Dye Penetrant


What is Nano-Filtration?

Very simply, Nano-Filtration (or N/F for short) uses permeable membranes to separate water-based solutions, emulsions and suspensions.  Under pressure, the membranes allow smaller molecules (such as water) to pass through the membrane and larger molecules (like dyes and oils) to remain behind.  Unlike its sister technology Ultra-Filtration, Nano-Filtration is capable of removing the dye, dissolved metals, and even water hardness from the waste.  This makes it the ideal method of choice when strict discharge standards need to be met or the water is to be re-used in a closed-loop process.

Why would I need N/F?

When liquid penetrants are rinsed from the tested surfaces, a waste is created that contains the dye residues and often cleaners, other testing components, and any other contaminants. You then need to either dispose of the penetrant wastes off-site (which can be expensive) or treat them yourself to remove the dyes and oils.  N/F is usually the most cost-effective and least labor-intensive way of treating the waste so the water can be sewered.

What happens to the contaminants?

With N/F we process in batches, either out of a tank or drum.  The liquid being processed is pumped from the tank, through the N/F unit, and back to the tank – this is done as a constantly re-circulating loop. As the liquid passes through the N/F unit, a small amount of water diffuses through the membrane.  The volume of penetrant rinse in the tank drops as its contents become more and more concentrated with contaminants.  This continues until no more water can be extracted, at which point the batch is done.  The concentrated contaminants are then emptied to a drum or tank for eventual disposal.  Now the process tank or drum can be re-filled with a new batch of penetrant rinsewater.

How often do I need to change membranes?

One of the beauties of N/F is that the membranes typically last for one to two years.  All that’s needed to keep them performing properly is to run a detergent solution through the N/F unit to remove any contaminants that build up on the membrane surface.  The dirty detergent can than be transferred to the process tank for cleaning with the next batch if desired.  The frequency of cleaning varies with the nature and level of contaminants.  It can be after every batch or it could be on a weekly basis.  Experience will indicate what’s best.

How expensive is a N/F system?

N/F is almost always more cost effective than the alternatives when compared on a per-gallon basis.  Off-site disposal is one of the most costly choices and allows a third party to expose you to potential long-term liability.  Evaporators are expensive, have very high energy costs to operate, and often require permitting as a point source for air emissions.  Chemical treatment requires expensive equipment and chemicals and is labor intensive.

Activated carbon will remove the dye, but is expensive, both to purchase the carbon, and then to dispose of it when it’s expended.

N/F represents a one-time purchase of a machine, minimal costs for detergent, and replacement of the membrane every year or two.  INFINITEX  N/F machines are designed to be run with minimal labor.  Someone needs to turn the machine on, and empty the concentrated contaminants when it’s done.  The machines are fully automated and will shut themselves off when they finish a batch, if they run dry, if they get bumped or tilted, or if they sense any condition that could endanger either the machine or an operator.

The cost of a N/F system depends on the volume of waste you need to process.  Typically as the daily volume goes up, the per gallon system costs decline. Our models range from machines that can process up to 50 gallons per day on up to large units that can handle many thousands of gallons per day.

If you would like to learn more about processing penetrant rinsewater, contact an Applications Engineer at (716) 741-8381 or visit our Web site at www.splitter.com.