RESCUING PULSE CAPACITORS
Signification, Thu Mar 21 2019, 12:32PMHi all: My house went through the great Louisiana flood, and I am just now noticing my never-used oil filled metal-cased Aerovox energy capacitors that were sealed in transparent heat-shrink tubing started to show signs of a small rust-layer between the plastic and metal near the bottom (where the 90 degree bend is in the metal).
I decided to remove this plastic as I noticed some VERY small traces of rust forming between. It seems that they ALL had an oval bottom cut out separately and heat-shrink just inside the bottom of the tubing. These capacitors are oval in cross-section, like an HVAC app. (air conditioner type etc.) I think from the beginning, Aerovox had an idea that the thinness of this metal around the bottom of the perimeter was a bit on the "too-thin" side, but good enough for any normal use!
I have removed the plastic (no writing) and let the bottom ovals fall off. On the worst of them it seems that only a smear of oil (couple of fingertips) was on the bottoms--not nearly enough to form a drop that would fall off!
I think they could be perfectly good if lightly (VERY-lightly surface-cleaned wiped and then dipped to a level just above the bottom "seam" (which all appears to be a solid single piece). The ratings are mostly 196uF @ 2300V dimensions are ~ 1-1/2" TH. x 2-3/4" WD. x 6" HT about 1 pound ea.
The question is: After cleaned and dried: perhaps with emery cloth. WHAT CAN I DIP THE EXPOSED LOWER METAL IN FOR LEAK-PROOFING? I have thought maybe some kind of tar-based thick liquid, but really need help here!! I was even thing of that TV ad---'FLEX-SEAL' or whatever.
THANKS FOR EVERYTHING GUYS!!
Re: RESCUING PULSE CAPACITORS
Sulaiman, Thu Mar 21 2019, 12:54PM
Polyester resin is resistant to vegetable and mineral oils so I'd consider a car repar type of kit;
fibreglass matting, resin, catalyst etc... check your local car repair shop or Amazon or eBay.
The plastic disc at the bottom of the capacitor was probably for electrical insulation/isolation.
Sulaiman, Thu Mar 21 2019, 12:54PM
Polyester resin is resistant to vegetable and mineral oils so I'd consider a car repar type of kit;
fibreglass matting, resin, catalyst etc... check your local car repair shop or Amazon or eBay.
The plastic disc at the bottom of the capacitor was probably for electrical insulation/isolation.
Re: RESCUING PULSE CAPACITORS
MRMILSTAR, Thu Mar 21 2019, 03:42PM
I wouldn't encase it in anything. The problem with a sealant is the same as undercoating on a car. If any moisture does happen to find its way under the sealant, it will start rusting and you will never see it until it rusts completely through. I would just thoroughly clean the metal, prime it, and paint it with Rustoleum or something similar. That way if any rust appears you can attend to it immediately and then just repaint it. If you do a good paint job and don't let moisture collect on the surface you shouldn't have any further problems.
MRMILSTAR, Thu Mar 21 2019, 03:42PM
I wouldn't encase it in anything. The problem with a sealant is the same as undercoating on a car. If any moisture does happen to find its way under the sealant, it will start rusting and you will never see it until it rusts completely through. I would just thoroughly clean the metal, prime it, and paint it with Rustoleum or something similar. That way if any rust appears you can attend to it immediately and then just repaint it. If you do a good paint job and don't let moisture collect on the surface you shouldn't have any further problems.
Re: RESCUING PULSE CAPACITORS
Signification, Fri Mar 22 2019, 08:27AM
...going up the learning curve...I 1st used a very mild action with a circular drill wire stripper--got carried away a bit at the finish (the edge) and noticed a slight film of oil emerging.. I will have to use the very fine steel wool on the edge. That was now! I taped a paper towel with rubber bands and set the cap upside down. Will see how it looks tomorrow. Any suggestions if the film persists on the bottom? It's all shiny clean, BTW. Ready for the Rust-Oleum Primer and paint!? Perhaps ~ three scrubbing, rubbing & quick primer apps will 'overtake' any oil.
Signification, Fri Mar 22 2019, 08:27AM
...going up the learning curve...I 1st used a very mild action with a circular drill wire stripper--got carried away a bit at the finish (the edge) and noticed a slight film of oil emerging.. I will have to use the very fine steel wool on the edge. That was now! I taped a paper towel with rubber bands and set the cap upside down. Will see how it looks tomorrow. Any suggestions if the film persists on the bottom? It's all shiny clean, BTW. Ready for the Rust-Oleum Primer and paint!? Perhaps ~ three scrubbing, rubbing & quick primer apps will 'overtake' any oil.
Re: RESCUING PULSE CAPACITORS
MRMILSTAR, Fri Mar 22 2019, 03:09PM
Find the source of the leak and apply a small amount of JB Weld or similar 2-part epoxy around the hole in order to seal the leak. I would then prime and paint everything. Obviously, the surface must be completely clean and free from oil before any application of JB Weld, primer, or paint.
MRMILSTAR, Fri Mar 22 2019, 03:09PM
Find the source of the leak and apply a small amount of JB Weld or similar 2-part epoxy around the hole in order to seal the leak. I would then prime and paint everything. Obviously, the surface must be completely clean and free from oil before any application of JB Weld, primer, or paint.
Re: RESCUING PULSE CAPACITORS
Patric, Fri Mar 22 2019, 04:40PM
I use paraffin.
Patric, Fri Mar 22 2019, 04:40PM
I use paraffin.
Re: RESCUING PULSE CAPACITORS
johnf, Fri Mar 22 2019, 05:28PM
i presume the can is tin plated steel
if so just solder it up
if aluminium go withthe jb
johnf, Fri Mar 22 2019, 05:28PM
i presume the can is tin plated steel
if so just solder it up
if aluminium go withthe jb
Re: RESCUING PULSE CAPACITORS
MRMILSTAR, Fri Mar 22 2019, 05:59PM
Soldering will not work. The oil in the can will act as a heat sink and you will never get the can hot enough to flow solder. Even if you did, the oil will burn and possibly explode. Paraffin will not provide a suitable surface for painting.
If there is still a little oil after your capacitor has been upside down overnight, do the following. Prepare a small amount of JB Weld and have it ready for quick application. With the capacitor still upside down wipe around the leak with some acetone to remove ALL of the oil on the surface. Now, quickly apply some JB Weld to the spot. This will insure that the JB Weld is in contact with an oil-free surface. After the JB Weld cures you can then prime and paint. There are several types of JB Weld. I would use the JB Weld original formula. Another tip would be to place the capacitor in a cooler location for curing even though this increases the curing time. The reason is that you don't want the oil in the capacitor to expand from heat and push out of the hole while the JB Weld is curing which would contaminate the epoxy.
By the way, your experience with the plastic shrink-wrap tubing illustrates perfectly why you shouldn't encapsulate it. Moisture found its way in there somehow, possibly through condensation, and promoted corrosion because there was no way for it to dry out. With the water trapped in there, the metal just rusted away. Because of this mechanism just use enough JB Weld to plug the leak and no more.
MRMILSTAR, Fri Mar 22 2019, 05:59PM
Soldering will not work. The oil in the can will act as a heat sink and you will never get the can hot enough to flow solder. Even if you did, the oil will burn and possibly explode. Paraffin will not provide a suitable surface for painting.
If there is still a little oil after your capacitor has been upside down overnight, do the following. Prepare a small amount of JB Weld and have it ready for quick application. With the capacitor still upside down wipe around the leak with some acetone to remove ALL of the oil on the surface. Now, quickly apply some JB Weld to the spot. This will insure that the JB Weld is in contact with an oil-free surface. After the JB Weld cures you can then prime and paint. There are several types of JB Weld. I would use the JB Weld original formula. Another tip would be to place the capacitor in a cooler location for curing even though this increases the curing time. The reason is that you don't want the oil in the capacitor to expand from heat and push out of the hole while the JB Weld is curing which would contaminate the epoxy.
By the way, your experience with the plastic shrink-wrap tubing illustrates perfectly why you shouldn't encapsulate it. Moisture found its way in there somehow, possibly through condensation, and promoted corrosion because there was no way for it to dry out. With the water trapped in there, the metal just rusted away. Because of this mechanism just use enough JB Weld to plug the leak and no more.
Re: RESCUING PULSE CAPACITORS
Signification, Sat Mar 23 2019, 07:41PM
Thanks for all the help. I have cleaned and shined the bottom and ~3/4" above that (a label is there I don't want to disturb. I tightly covered the bottom with absorbent paper, and saw no signs of leak (even pressing). The next day, still dry. I just turned the cap upright and when I looked right back under it, I saw a wet spot. The hole on this one is not visible, many are much worse. I plan to dry it all again and use some of the suggestions mentioned. I just bought some Rust-Oleum primer and paint. With the minor leaks, I plan on using the Primer and paint and let dry upside down (with painter's tape covering the rest.
I also got the JB-Weld. I guess I just have to judge how I do the repair. Some caps have become a real mess (but I don't think as bad as it looks--just from being upright. They were all upright on a table which collected a fair amount of oil.
I plan to roughly dry them off, and position them upside down--I think this will stop any of the (slow) leaking.
I sure looks like, with all your suggestions, I will succeed; which means a lot to me. I will post the next observation.
YES, much rust is smeared inside the plastic almost to the top of the capacitors. Does anyone think there is any danger of water inside with the oil?
Thanks much again!!
YES, IT LOOKS LIKE THE PLASTIC WAS FOR INSULATING WITH NO REGUARD TO MOISTURE--WHICH CAN CAUSE SOME REAL DAMAGE.
EDIT:
Maybe i can get the caps dry (when upside down), apply the-JB Weld, make sure I see no moisture leaks when turned upright, and THEN if no leaks appear, apply the Rustoleum primer (let primer dry) and then the paint??
Signification, Sat Mar 23 2019, 07:41PM
Thanks for all the help. I have cleaned and shined the bottom and ~3/4" above that (a label is there I don't want to disturb. I tightly covered the bottom with absorbent paper, and saw no signs of leak (even pressing). The next day, still dry. I just turned the cap upright and when I looked right back under it, I saw a wet spot. The hole on this one is not visible, many are much worse. I plan to dry it all again and use some of the suggestions mentioned. I just bought some Rust-Oleum primer and paint. With the minor leaks, I plan on using the Primer and paint and let dry upside down (with painter's tape covering the rest.
I also got the JB-Weld. I guess I just have to judge how I do the repair. Some caps have become a real mess (but I don't think as bad as it looks--just from being upright. They were all upright on a table which collected a fair amount of oil.
I plan to roughly dry them off, and position them upside down--I think this will stop any of the (slow) leaking.
I sure looks like, with all your suggestions, I will succeed; which means a lot to me. I will post the next observation.
YES, much rust is smeared inside the plastic almost to the top of the capacitors. Does anyone think there is any danger of water inside with the oil?
Thanks much again!!
YES, IT LOOKS LIKE THE PLASTIC WAS FOR INSULATING WITH NO REGUARD TO MOISTURE--WHICH CAN CAUSE SOME REAL DAMAGE.
EDIT:
Maybe i can get the caps dry (when upside down), apply the-JB Weld, make sure I see no moisture leaks when turned upright, and THEN if no leaks appear, apply the Rustoleum primer (let primer dry) and then the paint??
Re: RESCUING PULSE CAPACITORS
MRMILSTAR, Sat Mar 23 2019, 08:16PM
Since it sounds like you are going to rely on the primer and paint by itself to seal some of the tiny leaks, I would find out how resistant your paint is to oil contact. Constant contact with oil may soften the paint. Its probably OK because engine paint doesn't soften even though there may be oil all over it. I know that the epoxy in JB Weld is quite resistant to oil after it has cured.
I wouldn't worry about any minute amount of water that may have gotten inside the caps. When they are upright, any water will sink to the bottom where it will not be in contact with the electrodes.
MRMILSTAR, Sat Mar 23 2019, 08:16PM
Since it sounds like you are going to rely on the primer and paint by itself to seal some of the tiny leaks, I would find out how resistant your paint is to oil contact. Constant contact with oil may soften the paint. Its probably OK because engine paint doesn't soften even though there may be oil all over it. I know that the epoxy in JB Weld is quite resistant to oil after it has cured.
I wouldn't worry about any minute amount of water that may have gotten inside the caps. When they are upright, any water will sink to the bottom where it will not be in contact with the electrodes.
Re: RESCUING PULSE CAPACITORS
Signification, Sat Mar 23 2019, 08:24PM
Sounds great, THANKS!! You may have missed the "EDIT" I added, so I will add it on here again now:
***********************************************
EDIT:
@MRMILSTAR:
Maybe i can get the caps dry (when upside down), apply the-JB Weld, make sure I see no moisture leaks when turned upright, and THEN if no leaks appear, apply the Rustoleum primer (let primer dry) and then the paint??
*************************************************
BTW: I have NEVER used rustoleum before this!
Signification, Sat Mar 23 2019, 08:24PM
Sounds great, THANKS!! You may have missed the "EDIT" I added, so I will add it on here again now:
***********************************************
EDIT:
@MRMILSTAR:
Maybe i can get the caps dry (when upside down), apply the-JB Weld, make sure I see no moisture leaks when turned upright, and THEN if no leaks appear, apply the Rustoleum primer (let primer dry) and then the paint??
*************************************************
BTW: I have NEVER used rustoleum before this!
Re: RESCUING PULSE CAPACITORS
MRMILSTAR, Sat Mar 23 2019, 09:22PM
Sounds like a good plan. I did miss the edit. I don't think that there is anything special about Rustoleum. I just know that it is a good quality spray paint. I am certain there are other brands equally as good.
MRMILSTAR, Sat Mar 23 2019, 09:22PM
Sounds like a good plan. I did miss the edit. I don't think that there is anything special about Rustoleum. I just know that it is a good quality spray paint. I am certain there are other brands equally as good.
Re: RESCUING PULSE CAPACITORS
Signification, Sat Mar 23 2019, 11:10PM
OK, I will follow this plan (JB-Weld, rustoleum primer/paint, and time). If anyone has any suggestions to add to it, take away from it, or modify the plan, please let me know. It will be a couple of days because of the other mess of very slippery, rusted caps (which are now just placed upside down in a box).
I should get to the first 'minor damaged' cap sooner. and post the results.
And YES, all the other oil-filled caps which did not have this kind of outer plastic construction seemed to dry out with no problems! This is certainly NOT a good way of enhancing insulation. I will try to think of an alternative.
Signification, Sat Mar 23 2019, 11:10PM
OK, I will follow this plan (JB-Weld, rustoleum primer/paint, and time). If anyone has any suggestions to add to it, take away from it, or modify the plan, please let me know. It will be a couple of days because of the other mess of very slippery, rusted caps (which are now just placed upside down in a box).
I should get to the first 'minor damaged' cap sooner. and post the results.
And YES, all the other oil-filled caps which did not have this kind of outer plastic construction seemed to dry out with no problems! This is certainly NOT a good way of enhancing insulation. I will try to think of an alternative.
Re: RESCUING PULSE CAPACITORS
johnf, Sun Mar 24 2019, 01:33AM
What you can not solder because of the oil
I have soldered many high voltage caps (plastic capacitors Inc and Maxwell pulse jobs, plus a few no name copies) to stop leaks favoured weapon is a pace soldering station with a BIG chisel bit with solder station set to 8 as hot as will go -killed spirits of salts as flux and 0.125 solder . I prefer this solution as the solder can not rust so the fix is permanent.
johnf, Sun Mar 24 2019, 01:33AM
What you can not solder because of the oil
I have soldered many high voltage caps (plastic capacitors Inc and Maxwell pulse jobs, plus a few no name copies) to stop leaks favoured weapon is a pace soldering station with a BIG chisel bit with solder station set to 8 as hot as will go -killed spirits of salts as flux and 0.125 solder . I prefer this solution as the solder can not rust so the fix is permanent.
Re: RESCUING PULSE CAPACITORS
Signification, Sun Mar 24 2019, 10:55AM
@johnf,
I am not sure of the soldering station wattage and tips you are speaking of. Can you give more information such as temperature, more specific tip size, etc. The largest iron I have is 60W. My two 325W guns were destroyed.
Signification, Sun Mar 24 2019, 10:55AM
@johnf,
I am not sure of the soldering station wattage and tips you are speaking of. Can you give more information such as temperature, more specific tip size, etc. The largest iron I have is 60W. My two 325W guns were destroyed.
Re: RESCUING PULSE CAPACITORS
johnf, Sun Mar 24 2019, 06:39PM
Pace Sensatemp PS90 I presume the 90 is watts
set to 850F approx 450C
Be ye warned that using killed spirits of salts does eat up soldering iron tips but a $10 tip is worth rescuing a rare expensive capacitor
johnf, Sun Mar 24 2019, 06:39PM
Pace Sensatemp PS90 I presume the 90 is watts
set to 850F approx 450C
Be ye warned that using killed spirits of salts does eat up soldering iron tips but a $10 tip is worth rescuing a rare expensive capacitor
Re: RESCUING PULSE CAPACITORS
Signification, Sun Apr 07 2019, 03:22PM
Thanks all.
BTW, Did I mention that there were three sizes of caps that I called small, medium, and large, + one 300lb pole pig?
I tilted over the large ones and it looked like I better treat then too! So I have some supplies and will get to work. There are 98 smalls, 10 mediums, and about 10 large caps--I sure don't want to lose them. I did manage to get the drone caps up high in time!!!
I just may be able to save then all, THANKS TO YOU GUYS!!! One more thing: I have a lot (~75) MOTs that need help...perhaps just a good heating (with tar or paraffin) will help? I do think the paraffin will go even with no load though! My favorite of the small xfmrs is a modified (15kV @ 60mA) NST from which I de-tarred and removed some shunts...got 25kVDC @ 70+mA from it, with the help of a hefty variac and a FWB.
Signification, Sun Apr 07 2019, 03:22PM
Thanks all.
BTW, Did I mention that there were three sizes of caps that I called small, medium, and large, + one 300lb pole pig?
I tilted over the large ones and it looked like I better treat then too! So I have some supplies and will get to work. There are 98 smalls, 10 mediums, and about 10 large caps--I sure don't want to lose them. I did manage to get the drone caps up high in time!!!
I just may be able to save then all, THANKS TO YOU GUYS!!! One more thing: I have a lot (~75) MOTs that need help...perhaps just a good heating (with tar or paraffin) will help? I do think the paraffin will go even with no load though! My favorite of the small xfmrs is a modified (15kV @ 60mA) NST from which I de-tarred and removed some shunts...got 25kVDC @ 70+mA from it, with the help of a hefty variac and a FWB.
Re: RESCUING PULSE CAPACITORS
Signification, Fri May 03 2019, 05:43AM
Hi all,
I will be finished with the capacitor repair process (WHAT A LOT OF WORK!) by the end of the weekend. I will post the results when all primer+paint (rustoleum) has set, the final capacitance is measured, and they are determined to be leak-proof. The last dozen were done with rustoleum primer two coats of 'flex-seal'. The rest with three coats of primer + two coats paint (all rust-oleum).
I had about 100 caps, however, two of them were so rusted (they were left outdoors for months) that they looked un-fixable. So I threw them out. Most were 196uF @ 2300Vdc and 115uF # 2300Vdc. I did find one 50uF in the bunch.
They look sonething like this:
(I hope that came out)
Signification, Fri May 03 2019, 05:43AM
Hi all,
I will be finished with the capacitor repair process (WHAT A LOT OF WORK!) by the end of the weekend. I will post the results when all primer+paint (rustoleum) has set, the final capacitance is measured, and they are determined to be leak-proof. The last dozen were done with rustoleum primer two coats of 'flex-seal'. The rest with three coats of primer + two coats paint (all rust-oleum).
I had about 100 caps, however, two of them were so rusted (they were left outdoors for months) that they looked un-fixable. So I threw them out. Most were 196uF @ 2300Vdc and 115uF # 2300Vdc. I did find one 50uF in the bunch.
They look sonething like this:
(I hope that came out)
Re: RESCUING PULSE CAPACITORS
Signification, Sun Jul 07 2019, 07:08PM
In over 100 leaking caps, most leaked through non-obvious ways. Some through visible holes at the bottom corners--especially when squeezed. The latter, I used J-B weld, and ALL with the bottoms 3/4" with rustoleum. 4-coats primer + 2-coats paint. Used a bit of 'flex-seal on a couple, maybe overkill, but in over 3 months and NO LEAKS! Many used! THANKS GUYS!!!!
Signification, Sun Jul 07 2019, 07:08PM
In over 100 leaking caps, most leaked through non-obvious ways. Some through visible holes at the bottom corners--especially when squeezed. The latter, I used J-B weld, and ALL with the bottoms 3/4" with rustoleum. 4-coats primer + 2-coats paint. Used a bit of 'flex-seal on a couple, maybe overkill, but in over 3 months and NO LEAKS! Many used! THANKS GUYS!!!!
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