Mechanical seal for ROV thruster

  • Thread starter BillBLack
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  • #26
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have you thought of using magnetic drive couplings this takes away the
need for mechanical seals as there are no holes in the drive chamber
everything remains dry
 
  • #27
Danger
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See post #13.
 
  • #28
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1
Arnt there motors that run wet? wouldnt it be better to use one of those?

There was a Scrapheap challenge on not long back where they built a sub craft, they had decided to use motors that ran wet rather than attempt to seal it ( i think alternator motors were used, or car radiator fans, which run wet ).
 
  • #29
Danger
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Ummm... an alternator isn't a motor. It's an AC generator driven by a motor. And, excluding accidents, an electric car fan motor does not run wet. If it does, it's for a very short time with not favourable results.
Although Zoom has only one post, it makes sense. I'd be inclined to agree with him/her.
 
Last edited:
  • #30
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I know how an alternator works, but thanks for patronising me anyway.
 
  • #31
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That's good enough. Insert into cylinder of shaft to greese. Seal is used to Lidaena. It should be waterproof in 100m depth of water.
 
  • #32
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Hi guys,

I'm also currently designing a ROV that can "dive" down to 100m deep. Looking at most of the underwater scooter's propeller designs, is it possible for me to use the "O-seal" with spring to seal the shaft? Can someone tell me how to what kind of motor can be "flood" by mineral oil?
 
  • #33
FredGarvin
Science Advisor
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For the shaft seal, the shaft linear speed is going to be the main factor in determining if you can use a lip seal. I would suggest looking at Chicago Rawhide's website for more information on all of their types of lip seals and configurations.
 
  • #34
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For the shaft seal, the shaft linear speed is going to be the main factor in determining if you can use a lip seal. I would suggest looking at Chicago Rawhide's website for more information on all of their types of lip seals and configurations.
is there any low-cost actuators, powered by peumatics or electric, that I can use to "press" a switch under such depth? I also trying to find ways to "press" or "click" movement devices.
 
  • #35
FredGarvin
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There are plenty of low cost DC solenoids out there. I guess it all depends on what you call low-cost and what the environment is and what it will need to do......
 
  • #36
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thanks for your advice fredGarvin
 
  • #37
FredGarvin
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You're welcome. If you can come back with some more specific requirements,we can help even more.
 
  • #38
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http://www.advancedsealing.com/

Try this site out. They make mechanical seals for all kinds of pumps. Unfortunatly, mech seals arn't my strong suite so I can't render much else in the way of technical advise.
 
  • #39
FredGarvin
Science Advisor
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Those are mostly all seal assemblies for pump stuffing boxes. That's the only place I know of where a hydraulicay balanced seal is ever mentioned. It's out of the scope of what is being discussed here.
 
  • #40
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does anyone knows whether aluminium profiles from Bosch automation, can restand sea-water? I thought of using aluminium profiles for body structure.
 
  • #41
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How do ROV obtain neutral buoyancy at all depths? The commercial ROVs uses "closed cell foam blocks under a quick release polypropylene shell", how does this concept work? Can I obtain neutral buoyancy using diver's Buoyancy Control Device (BCD) instead? Which method is cheaper or is there other method?
 
  • #42
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What about a seal they use on engine crankshafts? Just off the top of my head....they have to handle very high PSI and RPM's faster than what you need. Would something like this work?
 
  • #43
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What about a seal they use on engine crankshafts? Just off the top of my head....they have to handle very high PSI and RPM's faster than what you need. Would something like this work?
I had thought of using hydraulic cylinder sealing technique, which can restand fluid pressure of 3000 bars.
 
  • #44
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ROV weight estimation underwater

Hi guys,

I was wondering, if I maintain neutral buoyancy for the ROV at every depths, and the ROV weights 160kg, how much torque/ rpm is needed to move the ROV at neutral buoyancy and start off when floating on surface? Assuming two motors is required to move off ROV.

Also, if I want the ROV to move against 6 knots current, how much torque/rpm is required for 4 motors to thrust?
 
  • #45
Danger
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This is not my area at all, but I think that what you're asking is impossible to answer as is. To start with, any amount of thrust will move the thing.
The part about fighting a 6 knot current is so out of bounds that it can't even be considered. What shape is your fusilage? Do you know the Reynolds numbers and such-like? What is the size and pitch of your propellors? Are they ducted, or open? And etc...
 
  • #46
15
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This is not my area at all, but I think that what you're asking is impossible to answer as is. To start with, any amount of thrust will move the thing.
The part about fighting a 6 knot current is so out of bounds that it can't even be considered. What shape is your fusilage? Do you know the Reynolds numbers and such-like? What is the size and pitch of your propellors? Are they ducted, or open? And etc...
ok, another thing is if the ROV weights 160kg on land. In water, at neutral buoyancy, how much weight/mass issit?
 
  • #47
Danger
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Its mass is still 160kg. It's weight is zero. (This is based upon my understanding of the terms involved; the weight might be wrong.)
 
  • #48
can anyone help me out in designing a pressure compensation system in thrusters operating at 200m depth ? can any one explain me how a mineral oil can be used inside housing, i didnt get relevant information abt it, as explained by zoom in one of his posts?
 
  • #49
Danger
Gold Member
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Welcome to PF, Pradeep.
As long as your thrusters are independent of the vehicle's life-support system, there's no need for a pressure-compensation device. (That is, if they're stand-alone units outside of the pressure hull, which they should be.) Flooding the motors with mineral oil simply means that there's no chance of water infiltrating the housing. It won't interfere with the electrical functioning of the motor, although there'll be more drag on the rotor assembly.
 
  • #50
15
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Hi Guys,

I'm having some problems on my ROV designs. How do you seal the motor casing with the cables? Do you use underwater cable connectors? Is there other alternatives? I uses cable gland with the cables inserted through a metal pipe that can give the cable gland a good seal.

Next, I'm using 4 x 24VDC reversible motors, can a high speed motor (without gearbox) run well rather than to use a high torque motor?
 

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