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20 Ways to Cut Water Usage in Plating Shops


by Ted Mooney, finishing.com, Brick Township, NJ


The situation has changed: Water supplies are now strained to the limit. When restrictions aren't already in effect, they surely soon will be.

The economics have changed: Water rates and sewer charges continue to rise. It makes economic sense to employ low-costs methods to reduce water usage.

YOU CAN DRAMATICALLY CUT YOUR FLOW RATES WITHOUT SPENDING A LOT OF MONEY . . .

SOLUTION NUMBER 1 -- DOUBLE DIPPING . . .

Sure it's great to add extra rinse tanks if you can. But if you can't, then dip the work twice in the same rinse tank. Much more effective than leaving the work in the tank!
Easy to do on a hand line, and almost as easy with a programmed hoist. If the manufacturer won't/can't adjust your system for double dipping, try us.
Double dipping is rated as our number 1 solution for good reason so don't dismiss it.

SOLUTION NUMBER 2 -- DRAGIN/DRAGOUT . . .

Maybe you already have a reclaim or "save" tank (you should, you know). The reclaim tank should be the first stop the work makes after plating, of course.
But it should also be the last stop the work makes before plating! In this way, with no effort on your part, the reclaim tank will stabilize itself at about 50% of the concentration of the plating bath.
Thus, instead of carrying water into the plating tank with each load, you carry back a 50% solution. Cuts waste load in half and saves valuable chemicals. Also solves the problem of room-temperature baths that keep "growing".
Again, this principle is easily implemented on manual and programmed hoist lines. On continuous or full-automatic lines, a small pump will serve to "common" the rinse after plating with the one before.

SOLUTION NUMBER 3 -- TOP SPRAYS . . .

Barrel platers are excused, and may proceed directly to solution number 4. Most rack platers know what a top spray is, but few have taken the time to work out the numbers!
If you handle ten loads per hour, and you spray for ten seconds each time a load is lifted, then water is running for only 100 seconds out of each 3600 seconds.
Thus you can install a powerful 36 GPM spraying system while consuming an average of only 1 GPM. Mount a top spray on a rinse tank, and you have a very effective two-stage rinsing system that consumes very little water.
Automated lines can be programmed to spray during lift only; manual lines can be equipped with foot-operated valves or limit switches and timers.

SOLUTION NUMBER 4 -- RESTORE BARREL HOLES . . .

The next time you look at your barrels, look inside. It is the nature of polypropylene to peen over when subjected to the tumbling action of the work. You will probably see that the holes are virtually closed off!
It is not unthinkable to restore the holes to their original size with a hand-held electric drill--lots of shops do it. It's probably less than a day's work, and your 'loader' may even enjoy the opportunity to keep busy between loads by drilling out a spare barrel.
Not only will you greatly reduce dragout and the consequent need for high flow rates in your rinses, but plating speed will improve and you'll have far fewer headaches from barrels "floating".

SOLUTION NUMBER 5 -- EXTEND DRAIN TIME . . .

A rather obvious solution, of course: more drain time means less dragout means less need for dilution means lower flow rates. But extending your drain times does not necessarily mean that your productivity will suffer!
If your system incorporates two operators or two programmed hoists, then one probably finishes the cycle before the other. Drain time on the faster half of the line can be extended without any loss of production.
Even on single-hoist lines, there are invariably pauses while waiting-out an immersion time, etc. Usually, these pauses can be translated into increased drain time.

SOLUTION NUMBER 6 -- AIR AGITATION. . .

Air agitation not only keeps the rinse tank stirred, it scrubs the clinging solution off of the work.

SOLUTION NUMBER 7 -- COOLING TOWERS . . .

If you are using "once-through" water to cool a rectifier or as part of a refrigeration system or whatever, you are wasting a lot of money.
Cooling towers are cheap! They will reduce your water usage in this application by 80-90%.

SOLUTION NUMBER 8 --COUNTERFLOW . . .

In a multiple-rinse situation, introduce fresh water to the last rinse only; let the overflow from this last rinse be the supply source for the earlier rinse.
Studies and practical experience have proven that this slightly-contaminated overflow from the last rinse is just as effective as clean water. By counterflowing a two-stage rinse, flow rates can be cut in half.

SOLUTION NUMBER 9 -- BREAK AIR LOCKS . . .

Sometimes counterflow rinsing doesn't work too well because the water flows the wrong way (from the dirty rinse to the clean rinse) when a rack or barrel is immersed in the dirty rinse and raises the level in that tank.
One problem might be that you don't have enough elevation difference between the two overflow dams. More likely, the dirty rinse isn't draining right because of an airlock. Fix it for pennies!

SOLUTION NUMBER 10 -- INSTALL AIR LIFTS . . .

Suppose you would like to employ counterflow rinsing but have no elevation difference between the overflow dams. Or suppose you would like to re-use the overflow from plating rinses in earlier, less critical rinses.
A simple air-lift can be fabricated from platic pipe, and will handle this chore without pumps, level controls, or other expensive complications. See Plating and Surface Finishing, May '82.

SOLUTION NUMBER 11 -- TIMED WATER ADDITIONS . . .

It's easy, and relatively inexpensive, to rig up a timer and solenoid valve to deliver a fixed quantity of water to the rinse tank with each load.
The timer can be triggered by a limit switch, or from the hoist programming.
A user reported a water savings of more than 50%, and a payback time of 3 months!

SOLUTION NUMBER 12 -- CONDUCTIVITY CONTROLS . . .

A conductivity controller is adjusted to feed additional rinse water only if contaminants exceed an acceptable level.
This is an answer ideally suited to jobshops where the amount and type of work processed varies from day to day. No water is wasted regardless of changes in the workload.

SOLUTION NUMBER 13 -- MASTER SOLENOID PLUS FLOW RESTRICTORS . . .

Simple but reliable flow restrictors are available for less than $10 apiece. Unless you have a conductivity control setup, you simply must have flow restrictors. The payback time is measured in days!
But why waste water during lunch and breaks. Install a solenoid valve in the main, and an on/off switch near the operator station. A few hundred dollars will more than cover the cost, and you pocket the savings for every minute the switch is off.
Additionally, you save the labor and headaches associated with constant fiddling with the rinse tank fill valves; simply turn the master switch on or turn it off, and the flow restrictors take over from there.

SOLUTION NUMBER 14 -- FIBERGLAS HANGER ARMS . . .

Deteriorating plastisol coatings on barrel hanger arms are a continuing source of nuisance dragout, wasting chemicals and necessitating high flow rates in the rinse tanks.
Most manufacturers now offer fiberglas hanger arms, and others offer titanium or steel-reinforced polypropylene.
Replace those old cast iron arms, and reduce your rinse rates. Also reduce corrosion, stray currents, and high maintenance cost.
We know of dozens of shops who have converted and not a single one would consider reverting to cast iron arms.

SOLUTION NUMBER 15 -- REPAIR RACK COATINGS . . .

Your racks may drag out a lot more solution than the work!
Bubbles and pockets in the coating can hold several ounces of solution, and you may hopelessly contaminate a plating bath by operating in this fashion.
The more deteriorated the coatings, the more time wasted removing "trees" too. Perhaps a perfect example for the old adage "A stitch in time . . ."

SOLUTION NUMBER 16 -- RACK PARTS DIAGONALLY . . .

Studies have shown that, for small parts, only 15% of the dragout is associated with wetting of the surface; 85% is in the form of a bead or band of water along the bottom edge of the part.
By racking the parts so that the lowest point is a corner rather than an edge, drastic reductions in dragout result.
Small flat plates (1" x 2") dragged out only one sixth as much solution when racked diagonally.

SOLUTION NUMBER 17 -- BARREL DOORS UP . . .

Barrel doors typically are thicker than side panels, have fewer holes, and may even consist of two separate sheets stacked together thus impeding drainage.
Dragout reductions (and consequent rinse rate reductions) of 15-20% can be expected when doors face upward during draining.

SOLUTION NUMBER 18 -- COMMON RINSES FOR CLEANING AND PICKLING . .

No question about it. Use sepatate rinses after cleaning and after pickling if you can. However, . . .
If you have but a single rinse after cleaning and a single rinse after pickling, you may be better off designating one as the first rinse after both processes and the other as the final rinse after both processes. Substantially lower flow rates may be possible with this arrangement than with the original. Need re-programming to accomplish this? Call us!

SOLUTION NUMBER 19 -- TANKS IN PROPER ORDER . . .

Never drag the work over a final rinse enroute to dipping it in a preliminary rinse!
If your tanks are so positioned that a "clean" rinse is between a process tank and a "dirty" rinse, move the tanks. Don't live with this awkward, inefficient, situation.

SOLUTION NUMBER 20 -- FULL DEPTH SPRAY . . .

Very viscous solutions (etches, chrome baths, zincates) may be more effectively removed with high pressure sprays than by immersion.
Rather than using all fresh water, install a recirculating pump. Install an overflow dam near the bottom of the tank, and introduce fresh water through a flow restrictor.


Credits:
1. T.H. Cook, Metal Finishing, 5/79
10. W.H. Toller, Plating & Surface Finishing, 5/82
11. Jay Rotz, Plating & Surface Finishing, 6/82
16. A.J. Wallace, Jr., Plating & Surface Finishing, 11/79
17. Staff, Product Finishing, 8/81


To the best of our knowledge, the ideas contained herein are not the subjects of any patents existing or pending.
Contents copyright 1982-2014 by Ted Mooney, 523 Springfield Ave., Pine Beach, NJ 08741
All rights are reserved.



Please e-mail any comments to:
Ted Mooney, P.E. <mooney@finishing.com >



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