Electrical Transformer End-of-Life Hazardous Waste Disposal

Invented in the 1880’s, the job of adjusting the thousands of volts generated by power utilities to usable levels has always fallen to electrical transformers. They’re amazingly simple devices—but nonetheless require end-of-life hazardous waste management. Q&As in this blog entry include:

1. What is an electrical transformer?
2. What is a step-up transformer used for?
3. What is a step-down transformer used for?
4. Why do electrical transformers require hazardous waste disposal?
5. What kind of oil is used in electrical transformers?
6. What are the alternatives to using PCBs in electrical transformers?
7. Where can you get expert advice about disposal of end-of-life transformers?

1. What is an electrical transformer?

Basically, an electrical transformer consists of one wire coil encased closely to a second. When the first or “primary” coil is fed alternating current, another alternating current is induced in the nearby “secondary” one.  But that’s only half of it.

Consider: the voltages of the two AC currents will match the sizes of the two coils in exact proportion to one another.  For example:

• If the primary coil is half the size of the secondary, the voltage appearing in the secondary will be twice as large. This is called a “step-up transformer.”
• Conversely, if the primary coil is twice as large as the secondary, then the voltage appearing in the secondary will be half as much. This is called a “step-down transformer.”

2. What is a step-up transformer used for?

Utilities use massive step-up transformers to increase voltage (aka tension) in order to push electricity more efficiently through long-distance transmission lines (e.g., 36,000 volts). Thus, the term “high-tension wires.”

3. What is a step-down transformer used for?

Utilities use step-down transformers (in so-called “substations”) to reduce voltages. For example, to reduce high-tension voltage to distribution levels (e.g., 6,600 volts).

To reduce such distribution voltages to the relatively safe and familiar 120/220 VAC we have coursing through the walls of our homes, utilities use smaller step-down transformers. One kind is the type of things you see atop utility poles in front of houses; they look like big tin cans with wires popping out of the top. Another is the boxy monstrosities set on concrete pedestals, usually to feed underground wiring to nearby homes.

Thus, there are literally millions of transformers in use across America and the rest of the world.  And each will eventually wear out and require hazardous waste disposal.

4. Why do electrical transformers require hazardous waste disposal?

In a transformer, the enormous amounts of current applied to the primary coil and induced in the secondary together generate considerable amounts of heat: enough to melt them both.

To prevent this, the transformer encasement is filled with oil, so that both coils are effectively bathed in it. Oil is basically nonconductive, so it won’t short-circuit the coils, while its very high boiling point allows it to absorb a great deal of heat, thus preventing the copper from melting.

5. What kind of oil is used in electrical transformers?

Oddly enough, although they’ve been around for over 130+ years, the best kind of oil to cool electrical transformers is still a matter of debate.

At first, polychlorinated biphenyls (PCBs) were employed, since they’re nonflammable and highly nonconductive. Sadly, they’re also extremely toxic; they’re not biodegradable; and they’re absorbed faster than they can be metabolized (or excreted) by animals and humans. Incinerating PCBs generates such poisons as chlorinated dioxins and dibenzofurans, which are even more toxic to humans, animals, and the environment than the PCBs themselves.

Given that rogues’ gallery of drawbacks, production of PCBs was banned in the United States in 1979. Thereby, PCBs haven’t been used in electrical transformers for 45 years. This is good in the obvious sense, but it also means that there’s a lot of legacy equipment in existence that’s nearing end-of-life (or languishing in junk piles) that needs to be disposed of, and doing so will require careful hazardous waste management.

6. What are the alternatives to using PCBs in electrical transformers?

Mineral oil is the most common alternative, but its insulating properties are rapidly degraded by any amount of moisture. It’s also highly flammable. If a transformer were to leak mineral oil, it could easily start a fire.

Because of its flammability, fire codes often prohibit transformers that are cooled with mineral oil from inside buildings or structures. And although mineral oil is relatively more benign than PCBs, it’s nonetheless an environmental contaminant that requires careful hazardous material handling.

Another consideration: mineral oil is fully miscible with PCBs. This means it will form a homogenous mixture with them in any proportion; and years ago, the same drums, pumps, and hoses used to deliver mineral oils were used for PCBs.

Thus, PCB contamination can still be an issue for transformers that are ostensibly PCB-free. For instance, concentrations of PCBs greater than 5 parts per million are classified as hazardous waste in some states (see source).

Other oils that are used to cool transformers include natural esters and silicones (see source).

7. Where can you get expert advice about disposal of end-of-life transformers?

PCBs haven’t been specified inside electrical transformers for 45+ years. This is good in the long run. But it also means that there’s a great deal of legacy equipment that’s nearing end-of-life that will require hazardous waste management, as PCB contamination is particularly onerous, and the regulations surrounding its disposal are commensurately strict.

It’s also worth noting that mineral oil—the most common replacement for PCBs—might be contaminated with PCBs and thus require a more rigorous level of hazardous waste management than is common for less-toxic waste oils.

Don’t go it alone!

As an industry leader in RCRA-compliant waste management, Hazardous Waste Experts can help you facilitate the responsible and ethical disposal and/or recycling of your end-of-life transformers. Depend on us for PCB & non-PCB equipment disposal, PCB testing, environmental services, cradle-to-grave record keeping, and more.

Email or call 1.425.414.3485.

And thank you for reading our blog!