Pipeline design for pigging - general advise

[jamesbanda]

Dear sirs,

We are designing a 2 inch / 3inch line on a new project which will require regular pigging (once very 1 year) due to a slow buildup of material. This is detected by increased pressure on the line.

Line length is approx 600 meters and carbon steel.

I am looking for advise on what critiera should be spec'd on the line to ensure it can be pigged easily?
Is there a max bend size ?
higher mawp of linework..?
maximum lenght for pigging ? (breaks every xx meters)?
specalist pig catchers to be installed?

 

[zdas04]

In 2 and 3 inch, unless you're planning to run smart pigs I'd build it with standard fittings (long radius elbows, barred tees, etc). The MAWP does not need to change. Pigs run for miles, a properly designed system does not need receiver/launcher pairs within the system except for line size changes.

I like the Argus Pigging Valves (

http://www.argusmachine.com/pigging-valves.cfm)for

lines that small. They are a bunch cheeper than stick built traps and work very well.

David

 

[GregLamberson]

If you are using standard fittings, generally for that small a pipe you will want no less than 20D 90's (some intel pigs will nasvigate smaller and you can check with the pig manufacutrer), but to be safe go with a minimum of 20D. You will want full bore valves (including checks). Any tee's in the line should be barred.

As zdas04 points out, length is not an issue in your case, some offshore lines are hundreds of miles.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[jamesbanda]

Greg,


Sorry for a dumb question. what is the definition of 20 D elbow and how much is it different froma normal 90 C elbow.

Would the pipework runs be a lot more complex ? these lines are going into a crowded rack so i am conserned about its design if we impose such a constraint ?
would it be better to go for 4 inch pipe and less complex elbows..

 

[GregLamberson]

jamesbanda

Not a dumb question at all. The D refers to the amount of radius in the bend, the lower the number the tighter the radius. I would not go to any larger pipe than you need (cost), the fittings referred to are off the shelf stuff. When you physically look at a 20D vs a standard bend, yes, you can tell a difference, but it should not radically change your runs.

Don't know what your pipe racks look like or how complicated the system is, you will need to get the take offs from the fittigns and look and see how it fits.

I would suggest you look at what kind of pigging needs to be done and get the requirements from the manufacturer, the 20D I gave is a general rule of thumb for pipe 4" & under. Technology in pig manufacturers changes rapidly, before boxing your self in, find out exactly what is required. And go from there.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[zdas04]

Greg, You didn't answer the question. The "D" is the nominal pipe diameter. A 20D bend in a 2-inch pipe would have a 40-inch radius. Bends that big are normally referred to as "hot bends" which means that pipe is heated and bent in a fixture.

James, If you are going that way (I wouldn't) make certain that you specify at least 18" tangent on both ends of the bend. On one project I didn't specify and got bends that were less than 90 degrees and a serious pain to line up for welds. The tangent just gives you straight pipe to connect to.

A few years ago the smallest smart pig you could find was 6-inch, I hadn't heard that anyone was marketing a 2 or 3-inch smart pig these days--the industry tends to think of 2 and 3-inch pipe as disposable. If you aren't thinking of smart pigging then I would use forged elbows (the long radius is 1.5D radius and the short radius is 1.0D).

David

 

[dcasto]

Since there are no 2" smart pigs and only rumors of a 3", that shouldn't be a concern.

We just installed a DOT regulated 3" and we used 7D bends. The best part of the project was the new DOT inspector was not going to let us cut a 7D 90 degree bend to a 58 degree to make a field turn in the ROW. He thought the cut would reduce the bend to under 7D.

 

[zdas04]

Don't you just love inspectors. I had one like that a few years back. I ended up laying the bend on the ground and stringing lines to the center point of the bend and showing the idiot that cutting it back to 60 degrees would not change the bend radius. I guess his elementry school class was a bit light on geometry.

David

 

[GregLamberson]

I didn't see any mention of using smart pigs, just cleaning pig runs. Still need to look at the pig manufacturers recommendations for the minimum radius for the type pig you need and go from there.



Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com