Laboratory Blowers & Ducting
Laboratory Design and Supply Inc. can supply any blower for lab use. However, in your search for the right blower you might want to consider a few things.
- What type of blower do I need?
- What size blower do I need? What factors determine the size that I need?
- Blower Terminology
- What type of ducting do I need to consider?
- Who will install my lab blower/ducting?
- What are the electrical requirements to consider?
- How much ducting will I need?
- Do I need a centrally controlled system for all my hoods?
What type of blower do I need?
The types of fumes you exhaust are directly related to the type blower you’ll need. Many standard airfoil bypass hoods require a simple epoxy coated steel blower. This is the least expensive type blower you can buy, but it’s not right for every application. If you are working with any type of explosive materials, you will want to use an explosion proof blower, usually made from plastic or fiberglass. Explosion proof blowers usually have a totally enclosed motor so that any potential fumes that go through the air stream do not interact with the electrical current or spark of the motor itself. The fan impellers on this type of blower are also non-sparking. If your application is located in an area near a coast and you’re concerned about saltwater corrosion, go with an all-plastic blower. You won’t have to worry about replacing it nearly as fast as a steel coated blower.
What size blower do I need? What factors determine the size that I need?
Getting the right size blower is essential to
the successful operation of your hood. The hood manufacturer
will dictate the amount of air you need to move in order to
operate the hood at 75 feet per minute (fpm), 100 fpm, 125 fpm
or 150 fpm. The manufacturer will state the airflow that’s
needed, stated in cubic feet per minute (cfm), at a designated
level of static pressure, stated in inches. Static pressure is
best described this way:
S.P. Static Pressure. Resistance to air flow measured in
inches of water gauge (WG). The static pressure is the total of
the negative pressure on the suction side of the blower and the
positive pressure on the discharge side. Resistance is caused by
hoods, ductwork, elbows, stacks, filters, or anything else that
impedes the free flow of air.
An example of what a hood might require would be something
like this:
At 100 fpm, fume hood #1 requires 1400 cfm @ 0.37” SP
So you would use this information as a basis for beginning your
blower search. Any elbows, long duct runs (over 25 feet) and the
natural pressure loss of a duct system will add to the actual
airflow requirement of your system. The info above is only for
the hood at its face. A simple rule of thumb is to size the
blower up a little bit (10-15%); you can always use a damper to
reduce the airflow if it’s too great. If you need additional
information or want to ask a question about how to size your
blower or duct system, please contact LDS at
blowers@labds.com; we’ll be happy to assist you.
Blower Terminology
CFM: Cubic Feet per Minute The amount of
air
moving through a system. CFM = FPM x
AREA in square feet.
S.P. Static Pressure Resistance to air flow
measured in inches of water gauge (WG). The
static pressure is the total of the negative
pressure on the suction side of the blower
and the positive pressure on the discharge
side. Resistance is caused by hoods, ductwork,
elbows, stacks, filters, or anything else
that impedes the free flow of air.
RPM: Revolutions per Minute. Rotational speed of
the blower impeller.
FPM: Feet per Minute Velocity of the airflow
measured at a certain point in the
system. FPM = CFM divided by Area in
square feet.
VELOCITY: Speed of the airflow measured past a certain
point, measured in FPM. Velocity across the
face of the hood is the most important factor
in hood exhaust design. VELOCITY x FACE
AREA (in square feet) = CFM required.
BHP: Brake Horsepower Horsepower required to
turn the blower at a given RPM at a given
CFM and static pressure. Usually determined
from fan performance charts.
What type of ducting do I need?
While many types of ducting are available for
commercial applications, there are two main types that lab
applications might require: PVC and stainless steel.
What applications determine which one I need?
PVC is, by far, the most prevalent type of duct material used in
labs because it resists all types of corrosive and acidic fumes
and won’t corrode in high moisture environments. Stainless steel
can be used also in high moisture environments, but it will
corrode in some acidic environments. Sometimes, though, the
specification may call for stainless steel. Consult your
engineer or architect about this specification to find out if
there are viable alternatives. Most lab duct is either straight
or preformed elbows. Transitions are available in both PVC and
stainless steel to move from one size to a larger or smaller
size. In-line damper systems are available also. Flexible
stainless and PVC are available if the application demands it.
Normally, we do not recommend galvanized sheet metal ducting as
it will corrode fairly quickly. Trying to replace corroded
ducting is much more expensive after it’s already installed
compared to spending a little more up front for the right
material.
Who will install my lab blower/ducting?
LDS can install your blower and ducting system, but normally this is best when left to a certified and trained HVAC contractor that you choose. The reason is that the HVAC contractor will know how to wire the blower so that it complies with local and national electrical codes and standards. These codes vary by state and municipality, and your local contractor will know best how to comply. If you choose for LDS to install the blower and ducting system, we would ask that your electrician complete the hookups and test the system. Normally, lab blowers are mounted on a rooftop.
What are the electrical requirements to consider?
The electrical requirements are driven by the needs of the blower, the availability of electrical power and the distance between the blower and the hood(s). Some larger blowers operate more efficiently on 240v power. As long as the electrical power is available on the rooftop, you can request that the blower motor be 240v compatible. Most blowers, however, use standard 115v power. Again, consult your electrician or HVAC contractor for more information.
How much ducting will I need?
This is all based on the layout of the hood and blower using straight duct runs and elbows. You can, of course, shorten the length of duct by using flex duct. Flex duct also serves to absorb vibration from the blower system and will not transfer vibration to the hood. Normally, ducting comes in 10-foot sections and can be coupled together with PVC couplings. Try to mount the blower as close to the hood as possible so as to reduce the amount of duct and thus the amount of pressure loss in the duct system itself.
Do I need a centrally controlled system for all my hoods?
Many blower systems used in larger labs require a central control to maximize the efficiency of the airflow and maintain consistent temperatures within the lab. This is especially true in multi-hood installations. When more hoods are in use, the amount of conditioned air is increased and vice versa. Using an intricate system of airflow monitors and motorized dampers, a centrally controlled system works to keep you comfortable in any situation and season.
Call or
contact us today for your personalized quote on any of our
cabinet types or laboratory furniture We can meet your needs and your budget.
1-888-LDS-3100
ldscabinets@labds.com