Thermal degradation is kryptonite for heat transfer applications. It can lead to production complications and safety concerns, making it imperative to prevent thermal degradation altogether. Maintaining thermal stability requires balanced temperature controls, which is possible through control panels and a screwplug heater. But how?
Thermal degradation occurs when oil is overheated beyond its boiling point. As it continues to boil, the oil’s composition breaks down to form vapors. This reduces viscosity, which is detrimental for oil-based products that require the oil to be thick. Additionally, excessive overheating reduces oil’s flash point to levels that may cause it to ignite, posing a significant fire and explosion risk.
It’s important to note there are different forms of fluid degradation, not just thermal. Oxidative degradation is just as problematic and occurs when oxygen reacts with oil through free radical interaction.
Heat transfer oils subjected to excessive temperatures experience what’s known as “cracking, “where the molecules break down. Not only does that reduce viscosity, but it also leads to the calcification of the fluid. This calcification can damage the pipes through which the heat transfer oils flow. The damaged equipment may further deteriorate the quality of the degraded oil, creating a vicious cycle where the oil becomes unusable.
Preventing thermal degradation ultimately requires precise temperature control. This is where Wattco’s screwplug heaters (and temperature control panels) maintain suitable temperatures for heat transfer oils.
Screwplug heaters are ideal for this application because they’re small and mobile enough to facilitate heat transfer tanks. Their conical NPT screwplug also creates a seal that prevents oil leakage. More importantly, the screwplug heaters often use steel heating elements which rapidly disperse heat.
The rapid dissipation in heat, aided by adding a nichrome and magnesium oxide element, allows operators to use lower watt density. A lower wattage is beneficial because it lowers the risk of the element turning red to the point of overheating the oil.
It’s important to note that even with efficient heating mechanisms, there’s no guarantee oil will maintain a suitable temperature. External factors, such as ambient temperatures or internal factors, such as the oil blend itself, can lead to temperature fluctuations. The only way to maintain a desired and uniform temperature is with temperature controls, which are added to Wattco screwplug heaters when required.
First, we add temperature controls to a screwplug heater, allowing operators to adjust the amount of heat transfer coming from the heater. If the heat is too high, an operator can turn the knobs down (using a mechanical thermostat), so the oil is not overheating. This feature also allows operators to preserve the heating elements of a screwplug heater itself.
Second, we add a thermocouple and thermowell to the screwplug heater to prevent overheating (when using a digital temperature controller). The thermocouple is a sensor that provides temperature readings for operators to monitor. For certain units, high-temperature readings will automatically shut off the unit to prevent overheating of the oil.
The thermowell protects this sensor from corrosion and heat damage, which is vital because a damaged thermocouple can’t provide temperature readings. Wattco screwplug heaters are equipped with robust temperature controls. We customize them to suit your type of heat transfer oil and to counteract the conditions that may lead to overheating.
Thermal degradation is a complex issue in process engineering, yet temperature precision isn’t the only factor to consider. Improper maintenance promotes calcium and sludge buildup that clogs pipes, further contributing to thermal degradation and equipment damage. That’s why regularly scheduled maintenance is crucial. Techniques such as hot oil flushing remove these buildups.
However, we highly recommend using a screwplug heater equipped with temperature controls. We build screwplug heaters to match the size of your tank and select materials that will best suit your heat transfer fluid for your budget.
Get a quote for your screwplug heater today. Our representatives will help you find the exact setup needed for your industrial needs.