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Spark plugs???? JAX your ability to introduce irrelevent and meaningless
items into a post has just hit a new high (low?), I got my information from Nigel Calders book "boatowners mechanical and electrical manual" a very informative book that deals with everything a boatowner needs to know to maintain their boat. Nigel Calder is a well known and respected yacht owner who has written numerous books and articals over the years. JAX, you on the other hand seem to have trouble comprehending a simple posting, electric motors have the capability to produce sparks, something you do not want down in the bilges if they have a flamable mixture of gasses, they do no use "spark plugs" something I never even said. Even if the motor is "ignition protected" as you say, (which I agree with) there is still a very good argument to mount it as high as possible, to keep it clear of the gasses, to keep the wiring clear of the gasses and to eliminate as much of the hazzard as possible. I believe it was a Japanese aircraft carrier that was lost during the battle of Midway when a blower was turned on in a compartment that full of gasoline fumes. Eric "JAXAshby" wrote in message ... eric, that is a crock of squat. bilge blowers are required to be "ignition protected" (look it up, for it has nothing to do with spark plugs at all). "Eric Currier" Date: 10/16/2004 1:31 AM Eastern Daylight Time Message-id: cn2cd.73920$tU4.11401@okepread06 You mount the blower up high to keep electric motor above the expected fumes...a blower mounted low can have the fumes seep into the electric motor that drives it, a blower mounted high has the motor in fresh air and only the fumes are drawn up to the blower, and the fumes are in the fan section and from there they are quickly ejected overboard. Sump pumps are mounted low (in the bilge water) to pump out water and because they are ment to be submerged they are sealed to keep out water and fumes which should make them fairly explosion proof. as far as I know there are no submergable blowers, a blower is ment to move air and is not ment to work underwater. If the blower was mounted low when you turned it on you could set off the explosion you are trying to avoid. Blowers are mounted high to prevent explosions. Eric "JAXAshby" wrote in message ... Unless the blower is sumbergable (none that I have ever seen are) you would want to take care to mount the blower higher than any ----------------------------- expected ---------------------------------- accumulation of bilge water. Even unexpected amounts! expected??? unexpected? who the hell is worried about butane in the bilge when expected (WTF is that???) water or unexpected water is in the bilge? if you intend to have water in you bilge, there is still NO need to mount the blower "up high". just mount it above "expected" or likely "unexpected" high water level mark. duh. |
West Marine cataloge page 334.
JAX, what do you do for a living? Hopefully it is nothing that can affect me, and hopefully it is a critical post in the Democratic party. Eric "JAXAshby" wrote in message ... eric, have *you* ever seen a bilge blower, even on a shelf at West Marine? "Eric Currier" Date: 10/16/2004 2:06 AM Eastern Daylight Time Message-id: GT2cd.73921$tU4.63445@okepread06 Since when has JAX let facts determine how he thinks? "Wayne.B" wrote in message .. . On Sat, 16 Oct 2004 00:31:51 -0500, "Eric Currier" wrote: Blowers are mounted high to prevent explosions. ========================================= Careful, Jax is easily confused by the facts. |
"Me" wrote in message ... Maybe you can tell us, "How to make a 12Vdc Motor that has brushes and can't cause sparks between those brushes and the commutator"? It can't be done, Dufus. It can, actually, but it often isn't economically feasible. What can be done, is to seal the motor as best you can, That can be very unwise. There are much better ways of addressing the explosion hazard than sealing the motor case. Most motors need air for cooling. High current motors are going to get very hot and the resulting pressure increase would be very hard on seals. Maintaining an air tight seal, especially around a rotating shaft, can be very difficult. and then mount it above the expected location of the explosive gases, with a suction hose down to the lower bilge area, and a VERY short discharge line. And how do you regulate the level of the explosive gases? Gas fumes are heavier than air, and will tend to settle. They are not like water, however. You can't rely on the heavier fumes settling to the bottom and staying there. Think about that for a moment: If it really worked that way, the entire atmosphere of the Earth would separate into layers based on the relative weight of the gas. It doesn't happen. Air circulation causes eddy currents and stirs things up. You can't rely on the position of the bilge blower to keep it safe from explosion. If for no other reason it would be possible for the entire compartment to fill (top to bottom) with the necessary gas/air mix to create an explosion. The Coast Guard requirments state that all electrical components installed in the engine compartment be ignition protected. That does NOT mean sealed. The most common way of protecting a motor, generator or alternator is to put a metal screen across the air vents. Gas fumes can enter the motor, they can get to the brushes, and they can be ignited. They haven't been compressed so the potential engergy is fairly low, and volume inside the motor case if small so the resulting explosion is trivial. The gas fumes can be ignited: the flame traves out on a wave front until it hits the metal screen. The screen absorbs the heat from the wave front and quenches the flame. As long as the screen doesn't get so hot that it ignites the fumes on the outside the "explosion" stops there. No harm done. You should have a similar screen across the air intake of the engine (often referred to as a "flame arrester") so that a backfire through the intake system can't ignite any fumes. There should be one on the distributor. With the proper ignition protection it doesn't matter where the device is mounted. Note that the starter is usually mounted very low on the engine...... Rod McInnis |
"JAXAshby" wrote in message ... accumulation of bilge water. Even unexpected amounts! expected??? unexpected? who the hell is worried about butane in the bilge when expected (WTF is that???) water or unexpected water is in the bilge? Jax, I am not understanding what you are saying here. Are you suggesting that it is unusual for a boat to leak? An "expected" level of bilge water would be the level the water attained before the float swictch activates. I have seen this be 6 inches or more in some boats. In addition, you can have a situation where the low spot in the boat is fairly far forward when the boat is at rest, but at the stern when the boat is under way. You could have a few inches of water distributed along the length of the bilge while you were at idle, and then have it all run the back when you power up. This can easily cause the water level in the back to get fairly high until the bilge pump can pump it out (hopefully there is a pump at the back for this purpose). What I would call an "unexpected" level of water is something above the level of the float switch. Perhaps the operator forgot to turn the pump on. Maybe he forgot to put the plug in. Maybe he just took a wave/wake over the side. It is not unusual for a boat to get a fair amount of water it in. Not "swamped", but more certainly filled above the normal level. Just the fact that you have a little water in the bilge doesn't mean that you can quite worrying about explosive gases! if you intend to have water in you bilge, there is still NO need to mount the blower "up high". just mount it above "expected" or likely "unexpected" high water level mark. duh. Isn't that what I said????? You also have to make sure that the intake hose is above the bilge water levels. I have seen installations where the intake hose was allowed to drop all the way into the bottom of the bilge. In that configuration 4" of water would cover the intake and block the blower operation. Rod |
On Wed, 13 Oct 2004 22:05:11 GMT, "Mick Davies"
wrote: I understand there are sniffers to detect propane build-up but if such a pocket of collected gas is found how do you clean it out and make the boat safe again? Thanks, Mick I'm afraid the lunatic fringe contributed, so this thread deteriorated. But to answer your question. Explosive gas concentrations are cleared with a fan. Such fans are fitted with flame -traps. The principle of the flame trap is exceedingly simple - and was implemented in the miners' safety lamp more than 150 years ago. Two layers of copper gauze are fitted in any ventilation hole. This extracts enough heat to eliminate ignition. You can try this at home if you have a bunsen burner or a cooker with gas burners. You hold the gauze above the flame, and above the gauze there is no flame. Or if you turn on the gas, and light the gas above the gauze, the flame does not spread below. The method is due to (Sir) Humphry Davy, at the Royal Institution. Brian Whatcott Altus OK |
okay, people here is a bunch of blowers designed specifically to remove
explosive fumes from a bilge. They are damned hard to find so pay attention: http://www.westmarine.com/webapp/wcs...Display?catalo gId=10001&storeId=10001&categoryId=12111&langId=-1&subdeptNum=302&storeNum=12 note that every one is ignition protected, so have no need to be "mounted high to avoid explosions". Note that some are waterproof so can be mounted under bilge water. No mention is made to how those blowers blow bilge water overboard. note that none incorporate a flame arrester (trap? the term flame trap is unknown to me in the context of bilges), so if you feel the need for this "enhancement" you will have to fabricate it yourself (nobody does, but what do they know?). I understand there are sniffers to detect propane build-up but if such a pocket of collected gas is found how do you clean it out and make the boat safe again? Thanks, Mick I'm afraid the lunatic fringe contributed, so this thread deteriorated. But to answer your question. Explosive gas concentrations are cleared with a fan. Such fans are fitted with flame -traps. The principle of the flame trap is exceedingly simple - and was implemented in the miners' safety lamp more than 150 years ago. Two layers of copper gauze are fitted in any ventilation hole. This extracts enough heat to eliminate ignition. You can try this at home if you have a bunsen burner or a cooker with gas burners. You hold the gauze above the flame, and above the gauze there is no flame. Or if you turn on the gas, and light the gas above the gauze, the flame does not spread below. The method is due to (Sir) Humphry Davy, at the Royal Institution. Brian Whatcott Altus OK |
They use AIR (NOT electric) motors in explosion application.
You must mean "TENV" .... totaly enclosed/non-vented: For 'hazardous' atmospheres but certainly NOT for explosive atmospheres. Usually ONLY pneumatic motors and controls are used in 'explosive' applications. How do they make industrial electric motors explosion proof? Impossible you say? |
Me wrote: In article , (JAXAshby) wrote: eric, that is a crock of squat. bilge blowers are required to be "ignition protected" (look it up, for it has nothing to do with spark plugs at all). Maybe you can tell us, "How to make a 12Vdc Motor that has brushes and can't cause sparks between those brushes and the commutator"? It can't be done, Dufus. What can be done, is to seal the motor as best you can, and then mount it above the expected location of the explosive gases, with a suction hose down to the lower bilge area, and a VERY short discharge line. Me How do they make industrial electric motors explosion proof? Impossible you say? |
Rich Hampel wrote: They use AIR (NOT electric) motors in explosion application. You must mean "TENV" .... totaly enclosed/non-vented: For 'hazardous' atmospheres but certainly NOT for explosive atmospheres. Usually ONLY pneumatic motors and controls are used in 'explosive' applications. How do they make industrial electric motors explosion proof? Impossible you say? Obviously you have never seen TEXP motors. Check, for example, the Westinghouse site. Handy if you want to mount a 150HP blower in your canoe. |
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