5 Things to Know About Replacing nPB in an Industrial Cleaning Process

Although n-Propyl Bromide (nPB) has been widely used as an effective and reliable industrial cleaner for metal parts since the 1990s, it now is under scrutiny by the U.S. Environmental Protection Agency (EPA), Occupational Health and Safety Administration (OSHA) and American Conference of Governmental Industrial Hygienists (ACGIH).

In 2014, the permissible exposure limit of nPB went from 10 ppm (parts per million) down to only 0.1 ppm. In 2018, the EPA added nPB to its Toxic Substance Control Act (TSCA) list. In August 2020, the EPA reported that nPB presents an unreasonable risk to human health and should be restricted as a cleaner or degreaser. This report is only a preliminary step for the EPA. Many experts anticipate it will likely lead to a complete EPA ban on nPB by the end of 2022. Also, nPB is already sunset or banned in Europe as of July 2020.

This is leading manufacturers to strongly consider replacing nPB with cleaning fluids that are less hazardous for workers and the environment.

There are a number of nPB replacements that will clean just as well if not better than nPB inside a modern vapor degreaser. Many of the nPB replacement cleaning fluids are said to provide consistent cleaning quality, cost savings and better throughput. Plus, they have better toxicity profiles, making them safer for people and the environment.

Most nPB replacement cleaning fluids are lab-tested and analyzed to ensure the cleaning results are reliable and consistent. In most instances, cleaning efficiencies are often maintained or improved, even on hard-to-remove polar and nonpolar soils. Modern cleaning fluids perform well at removing a variety of soils from parts, including machining oil, grease, lubricants, adhesives, wax, marking inks and fingerprints.

Many modern nPB replacements have high solvency to dissolve contaminants yet are formulated to not damage delicate part substrates or materials. The strength of a parts cleaner is measured by its Kb value, which is a continuum of cleaning strengths from very mild to extremely aggressive. A mild, plastic-safe cleaner made of alcohol might have an approximate value of 10 Kb, while nPB has a value of 130 Kb. This means nPB is so strong that it might attack plastics, elastomers and adhesives. In contrast, most modern nPB replacements have a value of about 100 Kb which makes them safer to use on a variety of parts, especially those comprised of mixed materials.

Here are the five basic facts to know about replacing nPB:

1. Newer fluid saves time and money. Modern nPB replacement cleaning fluids typically have a lower boiling point and heat of vaporization than nPB. Therefore, less energy is required to heat the cleaning fluid, resulting in overall cost savings. Also, because modern cleaning fluids boil at a lower temperature than nPB, parts come out of the vapor degreasing machine dry and cool enough to handle. This speeds the entire production process, improving overall manufacturing efficiency.
2. Less maintenance is involved. Except under the most extreme conditions, such as exposed to a strong base or acid or extreme heat, nPB replacement fluids will not turn acidic as nPB does. They do not need chemical stabilizers, scavengers or the weekly acid acceptance tests that nPB needs.
3. It is more environmentally friendly. Many modern vapor degreasing fluids are based on more environmentally friendly Hydrofluoro-olefin technology. They typically have a zero ozone depletion potential and a global warming potential under 10, making them safe, sustainable nPB alternatives. And, unlike nPB, modern cleaning fluids are not considered a HAP (Hazardous Air Pollutant) and are exempt from state and local HAP testing, documentation and reporting requirements.
   

   There are a number of nPB replacements that will clean just as well if not better than nPB inside a modern vapor degreaser. Parts come out of a vapor degreaser dry and cool enough to handle. Photo Credit: MicroCare LLC

4. Replacement is safer for workers. Modern cleaning fluids are also nonflammable, making them a preferred choice of Occupational Health and Safety (OHS) officers. Plus, most modern fluids have an ACGIH long-term exposure limit, with a time-weighted average of 8 hours, or about 200 parts per million. That is 2,000 times better than nPB. Most also have a lighter, less offensive aroma than nPB, making the work environment more pleasant.
5. It is easy to switch. Modern cleaning fluid is appropriate for use with most existing equipment. After emptying and cleaning the vapor degreaser, the replacement fluid "drops in" to cleaning equipment without an appreciable change to the cleaning process. That means little disruption to production workflow and no retraining of operators on an entirely new process.

A complete nPB ban is likely to happen in the U.S. soon. It’s suggested that manufacturers work with a cleaning fluid supplier with vapor degreasing experience that can help find a replacement fluid that is already field-tested with proven cleaning performance. Also, they should look for a supplier with lab testing capabilities. Chemists can perform cleaning trials on parts and soils to verify the new cleaning fluid is the right fit for applications before making an investment. They should also provide ongoing support and training as manufacturers transition away from nPB and move toward a healthier and more sustainable cleaning fluid option.