Lead-free solder is such a PITA (rant/whinge)

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Have a gas wall oven with two supply gas valves/solenoids in series -
safeguard against one sticking open, one presumes.  Coils are
connected in parallel.  These are situated on TOP of (doh!) the oven
shell - not the brightest move but placed there no doubt for service
access - tick.

Original coils were by Goyen Controls, and lasted 20 years before one
failed.  By then Tyco had moved in (TYCO=TakeYourCompanyOver).  Tyco
replacement lasted about 18 months,during which time the other Goyen
coil died.  Ever since, the Tyco replacements (at ~$A70 each) have
lasted about 18 months.

It transpires that about the time I got the first Tyco coils, they had
transitioned the Oz factory to ROHS.  Now these coils are 240VAC so
the winding wire is as fine as all getout.  How is it terminated?  Ah,
it is SOLDERED to 1/4" QC/Faston terminals which protrude out through
the epoxy/"thermoplastic" former.  Evidently thermal cycling is
causing solder joint failures, but the necessary surgery with a Dremel
to reach the joint would - apart from compromising the overall
integrity and insulation characteristics - probably take out untold
turns of the coil itself, rendering the operation pointless.

Re: Lead-free solder is such a PITA (rant/whinge)

I should add that coil failure mode is open cct when hot - as in,
half-way through cooking a meal - and continuity returns when cooled
to near room temperature.  Also that replacing the wall oven comes
with a penalty of having to carry out significant kitchen mods.
Grrrr!

Re: Lead-free solder is such a PITA (rant/whinge)
wrote:

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Grid independence, I'm sure.

We went with gas because the power system here was flakey and could go
out for hours at a time.  Our gas hotplates have one 'D' cell
providing ignition, while the wall oven does require AC for the
igniter/flame-monitor/gas-control (BUT that's all able to be jury
rigged off a PC UPS in about a minute flat) so cooking during a
blackout is a non-event.

Re: Lead-free solder is such a PITA (rant/whinge)

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I think you can still buy Goyen valves, solenoids, and rebuild kits:
<https://www.baghouseamerica.com/dust-collector-parts/goyen-genuine-parts/
<http://cleanairsystems.com/products/solenoid-valves-for-air-gas-and-water.html
<http://www.uniairproducts.com/uap/goyen/goyen.shtml
etc...


--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Lead-free solder is such a PITA (rant/whinge)
wrote:

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BHA didn't seem to have the coils.  The other two are Pentair outlets
(Pentair is slightly majority Tyco owned) and will be selling the same
parts I currently repeat purchase (*) from Pentair/Tyco here in Oz.
These are surprisingly made locally (Sydney) as they were in the "old"
Goyen days.  It's fair bet that any I source nowadays will have the
ROHS curse on them.

I did some Dremel surgery today on one of the dead coils.  Despite
having differing copper resistivity figures at hand (no consequence)
and the wire diameter testing my micrometer, from known ohms of a good
coil and some spreadsheeted maths I guesstimate it is 33 or 34AWG.

Maybe Chris' suggestion is worth investigating.  The surgery wasn't
enough to find the dodgy termination, but thicker winding wire *may*
get a better joint.

(*) I date-mark the parts as they go in.  The one that just failed was
one day short of 18 months, on an oven that gets used about once a
week on average.

Re: Lead-free solder is such a PITA (rant/whinge)
says...
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Have you checked the voltage at the coils ?  No more than you are using  
that oven it seems there may be something more than just the coils going  
on.

I have had very little experiance with the lead free solder, but as it  
melts at a higher temperature it would seem to me that it should be  
beter for the simple joints as far as  the thermal cycling.



Re: Lead-free solder is such a PITA (rant/whinge)
On Thu, 8 Sep 2016 10:08:04 -0400, Ralph Mowery

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The line voltage is in the range 240-242, the coils are embossed 240V.

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In my relatively limited lead-free solder experience (just the service
bench - where I always use leaded solder for rework)> the joints seem
to develop a dry crystalline characteristic over time when in
situations subjected to thermal cycling.  IMHO it isn't a melting
point issue but an alloy characteristic.

Re: Lead-free solder is such a PITA (rant/whinge)

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Ok, I see you've done your homework.  Yes, ROHS is epidemic
everywhere.

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That's rather thin and could easily fuse.  According to the wire
table:
<https://en.wikipedia.org/wiki/American_wire_gauge
#34 will fuse at 5A.  What do you measure for coil DC resistance?

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I agree.  Heavier wire may solve or delay the problem.  Methinks it
would be interesting to know what temperature the solder joint is
experiencing.  A thermistor or thermocouple glued to as close to the
solder connection as possible might provide some interesting numbers.
If the position of the solenoid above the oven is the problem, that
will show it.  Perhaps adding a metal heat shield between the coil and
oven?

For fusing, perhaps a small value resistor or "surgistor" in series
with the coil might reduce the peak current enough to let the thin
wire survive.  With an inductor, there should NOT be an inrush peak,
but I'm thinking some kind of glitch, spike, or peak might be arriving
via the 240VAC line.

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Lead-free solder is such a PITA (rant/whinge)
wrote:

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Indeed.  It would be handy to have a thermoprobe with logging on it.
Note to self: see where I can borrow one.

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The dual valve mechanism is bolted to the oven.  The coils (see ebay
item# 322017672259 for the ones we "consume" - but at a much better
price than he's asking ...) sit over the metal housing which encloses
the valve plunger (armature) and has a metal spacer each end for
location and ?thermal separation?.  So it would be necessary to
elevate the entire incoming gas pipe/valve syhstem to relieve
conducted heat to any significant degree.  And if it IS the cycling -
rather than the actual temperature reached - which causes the failures
then reducing the latter may achieve nothing.

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Dunno.  Could do (but it'd be 18 months before I'd know if it made a
difference).

Re: Lead-free solder is such a PITA (rant/whinge)
wrote:

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Missed that bit.  Around 1600 ohms.

Re: Lead-free solder is such a PITA (rant/whinge)

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Assuming 240VAC, that's:
  P = E^2 / R = 240Vrms^2 / 1600 = 36 watts
That's way too high dissipation for a solenoid valve.  
Are you sure those are 240VAC solenoids and some other AC voltage? Are
the solenoids run by 240VAC or some other voltage?  

Also, could you check the eBay listing number?  I want to see the coil
specs.  Nothing found:
<http://www.ebay.com/sch/i.html?_nkw32%2017672259



  
--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Lead-free solder is such a PITA (rant/whinge)
snipped-for-privacy@cruzio.com says...
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Jeff I think you are mixing up the AC and DC power formulas.  

I am sure the impedance of the coil at 60 Hz is more than the DC  
resistance.

That would make the wattage less than what you have calculated using a  
DC equation.

A quick check of the Goyen catalog shows they draw about .05 to .07 Amps  
depending on the coil at 240 volts.
That is around 10 to 16 watts.  The DC resistance of the coils was not  
given.  The coils on many of the valves can be changed to several  
voltages.


Re: Lead-free solder is such a PITA (rant/whinge)
On Fri, 9 Sep 2016 15:37:02 -0400, Ralph Mowery

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The DC resistance averages around 1600 ohms.  According to my calcs
there are around 4700 turns in the coil, so at 50Hz the impedance
incorporates a significant reactance.  The coil (obviously) has a
ferrous valve plunger in its core.

They are marked 240VAC 50Hz (= our supply here in Oz) and the one I
attacked with the Dremel is marked 5W.

Re: Lead-free solder is such a PITA (rant/whinge)
On Fri, 9 Sep 2016 15:37:02 -0400, Ralph Mowery

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Oops.  Y'er right.  
Big rush -> No time -> No brain -> No excuse.

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Ok, that's better and less than the 5A fusing current for #34 awg.

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10 - 16 watts might get the coil quite warm if energized continuously.
Probably not enough to melt solder, but certainly will add a few
degrees to the heat from the furnace.

I don't think it's overheating from the furnace or the warm coil.  It
will get hot, but not enough to melt solder.  Since various other
solenoids have failed in the same manner, I don't think the failures
are caused by some kind of soldering defect.  The long time that it
takes to fail might be the copper wire slowly dissolving in the
solder.  However, my limited experience indicates that most of the
damage occurs immediately during soldering, not many months later.
With a 5A fusing current and the rather large inductance of the
solenoid, I don't see a high current "surge" fusing the #34 wire.  

Offhand, I was thinking something else might be happening here.
Something like a sharp edge on the solenoid terminal slowly cutting
its way through the copper wire every time the solenoid is energized.
It might be 50 Hz vibration work hardening of the wire causing
embrittlement.  However, these are unlikely to have also occurred in
the other replacement solenoids, that also failed.  It might be the
difference in coefficient of thermal expansion between the epoxy and
the copper wire.  Usually, some paper or tape wrapping will provide
room to expand, but again it would be an amazing coincidence if the
same problem appeared in a competetors solenoid.

That leaves external influences, such as line voltage glitches and
surges.  Get your Dranetz power quality monitor/logger back, borrow
something, or just setup a data logger on the AC line.


--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Lead-free solder is such a PITA (rant/whinge)
wrote:

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Sorry, that should be oven, not furnace (in multiple places).

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Lead-free solder is such a PITA (rant/whinge)
snipped-for-privacy@cruzio.com says...
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WE had hundreds of that brand where I worked and some were pulsed every  
30 seconds or so and some were almost always on.  Hardly any problems  
with the coils.  The ones that were on most of the time ran hot enough  
that you would almost burn your hand. Some of them were where the room  
temperature was over 100 deg F.  The plant made polyester and the  
process required about 300 deg C of heat.  I said room, but those areas  
were not occupied except to check on the equipment from time to time.

 Most problems were either the rubber disk wearing out or the plunger  
enlarging due to all the beating they take or the spring wearing out.  
The plunger is enclosed so no way for it to touch the coil form.  While  
it could be something in the coil, I would think that as many that he  
changed out it must be something external.  

One other thing, is the coil all the way seated on where the plunger is  
?  If not it could be drawing enough current to burn out the wire.  We  
often left the coil hooked up to the conduit and just changed out the  
mechanical part.  Mainly did that to keep from having to go to another  
floor and find the power source for the coil.    Found that we needed to  
stick a large screwdriver or other item in the core of the coil or a  
fuse would blow or the coil would burn out.

Re: Lead-free solder is such a PITA (rant/whinge)
On Sat, 10 Sep 2016 10:25:09 -0400, Ralph Mowery

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Ralph, should I presume that was with pre-ROHS vintage coils?  As I
mentioned in my O/P, the original pair (which were pre-ROHS) both
lasted two decades.  Subsequent ones were 15-18 months AND the oven
gets less use nowadays as the kids migrate outwards.  Not a
statistically significant sampling for some, but sufficiently damning
from where I stand/sit.

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We haven't had the moving parts show any issues, just coils.

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Nothing external has changed, except our supply voltage has been
"harmonised" with rest-of-Oz i.e. reduced from the original 254V rms
down to 240V rms.

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Appreciate the question.  It is seated down properly.  The frame which
sits over the coil/valve assembly as part of it is actually a snug fit
(you need to slide the coil into it and align the holes, it's a press
fit) and then the frame is held down over the valve plunger "cylinder"
and screwed down.  No unintended magnetic/air gaps.

There is also a "spacer" pressed into each end of the coil bobbin the
ensure it is located correctly (radially).

Pics of the valve assemblies in situ:

http://imgur.com/xGlio51
http://imgur.com/3NB4ALX

and of the coil post-Dremel (*):

http://imgur.com/An9XCk8
http://imgur.com/wH0l3eP

(*) I needed effective bobbin length/diameters to calculate turns and
hence deduce a credible wire gauge to match the known DC resistance.

Re: Lead-free solder is such a PITA (rant/whinge)
says...
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Most of them were from days before the lead free junk.  

 When you pulse them about once every 60 seconds they do take a beating  
after 5 or 6 months.  When they were first used in that application  
there were some complaints about how fast they were wearing out.  
However if you calculate the number of cycles , they lasted many more  
cycles than specified for by the manufactor.

You mentioned something about lowering the voltage from about 250 to 240  
volts. Have you checked to see if the voltage is still around 240 ?





Re: Lead-free solder is such a PITA (rant/whinge)
On Sun, 11 Sep 2016 11:00:01 -0400, Ralph Mowery

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It is.

<history>Western Australia's grid voltage was 254(+/-6%) as a result
of the move from 40hz to 50Hz a long time back.  Actually the single
phase voltage was never *defined*, rather it was 440V phase-phase
(3-phase system).

Although it was/is not interconnected with the eastern states' grid
(which was 240V as far back as the landing or the Ark), pressure to
fall in line was brought to bear, particularly as appliances etc made
for the 240V system suffered reduced lifetime at 254V, although there
were incandescent lamps made for 250V if one hunted them down.

So the supply authority relented and cranked the grid back to 240V
where it has been ever since as a statutory requirement.</history>

Re: Lead-free solder is such a PITA (rant/whinge)
says...
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Fine on the history of Australia's grid.  Too bad all the coutries of  
the world did not set one standard to go by.  Most of the US seems to be  
around a split system for the homes of 120 and 240 volts at 60 Hz.  
There are some places that may have other odd values.  

I worked in a large plant and most of the larger equipment was 480 volts  
3 phase.  The smaller equipment and offices were set for 120 or 240  
volts.  

Then we built a building of about 6 floors and while another and I were  
calibrating some 3 phase heaters we could only get about 380 volts out  
of the controler.  Checked the incomming voltage and that was what we  
had.  Seems that the engineer had bought some equipment from a country  
that required 380 volts.  We were not told of this to start with and  
found out about it when we were checking out the equipment.  

Years ago in the US it seems that the standard was 110 and 220 volts,  
then 115 and 230, now it is 120 and 240 volts. I hae a digital voltmeter  
on my ham radio desk that stays on all the time.  It is usually around  
122 volts, but I have seen it between 118 and 124 volts depending on the  
time of the year and day.  I know it is accurate as I checked it against  
some meters at work that were calibrated by a lab to the government  
standrds.


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