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topic 38160

Heating open-top tanks Q&A


2005

Q. I am a management consultant working with a large plating company with large tanks (up to 17'x5'x5') specializing in electroless nickel and hardcoat/anodizing. I have an extensive background in mechanical engineering, HVAC and energy conservation. I have easily identified huge savings potential by insulating steam lines and old ferrous tanks (as opposed to polypropylene) and using tank covers and/or floats (either balls or hexies). I have encountered overwhelming resistance particularly against floats. This resistance is based on the following concerns: (1) the insulation will get wet with chemicals and cause the pipes and other ferrous surfaces to rot, (2) the chemicals (particularly in the nickel tanks) will spoil if not fully ventilated, (3) the tanks cannot practically be completely covered (of course they can but some may have to be reconfigured), covers will not be used after a week, they will be mishandled and break, and they will generally take more time than they are worth, and (4) the floats will ruin the work if caught inside and not discovered. Though I concede that each issue may have some validity I can't help but conclude that the hundreds of thousands of dollars savings (gas, electric, chemicals, and water) more than compensate for the pain. Can anyone enlighten me? I would be interested hearing opposing views.

Gerald S. Berman
Management Consultant - Devens, Massachusetts


2005

A. Hi Gerald,

Ah, a Man of my own Heart ! Well done !

Energy conservation is to me a prime requisite ... and many moons ago I wrote a paper with the horribly exciting title of THE COST OF ONE SMALL INSIGNIFICANT CFM .

Have a look-see in the archives at #7794.

Yes, use PP balls ... available still I assume at up to 3" diameter. Damn the opposition !

Consider something else, too ... RECYCLE ...

This I've done even for chrome. But not your conventional mass transfer scrubber but a 3 micron horizontal blade type +++ inertial scrubber. Even Australia is copying this design.

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



2005

A. Gerald,

You have an interesting situation in which I have been involved in numerous times. The use of covers undoubtedly provides a tremendous potential for energy savings, including tank heat/cooling loss reduction, Exhaust CFM Reduction, Tempered Makeup Air Reduction, and more. The difficult part is convincing people to change the traditional way of designing a line and its required exhaust system, which is usually designed based on open surface tanks.

There is an article about energy conservation in the latest Nov. Issue of Metal Finishing Magazine that you may find interesting.

If you're looking for some hard data on energy savings, the EPA has an Environmental Technology Verification (EPA/ETV) Program which has studied the use of NON REMOVABLE mechanical covers on a particular tank line.

Retrofitting an existing line with covers integrated with the exhaust system is possible and proven to save lots of operational $$. But it must be done by professionals with extensive knowledge of the process, production requirements, and pollution control exhaust systems.

Kyle Hankinson
- Forest City, North Carolina, USA


2005

A. Hi again Gerald,

Kyle said that retrofitting had to be done by professionals. Um. Is that so? After all, YOU are a true professional in reducing energy costs more so than any plastics' fabricator, or me, judging by your text.

I still think that, in certain cases, air recycle is a hellish good idea.

Let's take G.M. and Delco Remy for an example ... where they charge batteries containing 36% sulphuric acid.

What do they do? They recirculate the air BUT l0% only goes to atmosphere to get rid of excess H and O. That was THEIR idea.

Their chief chemist at their Oshawa plant didn't believe in mist eliminators ... so we made him a mini unit to test out.

Then ... a year passes by after the big installation ... and the test results stated that the eliminators had met and beaten the EPA standards and were far better than the crude mesh type scrubbers. Then Delco Remy in Anaheim and in Muncie copied this design. I vunder vy !

Food fer thought, eh? After all most ambient temperature emissions of acids are neither gases nor fumes, as the text books would have you believe, but invisible droplets.
And just now the mega gold mine of Yanacocha in Peru is ONLY using these designs in their labs ...+ PERpLAB fumehoods and plastic fans.

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



2005

A. Hi once again, Gerald,

Whilst flipping through GOOGLE on the subject of the 4th Glosters, my father's old regiment, I came across thread 31383 "Solutions to heat loss from plating/rinse vats" ... which might be of some interest to you.

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

----
Ed. note: Thread 17485, "Tank Water Evaporation Estimates", may be interesting as well.


2005

A. Re. the "Insulating the tank" issue. Double wall tank with insulation in the middle solves that issue. Standard configuration for steam jacketed kettles.

Jim Feig
- Mansfield, New Jersey



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



Heat Loss from Phosphating Chemical Tank

2007

Q. Dear Sir,

I am currently running Zinc Phosphating on pipes with spraying type. The phosphating chemical is applied onto the thread of the pipe through spraying method. However, I have experienced tremendous heat loss from the phosphating chemical tank. I would like to know if there is any method to prevent the heat loss. What shall I do to the chemical tank in order to prevent heat loss? Please advise. Thank you.

Ronnie Wong
Oil & Gas - Malaysia


2007

A. The principle of cooling towers, of which countless millions are in use, is that if you spray a solution there will be tremendous evaporative losses which cause dramatic cooling. So, as far as researching the principles, if you get a book on cooling tower design you can learn how to make your system more efficient (or in your case hopefully less efficient) in cooling. The most dramatic improvement you can make is probably to seal in the humidity in some fashion because it is evaporation into a drier environment which is causing most of the loss.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2007

A. Dear Sir

If the heat loss is happening inside an open storage phosphating tank you can use solid polypropylene balls which can withstand high temperatures and forms a blanket on the surface of the tank and thereby arrest the fumes which escapes thereby reducing the temperature and requires more heating. Also cover up the sides of the tank with asbestos rope or cloth.Phosphating is exothermic process whereby the heat is lost by evaporation. Solid PP balls are the best solution if the tank is open to sky.

C S Rajaram
- South India


2007

A. Hi C.S. Rajaram

I had only in my limited experience (40 years in the heavy plastics fabricating field) heard of hollow balls for reducing heat loss ... from 1"Ø to 3"Ø ... which would be far less expensive than solid ones BUT sometimes they perforated and sunk to the bottom. I used to like 2 layers of them.

HOWEVER, some years ago a certain Indian manufacturer came up with solid PP 'floats' which he called, going by memory, flying objects or space doohickeys ... and even sent me one.

So try the local industry, OK ...but insulating the tank is always a good idea.

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



2007

A. If you are talking about the loss of temperature of the phosphate during the actual spraying operation of the Zn phosphate onto the pin end of the pipe (Usually the box end is Manganese phosphate). Try flood coating using a pump and manifold system rather than spraying, we've used this successfully in a number of plants for both OCTG and drill pipe for both Zn & Mn. A lot less heat loss than spraying.

Regards,

Richard Guise
- Lowestoft, U.K.



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



Heating vats to temperature

April 15, 2008

Q. I am a manufacturer of industrial heating equipment, and I am not very familiar with chrome plating or any plating processes. A customer of mine was interested in using tankless water systems to heat their vats in the process through a radiant system. My concerns are heat loss, and being able to provide enough radiant heat to bring X process to Y degrees. I have not received too much information at all on this project at this time, but I am trying to determine if anyone can shed some light on what temperatures are required in the plating process for rinse applications or plating. Any HELP would be great, as this is a new venture for our company.

Robert Lisowski
industrial heat systems - Woodstock, Illinois


May 1, 2008

A. Hi, what type of tanks /solutions are you hoping to design heaters for ?

you mentioned chrome vats, the type of heaters used in our vats are electric portable type. we wouldn't use a radiator type heater incase it burst in the tank and overflowed the chrome solution causing effluent problems, etc.
also you would need to know what materials to make the heaters for each solution as the chemicals could dissolve them.
also each solution will need different temperatures.

can you explain tankless water system, as I'm not sure what it is . and I may be able to more help

thanks

Jay Smith
- Essex, UK



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



How do I size a low pressure hot water boiler system for my plant

March 20, 2016

Q. I am moving from electric immersion heaters to a hot water boiler and really don't know how to size it. I am expanding my operation, so I cannot simply look at the heaters I have been using. Where can I get the best information on sizing my system and the heater coils for my tanks.
Thanks in advance for the help
Derek

Derek Kozlowski
Plating shop owner - Dalton, Georgia US


March 2016

A. Hi Derek. In easy cases, it's easy: a BTU is the amount of heat required to raise one pound of water by 1 degree F. So if you calculate the gallonage of each heated tank, convert it to pounds, multiply by the difference between the operating temperature and room temperature, and divide by the heat-up time, you have the BTUs/hour that the boiler needs to provide. If you size things based on a two-hour heat up time, you'll almost always be safe. Three-hour heatup time, and you'll still often safe.

If you extend the heating time to say 6 hours, the boiler is a lot smaller, but things can get dicey. The problem is that there are operational heat losses as well as heat-up losses, and they can start becoming very significant if you don't have the safety factor of 2-hour heat up. Very hot tanks lose a lot of heat to evaporation, for example; all tanks lose heat thru the sidewalls; heavy cold parts or drag-in of a lot of cold water can suck up a lot of heat, etc.

Tranter Platecoil has a helpful design guide at
http://na.tranter.com/Documents/Platecoil%20Data%20Manual.pdf
and their competitors like Mueller offer similar guides.

Hot water heat is best when the tanks aren't too hot, and the material of construction of the heating coils is inexpensive. The hot water doesn't have the "phase change" that steam has, so the coils must be bigger, and depending on the operating pressure, the water is probably not as hot as the steam either. It's tough to heat a 195 degree soak cleaner with 195 degree water because there is such a limited temperature difference. Those coils are, at least, plain steel though. If you have a very hot tank with aggressive contents that requires Teflon coils, the cost of the coils can kill you.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

----
Ed. note September 2020: Sorry, that Tranter design manual link went bad, but we've found a copy of the manual at
http://navalex.com/downloads/Tranter_Platecoil_Data_Manual.pdf
Times are changing and suppliers don't generally offer their deep technical libraries like in the old days; plus the internet became more about commerce than data, so the old gray Google ain't what it used to be when it comes to searching for technical data. So download it now or be sorry later!


March 21, 2016

Q. Thank you for the quick response
My main plating tanks are run at 193-197. I really didn't want to run the water heater much more than 205 to keep it below steam threshold. I am trying not to have to deal with steam, just from a safety and regulatory standpoint of high pressure systems.
Is this possible with hot water systems?
I sat down this weekend, and worked out the BTU's I would need.
The other issue is that my materials are highly caustic. We do chew through heaters quickly, even teflon lasts only about a year. I can get these coated from a stainless heater, but again I am looking at how to reduce cost overall.
Thank you for the quick, insightful answers.
Derek

derek kozlowski
- Dalton, Georgia US


March 2016

A. Hi again. Most of my career was with suppliers and as a plating equipment consultant so I specified steam boilers many times, and hot water boilers several times, and don't have a strong preference for one over the other. The hot water boiler is slightly less expensive, and its piping is less expensive, but the need for larger heating coils cuts into those savings. If exotic coil materials are required and/or the tanks are very hot, those costs overtake the savings in boiler and piping, and then some.

Although there could be something in your local codes that make the regulations easier for a hot water boiler, most plating shops use low pressure steam boilers (less than 15 psi), and these normally do not require a fireman or anything really burdensome. I think you should talk to a steam boiler manufacturer like Cleaver-Brooks and investigate a 15-psi low pressure packaged steam boiler to make sure you're on the right track.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



How to calculate chemical loss from open tanks

September 4, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am looking for a reliable calculator for evaporation on open tanks. There are some great articles on finishing.com but they all seem to be either assuming ambient temperature or missing wind speeds. The Aloha is too complicated and more for outside applications and I wondered if anyone has a comprehensive calculator or formula.
Typically I am setting up a Zinc Phosphating tank 1.2 m wide and 3.8 m long. It is maintained at a constant temperature of 82 °C. If the ambient temperature is at 16 °C but the area is ventilated with fume extraction of 0.62 m/s (1.5 mph) then how much heat are we losing from the surface of the tank? We are not using Croffles or any form of cover.
Thanks Daniel

Daniel Carter
- Providence Rhode Island


September 2020

A. Hi Daniel. We combined some of those threads which you refer to, and have appended your inquiry to that thread. You will see a link where you can download Tranter's Design Manual which, as a plating equipment & shop designer, I referred to for decades; for different employers I wrote computer programs to incorporate that data way back when.

But I also need to note that all you can do is an approximation based on general data. There will be dead spots on the tank surface, stray breezes at different times, loads going into and out of the tank to disrupt the air flow, unknown wet bulb temperatures based on this and that. If you also estimate wall losses, and losses to cold work entering the tank, you can get close to the total operational heat loss. Good luck.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

adv.    industrial heating systems

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