Hot Oil Systems for 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. And, in most areas of the country there is no need for expensive licensed operating engineers.

Productivity
While steam systems generally operate to 350°F, thermal oil systems can easily provide 450°F – 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.

Maintenance
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 pro-vide 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.

Environmental Concerns
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.

Operating Costs
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 350°F, generates 120 psig. At these pressures, most states re-quire 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 vapor 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.

System Economics
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 favor 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.

Notes:

1. 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 ”.
    
2. In selecting a heat transfer fluid for use in laundries, these areas should be given priority:

• Flash and fire points. The fluid has a flash point of 440°F, and a fire point of 500°F, higher than the operating temperature of the ironer.
• Low vapor pressure. Vapor 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.
• Low pumping horsepower requirement. The HE fluid requires among the lowest pump horsepower of any fluid available.
• 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.