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 Post subject: Oil filled switch
PostPosted: Mon Feb 05, 2018 10:16 pm 

Joined: Wed Jan 15, 2014 9:14 am
Posts: 198
A friend of mine is working on an old sheet metal roler. The switch is a large ge switch that is oil filled. We can't find any info on what kind of oil should be in this switch. Anybody know? Machine is probably 1940's or 50's.


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 Post subject: Re: Oil filled switch
PostPosted: Mon Feb 05, 2018 10:25 pm 

Joined: Sun Oct 19, 2008 12:58 pm
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Location: Chicago USA
If it's similar to transformer oil please be careful as that was around the time they came up with non flammable oil for transformers. Unfortunately they were based on PCBs which are carcinogens and cause old substation sites to require EPA-certified cleanup. And why the retired GG1's lost their transformers. I don't know if it applies to oil-filled switches but if so there might be contamination from the prior oil.


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 Post subject: Re: Oil filled switch
PostPosted: Tue Feb 06, 2018 9:02 am 

Joined: Tue Sep 22, 2015 12:36 pm
Posts: 198
Yeah I would replace that thing with a modern equivalent and "loose" the old one.

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 Post subject: Re: Oil filled switch
PostPosted: Tue Feb 06, 2018 12:58 pm 

Joined: Thu May 24, 2012 1:37 pm
Posts: 1003
Send pictures of it, both the outside and, if possible, the visible accessible parts of the inside.

I wonder if this is related to the cylindrical 'tanks' on the outboard end (later inboard end of the platform/'monkey deck') on NYC four-truck T-motors. That was a question on one of the Trains forums not long ago...

Keep in mind also that much of the risk of "PCBs" would not apply to examining the device, or even using it periodically for displays or making videos.

A substantial part of the severe risk from PCB exposure involved not the polychlorinated biphenyls themselves, but artifacts of the synthesis (which was a somewhat crude thing for many commercial versions, probably including Pyranol) such as dihydrofurans or dioxins (which will be familiar to many from the Agent Orange aftermath). In addition, the risk from environmentally-encountered PCB -- such as that in Hudson River mud, or shad, or sturgeon roe -- is many times greater than for the oil itself (Compare the toxicity of metallic mercury with methylmercury)

In addition, much of the literature on exposure fails to disclose a difference between acute or periodic exposure and chronic or employment-related exposure, something that unfortunately plagues too much modern science that has political implications. While there are likely to be some problems with casual exposure even to old oil that may have been partially degraded in service, I think logical use of PPE including contact and inhalation protection (which you'd always use around solvents or volatiles, right?) would keep you safe. In particular I would not anticipate the induction of liver cancer or melanoma from nonchronic exposure.

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 Post subject: Re: Oil filled switch
PostPosted: Tue Feb 06, 2018 1:42 pm 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2214
Location: Northern Illinois
Very likely oil containing PCB's, as it is my understanding that the purpose of the oil in these switches was arc suppression. That would seem to indicate that when the switch disconnects, the arc will volatilize some of the oil, which will likely escape from the case and enter the atmosphere in the general vicinity of the switch.

Here's a question that has yet to be asked; is this an antique machine being set up as a historic display, or are you guys just being cheap? If it's just for shop use, used modern era motor controls of sufficient capacity are likely available on E-bay for less than the cost of suitable replacement oil.

If it is a historic display, I would look into dielectric fluid as used in a sinker style EDM (Electro Discharge Machining). The traditional simpler oils were just light mineral oil with a high flash point; that does come with the danger that if the oil level is allowed to get low enough that the arch is exposed, the oil could catch fire. It is my understanding that the newer synthetic fluids are much more fire proof. Here's an example, 210 deg. F flash point:

http://tvuka.tjxve.servertrust.com/v/vs ... 00_tds.pdf

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 Post subject: Re: Oil filled switch
PostPosted: Tue Feb 06, 2018 1:52 pm 

Joined: Wed Jan 15, 2014 9:14 am
Posts: 198
I believe the machine is still being used in production. Not so much being cheap, but the old "if it ain't broke, don't fix it" applies here. Same reason my 1951 South Bend lathe has the same switch it was sold new with. Just like the lathe, the switch is over built. I'm sure replacing the switch would not be an issue if it is justifiable, which sounds like it almost is at this point. We were curious more than anything. Neither of us had seen anything like it, and nobody we talked to locally knows.


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 Post subject: Re: Oil filled switch
PostPosted: Tue Feb 06, 2018 5:08 pm 

Joined: Thu May 24, 2012 1:37 pm
Posts: 1003
I'd tend to agree both on research into finding a modern dielectric that could be used, or the use of an appropriate flammable oil to substitute for the Pyranol if the machine is to be used in production. The important thing is to remember to keep the oil level high enough to prevent arcing, and the connected equipment in good enough shape, and under good enough control, to limit any instantaneous overcurrent through the switch.

It was my understanding that the large mass of fluid in one of these switches effectively quenched any vapor that was produced in interrupting an arc between contacts, so there would be little if any vapor within the case and comparatively little pressure differential that would cause venting. I believe comparable material is used in high-temperature heat exchange precisely because of its low vapor pressure at elevated temperature.

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 Post subject: Re: Oil filled switch
PostPosted: Tue Feb 06, 2018 7:25 pm 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2214
Location: Northern Illinois
Not to be argumentative, but my background is EDM, where you can actually see what is happening in the tank, and even at a couple of amps, the burn sparkles away under the oil, and the bubbles come up. It's likely not oil vapor; I believe the arc actually destroys the oil, leaving carbon in the tank, and hydrogen to bubble out. I do know that if surface flushing and the flush volume is inadequate to cover the arc, you get neat little flames that go poof, poof in time with the ram cycle. Not good, because these can eventually start the tank on fire. Never had it happen, never want to.

But the fact remains that the arc is hot enough to locally vaporize the oil, but the surrounding oil keeps air away, and I suppose captures all the ions that cause flash-overs. It appears this switch is rated 5 HP at 220VAC, and is arranged to "plug reverse" the motor. I bet that draws some amps.

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 Post subject: Re: Oil filled switch
PostPosted: Wed Feb 07, 2018 1:26 pm 

Joined: Tue Sep 22, 2015 12:36 pm
Posts: 198
Forward/reverse switch off a Bridgeport mill would fill the bill pretty nicely as a replacement. Likely plentiful as well used as many home gamers switch out their 3 phase control equipment to single phase.

With all the low cost frequency drives on the market now coming from China able to do phase conversion. For a couple hundred bucks the days of not being able to run 3 phase equipment in your garage are gone.

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 Post subject: Re: Oil filled switch
PostPosted: Wed Feb 07, 2018 2:35 pm 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2214
Location: Northern Illinois
Nowhere near sufficient rating, unless the "oil" switch is seriously oversize. The plate in the photo shows it rated 5HP at 220 V 3 Ph., 7.5 HP at 440 V. 3 Ph. The largest motor Bridgeport ever offered was 2HP, unless you count the monster Series II machines Textron offered for a time; those were 4HP, but I think they used contactors to reverse, not a drum switch.

I don't think I'd want to plug reverse a 5 HP motor with the silly little switch on my Bridgeport.

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 Post subject: Re: Oil filled switch
PostPosted: Wed Feb 07, 2018 3:43 pm 

Joined: Tue Mar 10, 2015 10:29 am
Posts: 51
Location: Michigan
Transformer Oil (the same “stuff” used in submersible electric motor pumps etc.) will work just fine.

For reference, here’s the various connection diagrams for the General Electric CR2960SY105 switch.

John


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File comment: CONNECTION DIAGRAMS FOR GE SWITCH
CR2960SY105

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 Post subject: Re: Oil filled switch
PostPosted: Thu Feb 08, 2018 8:55 am 

Joined: Tue Sep 22, 2015 12:36 pm
Posts: 198
Sorry I guess I was thinking of the 5 hp Index mills I use at work, and now that I think about it they are contactor controlled in the the back with a small switch out front.

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 Post subject: Re: Oil filled switch
PostPosted: Thu Feb 08, 2018 9:56 pm 

Joined: Mon Aug 23, 2004 12:59 pm
Posts: 534
Dennis Storzek wrote:
Nowhere near sufficient rating, unless the "oil" switch is seriously oversize. The plate in the photo shows it rated 5HP at 220 V 3 Ph., 7.5 HP at 440 V. 3 Ph. The largest motor Bridgeport ever offered was 2HP, unless you count the monster Series II machines Textron offered for a time; those were 4HP, but I think they used contactors to reverse, not a drum switch..

WRM just got a government surplus Series II Bridgeport. You are correct: it is 4 HP, and does not use a drum switch. There are three large contactors in the control cabinet.


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