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Office buildings
present a wide range of operating conditions generally dependant upon their
location, age, and function. They vary widely in operating pressures, piping
layout and size, materials used, conditions, maintenance, as well as level of
services provided.
As many older buildings
continue in operation, questions raise as to their remaining service life.
Newer properties, due to various factors such as less corrosion resistant
steels, less effective corrosion inhibitors, and thinner materials, can often
begin to fail decades before their much older neighbors.
Review a summary of
piping quality, operating, and design changes which have
occurred.
Modern business and
commerce virtually demands trouble free, uninterrupted service for most modern
building properties. This is especially true for financial institutions, health
care facilities, and computer related business. At the same time, tighter
budgets and demands to minimize staff can frequently negate the attention,
preventative maintenance, and predictive testing so necessary to achieving
system reliability.
A high turnover of
property managers, owners, and operators within the commercial real estate
market is another major factor in providing less than satisfactory corrosion
protection or monitoring; leaving known problems to those next in line. All too
often, individuals entrusted with protecting critical and expensive piping
systems, are most interested in extending the retirement date of such
infrastructure just slightly past their own.
No office
building in a warm weather climate can function today without air conditioning.
While a variety of piping systems exist for any office building, the major
cause of corrosion related problems and concern to most facility operators is
the open cooling tower or condenser water
lines.
While problems may be very rarely
found in the total failure of a section of piping, the majority of corrosion
induced operating problems relate to components of the system such as the
condenser or heat exchanger tubes, cooling tower pans, pinhole leaks, threaded
joint failures, plugged strainers, worn pump seals, lost heat transfer, and
unnecessarily high energy costs, etc. In such cases, a localized failure may be
easy to address, while a system wide MIC condition may be almost hopeless to
correct.
Though not likely to shut down an
entire system operation, such corrosion problems impose tremendous cost in
manpower, chemicals, and repairs, and can become a predominant concern where
the reliable service of a building property is concerned. A failure to provided
contracted cooling water to the critical equipment of a building tenant can
result in enormous legal fees. Unfortunately, most corrosion problems are only
discovered many years after their initiation through some observation, rather
than through testing.
Aside from the
primary goal of cooling condenser water, a cooling tower is essentially a giant
industrial air scrubber. As such, it captures tremendous amounts of particulate
debris, plentiful microorganisms of every type, adds chemicals and nutrients
into the circulating system, provides abundant sunlight for growth, and
oxygenates the water to
saturation.
Corrosion rates, which can
range from 1-2 mil per year (MPY) at a well treated and maintained facility,
can easily increase to 10 MPY under certain conditions and still remain hidden
and unknown. Under deposit corrosion and MIC are the two greatest threats
existing, and can be usually identified where high corrosion rates exceeding 20
MPY are found.
Chemical treatment
programs vary widely in their effectiveness, but all suffer due to the
practical impossibility of chemically treating an open system to the higher
levels necessary for truly effective corrosion control.
See Technical Bulletin
# M-12 regarding why closed and open piping systems are treated to different
chemical concentrations.
Most
often, the true service life of a piping system is not based upon the corrosion
rate alone, but in combination with other factors such as pipe schedule and
quality, physical layout, engineering design, and construction methods. A 5 MPY
corrosion rate at an older property constructed of schedule 80 pipe, for
example, will generally outlast any new property having a 2 MPY corrosion rate
acting against an installation of thin wall schedule 10 pipe.
A piping system
can be reasonably assumed in uniform condition as long as corrosion rates are
under 3 MPY and significant pitting does not exist. As the level of randomness
increases in the wall thickness profile, the ability to generalize the overall
condition of the piping system based upon limited testing drops dramatically.
Much higher corrosion rates can coexist
within a well maintained piping system of low corrosion activity, but generally
require some physical isolating factor or event to produce significantly
different interior conditions. This is most often related to flow rate, which
in turn directly influences particulate deposition, under deposit corrosion,
chemical inhibitor, and microbiological growth.
See Technical Bulletin
# C-10 regarding some common corrosion
trends.
By-pass and dead end
lines are frequently the source of elevated corrosion rates 10 or more times
those found elsewhere in the system. We list below some common problem areas
for most commercial office buildings:
- By-pass
lines
- Long
horizontal runs
- Roof level
piping
- Heat exchanger
piping
- HVAC units
which may be shut down
- Drained
lines
- Dead end
areas
- Smaller run-out
piping to HVAC units
- Lowest floor
piping
- Low flow areas
- Return lines
- Black pipe to
brass or copper valves and connections
- Mud legs or
dead legs
- Small diameter
threaded pipe
- Threaded
schedule 40 pipe
- Alternating
equipment piping
- Future
lines
- Terminated or
abandoned piping
Most condenser
water systems at high rise office buildings offer an abundance of fittings
which are unused and available to install CorrView ®. For
the main lines, installation will generally require a shutdown, or to wait
until the next scheduled shutdown to install into an existing threadolet, or
weld on a new one. A modified version of CorrView ® which
can be inserted into a high pressure line through the use of a corporation stop
valve will be available after August,
2003.
For operations where CorrView
® is desired for installation in a specific location, it
will likely be necessary to coordinate with a future shutdown to install such
fixtures. This would be likely at the bottom of a by-pass line, or to and from
heat exchangers - both high priority locations for corrosion
monitoring.
No planning is likely necessary for larger installations
having multiple chillers, towers and pumps, and where some monitoring at the
individual distribution lines serving such equipment is acceptable. In such
cases, individual pumps or chillers can be valved off to either weld in new
threadolets, or to install CorrView ® in the abundance of
available plugged ports which usually exist. Some review of the piping layout
is always useful.
We generally recommend
the largest 1-1/2 in. version of CorrView ® because it
provides greater surface area to corrode, as well as offers a larger and more
noticeable viewing area. Smaller take-off lines to pumps and chillers, however,
often offer 3/4 in. and 1 in. ports suitable for our smaller models. All
CorrView ® models accomplish the same objective and
operate the same.
A 0.050 in. wearable
front wall thickness will provide long monitoring service where corrosion rates
are moderate, and yet adequate warning of a corrosion problem. As typical for
most pipe corrosion, the wall loss acting against CorrView
® will likely be comprised of an overall general corrosion
rate, and with some degree of pitting activity present which will first
penetrate the front wall to produce an
indication.
Some advance thought is
required for the installation of CorrView ® in commercial
building operations. Please feel free to contact CorrView International for
discussion and recommendation of your specific application needs.
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