Explanation of the rotational moulding Water & Chemical tank Standard that provides a recipe for success, using computer analysis technology and high performance long term UV protections. Extract of presentation given at SPE International Polyolefins Conference

1. Water and Chemical Tank
Standard for 21st Century
From SPE International Polyolefins Conference
Houston, Texas
Rotational Moulding
Design &
Manufacture

2. Regional Comparisons – Nth America vs Australia
Above Ground Tank Standard – Nth America vs Australia
UV Performance – UV8 vs UV16 vs UV20
Compounded colours
Long term design
Who is qualified to verify design
Long Term Service
Research on melt compounding
Assessment of 10 year old tank
UV36 protection possible
What’s important to moulders
Summary
Presentation Outline
Recipe For Quality Tanks in the
21st Century – Tank Standards
Presentation by Ian Hansen ianhansenconsult@gmail.com

3. REGIONAL COMPARISON
Industry size
North America 300,000+ tonnes
Australia 60,000 tonnes > 5 times
Large tanks (>5,000L or >1,300USG)
North America HDPE > 75%
Australia MDPE > 95%
Colouring method
North America Dry Blend > 75%
Australia Melt Compound > 98%
Population
North America 456m
Canada 34m
USA 310m
Mexico 112m
Australia 23m 20 times
Large tank geometry (H/D)
North America Tall tank > 50%
Australia Squat tank > 95%
Presentation by Ian Hansen ianhansenconsult@gmail.com

4. TANK STANDARD
1) ASTM D1998 Polyethylene Upright Storage Tanks
Originally published 1991
2) AS/NZS 4766 Polyethylene storage tanks for water and chemicals –
Above Ground
Originally published 2002
For a tank with no openings in the shell, the wall thickness calculated
using either ASTM D1998 or AS/NZS4766 will be similar.
However, in the real world, tanks have openings cut into the side wall
for outlets, along with a roof and a floor.
Presentation by Ian Hansen
FEA is simply much more capable of predicting real
life performance than simple HDS calculations.
There are two globally recognised Standards :-

5. STRESS AROUND OUTLET,
HIGHLIGHTED BY 4766, IGNORED BY 1998
HDS calculations in ASTM D1998 do
not take outlet stress into account

6. UV PERFORMANCE
UV8 NOT ‘LONG’ TERM ANYMORE
• AS/NZS4766 minimum UV rating is UV8
• ASTM D1998 specifies UV should give protection for the ‘intended’ service life
• In Australia, Qenos offer their tank grade (LL711UV) with UV20 rating.
• In Europe, Total Petrochemicals offer their tank grade (M4041UV) with UV16
rating
• In North America ChevronPhillips & ExxonMobil now offer their tank grades with
UV16 and UV 15 respectively.
• Novachem offer UV16 for their tank grade RMs341
• SCG in Thailand offer UV20 for their tank grade M9001RW
• Today you should aim for UV15++ to achieve long term sunlight protection
UV0 UV4 UV8 UV16 UV24
Hours of Exposure 0 4000 8000 16000 24000
0
4000
8000
12000
16000
20000
24000
UV0 UV4 UV8 UV16 UV24
UV Rating
Long term UV stabilisation now measured in double or triple the old UV8 rating

7. SOLAR ENERGY DISTRIBUTION
Average Solar Radiation per country Kly (Kcal/cm2/Year)
Canada 100 Kly/Yr Great Britain 70 Kly/Yr China 140 Kly/Yr
Florida 140 Kly/Yr Arizona 180 Kly/Yr Mexico 160 Kly/Yr
Singapore 140 Kly/Yr Australia 180Kly/Yr India 180 Kly/Yr
Average Solar Radiation Source : Cabot Corporation - UV Weathering and Related Test Methods Map Source : BASF

8. COMPOUNDED COLOURS
AS/NZS4766 only allows melt compounded colours
No dry blending or liquid blending of powder allowed because of negative
effect on performance
Source - http://www.cotene.co.nz/products.html?mode=display&parent_id=0&content_id=3031&id=3031&section_id=
Tank Colours
avail from 55lbs

9. LONG TERM DESIGN PROPERTIES
AS/NZS 4766 requires FEA to verify design.
Will require long term physical properties
 Hoop Design Stress according to ASTM2837
 Creep Data according to ASTM2990
Short term physical properties (ie.Tensile Strength) are typically
provided by polymer suppliers, instead of long term properties.

10. WHO IS QUALIFIED TO VERIFY DESIGN
AS/NZS 4766 only allows qualified professional engineers to
verify the design calculations.
Not every engineer or designer can meet the requirements of
AS/NZS 4766.
Being competent in FEA software is not sufficient
Presentation by Ian Hansen ianhansenconsult@gmail.com

11. LONG TERM SERVICE - RESEARCH
Impact strength decreased for
powder mixing (Dry Blends),
which was a consequence of poor
distribution of the pigment
agglomerates in the polymer matrix
leading to stress concentration points
Melt CompoundDry BlendLiquid Colour
Powder MixingPowder Mixing Compounded
No significant reduction of
impact strength of parts made
from melt compounds,
due to the superior distributive and
dispersive mixing of the pigment
within the polymer matrix
Source : BASF
Source : QUB

12. ASSESSMENT OF 10 YEAR OLD TANK
• Size, 10,000Litres (2,600 US gal)
• Tank location, Texas, New South Wales, Australia
• Solar radiation 160-180 KL/Yr
• LLDPE, 4.0Melt Index, 0.938 density
• Melt compounded Dark Green
• 0.4% pigment content
Magnified Roof X-Section
Source : Qenos
Presentation by Ian Hansen ianhansenconsult@gmail.com

13. UV36 POSSIBLE
Melt Compounding pigments for Smarter UV
performance
Source : ROTOWORLD®
DECEMBER 2013
Quality UV & AO additives combined with melt
compounding can achieve exceptional performance
Presentation by Ian Hansen ianhansenconsult@gmail.com

14. WHAT IS IMPORTANT TO MOULDERS
After short term evaluation and selection
• Long term physical performance
HDS & Creep
PLUS
• Long term outdoor service life
Sunlight and thermal protection
UV rating system exists
(Warning: AO rating for industry does not exist)
Short term protection
Faded Green 22,000L tank UV8 = good protection
UV16 = better protection

15. SUMMARY
The Australasian tank standard provides the global industry with a
comprehensive road map to manufacture tanks in the 21st century
Pigment dispersion and UV stability of the raw material are critical
features of the tank DNA. You need long term sunlight protection
to ensure your tank physical properties are maintained long term.
The exclusive use of melt compounded pigments has contributed
to the success of the Australasian tank industry over the past 20
years.
The recipe for Quality tanks in the 21st Century is to use a
comprehensive Tank Standard designed for rotomoulding.
AS/NZS:4766 is an example of the best Standard available.
Think long term for tanks
then think longer term for outdoor performance

16. If you would like any additional information please email me
at : ianhansenconsult@gmail.com
Or contact ARMA info@rotationalmoulding.com or check out
their web site www.rotationalmoulding.com
Recipe For Quality Tanks in the 21st
Century – Tank Standards
Extracted from presentation given to SPE Houston Polyolefins conference