Pipe to sleeper corrosion 3

[HRK1]

I am currently in a refinery, that when built, no wear pads or any type of isolation was used between the rack and pipe. Now we are seeing a lot of corrosion at these points. The plant right now is putting cold roll (C/S round bar) on top of the I-Beams. My problem with this, is that there is still a metal to metal contact and will rub thin on this location.

I have worked other refineries and used the fiberglass wear pads, which glues to the pipe, I do not see any issues with this method, but, I am looking for other alternatives that might exist for hot lines (500F) and cooler lines (propane). All lines being Carbon Steel. Has anyone used a Kevlar pad under these lines? I would need something that would not compress much. Use would be mostly on 16" and down.

I am trying to get out of having to build a scaffold, firebox, use of a firewatch and welder. This is also a safety issue, with all the hotwork that has to be done at each beam, and with the possibility of arc strikes on the pipe. There is also too many manhours being spent. Does anyone have fresh ideas or know of some websites that might be able to supply some information? I have to get the pipe off the steel, and would prefer some other method, other than the round bar. Thanks for any help

 

[11echo]

One question here, would your existing pipe racks be galvanized? ...And your getting a galvanic reaction on the bare carbon steel pipe?

 

[jte]

KHood1-

Interesting... We are dealing with similar issues at the refinery at which I work. Our plant was built with ¼" diameter round bars on top of the pipe rack beams. The piping at these supports is often wearing thin due to contact with the bar. Typically no repads. So we cut off the stinkin' bars when we can and install new piping with welded on repads.

Retrofitting fiberglass repads might work for you. We tried it, gluing them on with a Belzona compound. I replaced several of these with welded on CS pads after they fell off.

jt

 

[DSB123]

We have the same issue where I work. However what should be understood is that the contact stresses and "local" circumferential bending stresses developed in the pipe can be considerable when the pipe is supported on bars. We use flats of a width which results in acceptable "local" pipe bending stresses. When your plants were built the induced "local" bending (circumferential) would not have even been considered by the piping designers in my view as in our case. Suggest you check these circumferential bending stresses in the pipe wall before you add round bars between pipe and steel. Also pipes at 500 Deg F or propane line should really have pipe shoes between the pipe and the steelwork. Surely these lines are not pipe to steel.

 

[DSB123]

Forgot to mention that wear plates can be a problem with corrosion between the pipe and wear plate since generally these are not fully welded to the pipe and allow ingress of moisture. We have been removing wear plates from our pipes so inspection can be performed. With wear plates you cannot check for corrosion between pipe and plate.

 

[HRK1]

11echo, no, all supports are carbon steel and painted. We are getting the corrosion from trapped moisture.

jte, I am not sold on the c/s round bar, I am exploring other options. We don't have the luxury of replacing the pipe yet. Looking at putting a Kevlar type strip onto the top of the I-Beam or the fiberglass wear pad. I know Kevlar is good for high temps, don't know how it rates on the compression end. Thanks for your input.

 

[HRK1]

DSB123, Yes the propane does sit on the steel, and we do have 450F. lines also on the steel, but it doesn't operate at all times, and when it does, not for long. When building this refinery, they cut corners wherever they could. Now we are paying the price, some 30 years later. So now, I need the most practical and economical way to isolate these lines. Thanks for your info. and ideas.

 

[joeswoes]

We can help. We manufacture "Riload" pads. These are PTFE molded into perforated stainless steel and rolled to the specific pipe diameter. The 500F is not a problem, and provides lubricity and electrical isolation. Go to

http://www.pureflex.com

and see if these look like what you need.

 

[jay165]

HRK1:

We've used 1/4" "acetyl black" pads that were attached to the steel pipe supports with a Hilti gun. Worked pretty well. The acetyl black pads were the only ones that didn't shatter when using the gun. Sorry, but I don't any company data or contact info - too many projects ago and I've moved offices several times.