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CO2 v Helium

September 26, 2013

Q:
Novinium uses CO2 gases to push their fluids, and not helium. Why is that so? Is there a benefit of one over the other? Does the CO2 contribute to global warming?

A:
There are safety, environmental, and economic benefits of using CO2.

Safety Benefit

Effervescence limits the conductivity of fluid effluent along the vacuum tube interior. Carbon dioxide (CO2) is liberated when you open a soda or beer bottle, because the pressure on the fluid is released. CO2 is used in iUPR (improved Unsustained Pressure Rejuvenation) to provide the driving force to the rejuvenation fluid. CO2 is even more soluble in Cablecure® 732/733 and Cablecure iXL rejuvenation fluids than it is in beer and soda. As CO2-saturated rejuvenation fluid flows through the strand interstices and down the length of a cable the absolute pressure decreases almost linearly along the cable length. As the pressure decreases CO2 is liberated. The viscosity of gaseous CO2 is orders of magnitude lower than the liquid phase from which it effervesces, so it bubbles ahead of the fluid and rushes to the vacuum tank. Any fluid exiting the cable is interspersed between much more voluminous CO2 bubbles. Of course, gaseous CO2 is a great dielectric and its presence disconnects adjacent droplets of fluid and prevents there being a contiguous path for current to flow. Water, if present, does not wet the surface of the polyethylene tube, but instead stays as discrete droplets. The conductor voltage is not efficiently conveyed along the tubing length, greatly reducing the possibility that a collection bottle will become energized.

Environmental Benefit

Paradoxically the use of CO2 delivers lower net CO2 emissions. The primary industrial sources of CO2 are waste streams like the flue gas of fossil fuel power plants and CO2 contaminated natural gas.  If the CO2 were not captured by the suppliers, it would be vented to the atmosphere. There is no net CO2 created. It takes energy to provide pressure to inject fluid through a cable. Energy invariably means more net CO2. It takes 8-times more energy and 8-times more CO2 to make a standard cubic foot (SCF) of N2 than a SCF of CO2. It takes 15-times more energy and 15-times more CO2 to make a SCF of Helium than a SCF CO2. Not only is CO2 the most CO2-efficient gas, but the advanced Novinium process uses a lot less gas than the older injection approach. First the older approach requires air flow and pressure tests using compressed nitrogen (N2). Novinium uses flow and pressure tests less than 10% of the time, and when we do, we use CO2. The older approach uses helium (He) as a fluid driving force in its feed bottles, Novinium uses CO2. Not only does the use of helium have the adverse global warming impact resulting from the large amount of CO2 used to produce it, but helium itself is a scarce world resource. Of course, compared to the replacement alternative, rejuvenation has a huge net benefit to global warming.

Economic Benefit

CO2 is less costly and because it is delivered in cylinders as a liquid there is less effort required by our field teams to maintain a supply. Cheaper—safer—more earth-friendly!