Piping Systems Manual

Tuesday, April 5, 2011

I have for many years wanted to compile some thoughts about piping design. As a young engineer, I was often confronted with a problem that was new to me. Older engineers and superiors would often advise me to “check the Corinth job,” or “see what we did five years ago on the XYZ project.” I would dig through stacks of files and dozens of drawings, only to find that the problems were not the same, or what they had imagined as an existing solution existed only in their failing memories. Nothing was on paper that could be applied to the problem at hand. I suppose this sort of thing applies not just to piping design, but to every other aspect of engineering as well.

In any case, I would waste a lot of time looking for answers in the existing reference materials, only to discover that many texts were silent on the topic under investigation. I would then be forced to do a lot of research and draw my own conclusions.

An example of this was when I was responsible for the start-up of a hot oil calender system, circa 1984. The mill engineers and project managers were concerned over the cleanliness of the piping. My initial reaction was that someone should be watching what the contractors were doing as they fabricated and hung the pipe to ensure that the pipe remained clean. And although this seems to be a reasonable approach, it would
not have assisted in this particular case. Nor is it common to bird-dog the fitters to ensure that hard hats, wrenches, 2 x 4’s, etc. don’t get left inside pipes.

Cleanliness of piping is not often addressed in the reference books. While there are
standards for the cleanliness of hydraulic piping and piping found in the pharmaceutical
and food and beverage industries, there was not a lot to choose from in the general
arena of industrial service piping.

Many phone calls later, I was finally able to lay my hands on a copy of PFI Standard ES-5, Cleaning of Fabricated Piping. This was a three-page document published by the Pipe Fabrication Institute. At least now I had a starting point and was able to apply this standard to the system that was causing so much heartburn among my managers. Back in 1984, one had to rely on picking up a scent, persistence, and lots of phone calls and trips to the library. Now that we have the Internet, the playing field has been leveled, although a quick Internet search of “pipe cleanliness standards” proves that today the process is still no picnic.

There are many excellent reference materials available. Some of these are referenced in this manual, and no serious student of piping should be without the Piping Handbook by Nayyar, or earlier editions by Crocker and King.

This is not a scholarly manual. I have tried to organize it in a logical manner and make the information readable and easy to access. The reader will forgive me for stating certain opinions (which should be obvious in the text, and not to be confused with facts).

Further, this text is intended to be practical rather than comprehensive. I have tried to highlight the items a piping engineer will most likely encounter, rather than to attempt an encyclopedic volume. For example, while there is much wonderful information in ASME B31.1, I have touched only on the portions one might encounter in a “typical”piping job.

Throughout the preparation of this manuscript, I was faced with trying to strike a balance between solving the tough problems we face every day, and overstating the obvious. A review of online discussion sites indicated to me that there really was no shortage of elementary questions out there, but in fairness to those who appear to be new to the profession, the more you delve into an issue, the less you seem to know1. And though I tried to remain practical, some subjects are irresistible, and so I couldn’t resist footnoting that PTFE is the only known substance to which a gecko cannot stick.

The piping engineer for a project will encounter many issues outside of any strict definition of “piping.” There will be process equipment such as tanks, heat exchangers, pumps, structures, and so on. Early in a project, the piping engineer is asked to determine the horsepower of the pumps, so that electrical equipment may be sized. This often occurs before complete process information is available. As the project continues, it is most often the piping engineer who becomes the focal point, the lightning rod, the bottle-neck.

Operating and maintenance issues must always be considered, and are often left to the piping engineer to resolve. Broad knowledge of the other disciplines’ needs, as well as the industry served, is often required. My task in writing this book was to concentrate on the piping side, though I have made some minor excursions into some of the areas described above. Perhaps if the publishers and the engineering community enjoy this book, they may permit me an opportunity to examine a broader scope at some later date.

Some Miscellaneous Thoughts on Piping
1. The trades should always be made aware that piping cleanliness is of the utmost importance. This certainly applies to the inside of the piping, valves, and fittings but also to sumps as well. Stressing this point will save a lot of time on startups.
2. Take advantage of “non-traditional” piping materials such as HDPE for underground applications. While these materials have been around for some time, “old-timers” may be reluctant to use them.
 3. Determining the size of piping is usually a function of its velocity. Keep in mind that the installed cost of piping is primarily a function of labor costs and it really doesn’t cost much more to increase one pipe size to reduce friction and also to allow for future capacity. On the other hand, one has to be aware of the application. Bigger is not always better, especially if you are dealing with slurries.
4. Be aware of the possibility of back flowing through Y-type strainers since these screens may be very flimsy and will collapse when the flow reverses through them.
5. Don’t neglect startup considerations in the design of the piping system. Be sure that you have high point vents and low point drains, and have the spares and clearances to remove, clean, or replace strainer screens.
6. In some cases, you may have to consider the minimum and maximum flows through a line over its life. This is particularly important for slurries and gravity flow lines.
7. Nobody likes to pay for welders. This means that if you can minimize the number of welds, everyone (except the welders) will be happier.
8. Viton gaskets smell like cinnamon.

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H S Consultants July 20, 2011 at 8:32 PM  

This is not the first of your posts I've read, and you never cease to amaze me. Thank you, and I look forward to reading more.

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Admin October 10, 2011 at 2:04 AM  

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