Hi,
I am in need of empirical formula for calculating the temperature for the saddle of an horizontal vessel.
Any help will be appreciated.
Regards
Siv

Hi Siv

If you want to calculate the base temperature of a shoe for checking the slide pad temperature suitability, "Mechanical Design of Process Equipment" by Keith Escoe has a good exmaple where the heat transfer calculation is presented. Not sure whether this book is still in print.

NR ,
Thanks for the reference.
I am looking for the average temperature to decide thermal expansion.
Regards
siv

You can refer to the following article for heat transfer calc by FEA.
But, always judge your requirement & if really required, then go for detailed calc.

regards,

sam


http://www.bechtel.com/PDF/BIP/39201.pdf

Sam,
Thanks for the reference.
However,as you mentioned, this much detailed analysis may not be required most of the time.
What I am looking for is some thumbrule or empirical calculation to calculate the average saddle temperature .This may give more realistic thermal movements at the nozzle.
What is the general practise. Do you take this into consideration for your stress analysis.
Thanks
Siv

As a very general guide, MSS SP-58 section 4.11 (pipe supports) quotes for high temperature pipe installations, a reduction in temperature of 100 deg F per inch from the outer pipe surface. This ought to be applicable to a vessel saddle and an average could thus be easily obtained.

Siv

What you are asking for is unlikely to exist. In general, if you decide to go to the extreme of attempting to calculate the temperature profile of a Zick-type saddle support for a horizontal vessel, you are going to a lot of effort for precious little return. Many factor enter in to that calculation, and I would be horribly surprised to find that anybody had gone to the trouble of creating a "standard" that provides a quick solution for all possible problems.

What, precisely, are you hoping to learn from this exercise, or are you just seeking help for a grad school homework assignment?

Normal practice, at least in our office, is to assume that the vessel expands vertically from the lowest point on the saddle. This isn't quite correct; it overstates the thermal growth slightly since this assumption leads to the vessel being supported only at one point on each saddle. Obviously, the vessel would deform; as indeed it does.

But the effect you appear to be concerned about is going to add to the vertical thermal displacement of any tank nozzle. In fact, it may well overcompensate for the error. I would expect, for most of the saddles in my experience, that the effective error would be in the order of magnitude of 1mm. Most piping systems are not terribly sensitive to imposed displacements of that scale, and most of the rest are, IMHO, poorly designed. Perhaps your system is one of the few remaining. If so, it is not suitable for a professional to comment on it given the lack of detail that you have provided.