Newsgroups: sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: oil seepage from tanks
Date: Fri, 11 Oct 1996 16:47:29 GMT

af329@james.freenet.hamilton.on.ca (Scott Nudds) wrote:

>(charliew) wrote:
>: As usual, wrong again Scott.  The tanks that I deal with were
>: built several decades ago.  If my employer was going to build
>: a new tank today, I am certain that modern construction
>: methods would be used.

>  One wonders what tank construction methods have been "invented" in the
>last few decades that were not available when the tanks in question were
>constructed several decades ago.

One should consider visiting the library. I would suggest that a
comparison of the 1950s multi-volume Welding Handbooks and
Metals handbooks and their 1990s editions would surprise you.

Items you might like to consider are the huge advances in steelmaking
that have produced uniform steels that are specifically produced to be
fabricated in storage tanks for petroleum products. Advances in
metal forming technology and appropriate surface finishing ( of
the metal - improvements in the protective coatings applied have
also occured  ) have greatly reduced the flaws that resulted in premature
failure. Advances in stress analysis have also redefined the design
structure of the tanks to ensure that they can handle the appropriate
environmental factors over the long design life of the tank.

The associated improvements in the welding and fabrication technologies
that have resulted in far less degradation of metals ( such as the infamous
HAZ ( heat-affected-zone ) and joints ( inclusions from welding rods/fluxes ),
and the improved control of the power provided by the electric welders
themselves, when combined with the newer cutting, drilling and fabrication
techniques, all result in more durable structures.

Also, the huge improvement in NDT ( non-destructive testing ) used to
ensure consistent quality has greatly improved the durability of fabricated
structures.

>  Perhaps Charliew is under the impression that steel is a recent
>invention.

Perhaps Mr Nudds is totally ignorant of modern metallurgical
advances, modern metal fabrication techniques, modern
storage tank construction, and modern non-destructive inspection
and testing techniques. Perhaps Mr Nudds should visit a technical
library.

>  Clearly what has changed is <not> the technology needed to build
>tanks, but the regulatory requirements that tanks be constructed to
>higher standards.

Evidence presented so far by you to support this assertion equals
zero. I would suggest that the regulatory requirements for building
petroleum storage tanks today have very little to do with the long term
potential to leak, but are far more concerned about catastrophic
failure due to inadequate design or inappropriate materials selection
- I doubt very much that US regulations are significantly different to NZ.

The choice of storage tank construction materials is driven by the
industry. They choose the materials and construction techniques to
build the structure based on the intended design life,  the product to be
stored, and the environment the tank exists in. AFAIK in New Zealand,
the construction regulations usually only refer to appropriate
organisational codes ( eg ASME, ASM ), and civil engineers design to those.

The regulatory bodies seldom have any interest in materials selection
for long term corrosion resistance, just that whatever material is selected
is considered appropriate by ASME or ASM for the application, and
is constructed in accordance with the relevant codes. Perhaps charliew
can identify what the US practice is?

The transfer of nuclear and aviation industry fabrication practices to the
chemical and petroleum industries ( along with many others , such as
automotive, appliance, and even home handypeople now have MIG/TIG
welders with stable, controllable outputs and welding consumables
that result in more durable welds )  was driven by the obvious cost
advantages to the industry, not by regulatory pressures.

The petroleum industry worldwide has adopted the new materials and
fabrication practices because they offer major economic advantages over
the far less durable older practices. They  have reduced manufacturing costs,
maintenance costs, and  also resulted in improved long term durability.
This is technology that transferred for sound economic reasons, you can
choose to believe otherwise.....

        Bruce Hamilton