A Comparison between Thermal Fluid and Steam

Thermal fluid systems are substituting steam in a wide range of process applications. They offer uniform and accurate temperature control, resulting in better product quality and production, reduced maintenance, years of highly efficient service, and improved safety for humans and the environment. Hot oil systems offer considerable benefits in just about every category.

Efficiency

Manufacturers of thermal fluid heaters specify that efficiencies can be 5 to 8% higher than that of traditional steam systems. Better efficiency is also provided by hot-oil heated shell-and-tube steam generators, which need less water treatment and experience reduced fouling, thanks to the lower heat flux. The difference in efficiency becomes more pronounced if users account for the flash loss of a normal steam system of 6% to 14%, de-aerator loss of another 2%, and blowdown loss of up to 3%. These losses are not experienced by thermal fluid systems, and hence can be as much as 31% more efficient, except for the additional efficiencies of a steam generator and heater.

Licensed Operators

In most parts of the country, it has been stipulated that the operation of high-pressure fired steam systems should be managed by full-time licensed stationary operating engineers. However, the yearly cost for each engineer can be more than $60,000. Most thermal fluid systems, unlike steam systems, function at atmospheric pressure and are vented to atmospheric air at the expansion tank. The systems’ pressure is restricted to the pump discharge so as to maintain the fluid in disordered flow while offsetting the piping frictional drag. Pressures discharged by standard pumps can span from 35 to 65psi with slightly higher pressures needed for large systems. Thanks to the unpressurized and safe operation, licensed operators are rarely required for thermal oil systems.

Corrosion

Corrosion issues are common when it comes to steam systems. The air along with salts, hot water, and other reactive contaminants provide a tremendous potential for metal corrosion. Since steam is abrasive, it has almost no lubricity, which means deposits and scale from the minerals present in water supplies and the associated system issues are increased manifold. Paratherm provides non-corrosive fluids, which are completely derived from natural U.S. feedstocks and offer the same level of metal surface protection like premium light lubricating oils.

Maintenance

Continuous maintenance is required for steam systems — maintenance that is centered on valves, steam traps, expansion joints, condensate return pumps, and analysis and treatment of water. Moreover, during a power failure in cold climatic conditions, steam systems are often subject to burst pipes, freezing, and damaged components. In contrast, thermal fluid systems do not need any traps, blowdown/water additives, or condensate return. If the right fluid is specified, these systems can be shut down even in sub-zero conditions without any concern for freezing. On cooling Paratherm fluids below their pour points, they easily contract upon solidifying and thus do not raise concerns for burst pipes. Hot oil systems work safely, efficiently, and quietly and require just minimum maintenance.

Environmental Safety

In a steam system, the water needs to be chemically treated to reduce rust, amongst other things issues, and discharging the chemicals into sewers can pose a major environmental hazard. Further, the discharged water temperature is usually regulated by law. As such, special cooling provisions are needed if water has to be drained into sewers. In many areas, water temperature more than 140°F cannot be discharged. Unlike steam systems, thermal fluid systems do not need blowdown and do not experience incessant leakage.

In case Paratherm fluids leak from the system, the same simple protocols used for spills of light lubricating oil are followed to clean up the fluids. Paratherm heat transfer fluids, unlike heavily treated boiler feed water, can be disposed of in a safe and easy manner. These fluids can be integrated with spent lube oils, deployed to the local motor oil recycler, and developed into another handy product.

Safety

Steam systems would need to work at very high pressures to provide the level of heat needed in most process operations. For instance, at 600°F, a saturated steam system develops approximately 1600psi, but even at 400°F the pressure continuous to be still high — approximately 235psi. Most thermal fluid systems, on the contrary, are vented to atmospheric air. Pressure discharged by pumps is sufficiently high to offset the frictional drag from components and piping while preserving turbulent flow. Paratherm fluids’ vapor pressures are just fractions of the atmosphere even at 600°F.

Temperature Controls

Steam systems generally depend on pressure control to regulate temperature. With this reliance on fragile pressure balance, precision is usually restricted to ±10°F more or less. As rust takes its toll and the system ages, temperature control begins to degrade over time. Another issue is uniformity of heating owing to differing rates of condensation and condensate removal in the heat system. These negative factors are before taking into consideration the negative impacts of plating-out and metal surface corrosion.

Thermal fluid equipment manufacturers, in comparison, have reported the ability to control temperature swings to ±1.5°F or less. This accuracy is realized by the metering and merging of warmer fluid from the supply line with the cooler return fluid. Uniformity and accuracy of temperature control throughout the whole user surface is ensured with the inclusion of high-velocity turbulent fluid flow to the equation. Thermal fluid systems offer uniform, efficient heating and cooling. Certain fluids can offer efficient heating from more than 400°F to cooling at -40°F and lower.

System Cost

Although the cost of steam systems can be less than that of thermal fluid systems, there are paybacks in the case of less-complicated thermal fluid systems, such as reduced environmental concerns, operating costs, and maintenance costs, with better production and product quality due to better control of cooling and heating. These benefits, combined with reduced manpower cost and enhanced safety, make the overall cost of thermal fluid systems far better than that of steam systems.

This information has been sourced, reviewed and adapted from materials provided by Paratherm.

For more information on this source, please visit Paratherm.

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