Fibre reinforced storage tanks for sodium hypo

[vjr0512]

There is a proposal from vendor for the sodium hypo service storage ( day tank) in FRP material. Drawing is enclosed.I am concerned on the base plate arrangement of this tank. Thanks to provide a recommendation for a better design.

 

[europipe]

Don't think there is a problem, vinylester is very strong.
However, des. press. must at least be 0.1 barg for that height.

 

[EdClymer]

VJR0512


Item is a vertical, cylindrical, flat top vessel with base disc to plinth.

Volume is small. Over pressure (+ve 500 Pa) and (-ve -1000 Pa) which make very little difference to
bottom pressure of 0.0135 MPa (N/mm²).

Depending upon code; this would indicate < 1 x 600 gms csm layer - but code minimum would apply
(BS4994: 3 mm for static head and 5 mm for pressure) and (EN13121-3: 3 mm for static head and 5 mm for pressure)

The cylindrical shell has to be linked/joined to base disc by interweaving/overlapping laminate in both directions,
maybe plus additional laminate to form a knuckle (a short localised thicker region at the junction).

This calculates to BS4994 (at F = 1.5 for 50 mm radius) no additional laminate required other than overlaps/interweaving.
Calculated lengths (to shell and disc) are 43.7 mm (experience says 100 mm/150 mm minimum - more if hold-down lugs are
to be secondary bonded to knuckle.

The problem, is that a void is created inside the knuckle area on the bottom disc. Static head will tend to force
bottom disc to plinth, and (given time) radial cracks will be initiated due to bending at about 200 mm from shell.

There are two choices;

1) Bed tank to flat mass concrete plinth with a shallow cone of bitumen/sand (a mixture of fine aggregate/sand/ordinary
portland cement and hot bitumen) this is a 'sqidgy' mix. Water is added to tank to remove entrapped air and within 24
hours bitsand will set hard - vessel is then fully supported. In UK we have great difficulty in obtaining bitsand (it
always arrives on site cold).

or;

2) During build, invert shell/disc (fully support) and flat fill with layers of chopped strand mat and resin. Then
use two layers of decent bitumen roofing felt between underside of base disc and plinth. This is by far the cheaper
option.

Trust this is of help.

PS: If anybody understands this post, and are trying to comprehend EN13121-3 (new European code - fourth attempt) could
they make contact?

Regards

Ed






Ed Clymer
Resinfab & Associates
England

 

[bimr]

What is the concentration of sodium hypochlorite?