Specific gravity ratings on UN totes

What specific gravity is

Specific gravity is a liquid's density compared with water. Water is 1.0 and weighs about 8.34 lb a gallon. A product with a specific gravity of 1.3 weighs 1.3 times as much: about 10.8 lb a gallon. Most oils and solvents are below 1.0, so they float on water. Many acids, caustic solutions, brines and fertilizer solutions are well above it.

A tote is drop-tested and pressure-tested full. The heavier the product, the harder it hits the floor in a drop and the more it loads the bottle and cage. So the design is approved for a maximum density, and that limit is printed after the packing group letter. Mauser, for example, lists its composite IBCs with Y1.9 approval for products up to 1.9 and Y1.6 for products up to 1.6 (Mauser, composite IBCs).

Finding your product’s number

It is on the safety data sheet, in section 9 (physical and chemical properties), listed as specific gravity, relative density or density. If the SDS gives density in g/cm³ or kg/L, the number is the same as the specific gravity. If it gives lb/gal, divide by 8.34. If the product's density changes with temperature or concentration, take the highest you'll fill.

Which rating to ask for

Your product’s specific gravity	Rating to ask for
Up to 1.6	Y1.6 or Y1.9 both cover it
Above 1.6, up to 1.9	Y1.9
Above 1.9	Not a standard caged tote; ask us about the product

If you fill several products, quoting every tote at the rating the heaviest one needs keeps one stock for all of them. The rating covers transport of regulated products. For a non-hazardous product it still tells you how robust the design is, but no rule ties your fill to it.

Weight still has to fit the plate

Specific gravity isn't the only limit. The maximum permissible gross mass on the plate caps the weight of tote plus product, and the hazmat rules require enough room left at the top that the tote is no more than 98 percent full at 50 °C (122 °F) (49 CFR 173.35(d)). For a 275 gallon tote of a 1.5 product, the product alone is about 275 × 8.34 × 1.5 ≈ 3,440 lb, or about 1,560 kg. Add the tare and compare the total with the plate's gross mass before you fill.

Examples of common products

Specific gravity varies with concentration and temperature, so use the figure on your own SDS. As a guide to where products fall: water is 1.0; most vegetable and mineral oils are below it, around 0.8 to 0.95; many glycols and detergent concentrates sit between 1.0 and 1.2; corn syrups and sugar solutions run from about 1.3 to above 1.4; and strong acids and some salt solutions go higher. Concentrated sulfuric acid is about 1.84, which is near the top of a Y1.9 rating and well above Y1.6.

Two products with the same name can differ. A 12.5% sodium hypochlorite solution is heavier than a 6% one; a 50% caustic soda solution is about 1.5, a weaker one less. Blends are heavier or lighter than either ingredient depending on the mix. If your SDS gives a range, use the top of it.

When the rating is short

If your product's specific gravity is higher than the tote's rating, the tote isn't approved for it, even part-filled to keep the weight down: the rating is part of the design type that was tested. The choices are a design rated higher, a steel IBC, or a smaller packaging. Tell us the product's figure and we will quote a design that covers it.

Temperature and density

Liquids get lighter per gallon as they warm and heavier as they cool. The figure on an SDS is usually given at 20 or 25 °C. If you fill hot, as some syrups, waxes and resins are filled, the product is lighter at filling than it will be once it cools in the tote; use the density at the coolest temperature it will reach.

Short answers

Can I put a product with specific gravity 1.8 in a Y1.6 tote?

Not for regulated transport. The design was tested to 1.6. Ask for a Y1.9 tote.

Where is the specific gravity on an SDS?

Section 9, physical and chemical properties, as specific gravity, relative density or density.

Does a non-hazardous product need a rated tote?

No rule requires it, but many buyers order rated totes for everything so one stock covers every product.

Is oil heavier than water?

No. Most oils have a specific gravity below 1.0, so a tote of oil weighs less than a tote of water.

Is specific gravity the same as density?

Nearly: specific gravity compares a liquid’s density with water’s, so it has no units. A density of 1.3 g/mL is a specific gravity of about 1.3.

How do I measure specific gravity myself?

Weigh a known volume and divide by the weight of the same volume of water, or use a hydrometer. The SDS figure is simpler if you have it.

Does a higher rating cost more?

A Y1.9 design can cost more than a Y1.6 one. Ask for the rating your densest product needs, not the highest available.

What happens if I overfill a dense product?

The tote may exceed its permissible gross mass, overloading the cage, pallet and valve, and the shipment would breach the rules. Weigh to check.

Do plastic and steel IBCs use the same rating system?

Composite and plastic designs show a specific gravity after the packing group letter. Metal IBCs show a maximum gross mass instead; check that your product fits it.

Which common liquids exceed 1.9?

Very few industrial liquids do; some brominated compounds and heavy metal salt solutions are examples. Those usually ship in smaller or metal packagings.