Sciencemadness Discussion Board - Are there chinese hotplates & heating mantles as good as others but significantly cheaper?

Are there chinese hotplates & heating mantles as good as others but significantly cheaper?

fusso - 22-5-2018 at 18:04

Chinese glass labware can be as good as others but significantly cheaper, so what about hotplates & heating mantles? If they're significantly cheaper, should I trust them?

[Edited on 23/05/18 by fusso]

VSEPR_VOID - 22-5-2018 at 18:14

You can get some really good Corning hotplate/stirs for between 130 and 200 dollars, especially used. I would either buy one of those or make a heating mantle from parts.

JJay - 22-5-2018 at 18:38

I use Glas-Col fabric heating mantles, which I regulate using simple electronics equipment that I wired together. They are pretty inexpensive on the secondary market, less expensive than the Asian heating mantles. I don't think the Glas-Col mantles are extremely durable, but I haven't had any problems with mine. The tricky part is finding one with a power cord.

[Edited on 23-5-2018 by JJay]

coppercone - 22-5-2018 at 19:46

I don't know if you wanna go there.

Think about this, if you are doing something dangerous, you really don't want the regulation to fuck up do you?

I would recommend buying USA equipment and doing a internal inspection to verify its integrity, and replace things like worn wires, and keep it very clean (i.e. clean it after doing a reaction or having a spill, don't keep some messy ass crusty hot plate around because electronics don't like that shit at all). Polish it too if you can so its easier to clean up.

The chinese like to rate things about 2 or even 3 times more then they should be used for in moderately high reliability applications.

I can't speak for more simple things, like heating blankets... but things like Chinese Variacs, transformers, heater controller/PID, control boxes should be treated as suspicious. At least replace the fuses with ones you buy from a trusted supply chain (digikey.com, farnell, etc... don't buy safety components on eBay) And wire in a ground fault interrupt circuit in case a condenser blows up or some shit. And check your laboratory ground.

If you look at it from a 'my ass is on the line' kind of viewpoint, even American made is not that great due to bean counters.... if you work for a company unfortunately you can be considered 'good' if you say things like 'its safe enough'

For instance:

Chinese variac: rating : 20 amps or so, weight : 25lbs

American 1970's variac (sometimes regarded as a golden age of manufacturing certain goods): rating : 8 amps, weight :25lbs

Did silicone steel and copper conductivity increase by 200% while I was away?

Now, maybe you can run them somewhat hotter, because maybe enamel coatings on wire got better. But 300% ?

the last thing you want is a laboratory fire right?

case in point:
http://www.newark.com/superior-electric/3pn236b/variable-tra...

Rating : 10 amps, nice spec sheet, weight, 22lbs, 1600$ (like 100-400 on ebay)

https://www.circuitspecialists.com/variac-tdgc2-2.html
20 amps, 25lbs, 99$

lets divide the sale price by 4, because its industrial, and a bit niche nowadays since we don't use so much tube equipment and other things that require variacs as we did 30 years ago.

do you trust : 1/4 the price, half the weight, twice the rating?

(really 1/16th the price!, saying 1/8th is still being modest, 1/4th is generous).

I also want to say, given my knowledge of electrical code, that outlet looks to be a 15A outlet............

http://www.airforums.com/forums/attachment.php?attachmentid=...

[Edited on 23-5-2018 by coppercone]

JJay - 22-5-2018 at 21:13

I use a triac dimmer instead of a variac... they are much cheaper and lighter. My PID controller and relay are Chinese, but they are decent industrial-quality components, and they weren't cheap, although they were much cheaper than they would have been if I had bought them in an American electronics store. The controller functions well and accurately as long as it doesn't have to react to conditions like a flask suddenly boiling dry or the power getting immediately increased from 25% to 100% when only 10 C away from the target temperature. The PID controller has some sort of serial interface, but I haven't bothered with it. If I wanted to get really fancy, I'd figure out a way to automate the triac, but so far I have only needed a temperature controlled heating mantle for one experiment.

If you're afraid of playing with the wall current, the heating mantles made in India with built-in controllers might not be such a bad deal. Glas-Col does make temperature controllers, and I'm sure they are reasonably good quality, but they are rather expensive.

coppercone - 22-5-2018 at 22:50

It may work well but your chance of getting counterfit chips from the shenzen market increases drastically, as does things like proper assembly procedure not being followed (i.e. esd precautions leading to some kind of failure)

chinese inverters for instance are a complete joke.

also high power triacs may be significant noise generators so poorly shielded things may not interact well with them

[Edited on 23-5-2018 by coppercone]

wg48 - 22-5-2018 at 23:10

Quote: Originally posted by coppercone

case in point:
http://www.newark.com/superior-electric/3pn236b/variable-tra...

Rating : 10 amps, nice spec sheet, weight, 22lbs, 1600$ (like 100-400 on ebay)

https://www.circuitspecialists.com/variac-tdgc2-2.html
20 amps, 25lbs, 99$

lets divide the sale price by 4, because its industrial, and a bit niche nowadays since we don't use so much tube equipment and other things that require variacs as we did 30 years ago.

do you trust : 1/4 the price, half the weight, twice the rating?

Your comparing a current ratings of a 240V 50Hz, system with a 110V 60 Hz system.

You have to compare VA ratings for a fair comparison, and be careful as to how the ratings are defined,

For example the 20A variac is rated thus:
Rated up to 20 Amps or 2kVA Peak (16A Continuous)

The maximum current is frequently limited by the brushes in addition to the VA rating.

Edit:removed reference to 2kHz

[Edited on 23-5-2018 by wg48]

fusso - 23-5-2018 at 15:09

I cant understand what most of you are talking about???

Sulaiman - 23-5-2018 at 16:40

My observation is that members who have Corning hotplates are very pleased with them.

I used the cheapest (1500W) generic hotplate for a couple of years,
then I replaced the on/off internal temperature controller with a cheap Chinese triac controller (description=4000W) which, due to continuously variable constant power worked very well for distillations.
Eventually I killed it by overheating during a sulphuric acid concentration at >300^oC.
So I bought a used generic dual hotplate (1500W + 500W) that is still in use,
for heating beakers and an oil bath.

My favourite heater is my diy 500ml heating mantle, <£10 for the mantle and triac controller,
add a suitable container and some insulation and you're done.
Except - my diy magnetic stirring is not yet working as I want it to.

Overall:
IF you are comfortable working with mains electricity then together with one of the cheap Chinese triac controllers,
either a DIY mantle
or
a cheap hotplate (you can kill a dozen cheap ones for the cost of a used Corning hotplate)
is my recommendation.

P.S. Initially I did not appreciate the value of stirring - now I do

[Edited on 24-5-2018 by Sulaiman]

diddi - 23-5-2018 at 17:01

a friend of mine in china owns a lab glassware factory. he is well connected with lab equipment in china. he asked me to send him an australian stir-hotplate. i think that probably sums it up fairly well.

Sulaiman - 23-5-2018 at 17:08

Coming soon ... a cheap Chinese version of an Australian hotplate-stirrer

fusso - 23-5-2018 at 17:23

Quote: Originally posted by diddi

a friend of mine in china owns a lab glassware factory. he is well connected with lab equipment in china. he asked me to send him an australian stir-hotplate. i think that probably sums it up fairly well.

Conspiracy theory: he probably wants to study its structure and electric circuits so he can replicate it and sell at a lower price

[Edited on 24/05/18 by fusso]

JJay - 23-5-2018 at 17:28

Quote: Originally posted by Sulaiman

Coming soon ... a cheap Chinese version of an Australian hotplate-stirrer

How exciting

The Corning stirplates are satisfactory for most purposes. They have a strong magnet and a reasonably high heat output, not to mention a chemically resistant top surface. They are not really designed for extremely precise temperature control, but it's usually unnecessary. I remember seeing a Chem Player video where a Corning stirplate was used to hold the contents of a flask within a narrow temperature range for hours.

ausnewbie - 23-5-2018 at 17:57

I have a cheap mag stirrer hotplate from china. its called 85-2
https://www.ebay.com.au/itm/AU-220V-85-2-Lab-Magnetic-Stirre...

it works as a starter unit ( but it only cost $70 aus) its slow to heat and its probably crap. but it seems ok as a starter for me. the temp regulation seems OK,

Just My humble option, but unfortunately as a newbie - i dont know yet, what I dont know.

JJay - 23-5-2018 at 18:16

I also have an 85-2. I don't really recommend them, but I do use mine occasionally for heating mixtures slightly above room temperature or stirring reactions that don't require heating. I used to use my 85-2 at temperatures up to about 220 C with an oil bath heated by an immersion heater, but it is more convenient to use a higher-temperature stirplate.

alking - 24-5-2018 at 20:29

Quote: Originally posted by fusso

Quote: Originally posted by diddi

Conspiracy theory: he probably wants to study its structure and electric circuits so he can replicate it and sell at a lower price

[Edited on 24/05/18 by fusso]

We can hope.

XeonTheMGPony - 25-5-2018 at 03:45

Send him a good quality unit! then we can get a half descent knock off!

Trick with allot of Chinese gear is divide the continuous rating by 3 to get the real one.

zed - 25-5-2018 at 13:45

I bought a couple of ancient, semi-functioning, American stir-plates, a few years back.

Cheap as dirt, on e-bay. It was almost embarrassing, price-wise.

No fancy bells and whistles, just high-quality component, low-tech construction.

After about an hour, by skillful use of a screw-driver and a scribe, both were humming along like new.

"Parts left out of the design, do not break!"

The more sophisticated the electronics, the greater the probability of failure... And, the greater the difficulty of repair.

I've purchased some great things from the Chinese, at great prices. Electronics however, are not on my list of acquisitions.

[Edited on 25-5-2018 by zed]

[Edited on 25-5-2018 by zed]

zed - 26-5-2018 at 14:28

So...... The Staco-type Variacs, that are so common(used), in the U.S.A., currently list for about 1,500 Dollars per unit....New?

I'm sold! Just bought one used, in very nice condition, off of e-bay, for 60 Bucks, including shipping!

Guys, you are golden! Thank you, for your continuing wisdom.

coppercone - 26-5-2018 at 14:58

there is maintenance you can do on them like polishing the slider, cleaning off dust, checking the wiring, etc.

I highly recommend building it into a (properly grounded) steel box with a current, volt meter and power meter (might be more useful for chemistry), fuses, outlet plug, ground fault interrupt if you does not have one already (I would put 2 outlets one with GFIC and one without)

Possibly a new extension cord

For electronics work you might want to buy like a sufficiently rated EMI-Mains filter and wire it in to the front.

Unless you got a finished one in a sheet metal enclosure they sell it in, then you just need to check it. I got my variacs cheap but they were without enclosures, just the magnetic element.

https://www.ebay.com/itm/100A-AC-LCD-Panel-Digital-Power-Wat...

shit like that kind of works, but I have one without a independent power supply, so it stops working when you get under like 30 volts. Best would probably be either an electronic one powered by separate power supply

I actually don't know if the analog power meters will actually have a multiplication circuit and measure voltage/current independently or if they will make an assumption.

I think they do:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l...

one of those should work even better since you only care about watts for things like heating mantles

most of them are for RF but here is one, but the current is too low
https://www.ebay.com/itm/Lab-Volt-Simpson-Single-Phase-750-W...

something like that but going to 1000 or 1500w is what would be best imo

here we go:
https://www.ebay.com/itm/TEST-EQUIPMENT-WATTMETER-SIMPSON-13...

not the best resolution but for 15$
should put current meter too though, so you know if fuses are gonna blow

[Edited on 26-5-2018 by coppercone]

diddi - 26-5-2018 at 20:21

LOL to all the knock off conspirators, but it was for himself. i had a cheap one with digital display etc from china and it nearly burnt my place down. luckily i was using it outdoors when it literally melted itself into a fuming pile and i was close by to avoid a disaster

coppercone - 27-5-2018 at 06:41

a chinese variac? or the little panel meter? Those meters should be fused so it should not be too much of a fire hazard..

how come fuses did not work?

also a good mod would be to put a fusable thermal fuse on the transformer body to disconnect it if it gets more then like 150c

[Edited on 27-5-2018 by coppercone]

[Edited on 27-5-2018 by coppercone]

diddi - 27-5-2018 at 14:10

i was concentrating some H2SO4. the whole plastic surround simply caved into a molten mass. i had it outdoors because i dont have a fume hood. i noticed the beaker was on a lean and went to investigate. no fuses blew tho.

aga - 27-5-2018 at 14:46

My Cheap Korean hotplate/stirrer has been through hell and back.

Still trucking almost 100% after 4+ years of daily abuse, including 2 cycles of grinding/repainting.

The 'off' position for the heating control gave up about 10 days ago.

Easy to fix (replace the pot) however i have other, more interesting plans for it.

Dear 'fusso', just use a cigarette lighter or candle or something until you decide on the most appropriate hotplate/stirrer to buy.

Reporting your Chemistry experiments would be far more interesting than a re-hash of many old threads.

I'd get all giddy if a noob even made copper sulphate crystals.

[Edited on 28-5-2018 by aga]

fusso - 2-6-2018 at 03:05

Quote: Originally posted by aga

Dear 'fusso', just use a cigarette lighter or candle or something until you decide on the most appropriate hotplate/stirrer to buy.

Reporting your Chemistry experiments would be far more interesting than a re-hash of many old threads.

I'd get all giddy if a noob even made copper sulphate crystals.[Edited on 28-5-2018 by aga]

I do have experiment plans and chemicals in my "base" in my home country but I'm currently in another country so I can only do experiments after going back home. I usually use a blowtorch to heat rxn mixtures but I need a hotplate for controllable temperature.

[Edited on 02/06/18 by fusso]

kulep - 2-6-2018 at 09:47

Cheap cooking hotplates have a threaded hole in the middle, although heat distribution across the top isn't optimal they are very robust and I don't think you would have a problem with the heating elements burning like him, and even if they do burn replacements should be very cheap.

In that hole (6mm or 8mm maybe?) you can screw a threaded k-type thermocouple and use it as feedback for a pid controller. The hole is intended to mount the element to the chassis but some models also have mounting holes in the rim, and in the ones that don't it should be easy to drill new ones.

It should all cost less than 30usd for at least 1000w power, you won't have stirring but maybe you can fit a motor and a hdd magnet under there, I don't know how feasible it would be because the element is pretty thick; there's also the option to use overhead stirring.

https://www.youtube.com/watch?v=s2Pbh29QxoM
https://www.youtube.com/watch?v=075D_tuswVU

[Edited on 2-6-2018 by kulep]

zed - 2-6-2018 at 14:48

Most of the stuff we use, isn't explosion or fire proof. So, in the event a container of flammable solvent breaks or is otherwise spilled on your hot-plate; expect fire. Likewise, a regular lab hotplate, may ignite Ether, or other dangerous vapors.

Now, if your are working with aqueous solutions, it is a little easier.

I recently bought a Brand new "Elite" type hotplate, at my local Goodwill, fer 5 bucks.

Just for boiling water, etc. https://www.amazon.com/Cuisine-ESB-301F-Maxi-Matic-Single-El...

It was able to boil a liter of water, in a Schott-Duran, Melita coffee pot, pretty quickly. So, for boiling water= decent. The large flat plate, should minimize "Hot" spots, and as long as I avoid putting cold glass on a blazing hot heating surface, it should be OK.

It wouldn't get hotter though. Set on high, it shut off, at about the BP of water. Has a thermostat. My argument is for less sophistication. Without that thermostat, the hot plate would do what I want it to do.

As it is, if I want it to do more... I'll have to gut it like a fish, and rewire it.

[Edited on 2-6-2018 by zed]

[Edited on 2-6-2018 by zed]

coppercone - 5-6-2018 at 08:16

An explosion proof hot plate stirrer is an interesting design idea. I mean so long its not the heat from the heating element that sets it off.

It might prevent a reaction occuring in butane, ether, gasoline from blowing up.

Ideas for design:
-use alot of poles in the motor to decrease bulk inductance and design it to operate at low voltage. Brushless kind.
-use low voltage to heat the plate
-desifn the electronics with lots of transient voltage supressors to eliminate arcing from broken connections
-seal it real good
-power it from an external dc supply that is outside of the fume hood. Be sure to put heavy voltage clamps on it

I also wonder if you can make a solid state stirrer that uses a ring of electromagnets to rotate the solenoid rather then using a spinning bar magnet.

By eliminating the vibration generated by a motor you are increasing reliability that can be caused by vibrations of solder joints. And it would be nice and quiet.

weilawei - 5-6-2018 at 10:53

I work in environments with potentially flammable atmospheres, so we make heavy use of explosion-proof components. An interesting thing to note about them is that an explosion-proof device isn't required not to cause an explosion--merely to contain it and prevent propagation. For example, our lights are standard fluorescent, just inside a well-sealed housing.

coppercone - 5-6-2018 at 11:09

well thats the cheap way to do it, but there is degrees of saftey

An overheating component like a resistor can maybe ignite fumes, but a spark can do it much easier, but its best if there is no fumes in the first place.

There are layers of protection on everything, same with electrical isolation, how strong it is, how many different barriers need to be breached.

I would argue for intrinsically safe design of all system elements not to try to hide something that can be replaced...

I would argue for DC being brought in from outside the room into the lights.

What if someone hits it with something and vapor gets in?

[Edited on 5-6-2018 by coppercone]

kulep - 5-6-2018 at 12:28

Solid state electronics are intrinsically spark-proof, the only thing you would need is a tube of mega grey silicone and completely seal all holes and crevasses of the enclosure, to be sure. A brushless motor is nice specially because it is very long lasting.

Why would you have a hotplate inside a fumehood with an stoichiometric amount of gasoline and air anyways?

coppercone - 5-6-2018 at 13:10

if there is a high current and a wire or trace breaks it can spark because of inductance though. You need to be careful. Potting is kind of a mixed bag because it can degrade the life time of electronics because of thermal properties and sometimes mechanical behavior.

more of an issue for operating in a gas filled mine shaft I think

sealed enclosure is a good start always

[Edited on 5-6-2018 by coppercone]

zed - 5-6-2018 at 16:17

I'm thinking my LED bulbs are a lot safer than my old incandescents.

The bulbs don't get very hot, and they surely don't do that trick where the glass bulb section, de-laminates from the metal base... Falls straight down, and abruptly exposes the white hot tungsten filament to the ambient atmosphere.

As a bonus, since switching from florescent bulbs, to LEDs... My electric bill has dropped by about half. I use a lot of light.

As for motors, my buddies used to do a lot of large scale LiAlH4 reductions in Diethyl-Ether. The sludge generated at certain stages, required strong overhead stirring. They used high torque, low speed, explosion proof, DC motors. I don't remember the details, but it was specialized equipment, and I remember the bitching. The motors and controllers were quite expensive.

I've considered induction as a possible method to provide reactant heating, utilizing appropriate vessels; but the economically available units have a very high incidence of quickly failing. And, then....there is an internal fan, that cools the guts. But, at what peril?

[Edited on 6-6-2018 by zed]

Funkerman23 - 7-6-2018 at 16:30

Quote: Originally posted by JJay

I use Glas-Col fabric heating mantles, which I regulate using simple electronics equipment that I wired together. They are pretty inexpensive on the secondary market, less expensive than the Asian heating mantles. I don't think the Glas-Col mantles are extremely durable, but I haven't had any problems with mine. The tricky part is finding one with a power cord.

[Edited on 23-5-2018 by JJay]

All due respect: As far as I knew Glas Col was the standard by which all other mantles are measured by. If they aren't that to you, what brand of mantle is the standard? I may have missed something but Glas col is like the Corning of mantles here. They are dead nuts reliable.

zed - 11-6-2018 at 13:30

"Why would you have a hotplate inside a fumehood with an stoichiometric amount of gasoline and air anyways?[/rquote]"

Well, that's pretty much the kind of thing, that we are constantly required to do.

Like in Henzelmanns famous procedure; where toluene, nitroethane, and benzaldehyde... Are refluxed under a Dean-Stark trap, which is removing formed water, as the reaction proceeds.

Ideally, no toluene escapes into the atmosphere, but we don't live in a perfect world. So, this project needs plenty of ventilation.

In the case of Diethyl ether; you may be required to boil it, for your reaction to proceed. And, despite all precautions, some Ether always seems to escape containment. Gotta disperse the vapor and blow it away, otherwise it may "Blow you away".

[Edited on 11-6-2018 by zed]

nimgoldman - 11-6-2018 at 15:57

The main issue I have with the chinese hotplate/stirrer (FAITHFUL SH-3) is the regulation of stirring. It is very sensitive to variation in voltage so the stirring is not constant, especially with low revolutions - sometimes the stirring even stops completely by itself or speeds up randomly!

Another problem is quite weak magnet so the hotplate for 2 liter beaker does not handle anything large than a 2 cm stirrer - it just wiggles but does not do any mixing.

Other than that, it mostly does the job, but I wouldn't use it for mission-critical application.

Expensive stirrers like IKA have special circuits to smooth out voltage just to keep the stirring constant, apart from other tweaks like precise temperature control.

Dr.Bob - 11-6-2018 at 17:37

I can agree that some Chinese glassware is fine. But having used some Chinese electronics, I would stay away from them.

As stated, you can buy used US hotplates, stirrers, and heating mantles used for a low price, maybe not even as cheap as Chinese ones, but they will generally be better. I use Corning and other US made stir/hotplates daily, some of them are 10-20 years old. They have been abused, corroded with acids, and had goo spilled on them, but still work. Not to say that they cannot break, I have had to have a few fixed, but the parts are available, and I have had a few people fix them from here. But you can buy a good used one for $80-160 typically.

As for heating controllers, I would go with a triac dimmer anytime, a 10 amp light dimmer works fine, easy to splice into an extension cord in a metal electrical wiring box, cost is about $10. They work fine for most mantles and they are not expensive. But if you want a nice Variac, for nice, clean voltage control, I have a few used ones for about $80-100. They are well made and not junk like the Chinese ones. Others are also selling used good quality stuff on Ebay, just make sure that they have good ratings.

[Edited on 12-6-2018 by Dr.Bob]