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Methanol Matters

September 19, 2013

Q:

Methanol is both poisonous and explosive. What precautions will be taken by the circuit owner or Novinium if the cable, cable components, or injection equipment were to leak Cablecure 732 fluid and mix with water (i.e. flooded vault scenario)?

A:

First let’s chat about the word “explosive.” Flour is explosive if you mix a bunch of flour with air in just the right concentration. I suspect you have flour in your house, but I doubt you keep it in an explosion-proof cabinet. Analogous to the flour in your home, the methanol that is liberated by the reaction of methoxysilanes (The predominant class of materials employed to rejuvenate URD cables and including Cablecure 732 fluid) has an extremely low explosion risk. I’ll explain why that is so later.

Next, let’s talk about the word “poisonous.” Methanol can be found in your garage. Methanol is typically 30% to 50% of the blue windshield washer fluid used in your automobile. There are two primary precautions to avoid methanol poisoning. The first precaution is to not drink the water in your flooded vault scenario. That’s good advice for a host of reasons. The second precaution is to avoid breathing methanol vapors. This is easily achieved by ventilation of vaults before humans enter. When present, methanol vapors register with the devices commonly utilized to test the safety of air before people enter a confined space. In unconfined spaces, natural ventilation will keep the methanol concentration very low. There is methanol in wine and apple juice, so small quantities are not at issue. If somebody smells a strong solvent-like smell the space should be exited. To reduce the methanol concentration increase the ventilation, remove the spill with a vacuum truck or other means, and/or dilute with more water.

There are four reasons why methanol is not a particularity great explosion or poison risk with Novinium brand rejuvenation:

1. Novinium’s preferred, patented injection method, Sustained Pressure Rejuvenation (SPR), does not involve unattended feed tanks. In the unlikely event that a leak does occur it can be stopped quickly, limiting the magnitude of the spill. The patented injection adapters (IAs) used at the cable ends are extraordinarily robust and unlikely to leak. The cable itself cannot leak unless it fails dielectrically. Failure with SPR occurs in fewer than 0.2% of treated cables. In the event of a dielectric failure only a small amount of fluid is likely to leak. The amount of fluid that can leak depends on the size of the cable and how long prior to the failure the cable was rejuvenated. Rules of thumb to estimate leak size are available in Novinium Rejuvenation Instruction 99, Cutting a Treated Cable (NRI99). For a typical URD cable the spill size is most likely less than a cup of coffee.

2. When the second-best approach is utilized, Improved Unsustained Pressure Rejuvenation (iUPR), a feed tank is typically left attached to the cable for about 24 hours. There is no soak period. A soak period involves the use of soak tank reservoirs for multi-month periods. The exposure to a potential leak with iUPR is typically 60-times less than the 25-year old unimproved-UPR technology. iUPR is made possible by Novinium patented technology.

3. Methoxysilanes react slowly with water to liberate methanol. The speed of this reaction is limited by two main factors. First, alkoxysilanes are not appreciably water soluble so a spill into water creates two liquid phases—like vinegar and oil. The reaction occurs primarily at the phase interface—this slows the evolution of methanol. Second the reaction is naturally slow—full reaction would occur over the course of hours. The volume of methoxysilane, such as Cablecure 732 fluid, used to treat cables is very small. For example, 19 strand cables require less than a gallon to treat 1000 feet. In your “flooded vault scenario” there will likely be many, many gallons of water and any methanol formed is quickly diluted in the water. The volume of patented Cablecure 732/733 fluids required to treat cables is typically about 30% less than the volume required by older approaches.

4. Methanol is very soluble in water—in fact water and methanol are infinitely miscible. When methanol is mixed with water its vapor pressure is greatly reduced as is its toxicity. In other words, water mitigates methanol issues with all Novinium technologies. The more water the better. Unfortunately the flammability and explosion risks associated with Cablecure XL fluid are not mitigated by water, because that material includes a highly flammable material, trimethylmethoxysilane (TMMS), that is not water soluble. For a thorough discussion see Flash Point Matters.