Creep measurement
Creep measurement
(OP)
I'm looking for advice on techniques to measure the amount of creep that has been sustained by a furnace tube.
Also, what is considered an acceptable amount of creep.
Are there any codes or standards that provide guidelines.
Also, what is considered an acceptable amount of creep.
Are there any codes or standards that provide guidelines.





RE: Creep measurement
RE: Creep measurement
You need to get your hands on a copy of API Standard 530, "Calculation of Heater Tube Rhickness in Petroleum Refineries." Annex A, "Estimation of Remaining Tube Life" should be particularly useful.
btrueblood was right, you probably would get more responses from the B&PV forum.
jt
RE: Creep measurement
RE: Creep measurement
RE: Creep measurement
Perhaps you're referring to the "Peaking" measurement for the longitudinal weld? (Nod, Nod, Wink, Wink).
Brian
RE: Creep measurement
This involves grinding, polishing and etching part of a tube and/or weld to a mirror finish. The area is then coated with acetone and a plastic film placed over the prepared surface. After drying the plastic film (which now has a replica of the grain structure) is removed and examined under a microscope. The examination will allow the creep damage to be placed into one of eight categories. VGB standard TW507(1997) has eight such categories and provides guidelines for classification of creep damage.
athomas236
RE: Creep measurement
briand2,
I'm not sure what is meant by "Peaking" measurement.
RE: Creep measurement
1. I thought you were a different "MalcolmA"...sorry.
2. "Peaking" measurement is what's done on fire-tube / shell boilers (here in the UK). It measures the extent to which the longitudinal weld on the shell protrudes radially outwards from the surrounding shell. Over time, this measurement increases (it's measured with a simple gauge) due to cyclic operation.
Regards,
Brian
RE: Creep measurement
athomas236
RE: Creep measurement
Be aware that peeking has got diddly squat to do with creep.
It is to do with poor quality manufacture resulting in a "peek" or flats either side of the long seam of a fabricate cylinder. This out of roundness induces a Moment in addition to the stress field normally expected in a cylindrical shell.
This was a major problem in the late 80's / early 90's here in the UK, specifically with the shell of Fire Tube (also known as "Shell" or "Package") Boilers which resulted in a number of catastrophic failures. The problem was addressed by a SAFed (Safety Assessment Federation) committee who have derived a methodology of addressing this problem.
As always, a little bit of knowledge can be a dangerous thing!