Hastelloy piping and plastic tanks?

[MrAnxious]

Hi all, a project engineer is offering me a hastelloy piping system connecting to some ~15 foot dia x ~15 foot tall buffer tanks. He says that the most economic solution is to build the tanks from plastic or plastic/grp rather than metallic construction. He says not to use plastic piping due to the possibility of erosion from particles in the liquid. I have no experience of combining metal piping and plastic tanks. Is it an OK thing to do? Thanks all!

 

[unclesyd]

I cna't see any problem with a properly designed system.

We run this exact pipe and tank combination for numerous tanks in our scrubbing and recovery system.
All tanks in this service have a much more substantial boss when connected to metallic pipe that you normally use for plastic pipe. All efforts are made to keep the piping reactions off the tanks.
We also have a lot of plastic tanks connected with large sizes,10"-20" GFR piping. We also reinforce all these penetrations in these tanks.

What are your MOC and process materials?

Some plastic pipe is very abrasion resistant

 

[MJCronin]

Anxious...

Be careful about areas that could undergo a "pool type fire".

NFPA 30 and several other fire protection and building codes caution about the use of plastic/FRP tanks in areas where a fire could destroy the tank.

Although more expensive, metallic tanks are superior for fire integrity.

-MJC

 

[unclesyd]

MJCronin,
In our case we have largely mitigated the fire hazard by the use of a fire retardant resin, Atlac 382, with a high Antimony content. The RFG tanks are also protected by an extensive sprinkler system as well a steam injection system on the process side.
This area has undergone the test of fire twice since it was installed in early 80's

 

[MrAnxious]

Thank you all. The fluid is high in Chloride and Fluoride salts but are water based so although Hastelloy is chosen for stress corrosion cracking and pitting corrosion resistance, fire should not be an issue. Thank you again for the advice.

 

[unclesyd]

Our system is also for scrubbing and recovery of HCl vapors with a touch of organics operating a max temperature of 60C.

 

[moltenmetal]

If the tanks are OK as FRP, chances are you could do this in FRP piping and get a perfectly acceptable solution- for far less money than to do same in Hastelloy.

Too much fluoride and you might be worried about the durability of the glass- make sure the correct construction (corrosion veil etc.) are specified.

Erosion concerns are in my experience very frequently over-stated. You may actually get better service life out of FRP piping than you do out of the Hastelloy in some erosive situations. There's more to erosion- (or more properly erosion-corrosion) resistance than simply making the piping material harder.

Any metallic piping and support system you put in is going to have to be very carefully designed to avoid putting excessive forces and moments on the FRP tanks' nozzles. The nozzle attachments will need to be designed and fabricated properly. It's not impossible but is far more challenging than designing same for a metallic tank with inherently stronger nozzles.

 

[JoeySoap]

Thank you for the comments.