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Water and Chemical Tank
Standard for 21st Century
From SPE International Polyolefins Conference
Houston, Texas
Rotational Moulding
Design &
Manufacture
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 [email protected]
REGIONAL COMPARISON
Industry size North America 300,000+ tonnesAustralia 60,000 tonnes > 5 times
Large tanks (>5,000L or >1,300USG)North America HDPE > 75% Australia MDPE > 95%
Colouring methodNorth America Dry Blend > 75% Australia Melt Compound > 98%
PopulationNorth America 456m
Canada 34mUSA 310mMexico 112m
Australia 23m 20 times
Large tank geometry (H/D)North America Tall tank > 50% Australia Squat tank > 95%
Presentation by Ian Hansen [email protected]
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 :-
STRESS AROUND OUTLET, HIGHLIGHTED BY 4766, IGNORED BY 1998
HDS calculations in ASTM D1998 do not take outlet stress into account
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
SOLAR ENERGY DISTRIBUTION
Average Solar Radiation per country Kly (Kcal/cm2/Year)
Canada 100 Kly/Yr Great Britain 70 Kly/Yr China 140 Kly/YrFlorida 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
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§ion_id=
Tank Colours avail from 55lbs
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.
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 [email protected]
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
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 [email protected]
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 [email protected]
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 protectionUV16 = better protection
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
If you would like any additional information please email me at : [email protected] contact ARMA [email protected] or check out their web site www.rotationalmoulding.com
Recipe For Quality Tanks in the 21st
Century – Tank StandardsExtracted from presentation given to SPE Houston Polyolefins conference
