Hot Oil Systems for Industrial Laundries
Gaining in popularity, thermal oil systems used to heat flatwork ironers offer greater productivity per unit floor space. System corrosion, condensate return and steam trap maintenance are eliminated. There is no water treatment or discharge problem, and operating costs are substantially reduced through system efficiencies. In most areas of the country there is no need for expensive licensed operating engineers.
While steam systems generally operate to 176°C, thermal oil systems can easily provide 232°C – with the pump discharge providing only enough pressure to overcome pipe friction. To compare, an oil heated 3-chest ironer with parallel flow can provide about the same output as a 5-chest steam-heated unit.
And because of the low pressures common in thermal oil systems, the chests can be fabricated of steel rather than the cast-iron required for steam systems. Not only is this a cost savings, but heat transfer is improved with steel, and the lower number of chests saves valuable floor space.
With steam systems, corrosion is a foregone conclusion. The goal is to reduce corrosion as much as possible, principally through water treatment – which is expensive and time consuming. And because of corrosion, traps and other components must be constantly maintained.
Thermal oils will not corrode the materials commonly used in laundry systems. In fact, oils provide a protective coating to metals in the system and offer high lubricity to moving parts. And barring leaks or spills, no make-up is necessary.
The water used in a steam system must be treated to reduce corrosion and increase lubricity, among other requirements. The chemicals used, in some cases, are considered regulated and/or hazardous wastes. Blowdown and system leaks must be closely monitored, and the system’s water cannot be allowed to enter floor drains or flow into waterways. There is no blowdown in thermal oil systems. And spills can be handled using the same procedures used for releases of lubricating oils.
Steam systems lose energy through flash, blowdown and de-aeration cycles. Thermal oil systems operating at higher temperatures use less fuel because these losses are eliminated.
Licensed Operating Engineers
A steam system operating at 80°C, generates 827.371 kPa. At these pressures, most states require a licensed operating engineer be employed to supervise the system. Thermal oil systems operate at pressures dictated by the discharge of the pump, static head of the expansion tank and vapour pressure of the fluid (usually well below atmospheric).
If high pressure steam is required, the laundry can specify the use of an unfired, hot oil heated shell and tube steam generator. Thermal fluid heat exchanges can produce hot water and hot air as well. These units have proven extremely reliable. And, in hot water exchangers, fouling tends to happen much more slowly than fired steam, principally due to the low heat flux.
A thermal-oil heater costs more than a steam boiler. A 3 or 4-chest oil-heated ironer, however, costs less than a 5 or 6-chest steam heated unit. With thermal oil, additional savings are generated in the elimination of deaeration, blow down and chemicals used to treat the water, not to mention low maintenance, smooth operation, and tight temperature control. The biggest savings involve the elimination of the licensed operating engineer. If local regulations permit this with thermal oil systems (as many do), the balance swings heavily in favour of the oil system.
We strongly suggest you consult a competent engineering consultant for a thorough evaluation of your requirements and a balanced approach to the decision for steam or thermal oil. Call us with questions. Or, visit us at The Clean Show.
- We strongly recommend you consider an expansion tank equipped with a cold-seal tank, or inert gas blanketing. These can largely eliminate oxidation of the heat transfer fluid. One of the most insidious types of fluid degradation, oxidation, is discussed more thoroughly in our data sheet entitled “Oxidation in Heat Transfer Fluids”.
- In selecting a heat transfer fluid for use in laundries, these areas should be given priority:
- Flash point. The Paratherm HE fluid has a closed-cup flash point of 210°C, which is higher than the operating termperature of the ironer.
- Low vapour pressure. Vapour pressure of the HE fluid is among the lowest of any fluid available
- Non-toxicity. The HE fluid is non-toxic and has passed stringent Bioassay, while many heat transfer fluids are considered hazardous and/or regulated waste.
Broad industry acceptance. The HE fluid is currently used in a wide range of hotel, institutional and central laundries and is fuly approved by leading manufacturers of laundry equipment
Maintaining Thermal-Fluid Ironers Process Heating Magazine
Thermal Fluid vs. Steam Paratherm User’s Guide
Analyzing Your Fluid Paratherm User’s Guide
Thermal Fluid System Leakage Paratherm User’s Guide
Laundry Industry Links
NAILM (Natl Assn. of Inst. Linen Mgmt.) Industry Information, Public Policy, News
Laundry Novelty Film: Ironrite Ironer(1946) Archive.org, Just for Fun
Textile Rental Services Association Trade Organization, Uniform and Linen Rental