Tag Archives: API

API, mechanical seal, SealFAQs, Uncategorized, Wikipedia

Blogs about Mechanical Seals

A blog is a “weblog”, that is, an online journal or informational website.  Posts to a blog appear in reverse chronological order. A blog can be about anything. Many blogs are personal in nature and often are similar to a diary.  The first blogs began to show up about 1994 and were primarily text with a single author.  A blog is expected to be updated more frequently than a website and also to be somewhat less formal.  Blogs usually have a byline or author and the blog site includes the ability to find previous posts by author, date, category and tags.

A blogger is simply someone who operates a blog or blog site as opposed to someone who authors a post for a blog or website.

Blogs can generate money through sponsors and links to commercial sites; however, SealFAQs does not do this.

One problem with hosting a blog is the commitment to maintain it and to add new posts regularly.  Having neglected my own blog for several months, I’m well aware of this problem.  After a while, the newness and uniqueness of the blog sort of wears off and the blogger runs out of things to write about.  Fortunately, I have plans and topics for 2020.

Manufacturers Blogs

There are several different types of blogs.  Some seal OEMs operate a corporate blog to provide information and updates about their products.  Here are some links to OEM “blogs” that are specifically labelled blogs.

John Crane has a blog, https://resources.johncrane.com/blog/, attached to its main website, JohnCrane.com.  The Crane blog addresses a variety of subjects and appears to be somewhat irregularly updated.  The Crane blog appears to be a mix of technical articles, product announcements, news and field experience.  The author(s) name is not given.  The Crane blog began December 13, 2018.

Chesterton has a blog, https://blog.chesterton.com/, attached to its main website, Chesterton.com.  The current topic is part 4 of a series on double seals and barrier fluids; it dates to October 31, 2019.  Although good information, the overall feel is not that of a “blog”.  Apparently several authors contribute.  The Chesterton blog dates back to at least 2017.

Sepco has a blog, “Seal Connect”, at https://www.sepco.com/community/blog/, with posts by various authors dating back to July 23, 2019.

Flowserve does not appear to have a blog, as such. 

EagleBurgmann does not appear to have a blog, as such. 

Non-Manufacturers Blogs

SealFAQs is not a manufacturer sponsored blog.  There are a few other such blogs, but not many.

The Fluid Sealing Association (FSA), the International Trade Association for mechanical seals, has a blog, http://www.fluidsealing.com/mechanical-seals/mechanical-seals-blog/.  The FSA blog doesn’t feel like a conventional blog.  Posts tend to come from the various member companies of the FSA.  Many of the FSA posts were published in Pumps and Systems Magazine as part of the “Sealing Sense” series.  The most recent post was published in June 2019.

There is a relatively new blog at https://www.mechanicalseals.net/Mechanical-Seal-Blog/index.php?frontpage, with the title “Mechanical Seal Tips and Details”.  It has only three posts and has the feel of a project that was undertaken and then stopped.  However, it was off to a good start.

Seal Websites

Of course, there are other websites containing information about mechanical seals and a few use the word “blog” in their description but don’t really have the feel of a blog.

Wikipedia has a page for mechanical seals, https://en.wikipedia.org/wiki/End-face_mechanical_seal as well as a page for the seal standard, API 682, https://en.wikipedia.org/wiki/API_Standard_682.

If you are aware of other mechanical seals blogs and especially if you have a favorite mechanical seals blog, please leave a comment.

API, API 682, mechanical seal

Seal Codes

22A-PFR-075-11/52

Anyone recognize the above line?  This is a seal code from API 682 4th Edition.  A seal code is an abbreviated method of communicating the basic specification for the mechanical seal. Sadly, the seal code has been changed with every edition of API 682.  Fortunately, the new code, described in API 682 4th Edition Annex D, is the best to date and includes some concepts and codes from the historical API 610 seal code. The new code uses eight fields:

  • Seal category
  • Seal arrangement
  • Seal type
  • Containment device
  • Gasket material
  • Face material
  • Approximate shaft size (in millimeters)
  • Piping plan

For example, based on the 4th edition codes, a seal code of 31B-LIN-100-53A indicates:

  • 3 – Category 3 seal
  • 1 – Arrangement 1 seal
  • B – Type B seal
  • L – Floating bushing
  • I – Perfluoroelastomer (FFKM) secondary seals
  • N – Carbon (vs. reaction-bonded silicon carbide)
  • 100 – Installed on a nominal 75 mm shaft
  • 53A – Plan 53A

Recently, a visitor to SealFAQs was attempting to find information about the API seal code.  I thought sure seal codes had been included as a SealFAQs page but was surprised to find that I had neglected to do so.  That oversight has been corrected and SealFAQs now includes both the API 682 4th Edition seal code and the old API 610 (pump standard) seal code.

API, API 682, mechanical seal

TRL, API RP-691 and API 682

“TRL” is an acronym for Technology Readiness Level.  This is a new acronym for me.  I’m trying to learn more about it and its implications for mechanical seals — especially for API 682 5th Edition because the API lawyers are insisting that the TRL method and reference to RP-691 be added to API 682 5th Edition.

API RP-691 is a Recommended Practice from the American Petroleum Institute (API).  An API Recommended Practice is a document that communicates recognized industry practices.  In contrast to a Recommended Practice, an API standard appears to be much more binding and rigid.  API standards typically include references to Recommended Practices.

API RP-691 is titled “Risk-based Machinery Management”.  This 198 page document was published in June 2017 and is in its first edition.  It is available through API; costs $163 and can be purchased here.  Although I do not have a copy (and, apparently, API will not give a complimentary copy to the API 682 Task Force), RP-691 does not appear to have specific recommendations for mechanical seals.  It does, however, include pumps.  A preview of RP-691 is available here.  Be sure to click on the “Look Inside” icon to get a preview of RP-691.

In its description, RP-691 is said to define “the minimum requirements for the management of health, safety, and environmental (HSE) risks across the machinery life cycle. It shall be applied to the subset of operating company and/or vendor defined high-risk machinery.”  The proposed seal standard, API 682 5th Edition, certainly includes high risk machinery as defined in RP-691:  high temperatures, pressures exceeding 600 psig and specific gravities less than 0.5 even though all services may not be high risk.

From other sources, I learned that Technology Readiness Levels range from TRL 0 to TRL 9 with TRL 0 marking the beginning of research and TRL 9 being proven technology.  API appears to be assigning TRL 7 to machinery that has been used successfully in the field for three years.  That being the case, seals having been successfully Qualification Tested per API 682 would probably be assigned TRL 5 or TLR 6 but I’m just guessing at this point.

I have no objection to API inserting the reference to RP-691 into API 682 and it wouldn’t matter if I did.  I understand that the new TRL clauses are written somewhat generically in order to be inserted into other API standards as well.  I was told that the same clauses would be inserted into the next edition of the pump standard, API 610.  The API 682 Task Force was told that the paragraphs referencing RP-691 were mandatory and could not be edited or revised.  My concern is that, as written, the new clauses appear to completely overlook the Qualification Tests of API 682 and leave evaluation up to the judgement of the purchaser.  

Technology Readiness Level especially irritates me because, during the development of API 682 1st Edition, we were specifically told that field experience did not count.  As a result, the seal OEMs were forced into conducting expensive Qualification Tests by the API some 25 years ago and have spent many man-hours and millions of dollars on those tests.  If the TRL requirements had been available/required at the time of developing  API 682 1st Edition, not only would those requirements have been incorporated into the 1st Edition but there would have been no reason for developing, much less conducting, the Qualification Tests.  

Mechanical seals are a mature and proven technology.  Every seal OEM almost certainly has products that have been around for 30 – even 60 years – and also has many end users that have achieved 6 to 8 year MTBR with their products.  Therefore, a TRL rating of 7 for mechanical seals will quickly become the norm.  The TRL requirements will soon be taken for granted and become meaningless and ignored except that the TRL will take precedence over the Qualification Tests.

Obviously, passing a Qualification Test will not and should not result in a TRL higher than the rating of 7 granted for 3 years of actual service.  That being the case, why should a seal OEM bother with the Qualification Tests at all? I predict the demise of the API 682 Qualification Tests.

Here are some links for information about Technology Readiness Levels (TRL):

https://www.nasa.gov/directorates/heo/scan/engineering/technology/txt_accordion1.html

https://en.wikipedia.org/wiki/Technology_readiness_level

https://www.ncbi.nlm.nih.gov/books/NBK201356/

http://www.airforcemag.com/MagazineArchive/Magazine%20Documents/2016/August%202016/0816infographic.pdf

API, API 682, mechanical seal

API 682 “Engineered Seals”

The term “Engineered Seal” is widely misused and misunderstood with respect to API 682.  Let’s see how this came about.

API 682 imposes a wide range of design details for mechanical seals including materials, clearances, and design elements; however, it is not all inclusive of all seals and services. The 4th Edition Taskforce believed that this subset of details was prudent for seals which would be applied within the scope of the standard.   At the same time, the Taskforce recognized that at higher pressures, temperatures, speeds, or sizes the design details of the standard might be inappropriate for the intended application.   Outside of this scope, the seal OEM is permitted, even encouraged, to deviate from the prescribed requirements and to “engineer” a seal with specific characteristics that are appropriate for the specific out-of-scope application. By definition, this special seal will then not fall into the strict definition of a Type A, B or C seal – it is an Engineered Seal.

So, what is the scope of API 682 4th Edition and what is the official definition and description of an “Engineered Seal”?

The Scope of API 682 4th Edition is, or should be, given in Section 1, “Scope”, of the standard.  As written in Section 1, the scope includes pump shaft diameters between 0.75 and 4.3 inches; unfortunately, Section 1 does not address pressure, temperature or speed.

The official definition of an “Engineered Seal” per API 682 4th Edition, Clause 3.1.29 is:

Mechanical seal for applications with service conditions outside the scope of this standard.

NOTE Engineered seals are not required to meet any of the design or testing requirements of this standard. See 4.1.3 and A.1.2.

Why are Engineered Seals not required to meet any of the design or testing requirements of API 682?  Simple: standards cannot impose requirements on things that are outside the scope of the standard.  For example, a standard limited to a scope of, say, 600 psig would not state “for higher pressures, double the thickness of everything”.   Similarly, API 682 cannot state “Even though a seal may not be intended to be in accordance with this standard, it still shall meet the design and testing requirements of this standard”.

Section 4 is about sealing systems.  Clause 4.1.3 defines seal types — A, B and C — and notes that Type A and B are suitable for temperatures up to 350 °F whereas Type C is for temperatures up to 750 °F.  Clause 4.1.3 then states that seals outside the scope of Type A, B and C are termed engineered seals.  Although “Engineered Seal” is sometimes written as “ES”, there actually is no “Type ES” seal.  Seal type is either Type A, Type B or Type C.

It is worthwhile to note that pressure limits are included in the definition of seal category which is given in Clause 4.1.2.  Category 1 is limited to 500 °F and 300 psig whereas Category 2 and 3 are limited to 750 °F and 600 psig.  These limits are usually taken as part of the scope of API 682 but were not included in Section 1.

Annex A is an informative annex entitled “Recommended Seal Selection Procedure”.  However, since Annex A is informative, it cannot not impose any requirements.  Clause A.1.2 is entitled “Additional Engineering Required” and is a list of eleven concerns which might provide reason for a more detailed engineering review of the seal.  The list includes size, speed, temperature, pressures and seal chambers that are outside the scope of API 682 4th Edition.  Again, this list is informative, not normative.

To my way of thinking, an Engineered Seal is simply an “other” with respect to API 682 and shows attention to detail for a particular service that is not otherwise included in the scope of API 682. As a practical matter, API 682 Engineered Seals typically have some basis in API 682 — certainly that is the expectation of the Purchaser.  But again, as noted previously, API 682 cannot impose requirements on these out-of-scope designs.

An otherwise true API 682 seal is still an API 682 seal even if the seal chamber does not precisely conform to the API 682/610 dimensions.  Here is an example:  Suppose a seal OEM has designed a product that (somehow!) fulfills every requirement of API 682 when fitted into the proper seal chamber.  However, someone wishes to use this API 682 seal in a pump having a smaller seal chamber.  The API 682 seal fits into the chamber but its clearances no longer meet API 682 requirements.  The seal OEM could

  • Offer its standard API 682 design but take exception to API clearances
  • Offer a custom version of its standard API 682 design that meets API clearances in this particular pump but
    • Has a reduced pressure rating
    • Does not have multi-point injection
    • , etc.

The “custom” seal would be an API 682 “Engineered Seal”.  It is (most likely) a one-off design that has never been tested.  In a similar manner, an existing API 682 seal might be tweaked (materials, balance ratio, flush design, etc.) for somewhat higher pressures or temperatures as a one off “Engineered Seal” but never tested – it would be an Engineered Seal.

I hope that the 5th Edition of API 682 does a better and more concise job of defining the scope of API 682 as well as an “Engineered Seal”.  I believe that the “scope” of 5th Edition is likely to be clarified as well as expanded and therefore the need for “Engineered” seals will be reduced.  I’m on the taskforce and will be trying to do my part to make this happen.

API, API 682, SealFAQs

SealFAQs statistics for June 2018

SealFAQs has now been officially launched for six months.  In June, unique visitors decreased slightly from May by about the difference in the length of the month and the fact that June had five weekends whereas May had only four.   Here are the statistics according to Awstats (Advanced Web Statistics).

SealFAQs had 1149 unique visitors during June and a total of 1847 visits (1.61 visits/visitor).  Visitors averaged looking at 4.7 pages per visit – a significant increase.  Bandwidth was up to 1.1GB.

Visits per day during June increased from the May average of 60 to 61 with the most visits in a day being 87 – twice!  As usual, most people visit during the week and the middle part of the day.

By far, the most visitors are from the United States and distantly followed by India, Russia, South Korea, Poland, China, Canada and others.

The average time of a visit has increased to 442 seconds in duration but 77% of all visits are still for less than 30 seconds.  It appears that some people are logging in and staying on the site an hour or more.

Access to SealFAQs via search keyphrases was down a little with 5 different keyphrases including “api 682”.  The most common keyword is “seal” of course.

June was a decent month for SealFAQs with some gains in viewing.

API, API 682, end face mechanical seal, mechanical seal, Wikipedia

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.

API 682, end face mechanical seal, Wikipedia

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.