Category Archives: end face mechanical seal

What Do You Want from Your Seal Supplier?

In the early 1970s, I was part of a centrifugal pump inspection team whose goal was to increase pump reliability.  At the same time, we were converting many pumps from packing to mechanical seals.  We were also converting some pumps with single seals to tandem seals.  We were a busy group and I was on a very steep learning curve.

Even though I was new to pumps and seals (well, bearings, lubrication, — ok, everything!) our group leader made no bones about what he wanted and expected from our seal suppliers:  SEALS.  That was just about it.  He expected our suppliers to have lots of spare parts on hand for essentially immediate delivery.

Of course, we also wanted to be kept informed of the latest developments in the world of seals.  We wanted to see lab tests, technical papers, advances in materials such as perfluoroelastomer and silicon carbide, etc.  Finite element analysis was beginning to be used to study seal design and performance.  This was an exciting time to be learning about mechanical seals.

In those days, we did our own failure analysis and we had plenty of failures to examine.  By our rules, Mean Time Between Repairs (MTBR) was only about a year (some would have called it 2 years or more).   Improvements in reliability through failure analysis was one of the main functions of the inspection group.  We used failure analysis to point towards specific and general methods of improving reliability.  We did not want to be simply “parts changers”. 

We also did our own seal repairs, including lapping, and rebuilt our own seals.  Training was done by our group leader.  I actually heard him say, somewhat arrogantly, to a seal salesman:  “What can you teach me about seals?”  But then, he enjoyed challenging people – including our own group members.  We actually did go to a few outside, independent seals training courses and sometimes even asked a seal OEM for a detailed failure analysis report.  But, for the most part, we did not rely on the seal OEMs.

Of course, we had our own inventory of critical pump and seal parts in addition to the seal supplier’s inventory.  The relative proportions of these inventories were always a bone of contention.  I have to laugh when someone says that, long ago, inventory did not matter.  Of course inventory mattered – the “optimum” was simply a different amount than it is today.

We even had an equipment records system that used a computerized database (yes, even in the ‘70s!) of equipment, services and repairs.  Querying this database provided statistical evidence of problem pumps and problem components.  Yes, mechanical seals were the main component causing pump repairs.  In addition to the computer databases, we also had good old paper files for each pump which included the original specifications and datasheets, notes on repairs and, occasionally, a photograph but more often a sketch.

I realize that every process plant was not so well staffed, directed and equipped but mine was and I have greatly benefitted from that experience.

Fast forward some five decades and the relationship between seal supplier and end user is vastly different.  Most end users do not do failure analysis and do not rebuild their own seals.  They may not have their own equipment databases and failure records.  They even may not have an inventory of seal parts.  Instead, most end users seem to rely on their seal suppliers to provide not only goods but also services.

As a result of the changes in this relationship, it is the seal supplier who gains the experience and the knowledge that I received as an end user.  The seal supplier typically provides a technician or engineer, very nearly a contract employee, to his customer, the end user.  This person collects data, examines seal failures, makes recommendations (and gets to see the effect of those recommendations!) and builds up an equipment and failure database.  The loss of experience for the end user is definitely a gain in experience for the seal supplier.

So, what do you want from your seal supplier?

Wikipedia Gripes

We interrupt the series on cell phone documentation to gripe about Wikipedia …

Previously, I posted about editing the end face mechanical seals article on Wikipedia.   Those edits are still holding as written.  However, the editors at Wikipedia did not like my link back to this site so it has been removed.  They said that SealFAQs was a self published blog and therefore a conflict of interest.  They also removed links to SealFAQs that I’d placed in a few other articles.  Surprisingly, they allowed a link to a commercial seal distributor!

Not my day at Wikipedia.  Unrelated to mechanical seals, I had created an article about my great, great, great grandfather, William Calmes Buck who was a noted Baptist preacher in the 1800s.  My submission was declined on the basis that, as a relative, I had a conflict of interest.    They also did not like that I used his memoirs as a major reference.  The article is still on Wikipedia but as a draft.  I’ve appealed and am modifying the references as requested but expect it will not be acceptable.

Oh well.

… and now we return to cell phone photography.

 

 

Wikipedia: API Standard 682

Although Wikipedia, the online encyclopedia, has a page for the American Petroleum Institute (API), it does not have a page for the seal standard API 682.  I’ve created a new page “API Standard 682” and written an encyclopedic type description.  Because this is a new page, it must be approved and I was told that approval might take several months because of the large backlog of new pages (2415 pending submissions!) waiting for approval.  In the meantime, the draft page can be accessed by searching for “Draft: API Standard 682” or by going directly to https://en.wikipedia.org/wiki/Draft:API_Standard_682.  The draft article can even be edited if you wish to revise or add to it.

The draft article on API 682 does not contain nearly enough detail to replace the complete standard and is not intended to do so. Instead, the draft article builds up to the content of 4th Edition by providing the background and development of previous editions.  The draft article includes the Table of Contents for 4th edition and a brief descriptions of piping plans.

Whereas the terms “tandem” and “double” were used in the more general “End Face Mechanical Seals” article, I used the terms “Arrangement 2” and “Arrangement 3” in the API 682 article.

At this point in time, the Wikipedia draft page on API Standard 682 is in sync with SealFAQs but you can be sure that will change in the future.

Wikipedia: End Face Mechanical Seals

Wikipedia, the free online encyclopedia, has a page about mechanical seals:  “End Face Mechanical Seals”.  The “End Face” term is to distinguish the “mechanical seals” that are featured in SealFAQs from the many other types of seals and mechanical seals that are also on Wikipedia.

The Wikipedia page on end face mechanical seals is a pretty good one – I know because I wrote much of it. In fact, some years ago, I edited the page and convinced other editors to use the term “end face mechanical seals”.  Of course, Wikipedia is a collaborative effort and anyone can edit Wikipedia articles so much of my previous revisions had disappeared – just as my current revisions will also disappear over time.

This time around, my edits were largely to make the Wikipedia article consistent with API 682. Therefore, I insisted that an end face mechanical seal is comprised of five components:

  • Seal ring
  • Mating ring
  • Secondary sealing elements
  • Springs
  • Hardware

whereas the previous article had listed only four components by virtue of grouping the seal ring and mating ring into “primary sealing surfaces”. This combining has happened in the past and will probably happen again.  Obviously someone believes strongly in grouping the seal ring and mating ring.

I also added a very brief overview of seal piping plans, expanded the section on origins and development of mechanical seals and provided a list of references – including a link to SealFAQs.

At this point in time, the Wikipedia page on End Face Mechanical Seals is in sync with SealFAQs but you can be sure that will change in the future.