XYZ” and they want to buy only the cheapest equipment, which excludes Vendor “A.” What do I do?”
In responding, I tried to keep my answer short and to the point.
THIS WAS MY FINAL EMAIL IN OUR EXCHANGE. . .
“Start every project with an approved-bidders list. Keep the inexperienced away.”
I offer the same advice to others.
COMING UP
Please stay tuned. My next post for The RAM Review will offer more details (and, of course, my opinion) on another problematic, bidders-list-related, real-world, equipment-upgrade situation.TRR
Editor’s Note: Click Here To Download An Updated (May 2020) List Of Heinz Bloch’s 22 Books
ABOUT THE AUTHOR
Heinz Bloch’s long professional career included assignments as Exxon Chemical’s Regional Machinery Specialist for the United States. A recognized subject-matter-expert on plant equipment and failure avoidance, he is the author of numerous books and articles, and continues to present at technical conferences around the world. Bloch holds B.S. and M.S. degrees in Mechanical Engineering and is an ASME Life Fellow. These days, he’s based near Houston, TX. Email him at [email protected].
Tags: reliability, availability, maintenance, RAM, professional development, workforce training
