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We’re using this space to wrap up our short series on the importance of machinery-quality assessments (MQAs) that began on Sept. 4, 2020 (see list of previous articles below). The overall message: MQAs can be an important tool for those seeking to zero in on best-available technology for their operations.

The two most recent articles in this series focused on MQAs associated with mechanical seals and seal-flush plans. Here we’ll get into some additional “how to” specifics, as well as point out the rationale for reliability engineers (and other RAM professionals) taking an MQA approach in their work. (Note: While much of this series has highlighted use of MQAs in the area of mechanical seals, the same approach can be used when evaluating any type of plant equipment or component.)

Click These Links To Read Previous Articles In Heinz Bloch’s MQA Series

“Zero In on Best-Available Technology with MQA” (Sept. 4, 2020)

“An MQA Approach to Seals and Flush Plans” (Sept. 12, 2020)

“Notes on Seal-Flush Plans: Consult Application Engineers” (Sept. 17, 2020)


In the early to mid-1970s, the author was asked to participate in the selection of mechanical seals for six pumping services in a large petrochemical plant. His group of reliability engineer-colleagues sent out a request for quotation to four mechanical seal manufacturers.


The four competent seal vendor-manufacturers were asked to fill out a simple form with 20 or so single-line questions. Among these were at least six questions and answers that were later placed on a spreadsheet for ease of comparison:

♦  Seal type (single or dual; flexing face rotating or non-rotating; material combination flexing face
versus non-flexing face; etc.)

♦  Elastomer material used as secondary seal.

♦  Pressure against which the seal operates.

♦  Average face velocity of the mechanical seal being offered.

♦  Location where the seal was used in the fluid-flow or pumping service of interest to the purchaser.

♦  How long the offered seal type had been in successful use at the top two locations where that
exact seal was in service.

Cost and delivery were of subordinated interest to the reliability engineers. Their primary focus was on deviations such as, suppose, Vendors A/B/C/D listing as their elastomers Viton (Vendors “A,” “B,” and “C”), and Teflon-encased Buna N (Vendor “D”).  The reliability engineers then made it their business to explore if Viton was the right material or if Teflon-encased Buna N was the right material for the pumping service where mechanical seals had experienced frequent failures.

Suppose Vendor D replied, “Sorry, we made a mistake; we use Viton, like everybody else.” The reliability professionals would have forgiven Vendor D. After all, everybody occasionally makes mistakes. But suppose Vendor D’s answer had been, “We carefully looked at your startup conditions and realized that your fluid is gassing out for about 5 minutes. That’s why we chose the considerably more expensive Teflon-encased Buna N.”  In that case, Vendor D would not only have made a sale, but would have gained our admiration and respect. We would probably have cherished and cultivated a true professional relationship with Vendor D. Moreover, we would certainly have learned from Vendor D.

Our take-away from this example, especially with regard to the work of reliability engineers in a plant, is multi-pronged. We hasten to point out that each bulleted item below suggests effort and reward:

♦  Reasonable efforts to find facts will meet with substantial rewards.

♦  Working with innovators and principled suppliers pays dividends.

♦  Becoming Best-of-Class (BiC) is not a fluke; it takes work and forethought.

♦  BiC suppliers help turn their customers into BiC end-user organizations.TRR


Editor’s Note: Click Here To Download A Complete List Of Heinz Bloch’s 22 Books

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 heinzpbloch@gmail.com.

Tags: reliability, availability, maintenance, RAM, machine-quality assessments, mechanical seals, seal-flush plans