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ECONOMIC.TXT
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1994-11-01
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The following guidelines will assist you in choosing the most economical
grade of stainless steel for a particular application. Basically a
stainless steel alloy is chosen for an application because ordinary
carbon steel is not considered adequate for the intended use. As a
prime requisite the stainless steel selected must have the property or
combination of properties (strength, corrosion resistance, temperature
resistance, etc.) to be suitable for the application. In addition the
stainless alloy should be readily available in the product form needed.
The listing that follows ranks some of the stainless steels by decreasing
cost, (Type 330 the most expensive) and by decreasing corrosion
resistance (Type 409 being the least corrosion resistant). Cost
relationship may vary by product form. It is important to consult your
stainless steel supplier for exact comparisons.
Alloy Relative Cost Based on Sheet/Strip Forms
----- ------------- -----------------------------------------
330 Highest 2.5 These are relative guidelines only. Cost
310S 2.3 is dependent on product form, quantity
309S 2.0 and other factors.
316 1.3
304L 1.1
304 * 1.0 ----- Used as reference base.
301 0.9
201 0.8
430 0.7
409 Lowest 0.6
* Type 304 is often a good choice for the best combination of properties
and cost.
It is important to take into account the overall, or end use, cost for a
product or application when considering the use of a stainless steel
alloy instead of carbon steel. When total service life is considered
the use of a stainless steel often is not as expensive as would be
thought from just comparing material cost alone. Long life free from,
or with minimal, maintenance (cleaning, painting, repair or replacement)
may enable stainless steels to provide an attractive economic picture
for many applications.
The engineer's objective is to select and use the least expensive material
which will meet the requirements of the service conditions, and perform
in a safe and reliable manner over the desired service life of the
equipment. When fabrication, installation, and maintenance costs are
factored into the overall picture, in addition to the cost of the raw
materials, it is often found that the most durable material is only
slightly more expensive than the least durable.
In comparing costs, it is desirable to consider costs under the
following general headings.
1. Cost of raw materials
2. Manufactured cost - Materials plus labor to manufacture.
Includes items such as pumps, valves, filters, pipe, fittings,
pressure vessels, heat exchangers, etc.
3. Installed cost - Manufactured cost plus labor to install. The
cost of installing piping greatly alters the comparative costs
of the pipe and fittings.
4. Life cycle, or maintenance and repair costs - The costs of
periodic maintenance and renewal can make the lower cost
material the most expensive to use in the long run.
Manufactured or OEM costs are obtained from the manufacturers.
Installed costs can often be found in the literature under costs.
Chemical Engineering magazine has published a number of excellent
articles on equipment and installed costs. Life cycle and downstream
costs are tracked by individual companies and by the larger
engineering firms but are seldom published.
For further information consult NiDI Publication 10 002 "Evaluating
the Installed Cost of Corrosion Resistant Piping".