ROOFING TECHNOLOGY, INC.

Is Cross Web Temperature Measurement important?

With the onset of hot weather and even faster machine speeds, product temperature control has never been more important! This is fax 1 in a series on cooling control for roofing manufacturers. We get a considerable number of questions from manufacturers relative to cooling. We thought it would be beneficial to fax a few comments on frequently asked questions.

Question; Why is cross web temperature measurement so important? I have an IR spot sensor that measures at the cutter entrance and it measures and indicates accurately.

Answer: Infrared (IR) measurement is a good means of measuring product temperature of roofing web processes if you have selected a unit that senses the proper wave length (spectral response - 8-14 micron). Roofing materials typically have a very high emissivity (0.95) and have a very low reflectance thus making them an excellent application for IR temperature measurement. The range of product temperatures which a Roofing Plant can run vary significantly from plant to plant. But, consider for a moment the following scenario;

Suppose your plant can package shingle product between the temperatures of 80 - 105 Deg F without any problems with tabbing, knife build up, adhesive sticking, bundle straightening, limpness jamming, cold form jamming, product moisture, and clean cuts. Your product temperature would need to be an average of 92.5F with a standard deviation of 4.2F to reliably perform within your limits of operation. If you are like many plants, you haven't a clue... Can operators and maintenance personnel be expected to separate mechanical or electrical machine problems from product temperature variation problems? Do they have access to historical trend charts and cross web variation when called to the cutter for jams and cutting problems? Do they have the same type of information to determine if FPL breaks are temperature related? Do your operators typically raise the cutter head when tabbing occurs, or do the consider the temperature in the area of the web that is tabbing. Raising the cutter head prematurely will significantly lower your cutter knife life raising your annual operating costs significantly.

Consider spot sensors. Can a spot sensor (spot size is typically 4-12" diameter - see your equipment manual for spot size) represent the total web temperature? My observations indicated that the average industry cross web temperature range is approximately 12 Deg F. If you have no cross web temperature indication, yours could be much higher ( I've seen plants with consistent ranges of 48 Deg F). The indication seen by your operator (from an accurate sensor ) could be 20, 30 or 40 Deg F different from another portion of the product web. This would leave operators hopeless in diagnosing process temperature problems. In some cases, the spot sensor can be worse than no indication at all.

This and other Roofing Technology - Roofing Industry Process Discussions are written by John E Youngk, President- Roofing Technology, a Mechanical Engineer (BSME) with 16 years of roofing machine design, process engineering , and machine automation experience. If you have any questions please call John at 1-800-879-7955 , email at youngkj@roofingtech.net, or visit our web site at http://www.roofingtech.net.