Pressure Vessel Cost Estimating Book 4

[vwmeche94]

E-Tips forum,

Good afternoon. I am new to cost estimation as an engineer and am wondering if anyone knows of any good books or resources related to estimating pressure vessel assembly (i.e., cutting holes into shells of varying thickness then installing/welding-in nozzles, TOL's, COL's, etc.)

John S. Page has a great Man-Hour estimator book series, but nothing specific to pressure vessels.

 

[MJCronin]

I have developed many, many project cost estimates for pressure vessels.

There is a reason that you cannot find a book with pressure vessel prices. Prices vary considerably with the cost of raw materials and with the expected workload of various fabrication shops

It has been my experience that no book can be developed.

About the best you can do is to develop preliminary sketches and datasheets for the components and ask various fabricators for "budgetary grade estimates. It is my experience that most fabricators can produce a "quickie" estimate within a week. Get 3 or 4 for each component. Discard the lowest cost estimate. Average the others and add 15%

Pay no attention to the screaming of the new MBA running the project estimate. He will be upset that you cannot magically produce estimates out of thin air. You will, of course, need some engineering involvement to develop these important budgetary grade sketches and datasheets.

When he tells you that the PIDs are not yet complete, make estimates on the dimensions, temperatures, pressures and nozzles

Because of the typical long lead time of these components, you will also need a preliminary fabrication timeline (in weeks) for each of these vessels. Add 4 weeks to the average lead time given to you by the fabricators.

Be aware that the MBA will then take your undeveloped datasheets and sketches and send them out for fabrication.

The project and the process will progress onward ....materials will change ..... design pressures will change ...... you will not be told of these changes ...... The client will wake up ......

When the vessels are delivered to the worksite, you will be blamed by the MBA for your oversights and mistakes....


MJCronin
Sr. Process Engineer

 

[EdStainless]

AIChE publishes some useful guidelines for process equipment estimating.
But remember, it will always cost more and take longer than first estimated.
the reason is that the project will always be more complicated that stated at first.


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P.E. Metallurgy, Plymouth Tube

 

[JStephen]

If you're wondering where fabricators get their information, it's all proprietary information, so far as I know. Part of the reason is that the manhours will vary depending on the people involved, the welding processes involved, the equipment available, etc. Manhours will vary considerably depending on plate thickness and nozzle details as well. If you have a big enough shop, you can have people stand around with stopwatches and time some of that. Otherwise, somebody sits at a desk and things "That ought to take a couple of hours", and it gets refined in later bids. Some of that information does get passed from company to company also, either in the heads of employees or in paper form, so not everybody is starting from scratch.

 

[SnTMan]

MJCronin, priceless

The problem with sloppy work is that the supply FAR EXCEEDS the demand