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kyliemax (Mechanical)
9 Mar 09 22:42
Hi - I want to specifify a long bend or long sweep type for all of the 90 deg elbows in a cooling water system.  What are the definitions (if any exist) for:

(1) Standard Bend
(2) Long Bend
(3) Pipe Bend

How do I specifiy these - is there a convention for the bend radius or??  My syste will have hundreds of feet of 4 and 5 " schdedule 40 CS pipe.

-JV
 
MikeHalloran (Mechanical)
9 Mar 09 22:54
An elbow is a discrete fitting.
They come in a standard radius, and a long radius, neither of which is particularly large.  Machinery's Handbook has dimensions for common sizes.  Manufacturers don't always pay attention to the standards.

Bends are made from the pipe or tube to be redirected.
Standard radius is that produced by the bending tool that you have.  
The radius you need always requires a tool that you don't have.
Bends are also sold as discrete components, with and without tangent ends, in a radius made by someone else's tool.  They're never the radius you need, either.


 

Mike Halloran
Pembroke Pines, FL, USA

kyliemax (Mechanical)
9 Mar 09 23:14
Thank-you Mike.  This is humorous and depressing. I will check the Machinery's Handbook as suggested.

-John
 
racookpe1978 (Nuclear)
9 Mar 09 23:19

Mike:  8<)

I thought that was:

Your foreman can always find elbows.  (But they never fit.)
Your planner can never purchase the speciality bends you think you want.  (They won't fit either.)

Solution:  Tell your planner (and your General Foreman) where you want to pipe to go.  Don't look (or look twice!) at how it got there.
racookpe1978 (Nuclear)
9 Mar 09 23:26
Seriously:  SPECIFY what your planner can realistically BUY.

NEVER specify a "bend" (a unique,  one-of-a-kind speciality radius and length and angle) pipe bend.  Unless you really, really, really, really have to.

Spec long-radius bends as your standard: the "long radius" elbows is 1.5 times the NORMAL diameter of the fitting.  A 6" long radius elbow is 1.5 x 6" = 9" radius.   An 8" long radius bend = 1.5 x 8" = 12" radius.  Doesn't matter what schedule pipe it it.

If you really have to save space (and can tolerate the increased resistance) - use short radius elbows = 1.0 x the normal dia = 6" radius or 8" radius in the above cases.

...

But these will never fit anyway.   8<)

Metric system?  Same solution.  Same specs.   Dollars or euros or yen don't matter.
BigInch (Petroleum)
10 Mar 09 2:15
SR = short radius, 1D
LR = long radius, 1.5D
XD = specified standard bend where X = 3, or 5
R = X in, ft, m, custom bend radius dimension to centerline.

so on a material list you might see something like this,
8" ELL, 90ºLR, 0.500 WT, ASTM A234 WPB  

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

pennpiper (Mechanical)
10 Mar 09 6:27
Don't use 5" pipe (and fittings) use 6".

The 5" is NOT a standard size and would be very expensive to buy all the fittings, flanges and valves.
Helpful Member!  JohnBreen (Mechanical)
10 Mar 09 7:40
Kyliemax,

Welding fittings are defined by the ASME B16.9 - Standard for Forged Welding Fittings (and other Standards that are used outside North America).  The ASME B16.9 welding elbow is manufactured in long radius (1.5 times the NOMINAL diameter) or short radius 1.0 times the NOMINAL diameter).  The B16.9 Standard really does NOT "standardize" ALL the dimensions - just end-to-end, center to end and some "squareness" tolerances (NOTE - wall thickness, per se, is not defined).  B16.9 fittings are pressure rated.  That is to say they must pass, or be shown to be able to pass, a "pressure test".  If you were to weld a B16.9 Standard elbow between two pieces of straight pipe and weld two B16.9 Standard welding pipe caps to the ends of the straight pipe (as closures with all fitting schedules being the same as the straight pipe schedule) and pressure test the weldment to destruction, the straight pipe would fail first.  It is NOT UNCOMMON for the fitting manufacturer to make the elbows of greater wall thickness in order to assure that the extrados (outside of the the elbow radius) will be thick enough to pass a pressure test.  When the elbows are of a thickness that is greater than the matching straight pipe wall thickness (for a given schedule) the elbows must be "end bored" so that the elbow wall thicknesses match the straight pipe nominal thickness at the weld lines.  This facilitates the welding process.

Bends are not necessarily "standardized" and are made from straight pipe that is hot or cold formed into a bend.  This usually means that the extrados will be thinner than the nominal wall thickness as a result of bending the pipe.  It is common practice to buy pipe bends to a "minimum wall thickness" specification where the required "as bent minimum wall thickness" will be NO LESS than is specified at any point on the bend.  As stated above, bends are usually of longer radius than elbows (they are specified when a longer that LR bend radius is needed by the design) and the required radius is specified as a function of the nominal pipe diameter - e.g., 3.0 times the nominal pipe diameter or 5.0 times the nominal pipe diameter.  The B31 Code for Pressure Piping, B31.3, Process Piping includes equations for calculating the required wall thickness for formed pipe bends (note, these equations do not apply to ASME B16.9 forged welding elbows elbows).

Regards, John.
kyliemax (Mechanical)
10 Mar 09 11:44
Everyone – Thank-you for the information and comments.

Pennpiper - I am rather stuck with the non-standard nominal schedule 40, 5" pipe as the connections at the remote radiator and at the engine are all 5" (150# flanged) and I have to accommodate all of the pipes into an existing pipe chase.  I looked at going to 4" to gain a little more room in the pipe trench but the pressure drop becomes too high (due to the increase in pressure drop across all of the valves and fittings).  Moreover, the engine manufacturer requires that all field piping be of a diameter equal to or greater than their connection.

Incidentally is there a difference between a pipe trench and a "pipe chase".  I have a concrete formed trench in the floor of a building.  The trench will be covered with removable deck plates.  Can this rightly be called a pipe chase or am I confusing terminology?

John Breen – this is more or less exactly the source of a standard I was seeking – thank-you for the detailed information presented here

ASME B31 code for pressure piping – what is the definition of "pressure piping".

-JV
 
racookpe1978 (Nuclear)
10 Mar 09 12:04
Only non-standard connections at the ends?

Buy the two 5" 150 lb flanges - one for each end, two 5"-6" reducers, and use standard 6" pipe and fittings through the middle.   Much, much, much cheaper.  Faster.  Less flow resistance as well.

Yes, the pipe trace/trench  will be a little more cramped with a 6" pipe in it.   
Bribyk (Mechanical)
10 Mar 09 13:42
There are some exemptions in the ASME Boiler & Pressure Vessel Code for parts of internal combustion engines that are required for it to function.  I would think there are exemptions for the piping as well as some manufacturer's use slip-on automotive-style radiator hose connections for coolant.

And you can never have too much room in the trench, add some width and depth if/while you can.
kyliemax (Mechanical)
10 Mar 09 14:21
Dear racookpe1978 - I came to this project a little late so I am having to revise a poorly thought out design.  The contractor has completed most of the civil works.  Unfortunately, this includes pouring if the pipe trench - so I am stuck with it.  No way can I get qty 12, 6" inch pipes in there with all of the other stuff that has to be in there as well.  I do appreciate the heads-up that 5" is not a standard size.

Thanks again forum.

Can anyone recommend a couple of domestic manufacturers / or sources for high-quality gate valves and wye strainers for service in 50/50 ethylene glycol at 60 PSIG and 250 deg F operating temperature?
 
-John

 
MikeHalloran (Mechanical)
10 Mar 09 18:27
If regular flanges won't fit, consider Victaulic or Dresser couplings...

 

Mike Halloran
Pembroke Pines, FL, USA

unclesyd (Materials)
10 Mar 09 19:09
I have to take exception to the statements that 5" pipe and fittings are hard to procure. We use a lot of 5" line pipe and 5" core pipe for jacketed pipe spools. The pipe is Sch 40 through XXS.  The fittings are 300 RTJ to Class 2500 RF.
I would check your piping supplier prior to changing design or generating a work around.
 

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