Steam Velocity and Erosion
Steam Velocity and Erosion
(OP)
Is there a correlation between steam pressure and velocity? Is there a velocity at which erosion will occur?
Would this erosion be FAC?
I realize particulates have an impact, but I'm more concerned with the steam and its behavior.
Thank You.
Dale Simonds
Would this erosion be FAC?
I realize particulates have an impact, but I'm more concerned with the steam and its behavior.
Thank You.
Dale Simonds
RE: Steam Velocity and Erosion
RE: Steam Velocity and Erosion
RE: Steam Velocity and Erosion
RE: Steam Velocity and Erosion
I wrote an FAQ that partially answers this question.
The design velocity depends on the dsteam conditions(saturated or superheated) an a method is contained in Crane #410 and the "Piping Handbook" by NAYYAR
MJC
RE: Steam Velocity and Erosion
Thank you for your posts.
I am looking for more of an "educational" answer to my questions. I know absolutely nothing about Piping and Fluid Mechanics. Or the design requirements for steam piping or tubing. I have seen examples of steam erosion in my career as a welder, but I don't know very much about the root causes for the erosion.
Is there a pressure that, above which, erosion is likely to occur? Or is it strictly a velocity issue?
Are suspended particulates in the steam, such as exfoliation of the steam-side scale in a boiler tube, necessary for erosion to occur? Is a physical impact required for erosion to occur?
Is the temperature of the steam a factor?
I have seen, and repaired, examples of "particulate" erosion(is there a special term for this?.
By saying "particulates", I mean dirt, lime, wood chips, etc... .
I don't know if the examples of steam erosion I've seen had particulates in it or not.
"Rules of Thumb" would be great.
Thank You
Dale Simonds
RE: Steam Velocity and Erosion
The rule of thumb we use around here for max velocity in saturated steam (less than 100% quality, or, what some people call 'wet steam') piping is - the velocity should be less than about 90 feet per second for CLEAN saturated steam. Velocities greater than this CAN, but not always, cause erosion at direction changes (ells and tees). If you have particulates, e.g. boiler scale, rust, red rags, beanie weenie cans, then the erosional velocity will be smaller. In our business (steam distribution for enhanced oil recovery) we use a target design velocity of about 60 ft/sec because that gives a reasonable pressure drop and reduced energy loss for a given pipe size and length, it gives decent flowsplitting (i.e. you don't get all liquid down one leg of the tee flowsplit and all vapor down the other leg). Some owners will want a max velocity lower than 90 ft/sec, some will allow greater, but 90 ft/sec is a good conservative starting point.
Erosion is strictly a velocity issue, and velocity is based on pipe diameter, flowrate, and pressure drop.
A pretty good reference for this is "Crane Technical Paper 410". It is relatively non-technical. Hope this helps!
Thanks!
Pete
P. J. (Pete) Chandler, PE
Principal Engineer
Mechanical, Piping, Thermal, Hydraulics
Processes Unlimited International, Inc.
Bakersfield, California USA
pjchandl@prou.com