Minimum pipe spool length 2

[abba7114]

Can some one out there advice on minimum pipe spool lenth between fittings, I have been using 50mm for 2" pipes and 75mm for 6". The service is oil production I could not lay my hand on any material to back my practice.
Thanks

 

[pennpiper]

abba7114, See this thread:

Dummy spool fabrication
thread 378-145824

it may help.

 

[NozzleTwister]

abba7114,

When you say fittings, I assume you mean weld-o-lets, etc, as welding tees and elbows can be welded fitting to fitting.

I haven't seen written rules on minimum spacing. When branch connections are very close, I space them so that the REINFORCEMENTS ZONES don't overlap. The reinforcement zones are illustrated in ASME B31.3, Fig. 304.3.3, Branch Connection Nomenclature.

NozzleTwister
Houston, Texas

 

[Zapster]

I believe that this might be the written rule that NozzleTwister might be talking about:

PFI ES-7, Minimum Length and Spacing for Welded Nozzles

 

[NozzleTwister]

Thanks Zapster for putting me on to PFI ES-7. I'm familiar with some of the PFI standards but not this one. I located a copy of this from our standards provider, reviewed it and have the following comments.

The dimensions given in the tables seem to focus on maintaining a minimum distance between welds on adjacent nozzles for a given size. While paragraph 5.3 recommends not overlapping reinforcement zones, the dimensions for Figure 1 certainly don't guarantee that. Dimension C in figure 1 may need to be greater. They leave that evaluation up to the user. For reinforcement zones, this dimension will vary on a case by case basis.


NozzleTwister
Houston, Texas

 

[Zapster]

NozzleTwister, not sure what you mean:

Figure 1 is for nozzles without saddles or ring reinforcement.

Figure 2 is for nozzles with reinforcing saddles or rings

Figure 3 is for nozzles integrally reinforced (olets)


Seems you are looking at the wrong figure. Perhaps, you have an older version, ours shows “Reaffirmed March 2002”

 

[Hench]

abba7114,

As pennpiper has noted, this topic has been discussed before. I think that both this thread and the previous thread may be miss labeled though. Might you be looking for minimum distance between welds. Because if it's not welded, the minimum length is the shortest piece of pipe that can physically connect two components.

For rule of thumb on min weld distance, we use 6 times the wall thickness or 2”, whichever is greater.

Our stress engineer will usualy check branch connections on critical systems.

Good Luck!

Hench

 

[NozzleTwister]

Hench & Zapster,

Hench, I re-read the original post and maybe you and pennpiper are correct. I read the post with something else in mind. I assume abba7114 will clarify if he doesn't get his answer.

Zapster, whether I'm off-track or not, let me answer your last question anyway.

For pressure, ASME B31.3 requires Area Replacement for the cut-out removed for a branch opening. The area to be replaced is basically the calculated header thickness required for pressure times the branch ID. This area is to be within the reinforcement zones defined in ASME B31.3, Fig. 304.3.3. Surplus wall thickness in the header and branch not already used for Pressure, Mill Tolerance, corrosion or other allowances can be applied towards the required area replacement as well as branch weld areas. In many low pressure systems, the area replacement is satisfied for stub-in connection without the addition of a reinforcement pad. The reinforcement zone is present whether you have a reinforcement pad or not.

The extent of this zone will vary case by case and need not extend any further than what it takes to meet your requirements and won't extend beyond what's defined in Fig. 304.3.3. Of course you may need to add a pad to meet the area replacement requirement.

This is loosely paraphrased so refer to your governing piping code for specific facts.


NozzleTwister
Houston, Texas

 

[abba7114]

Hench (Petroleum)
Thank you all for the valuable contribution,Hench hit the nail on the head, actually what I have in mind is weldolets for instruments attachements on a pump discharge lines between the first elbow and the valve flange.
Other refferencies has really broaden my knowledge especially ASME B31.3 branch reinforcements.
Abba7114

 

[pipingdesigner]

I agree with Hench, usual allowance is 6T (6xWall thickness) or 50mm, whichever is the greater.


pipingdesigner

http://www.pipingdesigners.com

 

[rossmail]

I was always told the minimum cut distance or between welds was the od of the pipe but I have only done large diam pipeline.