Heat Treatment of Structures and Spaces—A View From the Steam Side

James R. Smith
Certified Energy Manager
Product Manager
Armstrong Heat Transfer Group
648 Moeller St.
Granby, Quebec J2G 8N1
e-mail: jrsmith@armstronginternational.com

The Armstrong Heat Transfer Group of Armstrong International Inc. has been a leading heat transfer systems supplier to the food industry and other major industries for over 50 years. Armstrong International Inc. is also a global supplier of steam, air, and hot water systems solutions for major industrial, commercial, institutional, and governmental facilities. Armstrong's Heat Transfer Group has supported insect-related heat treatment of food industry facilities for over 30 years. However, there has been a noticeable increase in the demand for this type of pest management in recent years.

Using the available utilities infrastructure found in many food facilities, which often includes steam as a major installed utility, Armstrong's Heat Transfer Group has developed both fixed and portable solutions for heat treatment as part of an integrated pest management program. Directing steam-heated air as a clean, reliable, efficient thermal source results in proven kill rates of targeted insect populations in food facilities.

Major companies, such as General Mills, Nestle (Ralston) Purina, Quaker (Pepsico), Nabisco, and Kraft, have utilized steam-sourced heating equipment from the Armstrong Heat Transfer Group for successful pest elimination programs.

Armstrong coordinates activities as requested by clients with major pest management firms to ensure that a coordinated program for pest control is accomplished.

Armstrong's involvement with the Department of Grain Science and Industry at Kansas State University, Manhattan, Kansas, extends over 10 years of support, equipment supply, and workshop participation. Refer also to recent technical articles produced by Armstrong such as "Equipment Consideration for Steam Heat Treatment as Part of Integrated Pest Management," which discusses technical issues related to selection of steam heating equipment for use in heat treatment.

Because different steam heat treatment applications have some common characteristics but many site-specific variables, it is often not possible or practical to use only standard-sized equipment. However, Armstrong has 22 standardized unit heaters ranging from 10 to 48 in, delivering approximately 800 to 22,000 CFM of air at various output temperatures based on the supplied steam source. Any unit heater can be modified for portable service or be used in multiples depending on the requirement of the applications.

Construction of the Armstrong Unit/Space Heating equipment is designed around industry-requested heavy-duty construction. This incorporates heavy wall tubes, thick and cleanable fin surfaces, special fin/tube bonding techniques, and all welded construction for pressure parts. TEFC motors are standard, along with OSHA fan guards, heavy gauge enclosures, and louver materials. The units are cleanable in place with compressed air, or the heating cores can be removed for pressure washing. Explosion proof or special electrical considerations can be furnished as applications require.

Initial evaluation of a facility for heat treatment should incorporate initial goals and scope meetings involving not only quality assurance/sanitation personnel and contracted pest management personnel but also utilities/energy plant management, housekeeping, and financial managers. A key factor to success is a site-wide audit to evaluate the true energy infrastructure so that current energy sources can be fully determined for use and the best alternatives can be considered. This should be an in-depth review (available through Armstrong), which, though a chargeable service, can often be rolled into the cost of lease or ownership of equipment.

Placement of steam heating equipment for pest elimination is a combination of art and science. The thermal heat loss calculations determining the BTUs (energy) needed for the service are determined through accepted industry heat transfer calculation criteria and proprietary sizing software. Once total heat loss is determined, several factors govern the selection of the number of units required to deliver properly distributed heat. These include area layout, mounting height (for fixed/permanent units), throw or spread of coverage per unit, and special targeted area coverage determined through input from plant quality assurance/sanitation or the integrated pest management firm.

A common problem is the desire to have fewer units with higher output temperatures, and higher total BTUs per unit to reduce numbers of heat treatment units required. Often, steam will be used at a much higher pressure (and temperature) than is required for the application. Although this may appear initially to be more economical, such an approach can severely reduce the coverage and lead to stratification of heat, causing much higher temperatures at ceiling levels than at the floor. This results in gradients that are unacceptable and may result in lower kill rates because of some "cool" spots below target temperatures. (Required temperatures are determined by pest management personnel or quality assurance/sanitation personnel with specific targeted insect requirements.)

Armstrong uses proprietary software to determine the optimum number and size of steam heaters to provide adequate, but not excessive, discharge temperatures. This results in full heat blanketing in the space to ensure reduction of any stratification issues. It has been determined that heating equipment that seemed not to do the job would actually show coverage improvement if steam pressures were varied. The result of slightly lowering outlet temperatures from steam heaters provides for longer throws and spreads of hot air to the targeted space.

The future of steam-based heat treatment design and equipment is to develop the integration between the basic heat transfer device (finned coil air heater), to blend with integrated temperature sensing, control systems, and drainage in units that are fully portable. These designs allow for plant-wide flexibility and ease of storage when the equipment is not needed and result in greater potential use for spot applications as well as larger plant-wide scenarios.

Technological advancements within Armstrong have improved monitoring, reporting, and controlling functions in the steam marketplace. Current control systems being used in energy plant monitoring over wireless control loops and even web-based systems can be adapted to these applications.

Implementing these technologies in heat treatment projects will further advance the flexibility, accuracy of control, and reduction in labor requirements for these critical applications to the food industry.

Last Updated: April 9, 2004