Stones Posted August 19, 2017 Share Posted August 19, 2017 As a consequence of heavy rainfall: the air pump in our Sewage Treatment Plant was submerged with surface water yesterday. Having removed the pump and replaced it, I have stripped down the submerged pump Most of the component parts, cleaned, will of course simply dry out and be in working order when reassembled. I am however unsure if I should be doing anything to the key electrical component: Is there anything I should or could do? Link to comment Share on other sites More sharing options...
dpmiller Posted August 19, 2017 Share Posted August 19, 2017 rinse with distilled water before drying completely. Link to comment Share on other sites More sharing options...
Stones Posted August 25, 2017 Author Share Posted August 25, 2017 I've now reassembled the pump, but other than the alarm light illuminating, no sign of life. I'm wondering whether the windings are still damp. A quick read online suggests drying the motor (stripped of diaphrams etc) out in a low temp oven. The other alternative would be a hot box using a fan heater, again with the intention of heating the motor up enough to drive out any moisture. Thoughts? Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 25, 2017 Share Posted August 25, 2017 Have you checked and compared the two coils with a multimeter? Do the MIs state the correct values for them? Link to comment Share on other sites More sharing options...
Stones Posted August 25, 2017 Author Share Posted August 25, 2017 No, neighbour has a multimeter I can borrow, although not sure what I would be checking Link to comment Share on other sites More sharing options...
Onoff Posted August 25, 2017 Share Posted August 25, 2017 We used to regularly take motors off site and dry them in the oven at home. Just watch the plastic doesn't melt. If a tiny bit damp when you stick a "megger" on them you can see them "dry out" as you whack 500/1000V thru them. I wonder if the "iPhone" trick would work. Sling it in an airtight bag with some dry rice to absorb the water? Link to comment Share on other sites More sharing options...
dpmiller Posted August 25, 2017 Share Posted August 25, 2017 I think it'd still work if damp, but your RCD wouldn't like it. IIRC those pumps have some kind of safety contact that breaks if there's a problem with the diaphragm or springs; best check that out with the DMM too when you're probing the coils. Link to comment Share on other sites More sharing options...
Stones Posted August 25, 2017 Author Share Posted August 25, 2017 Well, I decided to take it apart again and reassemble. Plugged back in and its working once more. Currently on test in the garage. Link to comment Share on other sites More sharing options...
Onoff Posted August 25, 2017 Share Posted August 25, 2017 27 minutes ago, Stones said: Well, I decided to take it apart again and reassemble. Plugged back in and its working once more. Currently on test in the garage. Didn't know you were Russian: 2 Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 26, 2017 Share Posted August 26, 2017 19 hours ago, Stones said: No, neighbour has a multimeter I can borrow, although not sure what I would be checking It would have been resistance across the live and neutral of each coil winding to see if they matched, or if one was a short / open circuit ( aka dead ). Nee botha lad, you've accidentally fixed it . Link to comment Share on other sites More sharing options...
Onoff Posted August 26, 2017 Share Posted August 26, 2017 Worth taking the resistance of the coils when you know it's working for next time! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2017 Share Posted August 26, 2017 Bear in mind that some of these pumps have a diode in series with the coils, in order to reduce the operating frequency from 50 Hz to 25 Hz. This means that, depending on where the diode is, that you may get an odd resistance reading on a multimeter, and the resistance may appear to change between one multimeter and another (because the diode forward resistance will depend on the test voltage and current that the meter uses in resistance mode). I've yet to strip and check the Secoh to see if it has diodes, and if so, where they are, but it's something I need to get around to doing in the next few weeks, as I pulled it out and fitted the spare, with the intention of servicing the old one, fitting new diaphragms etc and putting that "back into stock" as a spare. When I do I'll try and remember to post the details here, for reference. Link to comment Share on other sites More sharing options...
ProDave Posted August 26, 2017 Share Posted August 26, 2017 Not sure how a diode halves the frequency? the waveform is still 50Hz but now somewhat lumpy. I can see it as a crude way to reduce power, not one the electricity suppliers would like. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2017 Share Posted August 26, 2017 (edited) 37 minutes ago, ProDave said: Not sure how a diode halves the frequency? the waveform is still 50Hz but now somewhat lumpy. I can see it as a crude way to reduce power, not one the electricity suppliers would like. You're right, I was wrong - brain fade. The one I've already had apart (a smaller one I was playing about with) used a diode in series with each coil, and I'm guessing this is to create a crude pulse, followed by a pause when the coil is de-energised (because of the diode blocking the other half wave), that allows the armature to move back via the diaphragm springs. Without the diode in series with the coils, the armature would probably just stay at one end, rather like a contactor. Edited August 26, 2017 by JSHarris Link to comment Share on other sites More sharing options...
dpmiller Posted August 26, 2017 Share Posted August 26, 2017 No, it would attempt to shuttle at 50Hz and make a horrendeous noise. Contactors, solenoid valves and the like "stick" either because the laminations form a complete coil when closed or there's a "shading ring" acting as a second coil of sorts. Two diodes give you that 25Hz pulse and the diaphragms damp it sufficiently that it isn't clattering off endstops. Link to comment Share on other sites More sharing options...
ProDave Posted August 26, 2017 Share Posted August 26, 2017 If the armature was a permanent magnet, it would shuttle back and forth at 50Hz with just a simple coil energising the armature. I would have thought they would have designed the mechanics to be resonant at 50Hz so it would shuttle back and forth at 50Hz very efficiently. Any other mechanical resonant frequency and it will need more power to force it to move at an unnatural frequency. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2017 Share Posted August 26, 2017 (edited) The armature in the one I took apart (a smaller pump that I thought might be able to do the job) was just a bit of steel or iron. I would guess that a magnet would end up being demagnetised by the coils, as we used to have a tool de-magnetiser that was just a big coil with an open gap in the core, into which you could insert tools and then slowly pull them away to remove any residual magnetism. There were soft limit stops at either end of the one I stripped, intended to prevent the armature travelling too far and over-stressing the diaphragm as much as reduce noise, I think. There was also a switch, that would be operated if the armature moved too far off-centre, that turned off the pump. I have a feeling that the switch was there as a fail-safe in the event of the support springs breaking. EDITED: SEE POST BELOW THAT CORRECTS SOME INFO ABOUT THE SECOH PUMPS Edited August 26, 2017 by JSHarris Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2017 Share Posted August 26, 2017 OK, I've just pulled the cover off the old pump and started to take it apart. This is a Secoh JDK-60, without the alarm switch (the newer JDK-60 I used to replace this a couple of weeks ago has an alarm light on the top, so I assume also has a switch, like the small unit I stripped a couple of years ago). First off, there is no obvious sign of diodes inside this Secoh pump, unlike the Hailea pump that I stripped previously. Secondly, the armature inside the Secoh pump does seem to be magnetic, again, unlike the Hailea pump. I can see from just looking at the top of the core unit of the Secoh JDK-60 that the two coils are directly wired in parallel, with no diodes. I'll carry on stripping it down and replacing the diaphragms, and if I spot anything else that differs from the Hailea I'll edit this post. As a word of caution, it seems that not all of these pumps work on the same principle, so generalising about them may be unwise! Link to comment Share on other sites More sharing options...
Gone West Posted August 26, 2017 Share Posted August 26, 2017 2 hours ago, JSHarris said: There was also a switch, that would be operated if the armature moved too far off-centre, that turned off the pump. I have a feeling that the switch was there as a fail-safe in the event of the support springs breaking. The switch is there because when a diaphragm breaks the armature ends up offcentre and the switch turns on the warning lamp. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2017 Share Posted August 26, 2017 Thanks @PeterStarck The Secoh JDK-60 that I've just finished putting back together doesn't have the alarm light, nor does it have the switch assembly that detects that the armature is off-centre. It's the one that was supplied with the treatment plant, so is around 4 years old. Externally it looks exactly the same as the new one, except it doesn't have the small red alarm light on the top of the case. The good news is that replacing the diaphragms is pretty easy on the Secoh pump, all told it took around half an hour, and that's with me having to refer to the instructions. Overall, the pump seems to be a pretty well-made bit of kit inside. Nice quality die-cast alloy housing and parts and everything screwed together with decent quality screws. I didn't completely strip the unit down, but just removed the cover, then the valve housings on either end and unbolted the old diaphragms and fitted the new ones. Both the old diaphragms looked OK, with no obvious sign of wear, so I might just go a bit longer before replacing the ones in the new pump I've just fitted. Link to comment Share on other sites More sharing options...
Gone West Posted August 27, 2017 Share Posted August 27, 2017 15 hours ago, JSHarris said: The Secoh JDK-60 that I've just finished putting back together doesn't have the alarm light, nor does it have the switch assembly that detects that the armature is off-centre. It's the one that was supplied with the treatment plant, so is around 4 years old. Externally it looks exactly the same as the new one, except it doesn't have the small red alarm light on the top of the case. I'm a bit confused, my Secoh EL100C which is seven years old has a warning light switch and the warning light is remote from the pump. Are you saying the Secoh JDK series, which replaced the EL series, originally didn't have a warning light switch but now does and that the warning light is on the top of the pump? If so buying a second hand Secoh JDK pump you need to be aware of the differences. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 27, 2017 Share Posted August 27, 2017 1 minute ago, PeterStarck said: I'm a bit confused, my Secoh EL100C which is seven years old has a warning light switch and the warning light is remote from the pump. Are you saying the Secoh JDK series, which replaced the EL series, originally didn't have a warning light switch but now does and that the warning light is on the top of the pump? If so buying a second hand Secoh JDK pump you need to be aware of the differences. I'm not sure when the change was made, but the original pump was supplied in 2013 with the treatment plant, and is marked JDK-60, and has the same green lid and off-white case as the new one. The old one has no alarm light, nor separate box. The alarm unit that the treatment plant came with was made by another company, and has a pressure switch plumbed into the air line to the tank and a float level switch to sound an alarm if the level in the pump chamber rises too high (our system has a pumped outlet). The new pump, that I bought some time last year as a spare, has a red alarm light on the top of the cover. I haven't had that pump apart, as I just swapped it over with the old one a few weeks ago, in order to service the old one. Clearly there has been some internal change made to the pumps between the date that our original one was made and the date the replacement was made. It's possible that the original JDK-60 that I've just overhauled was made earlier than 2013, and may have been older stock. Link to comment Share on other sites More sharing options...
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