CASE STUDY: It's in the (Filter) Bag

Expanded polytetrafluoroethylene filter media has given a new lease on life to a filter employed in the production of pigments for the ceramic industry.

Figure 1. Reduced pressure drop results in energy savings.

Colores Cerámicos, Castillon, Spain, a producer of pigments and serigraphy for use in the ceramic industry, had been running into problems because the very fine enamel powder dust produced by its spray dryer was able to penetrate the filter media employed, clogging the fabric and causing high pressure drop across the filter. The result was reduced production rates and a useful bag life of less than four months.

The company is committed to ongoing research and development to ensure maximum performance of its processes. As part of this drive for continuous improvement, Colores Cerámicos chose to optimize the performance of the bag filter.

Figure 2. Tetratex membranes offer efficiency gains in comparison to traditional filter media.

Sourcing a Solution

Donaldson Membranes® was asked to inspect the filter, which contains 176 bags with a filtration area of 180 m2 manufactured from conventional glazed surface polyester needlefelt. The online pulse jet cleaning system handles a dust load of 60 g/m3, and the air/cloth ratio is 0.83 m/min. The operating temperature is 120-130°C with a peak of 133°C.

Jordi Ezquerro, Donaldson Membranes’ sales manager for Iberia, proposed to replace the previously installed bags with filter bags manufactured from polyester needlefelt with a Tetratex® expanded polytetrafluoroethylene (ePTFE) membrane surface. Tetratex high-performance laminates offer superior dust cake release, low pressure drop (see Figure 1), higher air flow, and high efficiency (see Figure 2), making them ideal for filtration and many other applications. Additional benefits include:
  • Increased bag life and less frequent cleaning, delivering lower maintenance costs
  • Reduced operational costs, leading to increased profitability
  • Near zero emissions, meeting required regulatory standards

Improved Performance

The filter bags, manufactured by Spanish bag maker ACMA, are still working to desired performance levels after more than 24 months in operation, a decided improvement in bag life compared with that of the previous bags. Pressure drop is maintained below 150 mm w.c. with emission levels well below the required 20 mg/Nm3.

“We are extremely satisfied with the performance of the #6214 filter bags,” says Angel Badenas, production manager at Colores Cerámicos. “The results after more than 24 months have completely fulfilled expectations from both a lifetime and performance point of view.”

For more information, contact Donaldson Membranes, 7 The Parks, Newton Le Willows WA12 0JQ, England; (44) 01942-711711; fax (44) 01942-711571; e-mail; or visit

Colores Cerámicos’ website is located at


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