Vibration Isolation Demonstration

hello everyone this is Tony Alice and a virus sonic control and today I'd like to talk a little bit about vibration isolators and the effect of deflection and what that does to isolation and how it affects equipment and selection of wood Isolators you want to use so what I have here in front of me is a fan it is has an imbalance which we put a bolt in here so it can throw out a balance and it's also got variable frequency drive so that we can adjust the RPM of the of the equipment so it's very out of balance even or small fan like this is a terrible piece of equipment but it's great for our demonstration so if I turn it on and I want to leave it on too long because it creates quite terrible noise annoying everyone in the building that's because it's way out of balance and it's sitting flat on this table it's got no isolation whatsoever so what do we do about that we've got it get some isolator so we've got isolated piece of equipment so step one we're gonna try some neoprene waffle pad rubber waffle pad you will see this quite a bit out there it's quite often use it under pumps or equipment like that it can be effective for equipment when it's you know some we're not critical or slab on great and it doesn't have a whole lot of deflection it's usually rated to about maybe a twentieth of an inch and in this case they're quite a bit larger than what I need for this fan so we're not even gonna get that we're getting get very very little quite honestly so I put it on there now we've got it isolated and Scout rubber between the piece of equipment and my table so we're good to go see how how it helps us out I think he didn't really help too much in fact kind of bounced around or more than it did before that's because we're really not getting any deflection and that deflection is what gives us vibration isolation efficiency the greater the deflection the better our efficiency you'll see those numbers sometimes isolation efficiency that is a percentage and that percentage is how much of that energy is being taken out and doesn't get into your structure so if you have a vibration isolation efficiency of 90% then only 10 percents getting down into your structure it's it's taking out that 90 in a case of these neoprene paddles that I would say it's both zero so we moved to something a little bit more robust something with the greater deflection that's neoprene mount yeah it's still neoprene or a rubber and it's thicker though so it's now it's got some deflection and it will squash down under load so if we move these out here you should have some increase in performance better isolation efficiency well you do see when I put this down on here it still doesn't deflect much quite honestly there under loaded and you're not gonna get much to flash not very noticeable anyway still more than the pads but it's just not a lot so let's see what happens when we when we use our neoprene melts as you can see it still wasn't that effective it was better than the past but you know I think this one here tried to sneak away it's letting the whole thing bounce around and and quite quickly you'll find that resonant frequency because we're not getting a lot of deflection here so it's again not really adequate particularly with this noisy fan and if we turn down that rpm it's gonna even be worse so it's not really a great selection for for our problem that we have here right now that's when we move into something with greater deflection which means greater isolation efficiency we have these small Springs here and the difference with Springs compared to neoprene is you know they give you typically a higher deflection greater isolation efficiency they also don't have any damping what that means is they're they're not trying to stop the movement and so they they move more freely in a their isolation efficiency even we have to spring up the same deflection is it Sonia playing out nice the spring isolator will outperform it so we get our our four Springs here and now we're getting a little bit more serious and maybe actually solving our problem let's see what we get and you'll notice right away when I put this this imbalance fan down on our Springs you can see that it it drops down at squat we're getting some deflection now probably not a whole lot maybe a quarter of an inch what we're getting something so let's see what difference is now she's pretty good at I can still but it's reducing significantly I'm gonna have to hang on to it I don't like the way this driving steak sounds working fairly well have you drop that frequency the isolation efficiencies slowly drops his left because we're approaching the natural frequency of the spring and see if we can find it now we're pretty 12 and that's why it's Luallen for all its movement and once you get to the natural frequency of the spring it actually makes your situation worse than have you just mounted it directly for so it's something you definitely want to avoid the typical rule of thumb for vibration isolation is that the natural frequency of your isolator should be no more than 1/3 that of your disturbing frequency of your piece of equipment so yeah units you know that's rotating at 1,200 rpm you would want an isolator that has a natural frequency at about 400 rpm so in this case it definitely worked fairly well the higher frequencies but you can see the lower we got the less desolation efficiency was so if we wanted to run this thing out of that lower frequency what we need is a spring with even higher deflection and Springs you can get them typically the standard ones will be at one or maybe two inch but they come in 3 4 or 5 inch depending on the type of equipment you're using of course you can see it's bigger so the the greater the deflection of spring you're using the bigger that's going to be so it's it's often be hard to isolate low rpm equipment if it's really small so we've got these big Springs here we're gonna move those into place they have a better reflection than our red ones so when we put the weight on it it will drop more and that's that's the deflection S and after a frequency of this system and so we turn this on to high much less vibration in the table I still feel it but quite a bit left if this thing wasn't so imbalanced you probably fit almost completely so have you dropped that speedo we're still going to drop the isolation efficiency and come closer and closer to the natural frequency of these Sprint's let's see if I can find these guys now you can see I'm getting close now but I've had to go play bit lower almost good point where the same stuff's now we're pretty much out of at the natural frequency and it's bouncing all over the place and this this is the situation you wanna boy but of course you look at this fan it's very smoothing at all it's a very low frequency that we've sent it to but judging by the deflection maybe getting closer to a half an inch at best so it's still not a whole lot of deflection for for what we're doing here we say you you're gonna want something higher than that when you get your data sheets from your manufactures you'll find that the reign of deflections on their so you think okay well I'm getting an inch and we can work that out and figure out your your isolation efficiency but you actually need to look at the actual deflection that's the amount when you put the weight on there then it actually drops down the rated deflection is only for if you happen to load that isolator right to its maximum capacity which is it very common so usually you're you know one inch isolator you're gonna get maybe seventy to eighty percent of that isolation or your deflection and your isolation efficiency is something to keep in mind and so that's basically how deflection how the frequency of the screwing frequency of your equipment all come together and why you've got to really pay attention to it when you're selecting Isolators for your clothes thank you very much

Channel: Vibra-Sonic Control

Views: 4,565

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Id: NduP7xUHnGA

Length: 8min 32sec (512 seconds)

Published: Thu Jun 04 2020