Glue Kitchen Adhesive Filter Maintenance

The filter in a glue kitchen is there to stop lumps, skins, fibre, and scale before they reach the pan. It is not there to finish a batch that was mixed short, and it is not a place to hide a torn screen behind a bypass. When the filter clogs, the pump cavitates, foam appears, and the sheet shows skip or a stripe. Crews then open the glue gap to compensate, and consumption rises while the real fault sits in a housing nobody opened. This page is the filter route. The mix itself stays in adhesive-batch-preparation-sop-corrugator. Foam that is really air on the suction side stays in adhesive-foaming-corrugator-troubleshooting. Without that split, a crew will treat skip as a formula fault. The filter card and the batch sheet need the same time, or the next shift cannot tell a blocked screen from a batch that never cleared.

Give the coarse strainer and the fine screen different jobs, and label them. The basket on the transfer pump should stop lumps you can see: undissolved powder, a skin from the tank wall, a piece of bag. The screen ahead of the glue pan should stop what would mark the sheet, and it must still pass the adhesive at the flow you run. Do not swap them. A fine screen on the pump suction collapses flow. A coarse basket at the pan lets grit through onto the roll. Write the mesh or the hole size on the housing. There is no single Xuegong mesh for every plant. Use the number the pump and the pan were bought with, and do not “upgrade” to a tighter mesh because the last shift found one lump. If the mesh is not written on the housing, that filter does not go to the pan. A spare whose tag has fallen off stays in quarantine and does not go back into the housing to make up the count.

Learn the clog from the instruments you have, not from the first skipped metre. If the housing has gauges, mark the differential pressure when the screen is clean at the normal flow. Many plants open the filter when that differential sits about 0.3–0.5 bar above the clean baseline at the same flow. Confirm the band against your pump; do not copy a neighbour’s gauge. If you have no gauges, you still have signs: the pump sounds dry, the pan level falls while the kitchen tank is full, or the return line surges. Those signs mean open the filter now. Waiting for skip on the board means the lump has already passed or the pan has already starved. Board that already shows skip before the screen is opened stays suspect for the front of that order.

Inspect on a clock, and inspect again when the furnish changes. At the start of each shift, before a long order, look at the coarse strainer. On recycled or high-fines mixes, open it at least once a shift and after any batch that did not clear of lumps in the usual mix time. After a tank clean, a grade change, or a dropped bag, look before you send glue to the machine. A filter that was acceptable on virgin liner can fill in an hour on a dirty recycled medium. The schedule is a minimum. Debris on the screen is the reason to shorten it. An empty screen for a month is not proof the filter is unnecessary; it may be proof the bypass has been open. An empty screen with an unsealed or unlogged bypass valve is not evidence that the filter is working.

Clean it as a pressure job, not as a quick twist of a lid. Stop the pump, lock it out, and read the gauge until the pressure is at zero. A housing that still holds pressure will spit hot adhesive when the cover comes off. Catch the glue in a labelled bucket. Do not hose it into a floor drain. Note what is on the screen before you wash it away: starch lumps, fibre, metal flakes, or a skin. Wash the screen with water that will not fight the next batch. Do not soak an alkali-free screen in a caustic wash “to make it bright,” and do not leave a caustic film in the housing if the next batch is the alkali-free series on /products/alkali-free-adhesive. Residual alkali in the mesh is enough to contaminate a caustic-free tank. Drain the wash water on its own. It does not go back into the alkali-free make-up tank.

A torn screen is replaced, not patched. Cloth, paper, tape, and a second torn screen stacked “for now” shed fibres into the adhesive and change the hole size you no longer know. Keep one spare of each labelled mesh on the wall, clean and dry, not on the floor where it collects dirt and is then installed dirty. If a spare is not in the rack, the job waits or you fit the correct spare from stores. You do not run with the cover clamped on an empty housing unless that bypass is a written, timed exception. A bypass left open for “the rest of the shift” is how grit reaches the applicator roll and how the next person inherits a pan full of lumps. Write the time the bypass opened and the name of the person who closed it on the same line. A bypass with no close time is still open at handover: check the pan before you send glue. Board made while the bypass is still open is unfiltered. Keep it out of released lots, hold it apart, and leave it pending a check.

Read the debris before you throw it out. Starch lumps that you can break with a finger usually mean the batch was short, the water was cold, or the powder was dumped faster than the agitator could wet it. That is a mix problem, and a finer filter will only clog sooner. Fibre mats point to recycled fines or to an upstream screen that has already failed. Metal flakes point to a pump, an agitator blade, or a failing bearing, not to the adhesive formula. A rubbery skin points to a tank that was left with a dried surface. Foam in the housing, with a filter that collapses and recovers, often means air on the suction side rather than dirt. Chase that in the foaming guide. Do not answer every find by ordering a tighter mesh. A clean that washes the debris away before the type is written cannot be used to improve the next mix.

A grade change includes the filter. Moving from a traditional caustic glue to an alkali-free batch without flushing the housing leaves alkali in the mesh and in the dead leg under the basket. The first minutes of the new batch are then not the product you think you are running. Flush with water until the discharge is clear, then drain that flush so it does not return to the alkali-free tank. The same rule runs the other way if you return to a caustic grade: do not leave a half-washed alkali-free skin to flake into yellow glue. The filter does not dissolve a caustic or borax sachet that was added by mistake, and it does not turn a concentrate that still needs starch into a water-only powder. Those are different products. A clean screen does not make their ratios interchangeable. The first tank after a grade change must say on the record that the housing was flushed.

Put it back so the flow can pass. Seat the gasket, match the flow arrow, and fit the mesh that the tag names. A filter installed backwards can look tight and still starve the pan or dump unfiltered glue down a relief path. Prime slowly with the pump vented the way the kitchen procedure says, and check the cover for leaks before you walk away. Run about 10–15 minutes and look at the sheet for skip and for a new stripe before you call the order released. If the pan level falls again in that window, stop and reopen the housing. Do not open the glue gap to hide a filter that is still blocked. If a stripe appears in that 10–15 minute window, mark that length of board on its own.

The log is what stops the same clog next week. Each opening needs the time, which housing, the mesh, whether you cleaned or replaced, what you found, the differential pressure before and after if you have gauges, and the name of the person who closed it. “Filter OK” is not an entry. If you are opening the same housing more than about once an hour on a normal grade, stop buying finer mesh and fix the mix, the tank clean, or the suction leak. Hourly cleaning is a kitchen failure that the filter is reporting. Write that on the batch sheet, not only on the filter card, so the next cook sees it before repeating the short mix. A line that only says “OK” is unfinished at review. A housing opened more than about once an hour is listed on the shift report, not only on the filter card.

Spares and tools belong to the route. A labelled rack with one spare of each mesh, a gasket, and the wrench that fits the cover means the job can be done at the housing. A spare that lives in a drawer three rooms away will not be used, and the bypass will. Mark the install date on a replaced screen if your plant retires screens by time as well as by damage. A screen that is intact but permanently narrowed by scale should be replaced, not scrubbed until the holes are unknown. Do not mix meshes in one unmarked box. The error is invisible until the pan starves or the roll is scratched. If the rack is short a screen, the shift does not fit a mesh of unknown size. If an unlabelled mesh is already in, stop and replace it with a tagged spare from the rack.

Train one supervised clean before anyone signs the route alone. Show a torn screen, a bypass left open, a housing full of skin, and a cover that was opened while the gauge was still above zero. The trainee should lock out, prove zero pressure, catch the glue, name the debris, and reassemble to the arrow. If they cannot point to the mesh tag, they are not finished. New hires should also hear the rule that a filter is not a formula: adding water, caustic, or another powder because “the filter is blocking” moves the fault into the tank. The tank then sends more lumps, and the filter blocks again. A person who has not finished a supervised clean does not sign the filter record alone.

Xuegong New Materials Group does not assign a mesh size to your pump. We can help a plant connect repeated lumps to the adhesive they are actually running, including a change onto the alkali-free series, so the housing is flushed instead of blamed. Mix practice stays with adhesive-batch-preparation-sop-corrugator. Air and foam stay with adhesive-foaming-corrugator-troubleshooting. Use /products/alkali-free-adhesive only when the filter and the tank are clean enough that the batch is the series you named. A clogged screen is a reason to stop and look, not a reason to change the starch ratio. A grade-change batch whose housing was not flushed is not written up as alkali-free glue already on the machine. If the flush is not on the record, hold that tank first and do not blend it into a released alkali-free batch.