installation cost for plate heat exchangers and shell&tube

[zzznook]

Dear all

Im calculating on the cost for an absorption stripping system and Im trying to estimate the installation cost in the case when shell&tubes are used and the one whrn plate heat exchangers are used. The method Im using now is distributive factors on the purchase cost. However Im afraid this method is not applicable on both s&t and PHE. Does anyone know roughly how much it costs to install a plate heat exchanger and a shell&tybe based on capacity or area or price?

Thanks

 

[Montemayor]

zzznook:

Actual experience has shown that the cost to install process equipment - especially heat exchangers - depends on the the application and the scope of work in question. Total installation cost will vary on a case-by-case basis. I could easily furnish you with a detailed example of where this is a clear case in the application of shell & tube exchangers versus Plate Heat Exchangers (PHEs).

No successful mechanical contractor will bid on the job unless he has a clear scope of work and detailed drawings as well as a clear understanding of the application. Plate heat echangers might have a smaller size and smaller footprint in one case, but they could force a major piping modification on an existing facility due to process requirements and the PHEs own maintenance requirements.

Additionally, your query is not specific as to whether you are dealing with grass roots installations or existing facilities. It makes a big, big difference. If you are going to apply cost estimates based on heat transfer area, heat duty, or as a % of the purchased price I wouldn't put the slightest faith on your figures. What you are proposing is an academic, Plant Design 101 method that simply doesn't hold water in the real world. If you are going to estimate your project costs that way, why not use the same logic and apply the same philosophy to the diameter of the absorber, the MDEA CO2 loading, and the whole 99 yards can be estimated similarly. You would be just as accurate in the engineering design as you would be in the costing estimate.

 

[zzznook]

Montemayor.

It concerns a new plant, I would be interested in the cost for all positions, the reboiler and condenser, the lean rich interchanger and the lean cooler.

 

[asv80]

Montemayor,

I would be interested to know the example you have for any case of comparison between PHE and S&Ts.

Thank you.

 

[rmw]

PHe's don't make good condensers. Oh they will condense OK, but their design doesn't lend itself to good air off take systems. If you insist on using one as a condenser, look at the designs that most major manufacturers have for sugar evaporators since these have probably the best provisions for air offtakes (Air equals non condensables.)

Second, do the PHe's fit within your temperature limits. As a general rule I use a 300/300 rule. In english units that is 300 degrees F and 300 PSIG, but not at the same time. The gasketing materials are generally the weakest link in the chain with plate thickness/geometry coming in a close second.

S&T's are more forgiving. Once you get one of those built it is what it is until it is damaged, abused or destroyed.

PHe's tend to be finicky about how they are tightened and will leak if not done correctly.

Also, buy yourself a spare plate pack when you buy the new unit(s). When you want to go back later and get a spare or replacement set, at spare parts pricng you can buy a whole new PHe for less than the price of a spare plate pack. That is a closely guarded secret of the manufacturers.

Phe's are also real finicky with respect to piping loads. S&T's are much more forgiving in that regard as well. You don't want bending moments from the piping loads warping the end plates of the PHe causing leakage.

All that said, the Phe's can and will get a whole lot closer approach temperature than will S&T's. The best S&T's work in the 10F range while the worst PHe's will get you 5F. (Rules of thumb-actualities vary with specific designs.)

PHe's are said to require less real estate since they don't require the clearance that a S&T does for bundle pulling.

These are a few points to ponder.

rmw