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Tankman650 (Structural) (OP)
14 Mar 03 16:27
Are there published tables for the maximum unsupported run of pipe per given pipe size???  I can calculate the maximun stress values but was wondering if there are standard tables for support apacing based on stress and deflection.
Helpful Member!(3)  ChasBean1 (Mechanical)
14 Mar 03 16:58
1996 International Mechanical Code, Table 305.4 - "Piping Support Spacing."

Also, "Pipe Hangers and Supports - Selection and Application" by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc., MSS SP-69-2002. Table 3 - "Maximum Horizontal Pipe Hanger and Support Spacing."

Neither are available without forking out cash. Since you are a valued guest of this forum, I'd be happy to email you pdf forms of these tables. I can't copy the whole publication for copyright issues, etc., but I don't see a problem with providing just the table info. (hopefully these folks don't either).

-CB
LSThill (Mechanical)
23 Mar 03 3:54
Hi  Tankman650 (Structural), cceballos (Mechanical)

ASME B31.1-2001:  

TABLE 121.5 SUGGESTED PIPE SUPPORT SPACING
Page 46. Suggested Manimum Span for Water Services and Steam, GAs or Air Service.

Need to read the General Notes on page 46
Helpful Member!(3)  StressGuy (Mechanical)
27 Mar 03 8:43
You're going to want to be careful with a 30" line, particularly if it is liquid full.  Most of these span tables are based on bending stress and deflection.  When you gets to pipes that large, local/horn stresses at the support location become a bigger concern that need to be address by the support design (typically a saddle).  A common reference in this area is the work of L.P. Zick on the design of support saddles for horizontal vessels.  I'm sure others here can suggest more references.

I haven't looked at Isthill's reference since I've not really worked with Power Piping, but I would imagine it probably makes some note of these issues.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.

LSThill (Mechanical)
28 Mar 03 2:14
Tankman650 (Structural)

The Piping Engineer will have the SUGGESTED PIPE SUPPORT SPACING in the Piping and Piping Stress Specification.

With the SUGGESTED PIPE SUPPORT SPACING spread sheet calculation for Wt. dead load.
1969grad (Mechanical)
29 Apr 03 6:03
I have calculated the pipe stresses for the given spans in the MSS publication and found that the stresses are usually less than the allowables found in either B31.3 or B31.8.  So the problem then becomes how much deflection is acceptable.

I might add that I do not think that the MSS publication includes 30" pipe but I could be wrong as it has been some time since I looked at it.

Does anyone have any deflection guidelines for services other than steam?
DLANDISSR (Mechanical)
29 Apr 03 8:41
Tankman650:
ITT- Grinnell publication "Pipng Design and Engineering" have a table of suggested pipe hanger spacing of Carbon Steel pipe filled with water based on a bending and shear stess not exceeding 1500psi and a deflection between hangers not to exceed .1". as follows:

Nom. Size     Span
1             7
1.5           9
2             10
2.5           11
3             12
3.5           13
4             14
5             16
6             17
8             19
10            22
12            23
14            25
16            27
18            28
20            30
24            32
26, 28        33
30, 32        34
34, 36        35
42            36
I have found this to be a good basic guide. These spans are for straight pipe only. Bends, valves and other added loadas will effect the span. If there is any question as to the span a stress analysis should be done.
CaesarII is an excellend stress program which is user friendly and easy to use. A 50 run version can be purchased for about $700. Look on the web.
StressGuy (Mechanical)
29 Apr 03 8:51
Be aware also that the B31.1 table is fairly conservative, particularly for smaller lines.  For B31.3 refinery piping, most engineering companies that I know of allow down to 2" diameter piping to span 20ft in standard pipe rack bays.  With that table, you need to have a minimum of 10" piping in your pipe racks.

Also, typical deflection criteria is 1/2"-5/8" for ISBL lines.  This span translates to a minimum natural frequency of 4Hz which is a suggested minimum to keep your pipe spans from galloping like the Tacoma Narrows Bridge.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.

umreng (Mechanical)
29 Apr 03 9:19
Previous replies and responses to the pipe span question  have not considered siesmic forces.  If the location of the piping installation is in an area with earthquake history, this may lead the engineer or officials to make certain site-specific recommendations or design requirements.
chicopee (Mechanical)
12 May 03 5:59
All horizontal pipe support equations that I have seen are based on the fundamental beam equations found in strength of material.  Bending stress and deflection are the two main criteria.  ASME piping code for power boilers  also requests the additional load of water filling the pipes.
Hookem (Mechanical)
29 Sep 04 22:19
Stress Guy:  I have many criteria for supports before, but not the 4 hertz.  Please advise on background and basis.  Thanks.

Hookem
aka TomChesney
chesney@uei-houston.com
bchesnfish@aol.com
StressGuy (Mechanical)
30 Sep 04 8:31
I'll have to do some digging for the documentation.  That one comes from my boss, who's been doing pipe stress since before I was born.  I'm pretty sure it comes from Kellogg's Design of Piping Systems.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

StressGuy (Mechanical)
5 Oct 04 16:08
I did confirm - the 4Hz criteria comes from the Kellogg Design of Piping Systems.  In general, if your piping system sags less than 5/8" between supports, the natural frequency will be above 4Hz.  You want it above this to avoid exciting a resonance with the wind blowing across it.  (Tacoma Narrows Bridge, anyone?)

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

KernOily (Petroleum)
13 Oct 04 18:20
OK Ed what do I have to do to get you to make me a copy of Kellogg's book?  How 'bout lunch at Pappadeaux's?  

Thanks!
Pete

StressGuy (Mechanical)
13 Oct 04 18:29
I gladly would if I could, as there is a lot of good information in that book.  I've written the publisher to let them know there's interest in a new printing, but they indicate they've no plans to reprint it at this time.

They show up on Ebay about once or twice a year and never go for less that $50.

For now, I have to rely on the library of my boss, Noble Stewart, who thankfully has managed to amass copies of just about everything in his career.

In fact, I'm currently borrowing a 30 year old catalog for a spring manufacturer that went out of business about 25 years ago to evaluate a piping system with some existing springs.  It's amazing how much information is simply dissapearing, save for a few pockets that are keeping it alive.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

KernOily (Petroleum)
13 Oct 04 18:37
AARGH!  Not good news.  What about the 25-years-and-the-copyright-expires/public domain thing?

The web is a good thing for manufacturer's catalogs in most cases.  A major excpetion to this is old equipment (as you related) which lots of owners still have in operation, forcing us to keep paper copies around.  Worthington pumps is one good example.

Guess I will have to watch ebay...  well I'll buy you lunch anyway next time I'm down there, how bout that.  Thanks Ed.

Thanks!
Pete

ctink (Civil/Environmental)
5 Jan 05 18:18
Any possibility that I could get a copy of the tables mentioned above?

"Pipe Hangers and Supports - Selection and Application" by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc., MSS SP-69-2002. Table 3 - "Maximum Horizontal Pipe Hanger and Support Spacing."
ApC2Kp (Mechanical)
6 Jan 05 14:49
Manufacturers Standardization Society publications are available from website,
www.mss-hq.com

Along with SP-69 for pipe support selection, also consider the SP-58, and SP-89 publications for the loads on the support components.
Helpful Member!(2)  pipingdesigner (Mechanical)
11 Jan 05 12:09
Hi guys,

Interesting discussion !
On my website, www.pipingdesigners.com you will find a file under the "tools" section called pipe and vessel data.

It contains a wealth of charts etc on excel, including allowable pipe spans (just tab through the pages).

Just download, unzip and leave on your pc. I use it everyday !!

Hope it helps,

Kind Regards

Anton
www.pipingdesigners.com
JohnBreen (Mechanical)
11 Jan 05 12:21
Hello All,

I am surprised that nobody mentioned that the classic "span length tables" always include warnings (in fine print) that these recommended spans are for simply supported piping (no moment connections) and do not address the presence of concentrated loads (valves, strainers, etc).  Also, changes in direction add some complexity to the equation.

I wonder if ye olde Grinnell publication on pipe support design is still available through Anvil.  EPRI members should look on the EPRI website for a PowerPoint presentation that some olde codger prepared.

Regards, John.
DSB123 (Mechanical)
12 Jan 05 7:36
JohnBreen,
          Good observations and post. Another thing a lot of people forget is that the pipe span tables are created in many instances for "ambient" piping systems and are then applied irrespective of the pipe temperature. Spans should be modified if high temperature lines are to be considered. I know that high temp lines are nearly always stressed out but the designer needs to account for the temperature in assessing spans. As you say a lot of the span tables are based on simple supports but in reality the end conditions are never simple and there is always some rotational restraint.
StressEng (Industrial)
12 Jan 05 9:23
Anyone know the formulae to calculate these spans?
So we can make a excel table for all diameters, thickness, materials, temperatures, etc.

Thanks to all.
JohnBreen (Mechanical)
12 Jan 05 14:41
Hi All,

Ed, don't I remember that Pete developed that spread sheet already?  How 'bout it Pete, did you ever get around to doing that?

Regards, John.
StressGuy (Mechanical)
12 Jan 05 14:49
I have a 500kb PDF file that has six pages scanned from the old Kellogg book on the span calcs.  I'll see about finding a place to put it and then I'll post a link to it.  Obviously, I can't scan the whole book, but this much ought to at least be able to spread the understanding on this topic.  Judging from the interest this thread keeps getting, it is quite obviously needed.  Stay tuned.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

Helpful Member!  sterl (Mechanical)
12 Jan 05 22:06
Lot of good stuff in this thread...

For my own $1./50 :

Certain pipe industries utilize normalized tabulations that yield support spacings "closer than" the ANSI B31 or Kellog spans due to the cumulative effects of low points in specific pipes that are deliberately sloped.  Normally these slopes are effected to ensure that flow variances do not result in unantipated flow phenomena, for example: Condensate induced shock when re-applying steam to what should be a dry header; pumped recirculaion return lines on many central refrigeration systems, where not only could there be a charge management problem due to sags accumulating liquid but also a temperature induced stress when the pressure is reduced on a pipeline carrying relative warm vapor and pockets of liquid at low points.

The practicalities of supporting even that slope over 1000 or so feet of pipe leads the refrigeration industry to use 1/240 as a practical, and manageable, design slope....With the Deflection in a 10-foot support span headed for 5/8" per some of the mentioned tabular data, the accumulation problem, with its inclemencies, is not solved by the "field applied" slope.  

As well, above and beyond the "stress" considerations:  At the lower and lower temperatures that "normal" end-user industries are requiring of large compression systems:  the Rigidity and (nil) Ductility Transition Temperatures become a very real concern and the incorporation of conventinal "expansion loops" exacerbates the problem...

So investigations of the rupture of a low temperature 2-phase pipe often establish the immediate conditions as:  Bottom of pipe broke while the pressure was reducing; the flow was near its lowest; in the midst of a long stright run; halfway between supports; where its most proximate area of support is at the immediate point of contact, a deformable or otherwise, flexible insulation material.  Conclusion: Minimal localized stress at the supports, minimal hoop and axial stress, minimal momentum forces due to changes in flow direction, minmal bending moment, on tensile side of pipe...Pipe still broke.

1974vet (Mechanical)
13 Jan 05 14:11
Here goes my efforts to explain (hope isn’t too long)-
A little more info on the “span charts”:
Looking at Navco, p150, the Navco suggested support spacing is based on 2300 psi bending stress.  MSS-SP-69, p8, is based on 1,500 psi, although I can’t seem to quickly find it in the text.  There are many “company” standard span charts also.  Anyway, most tables have notes and qualifications although I’ve seen some “company” charts copy other sources and leave this critical information out.  These notes may include items like the following:
*The pipe is assumed to have standard wall thickness with insulation,
*No concentrated loads present such as valves,
*There are no changes of direction in the spans,
*Spans are assumed to run in the horizontal plane,
*The maximum deflection of the span under load is limited to 0.1”, and
*The stress intensification factors of components are not considered.

I am almost certain that SP-69 was generated using allowable stress values from the power piping code.  The following is an attempt to show how the span tables might have been generated:

Select a low allowable stress value, e.g., 1,500 psi (Sall(weight)/i), for the combined bending and shear value, such that a sufficient factor of safety is provided, and allowing the standard span chart to be applied to a wide range of piping systems:

Beginning with the generalized primary stress equation,
PD/4t + iM/Z <= kSh
where iM/Z values are code dependent, and
k values are code dependent and occurrence of load (assumed = 1.0 here), and
Sh is code dependent

Using beam formulas for span:
M = 1/2[(wl^2)/8 + (wl^2)/12] is the average of a uniformly loaded simple beam and a uniformly loaded beam fixed at both ends.
This reduces to:  M = (wl^2)/10

Substituting this expression of M into the generalized stress equation and rearranging results:
L<=SQRT[(Sh-PD/4t)(10Z/iw)]

So then, an example of a non-critical type system might look like:
Assuming B31.1 and  A106 Gr B material
P = 150 psig
T = 350F
Sh = 15,000 psi
Let PD/4t = 3000 psi (approx)
This leaves 12,000 psi.  A system design of this type will utilize higher SIFs, say in the range of 6-8, so,
12,000/8 = 1,500 psi

An example of a critical type system might look like:
Assuming B31.1 and A181 material
P = 2600 psig
T = 1060F
Sh = 6,000 psi
Let PD/4t = 3000 psi (approx)
This leaves 3,000 psi.  A system design of this type will utilize lower SIFs, say in the range of 1-2, so,
3,000/2 = 1,500 psi
Note that the wall thicknesses will be greater and the fabrication control improved resulting in the lower SIFs.

I’ve left out several steps to save some space, because I think that the most important thing to know when using a standard span table is generally how it was constructed, and what simplifying assumptions were made.

Also related is a calculation (ref. Hick’s) to determine the minimum slope of a pipe to ensure complete draining.  On the one hand it is a little conservative since emptying is not considered, but there are other factors that can negate its conservatism.  If interest, I can post that relation also. . .
StressGuy (Mechanical)
17 Jan 05 21:10
Alright,

I found a spot to post the excerpt from the out of print Kellogg book.

http://home.houston.rr.com/edwardklein/Support_Spans.PDF

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

pipingdesigner (Mechanical)
7 Nov 05 7:03
superpiper (Mechanical)
8 Nov 05 4:13
To mr Klein,
I learnt more from reading those six pages than from spending 4 years in our stress department.thanks.


To 1974vet

I am after an equation to calculate pipe spans for sloping lines in the format of span being a function of slope,
so that no pockets occur. please post the hicks equation as commented.


Helpful Member!  UW1981 (Mechanical)
8 Nov 05 17:31
By the way, another good source for span charts is from Chapter B-4, Stress Analysis of Piping Systems, Piping Handbook, 7th edition. This has charts for various sizes of pipe (standard schedules), both empty and water full.  It also has a neat deflection chart.  

As most everybody has observed, these charts are good "estimates" or guidelines - given the assumptions they are based on......

For slope considerations, there is a good article available on the web titled "DETERMINATION OF THE OPTIMAL PIPE SUPPORT SPANS FOR GEOTHERMAL PIPELINES.  If you just type in the first four words of the title in GOOGLE, you'll find it.  Sectin 5.3 talks about sag and drainage.

Good luck!>
1974vet (Mechanical)
21 Nov 05 10:38
(please post the hicks equation as commented)

Sorry for delay . . .

From Hick's
1. Compute the allowable span between hangers
for a pipe filled with water, S = WL^2/8m, where S = bending stress in pipe, lb/in^2; W = weight of pipe and water lb/lin in; L - maximum allowable distance between hangers, in; m = section modulous of pipe, in^3.  by using a table of pipe properties, as in Crocker and King-Piping Handbook, L = (8mS/W)^0.5

2. Compute the pipe slope required by the span
to prevent pocketing of water of condensate at the low point in the pipe, the pipe must be pitched so that the outlet is lower than the lowest point in the span.  when the pipe has no concentrated lods-such as valves, cross connections, or meters-the deflection of the pipe is y in = 22.5wl^4/(EI), wehre w = weight of the pipe and its contents, lb/ft; l = distance between hangers, ft; E = modulous of elasticity of pipe, lb/in^2 = 30 x 10^6 for steel; I = moment of inertia of the pipe, in^4.
   with the deflection y known, the pipe slope, expressed as 1 in per G ft of pipe length, is 1 in per G ft = l(lower case L)/4y.  Thus, a pipe slope of 1 in in 4.53 ft is necessary to prevent pocketing of the water when the hanger span is 47.4 ft.  with this slope, the outlet of teh pipe would be 47.4/4.53 = 10.45 in below the outlet.

Personally, on the one hand I think this is a bit conservative since the deflection decreases as the pipe empties.  However, it may not be so conservative when some construction practices, creep, and so on are considered.
XELR8 (Mechanical)
22 Nov 05 18:13
First of all, each of the above response above are very accurate and well taught.

The best rule of thumb for hanger spacing for pipe is the pipe diameter in feet plus 10. Example: a 3" pipe would require a support every 3'+10" = 13'-0. Use that and you should be fine for small diameter pipes 1/2" - 12".

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