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Compressor Newsletter
Sample Issue
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Here are the topics in this sample issue.
1. Air Audit Investigation
2. 4 Opportunities To Save Energy
3. Tools for Trouble Shooting
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1. Air Audit Investigation
Have you ever been through an air audit?
We had the chance to tag along on a Level 1 Air Audit. It was at an
industrial facility with a total compressor horsepower of 1100.
The manufacturing company wanted an air audit because their existing
compressors were not keeping up with the air requirements of the production
process. Also, they were having trouble eliminating the moisture from the
compressed air.
The audit discovered the root cause of each of their concerns. The following
are the main points:
a) There were several locations where compressors and dryers were trying to
feed compressed air into the header through a pipe tee connection. This
creates a turbulence that leads to back pressure.
This interconnecting piping back pressure creates false unloading signals.
The compressors are prevented from operating at full load which makes it
impossible to deliver the required air to the production process.
The solution is to modify these connections to eliminate the back pressure.
This is done by using either a 30 or 45 degree angle entry instead of a tee.
b) The dryers were sized to handle the compressors capacity. However, under
performing aftercoolers caused these dryers to be undersized because they
were not supplying the dryers with 100 degree F air.
The dryers should have been oversized considering the long periods of heat
in the climate as well as the heat from other equipment in the compressor
room. A solution at this point is to either buy larger dryers or add water
cooled aftercoolers to the system prior to the dryers.
c) The use of timer operated drains contributed to the problem of moisture
in the air. These drains operate on a cycle that either leaves condensation
in the system because the drain is not open long enough or wastes air
because it
stays open too long. In this case, the drains were not staying open long
enough.
The solution is to install automatic condensation drains that are also zero
air loss drains. A recommendation was made on a drain that has been proven
to meet these requirements.
d) Leaks were noticed that can easily be shut off. In some cases, valves
were left open to help drain the condensation. This can be eliminated with a
small investment in the right type of condensation drain. The net gain is to
avoid
producing compressed air that is wasted.
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Key Observations
a) The audit was completed with a 2 day site visit. The experience of the
auditor made it possible to identify the problem areas and solutions without
the extra expense of measurement trending.
A verbal report was made with an outline of all the recommendations. This
included the details for correcting the piping problems so the customer
could begin to implement the changes.
A written report with recommendations and cost payback information was
delivered within 2 weeks. The complete air audit project was done for less
than $5,500.
b) It was demonstrated that a 200 horsepower compressor could be turned off
while still meeting all the demands of the production process. This will
produce a minimum of $60,000 in annual energy savings.
The energy savings alone are enough to pay for the modifications to the
piping system, the addition of a secondary aftercooler for the compressors
that have
marginally sized dryers, the expense of replacing the condensation drains
and the cost of the air audit.
A consistent supply of clean, dry compressed air will also lead to savings.
There will be less production downtime and less maintenance.
c) The air audit was a tremendous training opportunity for the maintenance
and engineering people that are responsible for supplying air for
production. These were intelligent and conscientious workers who simply had
not been informed
or trained on the basics for getting the most from their compressed air
system.
It was obvious that they were enthusiastic about what was learned and the
potential they now have to make a positive impact on their air system. The
Level 1 Air Audit provided solutions and a compressed air strategy that will
produce
immediate and long lasting benefits.
Conclusion
It is our opinion that the process should be undertaken by every plant with
an air system. Think about it, you get expert analysis on your system with
ideas that pay for the audit. What are you waiting for?
Send an email to
airsavings@compressorwise.com if you have any questions or would like
more information on a Level 1 Air Audit.
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2. 4 Opportunities To Save Energy
Air compressors powered by electrical motors will use a surprisingly large
amount of energy each and every year of operation.
These operating costs are commonly considered part of plant overhead and are
rarely evaluated as a separate issue. This contributes to the assumption
that compressed air is an inexpensive utility.
The annual power cost to operate a compressor can equal the initial cost of
the unit. The initial purchase price of a 100 horsepower air compressor will
range between $30,000 and $50,000, depending on the type and options.
The same 100 horsepower compressor with 6000 hours a year, a power rate of
$.07 per KW and a motor efficiency of .90 will have an annual power cost of
$34,800.
You can determine the approximate annual electric power cost of your
compressors with this formula. The first step is to multiply the horsepower
of the compressor times .746 times the hours of operation times your power
rate (HP x .746 x hours x power rate). Then, divide that number by the motor
efficiency.
Everyone in the plant should be made aware of the total power cost for
operating the compressors. This is especially important for anyone that
works with air operated equipment.
Choosing The Right Compressor
There is intense competition for your business when you are interested in
buying a compressor. The only way to make sense of all the options is to
understand what you want, and the limitations of your requirement.
You will probably have to make some compromises as you compare the options
and various types of compressors. You can prepare for this exercise by
determining the importance of the following key issues:
a) Can you handle maintenance in house or will you have to rely on outside
help?
b) Match the operating conditions of your environment with the sensitivity
of the various compressor types.
c) Consider the availability and quality of the cooling medium, either water
or air.
d) What is the required duty cycle?
e) What is the required air quality, lubricated or non lubed?
f) Will the compressor’s capacity control and regulator system be capable of
translating less air usage into less electrical power usage?
An often overlooked aspect of the compressor is the motor efficiency. The
compressors being sold today can be found with motors that range in
efficiency from .87 to .94 and higher. Remember, this factor will have
nothing to do with the compressor capacity, pressure loss, controls, etc.,
but it will determine how much you spend every year to operate the
compressor.
There is a trade off between the price to upgrade motor efficiency and the
available annual power savings. The idea is to know what you are getting and
to evaluate the potential of the upgrade.
Waste Management
Effective leak control in an air system can pay huge dividends.
A quarter inch leak in a 100 psi system will pass about 100 CFM of
compressed air. This is approximately $12,000 in annual wasted power cost
based on 24 hours a day compressor operation with a power rate of $0.07 per
KW.
The process of detecting and monitoring leaks should focus on more than the
basic header and piping system. The fact is that you will find a majority of
your leaks at valves, fittings, connections, tools and at the point of use.
Condensate drains or traps are a major source of wasted compressed air. They
are also one of the easiest to eliminate.
The problem begins with the limitations of the drains or traps currently
being used to remove condensation. Consider the following drawbacks to these
products.
The manual valves and level operated mechanical traps are often left open to
compensate for clogging. The electronic timer style traps will waste air in
the normal course of operation. They are designed to use compressed air to
force the condensate out the trap.
These are set for the number of times they will open each hour and for the
duration of the open cycle. However, they are usually left with the factory
setting and they are almost never adjusted to fit the application or for
seasonal temperature changes.
The solution is to install electronic or automatic drains. These receive
their signal to open and close by sensors measuring the level of
condensation in the housing of the trap. They waste no air and have been
proven more reliable than the other types of condensation traps.
However, customers resist the electronic or automatic drains because of the
price. Also, the contaminants in the condensate will cause problems for any
components that come in contact with the condensation.
A condensation drain should automatically remove condensate when it appears
at the drain without wasting air or clogging. In addition, it should be easy
to monitor, affordable and capable of handling a large amount of condensate.
We have found only one drain that meets this criteria. Send an email to
drain@compressorwise.com and we
will make sure you get the complete product specifications, pictures and
installation instructions.
Pressure Loss
The first consideration is to determine the specific pressure required for
all the air requirements in your plant.
This is important because every pound of increase or decrease in pressure
requires a one half of one percent increase or decrease in power. Therefore,
a 10 psig decrease can save you 5% in power which amounts to $1,740 in
annual savings for the 100 horsepower compressor in the earlier example.
Plants that have studied this issue have often found that they were
producing high pressure air for the entire plant just to satisfy an isolated
high pressure requirement. The solution was to install a small departmental
compressor designed to handle the higher pressure. This allowed them to
lower the pressure requirement of the main compressors and immediately save
energy cost.
In some plants, air pressure is raised to overcome system pressure drop. The
cause is usually found to be shortcomings in the piping system and pressure
loss at the filters and dryers. Each of these problem areas will cost you
money on an annual basis.
The key to selecting pipe size is to consider the length and flow required
and choose a diameter that generates no pressure drop. The pipe should not
be sized to be equal to a valve or connecting device. You can "bush up" to
larger pipe and avoid pressure loss.
The pipe fittings used for directional changes can also cause pressure loss.
A feed line of compressed air should not use a tee connection to a line with
a flowing steam of air. The turbulence will cause pressure drop that can be
avoided by using a 30 or 45 degree angle entry instead of the tee.
Air line filters and dryers are often purchased without considering the
pressure loss factor. In general, these products can be made smaller and
cheaper if you will accept a higher pressure drop. This is not a good
bargain when you consider the power cost to produce wasted pressure.
Always check the pressure loss of filters before installing them in your air
system. You can compare dryers in terms of inlet air temperature, CFM
handled, pressure loss and pressure dew point achieved. The objective is to
install a filter and dryer with the lowest pressure drop.
Train Your People
The operation and management of a compressed air system takes the efforts
and talents of many people. A decision to work towards energy savings will
require all of these individuals to be part of the process. However, they
can not be effective unless they understand the cost of compressed air and
the interdependency of the components of an air system.
The companies that have trained their people on the importance of saving
energy have reaped the biggest savings. This type of training has a very
fast payback with long term benefits. These energy savings will go directly
to the bottom line and can make a difference in the profitability of any
company.
Send an email to
training@compressorwise.com for details on customized training programs
that have helped others.
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3. Tools for Trouble Shooting
Temperature and pressure readings can organize your trouble shooting efforts
when dealing with a problem in the compressed air system. Specifically, you
can use normal condition readings as a reference point in order to isolate
the cause of the problem.
The normal condition readings are taken on a regular basis for historical
reference and to observe any trends that indicate the beginning of a
problem. The readings are usually taken at locations before and after air
equipment including, among others, the compressors, aftercoolers, dryers,
receivers, air tools and filters.
We have found some interesting methods of collecting the information that
will help you with trouble shooting.
Temperature Readings
Increasing temperature in a compressed air system is one of the best
indicators of a problem. If you monitor temperatures over time, you can
build a base line for normal conditions and create a model for predicting
when you will have trouble with your compressed air equipment.
The most useful tool for this application is an infrared thermometer. This
is a hand held device that gathers temperature readings by aiming at an
object.
There are a couple of points to keep in mind on this issue. The first is to
be aware that you are measuring the surface temperature, not the temperature
of the oil, air or water inside the object.
This method is not as accurate as putting a probe in the oil, air or water.
However, it is a practical way to get information that can be used in
trouble shooting.
The second point is to always take temperature readings when the compressor
is at full load. This gives you meaningful information that can be compared
to the design standards for the equipment.
There are several companies that offer infrared thermometers. However, you
have to decide what you want from the tool before you go shopping.
There are 2 basic decisions you have to make before selecting an infrared
thermometer. The first is to determine the maximum temperature you will have
to measure. The second is to decide if you will want to download the details
into a computer for trending.
The infrared thermometers manufactured by Raytek Corporation are considered
among the best products in this industry. They have a range of products that
can handle most applications.
You can visit
http://www.raytek.com or call them at 800.866.5478 for help in choosing
the right tool for your application.
Pressure Readings
The best idea we observed was the use of a single gauge that was adapted to
fit in an air line quick connection. The operator simply inserted the gauge
into quick connections that were mounted in key locations on the air system
piping.
Accuracy is critical when comparing readings and trying to isolate a
problem. It is important that you use a high quality gauge.
A superior gauge for this application is a Helicoid Digital Pressure Gauge
made by Bristol Babcock. They have a Series HG2000 with several different
pressure ranges (0 to 20 psi, 0 to 50 psi, 0 to 100 psi, 0 to 200 psi,
etc.).
These different ranges each have a unique part number, so be sure of your
pressure before ordering. The 0 to 200 psi gauge is the one we observed
being used during our research.
You can visit
http://www.bristolbabcock.com or call them at 860.945.2200 for more
information.
Summary
The right tools can make a huge difference in your trouble shooting efforts.
Those mentioned above make it easier to gather reliable information that can
help you isolate a problem in your compressed air system.
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