Shingle manufacturer achieves precise pump control with VEGA 80 GHz level sensor
The shingles on an overwhelming majority of roofs in North America are made with sheets of fiberglass coated in additive-treated liquid asphalt. This process has real implications for homeowners: The amount and type of asphalt on shingles is used to determine their lifespan. To coat its shingles, a Canadian manufacturer rolls its fiberglass sheets into a tank of asphalt.
Problem: An ugly process for attractive shingles
A durable level measurement solution was in order as conditions inside the coating area of the plant are extremely adverse with temperatures reaching well over 300° F. The application offered difficulties beyond heat: Different additives change asphalt's dielectric constant, and asphalt's adhesive nature leaves a nasty buildup similar to tar. This mess caused drift in the capacitance instruments the company installed in its asphalt tank and the level-conscience users in the plant could no longer endure this ongoing inaccuracy.
Solution: VEGAPULS 64 cuts through the buildup
A VEGA Regional Manager and Contro Valve, the shingle company’s local VEGA representative, took a look at the coating process and recommended the VEGAPULS 64 through-air radar sensor. The VEGAPULS 64 has a large dynamic range, so it is sensitive enough to measure liquids of any dielectric, and it is also intelligent enough to ignore false signals created by buildup, which, six months after installation, appears to be swallowing the antenna. Another advantage of a through-air radar sensor in this application is non-contact operation. Asphalt would have gummed up a mechanical level instrument, causing frequent maintenance and increasing the likelihood of instrument failure.
VEGA and Contro Valve assisted plant personnel in installing a VEGAPULS 64 approximately two feet above the asphalt coating tray. A sensor with a 1.5” NPT process connection was used because it offered the best microwave beam angle for the cramped application. An 80 GHz radar device, the VEGAPULS 64 can emit a beam as narrow as 3°. Such focusing is important in applications where microwaves have a tight path to travel to the product surface.
Impact: Level measurement to the last drop
The VEGAPULS 64 unit installed in this coating application have been humming along without measurement drift, maintenance, or failure. The sensor’s to-the-millimeter accuracy has the added benefit of allowing users to thread an incredibly tight needle regarding the operation of a pump.
Asphalt is pumped into a tank the shingle company wants to keep 80% full. In order to maintain that level, the pump runs at 40% capacity. If tank level drops to 79% pump capacity is cranked up to 100% but if level rises to 81%, pump capacity is dropped to 0%. This 1% difference in level capacity amounts to 4mm of asphalt. Few radar sensors can offer that kind of pinpoint precision, but the VEGAPULS 64 delivers accurate level measurement to the last drop.
Conclusion
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