Knowing which system is right for your
Air systems – integral or
many years now, compressor manufacturers and distributors have been fabricating
packages to combine compressors with accessories such as tanks, dryers and
filters. This popular concept allowed customers to customize their compressed
air system while reducing installation
costs. These package units were very popular with small shop and facilities in
the under 25 HP market.
Recently, larger compressors have
undergone similar developments with the inclusion of variable speed drive
technology and the addition of integral refrigerated dryers. In addition to
optimizing design time, installation costs are becoming increasingly affordable
with excellent return on investment.
Clearly, these integrated systems offer
advantages in many applications. However, there are other considerations. Many
factors should be evaluated and considered when choosing between integrated
package systems and conventional systems with separate components.
Generally speaking, industrial
compressed air installations include one or more compressors, receivers, dryers
compressed air systems are more complex than they seem. Compressors should
include internal controls, and multiple unit systems may use a master system
controller for optimum performance. Centrifugal separators or “wet tanks”
should be installed down-stream of the compressors’ after-coolers to ensure
effective water separation. Dry tanks to provide buffer capacity and compensate
for fluctuating compressed air demand are also recommended in most systems.
Refrigerated or desiccant dryers must be selected and sized according to the
application and specific environmental conditions.
The facility where the system is housed
has to meet technical ventilation requirements plus ambient air quality plays a
role in determining components. While integral systems might meet some of these
needs, conventional systems have their benefits as well. The best system for the
application results from a clear understanding of the specific process air
quality requirements, air demand profile and facility limitations or potential.
A refrigerator in an oven - a paradox?
Designing compressors with integral
dryers can present a real challenge to manufacturers. The reason? Compressors
and refrigerated dryers have completely opposing characteristics. A compressor
converts almost all of its input energy into heat, which is discharged into the
ambient surroundings. A refrigerated dryer requires cool ambient surroundings in
order to use as little energy as possible to cool and dry the compressed air.
Air systems manufacturers must address: How do I integrate a refrigerator
(refrigerated dryer), and other heat-sensitive components, into an oven
(compressor) so that both units still provide outstanding performance? While
this may seem like a paradox at first, it is technically possible.
Cheap comes at a cost.
Sadly, some "budget" solutions
offer a good deal on the initial purchase price by downgrading the refrigerated
dryer to nothing more than a "better" after-cooler and using
proportional control to regulate the compressor. These quickly prove to be
ineffective at best and wasted capital at worst. The real solution is to accept
the opposing characteristics of the compressor and the dryer, and design the
system to prevent the compressor from thermally affecting the refrigerated
Space is a premium.
Space limitations and other physical
design factors add to the challenge of component selection. Compressors are
often tucked away In a dark corner with little space and poor ventilation.
Components are placed "where they fit" without proper regard to intake
or discharge. These mistakes can drastically reduce efficiency and compressed
air availability. Combine these factors with harsh environments and contaminated
ambient air, and the cost of maintaining compressed air reliability sky rockets.
With these considerations, end users are
increasingly eager for solutions that reduce planning and installation work
while also providing considerable space-savings. Integral compressed air systems
are an excellent choice in these situations, and are even better when
manufacturers have piped and wired them for quick and easy installation.
Essential: Condensate separation,
efficient control and storage
Condensate separation is another
important aspect. A pre-separation system must be installed between the
after-cooler and the refrigerated dryer to eliminate the 70 to 80 percent of
condensate that accumulates there. This type of Integral system eliminates the
need to pipe and install individual components, plus it requires far less floor
space than a conventional installation.
It is a mistake to assume that only
large conventional systems require a "buffer" or "dry" tank.
Alt systems can benefit. An appropriately sized storage receiver helps maintain
a stable system pressure and provides buffer capacity for short periods of high
Integral units should also include an
efficient internal control system for both the compressor and the dryer. In
addition, if the system and cabinets is designed to allow easy access to all
service-relevant components, reduced maintenance costs can be added to the list
It is equally important to consider the
system's location in relation to where the compressed air is actually used. For
example, assume a situation where the ambient temperature is over 100 ° F, but
the compressed air is used in an air-conditioned environment at only 68 °F. In
an integral system with a refrigerated dryer, the pressure dew point is very
near or only fractionally above, the condensate precipitation limit. With the
air humidity above 50%, there is the significant risk of corrosion. However,
with a conventional air system installation air treatment equipment can be
specifically tailored and the compressed air can be delivered with a pressure
due point of 3a°F even under such difficult operating conditions. As a result,
there is no risk of damage from condensate accumulation or corrosion.
With the many advantages of integral
systems, users may assume that there is no longer a need for a separate
compressor room. Plus, today's fully enclosed rotary screw compressors are
exceptionally quiet. Once again, the complete picture should be examined. Is the
heat generated by compression ducted away for more efficient use? Or is it
allowed to dissipate in the surrounding environment? In dirty or contaminated
environments, the compressor will suck in the various contaminates through the
intake like a giant vacuum cleaner. This can lead to increased maintenance costs
and the risk of breakdown. To ensure maximum air availability and optimum
efficiency, carefully select the system's location to account for ventilation
and worker comfort.
The compressor and refrigerated dryer
will always discharge a volume of heat that corresponds to the unit's power, and
this heat has to be managed by the installation facility's ventilation system.
In many cases, end-users choose to duct both conventional and integrals systems
to recover the heat generated by compressed.
integral units make sense.
Systems with integral air treatment are
ideally suited to applications were floor space is limited, and the required
compressed air volumes are relatively low. Facilities such as machine shops,
automotive service outlets, and small-to-medium industrial manufacturers are
perfect examples of applications where clean dry air is essential, but large,
cumbersome systems are prohibitive.
By the nature of their design, the dryer
in an integral system is presized and it is not possible to control an
additional dryer or use a larger one. Integral systems produce pressure dew
points as lowas38°F. Higher ambient temperatures will increase the pressure dew
point. However, applications that require condensate-free compressed air can add
specific filtration downstream.
When conventional units provide better
Applications with precisely defined air
quality standards, such as surface coating, pharmaceutical or electronic
component manufacturing, or food processing will find that a conventional
compressed air system is required. These may require desiccant dryers to reach
lower pressure dewpoints than can be reached with any refrigerated dryer.
Further, facilities with varying ambient
conditions, or harsh environments should assess their specific needs as well.
Consulting a trained compressed air professional will ensure a compressed air
system and clean air treatment components precisely tailored to the specific
Reliability In the end.
End-users cite reliability as their top
consideration. In a conventional, component-based system, compressors can be
connected to more than one refrigerated dryer to provide redundancy and ensure
compressed air quality in the event of dryer malfunction. Because in an integral
system the compressor and dryer are directly connected in one unit, back-up
dryers are not possible. However, if the end-user maintains a routine preventive
maintenance program, the integral system will remain in top operating condition
and prevent unscheduled downtime.