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The core-blow is an automatic device used for cleaning the delivery pipe and the feed channel which is formed by pairing the filter plates in the filter press.
The process involves sending a blow of compressed air, usually between 6 and 8 bars, into the feed channel of the filter press, capable of removing any sedimented sludge.
In the “short” machines, which provide for the sludge to be fed only from the side of the fixed head, the entrance of the compressed air flow takes place from the mobile head.
The movable head plate is therefore characterized by the same hole present in machines with dual power supply; in this way the compressed air, passing through the entire plate manifold, will discharge into a branch of the supply pipe, also cleaning part of the pipe.
In automatic cycle machines, this device is essential to ensure correct operation. Suffice it to say that, in the case of a simultaneous or automatic machine (and this depends on the opening system), the cake filtering and unloading cycle is not always attended by an operator. Mostly in automatic cycle plants there are a couple of people who manage, from the control room, all the machines in the plant.
If the sludge present in the exhaust manifold, and this particularly applies to sludge with a high specific weight such as lead paste or very thick sludge such as molasses, sugar, etc…, should settle and “dry out” inside the hole of the plate feed, during the next cycle pressure imbalances would be created which could cause the plates to break.
The filling and pressing in the filter press, in fact, works correctly when the flooding/filling of the entire volume of the machine is first created and then the gradual pressing of the sludge by means of the feed pump.
If the settling sludge plugs up the feed hole in a filter plate, it can happen that the filling of the machine volume is partial; this will result in plates in which the sludge is present on only one of the two sides.
The increase in filtration pressure will therefore not be homogeneous on both sides of the plate, causing it to break (cracks or fissures in the plastic support).
In the filter press, the optional core blow is simply composed of an automatic valve (usually ball valve) for the compressed air inlet, a flexible pipe able to follow the movement of the mobile head during the opening and closing of the filter plate pack and by a non-return valve, positioned behind the loading hole in the mobile head plate, which prevents the sludge from coming into contact with the compressed air inlet piping.