Design of Thermoplastic and FRP Tanks

[TLHS]

Does anyone know of a good small firm or sole practitioner engineer that does thermoplastic and FRP tanks within the North American context? I've got a client who's doing work in them and I'm hoping to point them towards some options. I know all sorts of steel tank people, but I've seen people try to stretch into plastics when they don't really know it and it tends to be a bit ugly.

 

[LittleInch]

Sizes? Or range of sizes

Vertical?, Horizontal?, circular? Rectangular?

How many?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JStephen]

I would suggest contacting some of the manufacturers of the products and asking them for contacts.
If there are specifications for the items, there may be lists of committee members on there or available from the sponsoring organizations.

 

[TLHS]

Small stuff, which is why it's not a big engineering firm type of problem. It's in the vaguely regulated zone of a couple of meters in diameter, but due to process requirements some of the detailing items are a little weird and there are some slightly aggressive height to diameter ratios. I could do a straightforward plastic tank from scratch using the prescribed details in some of the codes, but evaluating other details is outside of my comfort level. Can't go into the specifics, but the fabricator is a European firm that has done a lot of this type of work but at the moment seems light on the engineering to me. Still chasing their documents, but my gut is currently that there's a bit of "we've done it this way for years" going on. My client is locked into them for commercial reasons, and it's a question of how much documentation and potential detailing changes need to happen to have a good comfort level if my client is selling these in North America.

From what I've seen these are generally vertical above ground tanks. Some are flat bottomed, some FRP tanks are cone bottom on legs.

I've contacted some of the FRP and plastic material suppliers, because it seems like some of them provide design support services and software to companies that buy materials from them.

 

[nackra]

we have used tanks from this manufacturer for a variety of chemicals including hypochlorite, alum, bisulfite:

https://www.polyprocessing.com/

 

[EdClymer]

Greetings from England


Some thermoplastics have superb chemical resistance and are often first material choice for liquid chemical storage.

For an example, in UK, for well over 25 years, many hundreds of bulk ferric chloride storage tanks have been fabricated using a Polypropylene
liner with external GRP (FRP) reinforcement - as part of a phosphate removal programme for waste water treatment plants (Phosphates acts as fertiliser
to river weeds after final discharge). The alternative material is titanium...

The thermoplastic has to be weldable (using hot gas/butt fusion) and suitably treated to give high bond strength to the resin forming the reinforcement.
Polypropylene, PVC-U and PVDF are common. In addition HDPE is used without reinforcement for thermoplastics only.

Most such tanks are cylindrical, vertical, flat bottom with cone top cover - but rectangular, horizontal and cone bottom versions are allowed by the codes.
The volume range is <10 m3 to >50 m3 - temperatures are dependent on materials chosen.

The design codes are BS4994 (UK); EN 13121-3 (EU) and ASME RTP-1 (USA). For all thermoplastic design EN 12573 and EN 1778 used.

Timber and steel can be combined with thermoplastic and laminate; also 'straight' GRP (FRP) (gel coat liner with glass or other reinforcement can be used -
but moulds are required. Mainland Europe prefers large (thick) thermoplastic.

The UK pioneered the use of thermoplastic lined GRP (FRP) tanks (which do not require a mould).

EN1312 part 3 is now in fifth edition (one day they will get it right!). BS 4994 dates from 1973 - that is fifty years of use..

Design basis (of BS4994) is loading (N/mm) is equated to allowable resistance (N/mm/kg m2 glass) after a factor of safety of (min) 8, to determine laminate in kg/m2.

I recognise TLHS conclusion that manufacturers seem 'light' on the engineering. That is why I have spent the last fifty years designing wholly in plastics -
by code, calculation and FEA (thank heavens for FEA!)

We have a serious skills shortage in UK and in 2019/2020 most of this specialised industry was destroyed.

My nearest co worker is in Austria.

Whilst horizontal tanks are permitted by code; probably best to avoid.

(Sorry for the rambling; but I am recovering from illness.


Ed Clymer
Resinfab & Associates
Birmingham. England