why must you operate the exhaust blower?
Welcome to solsarin, In this post on Solsarin we’re mentioning “why must you operate the exhaust blower”.
Ventilation System Requirements
All gasoline-powered vessels, constructed in a way that would entrap fumes, must have at least two ventilation ducts fitted with cowls to remove the fumes. At least one exhaust duct must extend from the open atmosphere to the lower bilge. At least one intake duct must extend from a point at least midway to the bilge or below the level of the carburetor air intake.
- If your vessel is equipped with a power ventilation system, turn it on for at least four minutes in either of these situations:
- After fueling
- Before starting the engine
- If your vessel is not equipped with a power ventilation system (for example, a PWC), open the engine compartment and sniff for gasoline fumes before starting the engine.
Vessels built after July 31, 1980, that contain power exhaust blowers in gasoline engine compartments must have a warning sticker like the one below placed near the instrument panel.
4 Reasons You Should Use a Remote Blower Instead of a Built-In Blower
Fume Hood Blowers: An Exhausting Subject
A blower, or exhaust fan, is a very important part of a fume hood system. It is the component that moves air through the fume hood. Many people are under the impression that all fume hoods come with a built-in (or integral) blower.
A built-in blower is mounted right above the fume hood. In that scenario, the blower pushes the contaminated air out from the hood, through the ductwork, to the outside.
In most labs, however, a remote blower is used, as shown in the Typical Fume Removal System graphic to the right. This means the blower is located remotely from the fume hood, on the rooftop typically, and pulls the air all the way through the ductwork to be exhausted outside.
There are many things to consider when choosing a blower. Here are four reasons why you should always use a remote blower over an integral blower.
1. Fume hoods with built-in blowers to duct outside do not meet ANSI Z9.5!
If your specification requires compliance with ANSI Z9.5, you must use a remote blower. Section 5.4.4 of ANSI/AIHA Z9.5-2012 clearly states:
Laboratory exhaust fans shall be located as follows:
- Physically outside the laboratory building and preferably on the highest-level roof of the building served. This is the preferred location since it generally minimizes the risk of personnel coming into contact with the exhaust airflow.
- In a roof penthouse or a mechanical equipment room on the roof that is always maintained at a negative static pressure with respect to the rest of the facility, and provides direct fan discharge into the exhaust stack(s).
So if your blower is mounted on top of your fume hood, it won’t be “physically outside of the laboratory building” and it won’t be located in a “mechanical equipment room that is always maintained at a negative static pressure with respect to the rest of the facility.”
2. Remote blowers are safer
A remote blower is a failsafe, meaning if there is a leak in the ductwork at any point, the duct is kept under negative pressure. In the event of a leak, clean air will be pulled through that leak and exhausted out, instead of pushing contaminated air out of that leak (as a built-in blower would).
If you have an application with hazardous chemicals or a building where your fume hood duct run goes through multiple occupied floors, a remote blower should be used.
3. Built-in blowers are not a one-size-fits-all
Every blower has a blower curve chart that shows under what circumstances the blower can operate properly. This includes the static pressure and CFM requirements (shown in the figure to the left).
The mechanical system has to fit the integral blower. So even though you have a duct run that is only 10 feet long, that does not mean it will work well.
It will most likely require a manual control damper to add resistance to the line. Blowers require a certain amount of resistance, or static pressure, to work effectively.
Think of it like using a blender to make a smoothie, if the ice doesn’t fall to the blades, the motor goes too fast and you can sometimes smell the motor burning up since it does not have any resistance to work against. It’s the same concept for a blower motor – it requires resistance to work properly.
4. Built-in blowers are louder
Noise issues can arise for a couple of different reasons, but there is no doubt when the blower is sitting right on top of the fume hood, it will be louder than if it were mounted on the rooftop. If there is noise sensitivity, for example in a classroom setting, it’s highly recommended to have a remote blower so the teacher doesn’t have to speak over the blower motor while teaching.
Things that contribute to the air noise are the duct material (metal is loudest), and the duct run design (the more bends, the louder). So it is always recommended to put 3 to 5 duct diameters of straight duct before and after each bend, and off the fume hood exhaust collar, in order to straighten the air colun and reduce the turbulence.
Those are the four reasons a remote blower should be used over a built-in blower. Obviously, there are scenarios where a built-in blower must be used, but one should always consider a remote blower first, then move from there.
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I would only recommend using a built-in blower if you absolutely cannot use a remote blower.
And now here’s a helpful graphic explaining positive (+) and negative (-) pressure as it relates to blower location and safety. Enjoy.
What Is A Bilge Blower On A Boat & What It’s Used For!
If you have run a boat with an inboard engine in it, then you have probably seen a switch that says blower on it! Leaving you to wonder:
What Is A Bilge Blower On A Boat & What It’s Used For? A Bilge Blower on a boat is a fan that is used to remove flammable fumes from the engine compartment. This is to help prevent an explosion in the engine compartment whenever the engine is turned on after sitting for an extended period of time. The fumes that build up are usually caused by a leak in a gas line or hose.
This article will teach you all about bilge blowers, what they are, how they operate, and the different styles of blowers that have been used over the years!
What Is A Bilge Blower & Where Is It Located?
Inboard engines can cause hazardous and potentially flammable gases to build up inside the engine compartment of your boat. If these gases are allowed to build up inside your boat. A tiny spark or static charge could cause an ignition, exploding your beloved boat to smithereens!
To prevent this from happening, the boats must exhaust the gases to remove the risk of explosion. For this purpose, boats utilize a device called a bilge blower.
A bilge blower (or blower motor) is a small exhaust fan that you install in the transom of your boat. Typically, you attach the blower to a hose that goes down to your inboard engine compartment. You connect the other end of the blower to a bilge vent on the outside of your boat.
The bilge blower sucks in the hazardous fumes from the engine compartment. And exhausts them out of the boat through the vent. This prevents the gas from building up in your engine room and increases the risk of an explosion on board!
When Should A Blower Be Operated On A Boat?
Whenever you start your boat after it has been sitting idle for some time. You should turn your blower on before starting the engine. If by any chance, any flammable gases have collected inside your boat, the blower will exhaust them out.
If they have not, no harm is done. You will have an easier time starting the boat knowing that you do not run the risk of accidentally blowing it up.
Many people think it is a good idea to leave the bilge blower on while they refuel the boat. They think that turning on the blower will exhaust any gases that build up inside the bilge. However, you don’t need to do this. And really, you shouldn’t.
Turning the blower on while you are refueling does the exact opposite of what you intended it to do. Since the blower is sucking the air out of the engine compartment. The air that is inside the compartment is being replaced. With the fumes of the fuel in the air while refueling.
It’s actually more possible to be pulling in fuel fumes!
Hence, you should generally not turn your bilge blower on while you are refueling. Turn it off when refueling, then turn it on once the tank is filled. If any flammable gases made their way into the bilge. The blower will exhaust them out so you can start your boat without worrying.
Thanks for your attention.
