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Engineer Talk

EHS on our Silicone Rubber Heater Line

by AJ Nidek & William Harris

Air Control

All employees within the Smiths Group family of companies are guided by a set of principles outlined in Smiths' Environmental Health & Safety (EHS) policy statement. One of the principles calls for continual improvement in pollution prevention, hazard reduction, and the protection of human health. Our Silicone Rubber Heater production line is a good example of Tutco-Farnam leadership in creating an injury-free and environmentally responsible workplace. In this article, we’ll look at EHS as it relates to water and air in our silicone heater manufacturing process.


Encased within a silicone rubber heater is a metal heating element. The heating element shape is created through a series of chemical processes. The etching is a subtractive process where metal is removed from a metal foil in a particular geometry to produce a resistive heating element. Trace metals from the etching process need to be removed from a chemical solution. This includes metal removed from the metal foil (that was used to make the heating element shape) as well as iron from the ferric chloride etchant.

Water Treatment

Filtering is done with a water treatment system like you’d find in a municipality but on a smaller scale. The first step of the treatment is called clarification. This is largely a chemical process. Ferric chloride and sulfuric acid work to create sulfite compounds that pull out trace metals. Caustic makes hydroxide ions with the other metals that will precipitate out. The ferric chloride removes the remainder of the iron and other metals. Ferric chloride with an anionic polymer drives the flocculation, a technique that promotes agglomeration and assists in the settling of particles. In the flocculation chamber, the coagulant along with some gentle mixing brings about the aggregation of suspended particles. These particles called 'floc' fall out of suspension resulting in a slurry. The slurry gets pumped through the filter press depositing an insoluble material called a ‘filter cake’. The liquid coming out is relatively neutral within 6 to 8 pH. Acid brings down the pH while caustic brings it up. Filter cakes are analyzed by a third party before disposal.


With this equipment, we’re essentially removing all of the trace metals. Federal, state, and local government limits are reported in mg/L (milligrams per Liter); whereas, the values that have come back from our analytical services after pretreatment show values in ug/L (micrograms per Liter). Our home county of Buncombe has the most stringent PPM (parts per million) regulation in all of North Carolina and we are orders of magnitude under local and federal regulations for our discharge of effluent.

Buncombe County, North Carolina
Fixed Upper Limits for Constituents (Milligrams per Liter, mg/l)
  Maximum Instantaneous Concentration (Grab Sample) Maximum Daily Average (Based on 24 Hour Composite Samples)
Arsenic 2.0 1.00
Cadmium 1.2 0.69
Chromium, T 2.5 1.00
Copper 2.5 1.00
Lead 0.6 0.40
Mercury 0.2 0.10
Nickel 2.5 1.00
Silver 1.0 0.43
Tin 2.5 1.00
Zinc 2.5 1.00
Cyanide 1.9 -
Phenol 2.5 -


With a line of wells holding 360 gallons anywhere between 90F - 130F, there are going to be some fumes. While the liquids are contained within the wells, there is still some agitation and spraying and that is going to put some chemicals in the air. Tutco-Farnam ultimately decided that overkill is the best solution to an underventilation risk. Our system uses large-diameter hard piping. Ventilation capabilities exceed normal production limits by such a degree that panels will get sucked off the table if throttled completely open. This gives us a wide range of control over our ability to ventilate air. Superior ventilation is something Tutco-Farnam employees were proactive from the beginning. To take it a step further, Tutco-Farnam designed the line to be in a room that is contained from the rest of the building. This separation means that no fumes can make their way to people in other parts of the building.

A Culture of Responsibility

Tutco-Farnam employees take pride in their commitment to achieving excellence in environment, health, and safety (EHS) performance. It is part of our culture. Every employee at Tutco-Farnam as well as the entire family of Smiths Group companies has a personal responsibility and an obligation to colleagues to uphold EHS principles. We do it because we care, because this is our home and because it is the right thing to do.

The extra mile in each of these examples was achieved by individual employees doing the right thing. That’s because EHS promotes a culture of responsibility throughout the business and it has become who we are. We are proud of our EHS culture and the measurably impactful initiatives that come with it.

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