Dog-Legs 1

[Tman1]

Hy all

Just wanna know if any one knows the acceptance criteria on dog-legs...
if so would like to know the reference..

Thanks

 

[pennpiper]

Everyone has their own opinion of this "Slang" term. I consider it to be the same as "L" shape, as in a "Dog Leg" left or a "Dog Leg" Right.
It is also not a real or common Piping term.

prognosis: Lead or Lag

 

[Tman1]

agree, but do you perhaps know tolerances for what the acceptable size of it...and the refference please.

 

[StevenHPerry]

Tman asks about "acceptance criteria." I'm not sure what that means. Why wouldn't you accept a dog leg piping arrangement? Personal or plant preference I presume.

As to pennpiper's post, I take the term to mean a change in direction considerably less than 90degrees as in a "L". Maybe I misinterpreted the post. A 45deg el in a line would qualify as a dog leg in my book, as would anything less than 45degrees. That geometry is also commonly described as a dog leg in golf and aviation.

I do agree it is not an official term. Since there is some discussion about its meaning, I would avoid the term.

- Steve Perry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[BigInch]

Most dogs accept them as long as they are more like "P" shaped. L are not favored quite as much. "Z" NOT WELL LIKED AT ALL.

Independent events are seldomly independent.

 

[TGS4]

The layout of a piping system, and the "acceptance" thereof, is generally not the prerogative of anyone other than the piping designer, the piping stress engineer, and the ultimate owner (who generally sets criteria a priori in the form of specification and standards).

The particular layout of any piping system is dependant on many factors, including (but not limited to):
- Size (diameter)
- Internal pressure (which will relate to wall thickness)
- Temperature
- Length
- Supports
- Attached equipment
- Wind and/or seismic considerations

One cannot accept a piping system without intimate knowledge of all of the above. My recommendation is that if you have a question about a particular piping layout, contact the piping designer and pipe stress engineer and ask them. Most things are done for a reason.

 

[msquared48]

Are you talking about vertical dog legs, or elevated?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[racookpe1978]

Mike:
The preferred elevation of a dog's leg depends entirely on the preferred impact height on the side of the fire hydrant. 8<)

 

[Artisi]

Seems as though Tesco have horse meat in their burgers - so can't see anything wrong with dog-legs being included.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[MickMc]

Tman1,

Just a thought but could you be referring to 'dead leg' which quote from a major operator 'refers to a section of piping connected to a flowing stream where it is not self draining and is not normally flowing' e.g. branch connection upstream of block valve.

This particular operator concern is corrosion and they consider dead leg to be 3 x pipe diameter or 2 metres whichever is less.

 

[Kiwi2671]

Guys,
Just another perspective from the Southern Hemisphere.
When we have two lengths of pipe joined by a butt weld and one side receives more heat than the other the resulting shrinkage at the weld puts a "dog leg" in the pipe.
Even harder to control with S/S.
Regards,
Kiwi

 

[Artisi]

Hence the saying "as straight as a dog's hind leg".

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)