Reagent storage tank: bulk tanks for corrosive treatment and process chemicals, rated for the chemical's specific gravity and set in a bund

01

Specific gravity rating and the stored liquid's temperature set a polyethylene tank's wall

Poly Processing explains that specific gravity, the chemical's density relative to water, sets the wall thickness of a polyethylene tank: a 1.9-rated tank meets ASTM guidelines for wall thickness to hold a chemical of specific gravity 1.9 or less. It offers wall ratings of 1.0, 1.35, 1.65, 1.9 and 2.2, and states that both the weight and the temperature of the chemical, meaning the liquid's own temperature rather than the room's, decide the rating; heavier chemicals, especially above 100 °F, need a thicker wall. [1]

Poly Processing designs a standard tank for a maximum of 100 °F and states that higher fill temperatures raise hoop stress; the maximum service temperature of its cross-linked polyethylene (XLPE) tanks is 150 °F at a specific gravity of 1.00. It describes water tanks as built for ratings between 1.0 and 1.35, and for hydrofluoric acid uses a 1.9 rating with cross-linked rather than linear polyethylene. For heavy oxidisers it adds an OR-1000 barrier layer on top of the calculated wall, not counted in the wall thickness. [2] [1]

Editorial calculation: 100 °F is about 38 °C and 150 °F about 66 °C. A 10 m³ tank of a liquid at specific gravity 1.84 holds about 18.4 t, against 10 t of water in the same tank.

Give the supplier the exact chemical name and concentration with its safety data sheet, specific gravity, the liquid's minimum, normal and maximum temperature, indoor or outdoor siting, fill and draw rates, vent or scrubber connection, and the bund it will stand in.

02

Bund capacity: 110% of the largest tank or 25% of all tanks, with incompatible reagents kept apart

SEPA's containment guidance for bulk hazardous liquids at COMAH establishments states that above-ground tanks shall be bunded, that bunds shall be impermeable, corrosion-resistant and durable, and that incompatible materials shall be stored in separate bunds. Bund capacity should allow for tank failure and firewater, with a stated default minimum of 110% of the largest tank or 25% of the total capacity of all tanks in the bund, whichever is greater; bunds should have no rainwater drain, or one into a closed system that needs positive action, no pipework through the bund floor, and periodic inspection by a competent person. [3]

An Environment Agency paper at IChemE's Hazards 28 lists the reasons CIRIA C736 gives for the 10% margin: less overtopping from the surge when a tank fails, room for firefighting agents, some protection against overfilling, and allowance for rainwater; it notes that three of these come from extra wall height rather than volume, and suggests at least 200 mm freeboard where firefighting foam may be applied. [4]

Editorial calculation: for three tanks of 30, 20 and 20 m³ in one bund, 110% of the largest is 33 m³ and 25% of the total of 70 m³ is 17.5 m³, so the bund must hold at least 33 m³. [3]

03

XLPE, filament-wound FRP and glass-lined steel for different reagents

Material ranges below are as each maker states them for its own tanks.

04

Send the chemical, temperature and containment details together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Chemical: [name; concentration; SDS; specific gravity]
Temperature: [liquid min/normal/max; indoor or outdoor]
Tank: [volume; material; resin or lining; wall rating]
Fittings: [inlet; outlet valve; vent or scrubber; level]
Bund: [tanks sharing it; capacity; lining]
Site: [foundation; access; transfer pump]

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