Chemical Engineering July 2013 - 41

1,000
1,100
Design
Minimum
500
600
700
800
900
Metering
pumps
Mixer/
reactor
Filtration
Evaporator
Packaging
Dehydrator
FIGURE 5.
Certain aspects
of a process
have higher
potential to
present process
bottlenecks than
others
* What are the availability of standard
parts?
* What is the availability of special
non-standard parts?
* What is the cost to purchase and
stock the recommended parts?
* Will your OEM put consigned stock
in your facility? What is involved in
administering consigned stock? Are
you prepared to safely store and protect
the parts?
by physical constraints. Without clear
access,
preventative maintenance
may suffer and repair time may be extended.
Factors involved in the installation
cost may include the following:
* Machine foundations
* Accessibility for maintenance and
repair
* Support structures and mezzanines
* Piping, valves and fittings
* Instrumentation
* Electrical controls
* Monitoring equipment
* Electrical switchgear
Operation
Operation and maintenance are two
areas that are critical to avoiding
downtime and both are affected by
equipment selection, design and operating
procedures.
If the equipment was sized properly,
there should be no reason to operate
it beyond safe design capacities.
Many types of equipment are tested
at, or designed for 150 to 200% of the
rated capacity, but operating at these
capacities may risk shortening the
life of the equipment. Other aspects
of operation costs include the training
of operations personnel, utilities
(electricity, gas, water, steam and
cooling tower capacity) and the time
that the equipment is offline for preventative
maintenance.
The costs of raw materials, water
treatment (demineralizing, pH adjustment),
purge gas (N2, CO2) and waste
disposal are also key operations costs.
Most CPI processes, even in the food
industry, have to dispose of waste product
or waste streams from washing, offspecification
product or simply contaminated
water coming from a wash step.
Maintenance
Generally, maintenance can be classified
into two types: preventative and
repair. Some failures occur randomly
and cannot be predicted, but other
failures occur as a result of a lack of
preventative maintenance (PM).
PM is an area that has evolved into a
service that can be subcontracted and
may be economical when considering
the total longterm value provided. PM
companies often have superior knowledge
of pumps, drives, lubrication and
routine maintenance issues, including
good record keeping. The PM record
keeping can also help support any
warranty claims and avoid disputes
with original equipment manufacturers
(OEMs). The cost of subcontracting
PM must be considered against the
benefits of avoiding downtime. Parts
availability is important in avoiding
downtime both for PM and unexpected
failures. Questions to consider in having
parts available when required are
the following:
* Do you know the supply chain for
the parts you need?
* Do you know your OEM parts and
service contacts?
* Are you considering non-OEM or
counterfeit parts?
* Do you have a recommend parts list
for each machine for the first few
years of operation?
* What is the cost to stock parts for
catastrophic failures? Some large
parts, such as motors, gear drives or
centrifuge scrolls and bowls, can take
weeks or months to obtain. The low
probability of failure may be offset by
the very long lead times and may require
investment in costly parts that
may sit on the shelf for years.
* Is maintenance staff knowledgeable
and prepared to identify symptoms
of failure early, and diagnose and
repair issues quickly and correctly
the first time? Check with the OEM
for guidance and training. Do you
have the installation and operating
manuals on file? Have they been
thoroughly reviewed?
* What are the anticipated preventative
maintenance intervals?
* What is the expected time between
failures for components like seals,
and bearings, and the expected time
between belt adjustments and filter
replacements?
* Should all or some PM be outsourced?
*
Does the OEM offer PM services?
* What is the repair turnaround time
for a specific failure?
Decommissioning
The concept of decommissioning is
not something most engineers tend
to consider as they are designing a
plant, but some plants will have finite
lives of just a few years due to licensing
agreements, patents, changes in
markets or plans to shift to overseas
production in the future.
Planning for decommissioning a
process plant can vary from simple
tear-down and selling of equipment
to preparing for a sophisticated decontamination
procedure. Chemical
process equipment has special considerations
that can increase the cost
of decommissioning. Not only will
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Chemical Engineering July 2013

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