Extrusion die cleaning

PCA already built many plants for wastewater treatment and process water production in the aluminium pre-treatment industry. In this way, the step towards cleaning aluminium extrusion dies was taken. Meanwhile, PCA has already built several installations which, by using NaOH, clean extrusion dies.

Basic principles

To design such an installation, we sat down with a number of aluminium extruders. A number of basic conditions were confirmed:

Automatic: without manual handling by the operator
The operator never comes in contact with NaOH
No fumes are released in the hall
The unit is ATEX compliant
The cleaning process must be fast and controlled
Controlled re-use of NaOH
No automatic crane as it is sensitive to malfunctions and expensive to maintain
Minimal discharge of contaminated flows

Starting from these basic principles, we developed an installation with a corresponding process. The installation consists of process tanks in which all processes take place. Specifically, this means that both the cleaning of dies with NaOH and the rinsing with water take place there. In addition, the installation ensures that the liquid is always in motion, which in turn makes the process go much faster.

Since all the processes take place in one and the same tank, the dies don't need to be transported from one tank to another. The operator therefore doesn't need to intervene during a cleaning cycle.

Buffer tanks

In addition to process tanks, buffer tanks are also provided to allow quick work with preheated liquids. These buffer tanks offer additional advantages:

They start from NaOH at 50% concentration, which is then diluted with the contaminated rinse water. This way, the contaminated rinse water can be reused internally and doesn't have to be disposed of. Moreover, NaOH 50% can be purchased which is much cheaper than buying more diluted versions.
The used, and thus contaminated, NaOH can be reused several times as the NaOH isn't saturated after one cleaning cycle. This also reduces the need for disposal and purchase of NaOH.

A strong extraction with fans is also provided so the process tanks are at a small underpressure. The vapours in the process tank are extracted by the fan and, in many cases, purified in a droplet trap or scrubber. In this way, no fumes are released into the environment.

Flexible elaboration of the installation

Because we design our installations entirely in-house, we are also flexible in their elaboration. The process tanks can be adapted to any existing baskets, available space, etc.

Usually, the tanks are built in stainless steel 304, but 316 is certainly an option as well. Moreover, all tanks are equipped with insulation to limit the heat losses.

Given the scarcity of liquid NaOH in 2022, and consequently high prices, we may also expand the installation with a system to use NaOH granules. The NaOH granules are placed in a hopper and the system will then automatically dose them in the mixing tank. In this way, we guarantee operation reliability, even when liquid NaOH isn't available.

Advantages

Safe: operators never come in contact with caustic soda
Very little manual input: all process steps take place in one tank, so no manual input is needed
Ergonomic: no fumes are released in the room thanks to the negative pressure in the baths and the high rate of air exchange
Efficient: the process runs a lot faster and more efficient thanks to PCA's engineering
Total concept: turnkey solutions from A to Z. We can also expand the extraction with gas scrubbers, drip catchers or other systems in cooperation with our air treatment department.
Flexible: the system is flexible and therefore suitable for all moulds, regardless of shape or size
Customised: the size and shape of the installation is determined according to the numbers of moulds and the available space
ATEX compliant: the installations are built according to the ATEX safety measures
Reliable: the maintenance team won't be confronted with any surprises as the installation only works with relatively simple components (valves, pumps..)