loss of pressure problem in filtration process

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Joined:Thu Dec 16, 2010 2:52 am
loss of pressure problem in filtration process

Post by cpender » Thu Dec 16, 2010 3:19 am

We have a process to produce a hot melt fluid (wax/resin) during its molten state. This product requires a final filtration of at least 3 micron. The process is as follows: melt down of ingredients in heated vessel. Approximately 120 liters per batch are produced. After the product is melted down, it reaches an average temperature of 214 F in its molten state. An average of 11 to 12 cPs viscosity.

The molten fluid is moved by a motor driven gear pump that draws the fluid into the pump and pushes it out to a flexible high temp stainless hose. Both the flexible stainless hose and gear pump are submerged at the bottom of the heated vessel in the molten fluid.

The stainless hose connects to an exit port at the bottom of the vessal (tank) and exits out to a straight pipe and into a filter housing designed for hot melt applications.

In the housing is a filter in which the fluid must pass through in order to exit the otherside of the filter housing and into a flexible heated hose which has a heated gun at the end of it for dispersion.

In the past, the filter used was a fiberglass 2 micron filter. These filters do the job, but can only be used once and then need to be discarded. Flow rate/pressure using this filter seems to work pretty well. Sometimes there is some fluctuation in the flow rate and drop in pressure at the point of dispersion, but overall seems to work well.

Recently we have switched to a stainless filter and it is a 3 micron design. We seem to get great flow initially for the first dozen to 2 dozen liters at most, then the flow rate and pressure drops off to a drool.

We cannot figure out what might be going wrong. We seem to not be getting enough pressure to move the fluid through the stainless filter, even though it is actually a more porous filter by design.

What could be causing our sudden and immediate drop in flow rate and pressure at the exact same time each time we try the stainless filter? Any help would be appreciated.


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