As the print demands for packaging papers continue to grow, it may be an opportune time to share some details for how we were able to provide technical and economic justification for adding screening systems to the size press starch.
My career in fine papers began in the 1980’s. During my first 10 years working in fine paper, I worked on at least four starch screening projects. Many of those fine paper machines are now shut down. However, as equipment continues to be repurposed or updated for production of packaging grades, and as the demand for better imaging for packaging grades only increases, the technical and economic justification for screening may again be relevant.
The first question to consider is, do you need to improve starch screening?
Start by investigating what is in place.
- Do you have pressure screens where a screen has been removed? If not sized properly, crews may remove a filter to ensure that starch flow is not restricted.
- Or, if there is a quality issue with the starch, such as high amounts of amylose formation, then the crews may be improvising past a production bottleneck? With severe cases of amylose, I have even seen crews cut slits in the vibrating screen to ensure adequate starch flow remained at the size press.
From a technical perspective, sampling the starch return from the size press is a good place to start. The size press starch washes lots of debris off the surface of the sheet.
- If there is any corrosion in or around the hoods,
- or if there is condensate dripping from the hoods or ceiling,
- or if there have ever been fires creating soot, then any of that debris could (and does) make it onto the surface of the sheet during drying.
Fortunately, the size press acts like a washer and rinses loose debris off the sheet surface.
The technical test is simply to run the starch sample through progressively finer mesh screens. You may be able to identify some of the debris and take steps to minimize or eliminate root causes.
However, documentation of the debris and screen size through which it has passed is the first step in determining the need and justification for improved screening.
A second justification comes in the form of complaint costs from customers. Debris from a customer’s press or even feedback about surface cleanliness tend to provide powerful economic justification. Asking sales or service representatives to provide samples is often the best justification for better starch screening.
If capital is approved for a starch screening project, then the work has just begun. The baseline testing is critical to document the debris and to document how much is removed with existing screens.
Following the project, better removal of debris with improved screening should be expected. If that does not happen, then different screen sizes (smaller slot sizes) should be evaluated to ensure that the project meets the needs of both your internal and external customers.
Finally, ask for help and support from vendors. Your starch vendor should be working with you to optimize the starch at both the wet end and at the size press.
If your current starch vendor is not helping, then please reach out to Starch Performance Services (SPS). Servicing and optimizing your starch is what SPS does best. Remember that the manufacturers of starch screens also have engineers and service technicians highly skilled at optimizing their systems. Collaborate with equipment vendors to ensure that everyone is working towards a common goal.
