THE BUSINESS OF VISCOSITY BLOG



    Three Keys to Getting Older Liners to Hold Tight Placement

    Posted by Mike Bonner

    Oct 31, 2016 9:42:00 AM

    image of tin cans.If you’ve been experiencing problems with placement and your stationary liners are older, you may be thinking that replacing them is the only solution. You also likely dread the capital investment, downtime, and mess associated with such a project.

    But it may not be your only option.

    Placement is NOT a Function of Age

    The fact of the matter is that there are a lot of things that affect placement – but age of the liner does not have to be one of them. In our recent blog, "Variation in Liner Placement Impacts Delivery, Quality, and Cost, too!," we noted:

    “…there are many factors that affect the placement of the compound when it is applied. This starts with the location and direction of the gun nozzle. Fortunately, this is mechanically fixed in position so, once adjusted, it will point the compound in the same direction on every dispense.”

    As parts wear, this placement can become more difficult to establish and maintain – and the machine may exhibit increased vibration, which exacerbates this problem.

    But worn machine parts can be replaced.

    And because of this, the mechanical integrity of the liner can be restored – at least those parts associated with placement – for a lot less than replacing it.

    Not All Issues Are Mechanical

    In that same post, we went on to demonstrate how temperature-based viscosity variations affect placement – and those have nothing to do with liner age! And as if that was not enough, in our post, “Improving Weight Control on Older Liners," we showed a host of real-world data which demonstrated the relationship between temperature and viscosity for a common compound, and the variation in temperature for a common liner. While we used that to demonstrate the impact on compound weight, it is clear that these temperature variations will affect placement as much as it affects weight.

    So why replace the liner, when all you really have to do is fix the temperature problem?

    Fixing Temperature is Easy, Right?

    As it turns out, not exactly…

    In our blog, “Stabilizing Compound Temperature: the Secret to Liner Placement Consistency," we identified the “secret” to liner placement as controlling the temperature of the compound as it exits the nozzle. But we noted that this requires:

    “…an in-line system that can bring the compound to temperature at a convenient point in its delivery path relative to the location of pressure regulation, and then carefully hold it at that temperature all the way to the nozzle. That’s how you balance viscosity, flow rate, and pressure drop to assure a consistent dispense.”

    This requires some pretty specialized skills and devices. When selecting your team for this project, be sure they can:

    1. Effectively determine the thermal load on your liner.
    Thermal loads are different for 202 ends than they are for 401 ends. They are also different if you are in Minneapolis as opposed to Houston. Make sure your team can accurately evaluate the various conditions under which your liner will operate.

    2. Specify the right temperature control equipment for your requirement.
    Heating and cooling are always required. How much of each depends on your particular conditions – and that’s why we put #1 first! Not only must this equipment have adequate capacity, it must be capable of fitting into your process – and there’s never enough space in a retrofit!

    3. Control temperature all the way to the nozzle.
    This is the kicker. It is also the key to success. Often, people will fall back on electrically heated hoses for this application.

    Big mistake.

    To begin with, these are famous for hot and cold spots – which runs completely counter to the goal of this project. But most of all, there is no way to cool with electric hoses.

    The solution must provide for heating and cooling of the hoses all the way to the gun – incorporating the gun into that circuit is even better.

    By following these three key guidelines, this can be a very successful project – eliminating placement problems forever!

    Download our free case study to see how temperature control improved operational quality and efficiency for a can manufacturer.

    free_process_temperature_control_case_study

    Topics: Can / Container

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