Introduction
In the manufacturing of Glass-Fiber wool for insulation a melt of a material such as glass is inductively heated at a stage intermediate an initial liquefying stage and a refining stage. Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency Alternating current (AC) is passed. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability. The frequency of AC used depends on the object size, material type, coupling (between the work coil and the object to be heated) and the penetration depth.
The function of the intermediate induction heating stage is essentially limited to raising the temperature of the melt a relatively minor amount to a refining temperature. Therefore, the induction heating stage may be compact with an intensified heating rate and rapid throughput, thereby permitting the induction heating zone to be a "cold" walled vessel without an appreciable effect on efficiency.
A stream of molten glass is dropped into a spinning cup that has numerous holes in its wall. Glass fibers extrude through the holes under centrifugal force and meet a high-velocity air blast that breaks them into short lengths. On their descent to a traveling belt below, the fibers are bonded together with an adhesive spray. The binder is cured, and the wool is gently packed into chopped batts or rolls.
Process
The molten glass will harden and collect in the spinner cup if allowed to cool. The spinner cup temperature must be controlled to maintain fiber quality and a functional spinner mechanism. The GD402 / GD40 gas density analyzer is used for control of the spinner cup temperature. By measuring the Specific Gravity (S.G) of the Natural Gas (N.G.) air mixture used for fuel gas, the BTU (heat) value of the fuel can be determined. The BTU value of the N.G. will change as air is mixed with it. The output of the GD402 can be fed to a control loop configured to hold an optimal fuel gas S.G.
There are usually multiple applications in each fiberglass-manufacturing site. The historic measurement technology is Gravometric or thermal conductivity. There are limitations in performance, supply and cost of ownership of each one. Calibration time, thermal stability, parts availability are the three most immediate issues faced by owners of thermal conductivity or Gravometric technologies.
* A table similar to the one below for Propane / Air mixture is used for control purposes
| Propane / Air Mixture | |||||
|---|---|---|---|---|---|
| % LPG | % Air | SGU | BTU/cuft | ||
| 47.54 | 52.46 | 1.252 | 1196 | ||
| 50.87 | 49.13 | 1.27 | 1280 | ||
| 54.24 | 45.76 | 1.287 | 1365 | ||
| 57.65 | 42.35 | 1.306 | 1450 | ||
| 61.11 | 38.89 | 1.324 | 1538 | ||
| 64.62 | 35.38 | 1.342 | 1626 | ||
| 68.16 | 31.84 | 1.361 | 1715 | ||
| 71.76 | 28.24 | 1.38 | 1805 | ||
| 75.4 | 24.6 | 1.4 | 1897 | ||
| 46.62 | 53.38 | 1.247 | 1173 | ||
| 49.88 | 50.12 | 1.264 | 1254 | ||
| 53.18 | 46.82 | 1.282 | 1338 | ||
| 56.52 | 43.48 | 1.3 | 1422 | ||
| 59.9 | 40.1 | 1.317 | 1507 | ||
| 63.33 | 36.67 | 1.336 | 1593 | ||
| 66.8 | 33.2 | 1.354 | 1681 | ||
| 70.32 | 29.68 | 1.373 | 1769 | ||
| 73.88 | 26.12 | 1.392 | 1859 | ||
| 45.76 | 54.24 | 1.243 | 1151 | ||
| 48.95 | 51.05 | 1.259 | 1232 | ||
| 52.18 | 47.82 | 1.276 | 1313 | ||
| 55.45 | 44.55 | 1.294 | 1395 | ||
| 58.76 | 41.24 | 1.311 | 1478 | ||
| 62.12 | 37.88 | 1.329 | 1563 | ||
| 65.51 | 34.49 | 1.347 | 1648 | ||
| 68.95 | 31.05 | 1.365 | 1735 | ||
| 72.43 | 27.57 | 1.384 | 1822 | ||
| 44.93 | 55.07 | 1.238 | 1130 | ||
| 48.06 | 51.94 | 1.255 | 1209 | ||
| 51.23 | 48.77 | 1.272 | 1289 | ||
| 54.43 | 45.57 | 1.288 | 1369 | ||
| 57.68 | 42.32 | 1.306 | 1451 | ||
| 60.97 | 39.03 | 1.323 | 1534 | ||
| 64.29 | 35.71 | 1.341 | 1618 | ||
| 67.66 | 32.34 | 1.359 | 1702 | ||
| 71.07 | 28.93 | 1.377 | 1788 | ||
| 44.15 | 55.85 | 1.234 | 1111 | ||
| 47.22 | 52.78 | 1.25 | 1188 | ||
| 50.32 | 49.68 | 1.267 | 1266 | ||
| 53.47 | 46.53 | 1.283 | 1345 | ||
| 56.65 | 43.35 | 1.3 | 1425 | ||
| 59.87 | 40.13 | 1.317 | 1506 | ||
| 63.13 | 36.87 | 1.335 | 1588 | ||
| 66.44 | 33.56 | 1.352 | 1672 | ||
| 69.78 | 30.22 | 1.37 | 1756 | ||
| 43.41 | 56.59 | 1.23 | 1092 | ||
| 46.42 | 53.58 | 1.246 | 1168 | ||
| 49.47 | 50.53 | 1.262 | 1245 | ||
| 52.55 | 47.45 | 1.262 | 1322 | ||
| 55.68 | 44.32 | 1.295 | 1401 | ||
| 58.84 | 41.16 | 1.312 | 1480 | ||
| 62.04 | 37.96 | 1.329 | 1561 | ||
| 65.27 | 34.73 | 1.346 | 1642 | ||
| 68.55 | 31.45 | 1.363 | 1725 | ||
Product Recommendations
Analyzer: GD402 Gas Density Meter
Sensor: GD40 Gas Density Detector
For more information contact you local Yokogawa Analytical Marketing Department.
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