- Email: [email protected]
Heard on the hotline
Heard on the Hotline by Ted Mooney, P.E. Dial 201/838-0113from your modem at any time or fax 2011283-0766.
Z
zzapp! ! It looks like we struck a nerve when we brought up the subject of substitutes for hexavalent chromium in September’s column. As we mentioned last month, a large captive plater wrote to say he is successfully plating tools by the millions using a proprietary cobalt-based pro&s. Then a chromium plater/process supplier from the New England area wrote to tell us of their proprietary tungstennickel replacement for chromium, which they claim has a silver/chromium color, many of the advantages of chromium, and in some cases exhibits superior wear and corrosion resistance. Also, an industrial research’ laboratory in the Midwest reported that vacuum deposition of chromium nitride can produce a highly corrosion-resistant finish that is even harder and more wear resistant than chromium plating when properly planned and integrated into the product and production system. The suppliers of trivalent chromium plating processes didn’t weigh in specifically for this round, but they have certainly made numerous contributions to the literature. The times are changing, and may the best finish win. Meanwhile, rush to your keyboard and post something! Sure, we’re very encouraged to see lots of new callers to the Hotline, and the total number of messages posted pushing the 6,000 mark; but the number of finishing-related messages posted here, on the Internet, and on other services doesn’t yet approach l/l ,000 of 1 percent of the billions upon billions of electronic messages posted annually. Yet, per the Surface Finishing Market Research Boafd, we in the finishing industry represent 1% of America’s GDP. Trying to account for this discrepancy isn’t pleasing-let’s correct it instead of struggling to account for it.
RECTIFIER RIPPLE Today we had a chance to look at the ripple some industrial rectifiers put out under normal loads. By normal I mean not the highest rated output, but anywhere from 30-80% of their capacity. I was shocked to record numbers as high as 50%. The lowest reading we obtained was 17%! Is that normal? Has anybody else looked lately at their rectifiers in terms of ripple? What kindsof filters are available for units running at several hundreds or thousands of amperes? Berl Stein, Plating Research, NJ. ‘Were the rectifiers you were studying tap-switch units? Then the ripple figures can’t be right, Berl. With simple diode rectification, and three phases 120” apart, even with no 52
capacitance or induction as voltage stabilizers, I don’t think the lowest instantaneous voltage can differ from the highest instantaneous voltage by more than about 10%. I’d have to look it up, or maybe Chris Smith knows the number right off hand. Ted Mooney, Finishing Technology, N.J. Most rectifier houses report 5% ripple when quoting, at least when I’ve spoken with them, which leads you to believe it comes with 5%. Ron Landrette, B+P Plating Supply, Conn. That’s what we thought, too. I’m not sure all the units we looked at were tap switches, but the majority certainly were. It looked as if the more you throttle a rectifier down to get>a lower voltage, the higher (relatively to the total voltage) the ripple gets. Then I checked the Metal Finishing Guidebook and Directory and found the following statement in it, “The ripple component of the output at full-rated power is nominally 5% rms of nameplate rating. This will increase as the thyristor’s phase angles are changed to reduce the output.” Doesn’t this sound a bit vague? How much does it go up? I don’t think we measured bogus numbers. Berl Stein, Plating Research, N.J. You sure have found an interesting topic! On tap-switch rectifiers, if all taps are set at the same position the ripple will be %%. This is true only if all of the diodes are operating, and all legs are passing current. With a powerstat, the ripple should be 25% throughout the range. Again, this assumes that all diode legs are functional. However, with a phase control rectifier, things are different. As you reduce the voltage, the ripple will increase. It can reach well above 50% at lower output voltages. The ripple voltage is also somewhat dependent on the output current level. Running a rectifier at less than full current will increase the ripple. But the main factor is the output voltage. All manufacturers specify 5% at full-rated output for their three-phase silicon-controlled rectifiers (SCR). If you want less than 5% ripple at full output, or want to controVlimit ripple at less than full output, you need a ripple filter. I have a chart that shows ripple measurement curves for a typical SCR operated from lO-100% output voltage and at lo%, 25%, 50%, 75%, and 100% load current. This chart is applicable to any six phase star rectifier. I will gladly fax or send it to anyone that requests it. Berl, if you were measuring a tap-switch or powerstat rectifier and got 17% ripple, I would guess that one of the six output legs was not conducting current. Most likely the
0 Copyright Elsevier Science Inc.
METAL FINISHING
. JANUARY
1995
diodes were open, but it could also be a connection. The same holds true for an SCR unit operated at full output. Hope this helps. Any questions, write or call. Whoops, forgot something! When I said *5%, it means 5% approximately, not f5%. Sorry if there was any confusion. Chris Smith, Process Electronics Corporation, N.C. Thanks for the detailed explanation, Chris. I would like to see the chart you mentioned; please fax it to me. I tried to find publications that studied the influence of ripple on electroplating in the Compendex Plus engineering database. The most important one is in Dutch - anybody out there speak Dutch? Talk to you later. Berl Stein, Plating Research, N.J. WASTE TREATMENT
Intro&wing the ProbeMa#ule “As soon as you see the Elcon$eter measuring instrundpnt, lot. And that’s exbctly t you get!!” ,(
I’ve designed a number of waste treatment systems over the years, and the single most troublesome step or component is the clarifier. I would like to design a system with dual filter presses instead of a clarifier. First, yes, there are difficulties-including the fact that while a clean filter can handle the flow rate easily, its flow capacity drops towards zero as it gets full, but it can be done. In fact, one of the major filter suppliers used to sell such systems as a packaged solution (perhaps they still do). I’m thinking of magnesium hydroxide as the primary precipitant because it builds a much thicker and less watery floe. The other thing I believe is that despite the complications and floor space required for a batch system, it may be the best way for the future. Not only for more effective reactions, but because you can take a sample of every batch and monitor and document the effluent quality. The effluent quality of a continuous discharge cannot be nearly as rigorously documented. Again, I recognize that batch systems can be complicated, what with the need for numerous level controls, keeping the pH probes wet, etc., but temporary excursions are getting too dangerous and costly. Any comments, suggestions, or discussion? Ted Mooney, Finishing Technology, N.J. Traditional thinking goes like this: by using a clarifier (a properly designed one), you substantially reduce the load on the filter by feeding into it more solids than water. Without one you are facing two problems: retention time necessary to develop the floe (will you use an intermediate holding tank for it to form?); and degree of dilution-your flow through the filter will have to be 10 or more times higher than with the clarifier. Do you really want to do it, Ted? Berl Stein, Plating Research, N.J. Well, the thing is, a clarifier provides no guarantee that floe is not burping up and going over the weir and right into the regulatory authority’s sample bottle. The filter press provides effluent that has passed through a filter cloth and is free of floe. I recognize that, theoretically, the floe can be forced through the filter cloth, but I’ve taken a number of samples of the filter press filtrate versus the clarifier overflow on a few systems and have never found the clarifier overflow to be cleaner than the METAL FINISHING . JANUARY 1995
& Parallel
Stan
I-.1
da
Telephone for a Brochure:
(810) 6m
0500
Fax: (810) 650 0501
(Toll Free 800-521-0635)
Circle
022 on ma&r
infomation card
53
filtrate. If someone feels my experience isn’t a proper sample of the universe, please tell me. Ted Mooney, Finishing Technology, N.J. Wastewater treatment is not really my bag, but batch treating is obviously a better system as all factors can be identified exactly for treatment. Floor space requirements, however, can be very large. Ron Landrette, B+P Plating Supply, Conn. SAFETY IN REFILLING ANODE BASKETS One safety violation that occurs in a lot of shops is people putting themselves in a dangerous position when filling anode baskets. Can we propose a safe method for filling anode baskets? I’d start by saying it may not be a good idea to put gaps between the tanks for anode service in an automatic line because my experience is that people will go into those gaps with the automatic equipment running. Ted Mooney, Finishing Technology, N.J. As far as anode baskets go, I’ve seen advertised, but never used myself, baskets that are fitted with a pickup of sorts. If this can be achieved, couldn’t a hoist pickup be adapted to lift the baskets to the unload station? Or maybe something could be designed to ride on the shuttle and operate from the aisle to fill baskets? Ron Landrette, B+P Plating Supply, Conn. Yes, some shops do lift the whole anode bar on the hoist and bring it to the end of the line for service. I would like
someone who doesn’t think that is a good idea to chime in here so we can understand the disadvantages, if any, of that approach. Ted Mooney, Finishing Technology, N.J. We used to lift anodes out of nickel tanks back in Russia and service them at the end of the line. Imagine how much solution was in the anode bags; no matter how long you let the stuff drain, you still had solution all over the place, to say nothing of the mess the’ anode sludge left behind. You almost need a dedicated area for all that. Besides, the hoists were definitely being overloaded while carrying the anode bars with baskets on them. How is all this for a disadvantage? Still, you might say this is a lesser evil than lost lives. Berl Stein, Plating Research, N.J. I must admit to walking around on the rims of tanks. It was absolutely stupid, and I won’t anymore under any condition, nor would I allow anyone else to do it if I were king. My only excuse, because that is what it is, was that I was young at the time, and thought I would live forever. To lift an anode basket and get all that junk in the tank through the bags is just more than I can take sometimes. There must be a better way. Tom Pullizzi, Team*Faraday, N.J. Ted Mooney is an independent consulting engineer based in Kinnelon, N.J. MF
Get MamaValveControlfar blastcleaning machines. rate control as easy as turning a knob-get low flow rate for delicate parts!
??Flow
??Control
costs, too! Save money on media due to less breakage!
* / ,, .*
.;‘,.’ ?‘ :+,‘,I,“,,J
\
The Magnavalve shot flow rate control will Improve your blast cleaning process and reduce waste by delivering the right amount of steel media to the blast wheel for every job... low flow rate setting for delicate parts, hlgh flow rate setting for large parts...or anywhere in-between. Magnavalve is in control. No moving parts to fall or wear out. Easllv. adaWed to remote Dre-sets. .
Electronics Inc. 1520 N. Main St. ?? Mishawaka, IN 46545 USA Telephone: I-800-832-5653 or (2191256-5001 Fax: (2191256-5222 _,.“.““__“...“I_...
54
. ...”
.
.
.
. “.._.._“._
METAL FINISHING . JANUARY 1995
Z
zzapp! ! It looks like we struck a nerve when we brought up the subject of substitutes for hexavalent chromium in September’s column. As we mentioned last month, a large captive plater wrote to say he is successfully plating tools by the millions using a proprietary cobalt-based pro&s. Then a chromium plater/process supplier from the New England area wrote to tell us of their proprietary tungstennickel replacement for chromium, which they claim has a silver/chromium color, many of the advantages of chromium, and in some cases exhibits superior wear and corrosion resistance. Also, an industrial research’ laboratory in the Midwest reported that vacuum deposition of chromium nitride can produce a highly corrosion-resistant finish that is even harder and more wear resistant than chromium plating when properly planned and integrated into the product and production system. The suppliers of trivalent chromium plating processes didn’t weigh in specifically for this round, but they have certainly made numerous contributions to the literature. The times are changing, and may the best finish win. Meanwhile, rush to your keyboard and post something! Sure, we’re very encouraged to see lots of new callers to the Hotline, and the total number of messages posted pushing the 6,000 mark; but the number of finishing-related messages posted here, on the Internet, and on other services doesn’t yet approach l/l ,000 of 1 percent of the billions upon billions of electronic messages posted annually. Yet, per the Surface Finishing Market Research Boafd, we in the finishing industry represent 1% of America’s GDP. Trying to account for this discrepancy isn’t pleasing-let’s correct it instead of struggling to account for it.
RECTIFIER RIPPLE Today we had a chance to look at the ripple some industrial rectifiers put out under normal loads. By normal I mean not the highest rated output, but anywhere from 30-80% of their capacity. I was shocked to record numbers as high as 50%. The lowest reading we obtained was 17%! Is that normal? Has anybody else looked lately at their rectifiers in terms of ripple? What kindsof filters are available for units running at several hundreds or thousands of amperes? Berl Stein, Plating Research, NJ. ‘Were the rectifiers you were studying tap-switch units? Then the ripple figures can’t be right, Berl. With simple diode rectification, and three phases 120” apart, even with no 52
capacitance or induction as voltage stabilizers, I don’t think the lowest instantaneous voltage can differ from the highest instantaneous voltage by more than about 10%. I’d have to look it up, or maybe Chris Smith knows the number right off hand. Ted Mooney, Finishing Technology, N.J. Most rectifier houses report 5% ripple when quoting, at least when I’ve spoken with them, which leads you to believe it comes with 5%. Ron Landrette, B+P Plating Supply, Conn. That’s what we thought, too. I’m not sure all the units we looked at were tap switches, but the majority certainly were. It looked as if the more you throttle a rectifier down to get>a lower voltage, the higher (relatively to the total voltage) the ripple gets. Then I checked the Metal Finishing Guidebook and Directory and found the following statement in it, “The ripple component of the output at full-rated power is nominally 5% rms of nameplate rating. This will increase as the thyristor’s phase angles are changed to reduce the output.” Doesn’t this sound a bit vague? How much does it go up? I don’t think we measured bogus numbers. Berl Stein, Plating Research, N.J. You sure have found an interesting topic! On tap-switch rectifiers, if all taps are set at the same position the ripple will be %%. This is true only if all of the diodes are operating, and all legs are passing current. With a powerstat, the ripple should be 25% throughout the range. Again, this assumes that all diode legs are functional. However, with a phase control rectifier, things are different. As you reduce the voltage, the ripple will increase. It can reach well above 50% at lower output voltages. The ripple voltage is also somewhat dependent on the output current level. Running a rectifier at less than full current will increase the ripple. But the main factor is the output voltage. All manufacturers specify 5% at full-rated output for their three-phase silicon-controlled rectifiers (SCR). If you want less than 5% ripple at full output, or want to controVlimit ripple at less than full output, you need a ripple filter. I have a chart that shows ripple measurement curves for a typical SCR operated from lO-100% output voltage and at lo%, 25%, 50%, 75%, and 100% load current. This chart is applicable to any six phase star rectifier. I will gladly fax or send it to anyone that requests it. Berl, if you were measuring a tap-switch or powerstat rectifier and got 17% ripple, I would guess that one of the six output legs was not conducting current. Most likely the
0 Copyright Elsevier Science Inc.
METAL FINISHING
. JANUARY
1995
diodes were open, but it could also be a connection. The same holds true for an SCR unit operated at full output. Hope this helps. Any questions, write or call. Whoops, forgot something! When I said *5%, it means 5% approximately, not f5%. Sorry if there was any confusion. Chris Smith, Process Electronics Corporation, N.C. Thanks for the detailed explanation, Chris. I would like to see the chart you mentioned; please fax it to me. I tried to find publications that studied the influence of ripple on electroplating in the Compendex Plus engineering database. The most important one is in Dutch - anybody out there speak Dutch? Talk to you later. Berl Stein, Plating Research, N.J. WASTE TREATMENT
Intro&wing the ProbeMa#ule “As soon as you see the Elcon$eter measuring instrundpnt, lot. And that’s exbctly t you get!!” ,(
I’ve designed a number of waste treatment systems over the years, and the single most troublesome step or component is the clarifier. I would like to design a system with dual filter presses instead of a clarifier. First, yes, there are difficulties-including the fact that while a clean filter can handle the flow rate easily, its flow capacity drops towards zero as it gets full, but it can be done. In fact, one of the major filter suppliers used to sell such systems as a packaged solution (perhaps they still do). I’m thinking of magnesium hydroxide as the primary precipitant because it builds a much thicker and less watery floe. The other thing I believe is that despite the complications and floor space required for a batch system, it may be the best way for the future. Not only for more effective reactions, but because you can take a sample of every batch and monitor and document the effluent quality. The effluent quality of a continuous discharge cannot be nearly as rigorously documented. Again, I recognize that batch systems can be complicated, what with the need for numerous level controls, keeping the pH probes wet, etc., but temporary excursions are getting too dangerous and costly. Any comments, suggestions, or discussion? Ted Mooney, Finishing Technology, N.J. Traditional thinking goes like this: by using a clarifier (a properly designed one), you substantially reduce the load on the filter by feeding into it more solids than water. Without one you are facing two problems: retention time necessary to develop the floe (will you use an intermediate holding tank for it to form?); and degree of dilution-your flow through the filter will have to be 10 or more times higher than with the clarifier. Do you really want to do it, Ted? Berl Stein, Plating Research, N.J. Well, the thing is, a clarifier provides no guarantee that floe is not burping up and going over the weir and right into the regulatory authority’s sample bottle. The filter press provides effluent that has passed through a filter cloth and is free of floe. I recognize that, theoretically, the floe can be forced through the filter cloth, but I’ve taken a number of samples of the filter press filtrate versus the clarifier overflow on a few systems and have never found the clarifier overflow to be cleaner than the METAL FINISHING . JANUARY 1995
& Parallel
Stan
I-.1
da
Telephone for a Brochure:
(810) 6m
0500
Fax: (810) 650 0501
(Toll Free 800-521-0635)
Circle
022 on ma&r
infomation card
53
filtrate. If someone feels my experience isn’t a proper sample of the universe, please tell me. Ted Mooney, Finishing Technology, N.J. Wastewater treatment is not really my bag, but batch treating is obviously a better system as all factors can be identified exactly for treatment. Floor space requirements, however, can be very large. Ron Landrette, B+P Plating Supply, Conn. SAFETY IN REFILLING ANODE BASKETS One safety violation that occurs in a lot of shops is people putting themselves in a dangerous position when filling anode baskets. Can we propose a safe method for filling anode baskets? I’d start by saying it may not be a good idea to put gaps between the tanks for anode service in an automatic line because my experience is that people will go into those gaps with the automatic equipment running. Ted Mooney, Finishing Technology, N.J. As far as anode baskets go, I’ve seen advertised, but never used myself, baskets that are fitted with a pickup of sorts. If this can be achieved, couldn’t a hoist pickup be adapted to lift the baskets to the unload station? Or maybe something could be designed to ride on the shuttle and operate from the aisle to fill baskets? Ron Landrette, B+P Plating Supply, Conn. Yes, some shops do lift the whole anode bar on the hoist and bring it to the end of the line for service. I would like
someone who doesn’t think that is a good idea to chime in here so we can understand the disadvantages, if any, of that approach. Ted Mooney, Finishing Technology, N.J. We used to lift anodes out of nickel tanks back in Russia and service them at the end of the line. Imagine how much solution was in the anode bags; no matter how long you let the stuff drain, you still had solution all over the place, to say nothing of the mess the’ anode sludge left behind. You almost need a dedicated area for all that. Besides, the hoists were definitely being overloaded while carrying the anode bars with baskets on them. How is all this for a disadvantage? Still, you might say this is a lesser evil than lost lives. Berl Stein, Plating Research, N.J. I must admit to walking around on the rims of tanks. It was absolutely stupid, and I won’t anymore under any condition, nor would I allow anyone else to do it if I were king. My only excuse, because that is what it is, was that I was young at the time, and thought I would live forever. To lift an anode basket and get all that junk in the tank through the bags is just more than I can take sometimes. There must be a better way. Tom Pullizzi, Team*Faraday, N.J. Ted Mooney is an independent consulting engineer based in Kinnelon, N.J. MF
Get MamaValveControlfar blastcleaning machines. rate control as easy as turning a knob-get low flow rate for delicate parts!
??Flow
??Control
costs, too! Save money on media due to less breakage!
* / ,, .*
.;‘,.’ ?‘ :+,‘,I,“,,J
\
The Magnavalve shot flow rate control will Improve your blast cleaning process and reduce waste by delivering the right amount of steel media to the blast wheel for every job... low flow rate setting for delicate parts, hlgh flow rate setting for large parts...or anywhere in-between. Magnavalve is in control. No moving parts to fall or wear out. Easllv. adaWed to remote Dre-sets. .
Electronics Inc. 1520 N. Main St. ?? Mishawaka, IN 46545 USA Telephone: I-800-832-5653 or (2191256-5001 Fax: (2191256-5222 _,.“.““__“...“I_...
54
. ...”
.
.
.
. “.._.._“._
METAL FINISHING . JANUARY 1995