AS-BUILT DRAWING 1

[picasa]

For an old heat exchanger, the detailed engineering drawing for the channel head (exchanger is AET type) are not available. The plan is to do as-built drawings from actual physical measurements on this head in the field when the hx is out of service.

* Has anyone done this before?
* Please share your experiences.
* Please provide precautions to take.

Thanks.

 

[waskillywabbit]

I don't know that you can honestly call it an "as built" drawing. Sounds more like the used car term where they state it "as is". "As built" infers to me that an item is "new" and "uncorroded", right off the lot so to speak, not something that is old and seen service. I just see it as misleading to label it "as built". Maybe "been built" would be a better stamp!

Obviously, you are going to have to run the appropriate tests to get current thicknesses throughout the channel head as I'm sure the corrosion/wear has not been uniform, so I don't see this drawing as even looking like an "as built" drawing anyway..or not the typical one I see day in and day out.

What do you need "new" drawings anyway? Why are the old ones "unavailable" or does that mean "lost"?



Brian

 

[jte]

picasa-

Making "as built" drawings well after the equipment has been placed in service is not horrendously unusual. This will especially be the case with plants which have inhereted or bought used equipment. You can usually determine what the original thicknesses were. For example, usually the ID or OD of the shell will be an even inch increment. So its not that tough.

There are times when, for equipment which can be pulled on the run, I've sent a drum or exchanger to our local VIII shop and said "Build me another one just like that one!" They get the job done at a reasonable cost and I get new drawings (and calc's) for the new components or equipment.

jt

 

[Patinlouisiana]

We repair or duplicate many exchanger shells & vessels.
I usually designate the drawing Either "AS IS" or "DETAILS OF EXISTING UNIT"

http://www.famco-enterprises.com

 

[JStephen]

The state boards of engineering publish their disciplinary actions from time to time. One of the items I see in there periodically is "as-built drawings" that didn't represent as-built conditions. Now, this usually relates to civil type work, but the problem is that an engineer designs or draws something, it gets built, and he then assumes it got built the way he drew it, and seals "as-built" drawings for it. However, the boards take sealed as-built drawings to represent a guarantee that it was really built the way the drawing shows.

My point is to be careful how you apply the "as built" term. For example, you can look at something and measure it, but you can't discern steel grades or whether welding is full penetration, radiographed, etc. If you're making a drawing of an existing unit, don't be afraid to spell out where the dimensions and details come from ("all dimensions measured on existing unit"), or to indicate items unknown to you ("carbon steel, grade unknown"). The "Details of existing unit" is a pretty good term. But don't call it an "as built" if you didn't watch them build it.

 

[vesselguy]

JStephen is correct. The problem here is just wording, I'm sure.

Picasa,
You sound like a maintenance guys working in a refinery. Correct? What you described is not doing an As-Built. What you propose to do is to take field dimensions of an "A" type channel that you want to "duplicate". From my experience working on this kind of activity, no big thing to watch out for. Just get your Maintenance crew to measure the key dimensions of the channel and have an Engineer there to supervise. Make sure you get the nozzle centerlines from channel face of flange best you can cause you need to mate up to existing piping flange. Next, have the Engineer do the TEMA calculations to size the thicknesses. Then get a fabricator to design it, fab it, and register the design with your local boilers branch.