The PSA Peugeot Citroen Sept Font foundry in the Allier department in France, produces Automotive casting in grey iron, mainly engine blocks and braking components.
Last year the production achieved about 121.767 tons spread in more than 1.014.000 engine blocks and more than 8.000.000 braking components, it means more than 34.000 pieces per day.
In 2005, it was restarted the project for upgrading the sand plant n. 1 on the moulding line n. 3, horizontal flask moulding line 260 moulds per hour dimensions 810 x 710 x 220+200 mm. for the production of braking components. The main target being the best control of the sand temperature in order to improve the quality of the casting, reducing as far as possible defects and scrap due to the sand characteristics/quality.
Technical features of the sand plant:
120 t/h capacity, temperature and moisture of return sand very unstable (between 50 and 100 °C and 1 to 1,8 %) required temperature about 40 °C after pre-mixer cooler and moisture between 1,8-2,2%.
Available surface for the installation was very small
In 2001, in the occasion of the sand plant upgrade dedicated to the Disamatic moulding line for the production of ventilated disc brake, the decision for the sand cooler was made in favour of the Italian company Space, already well known within the PSA Group because of the installations of return sand pre-humidification and process in operation in the foundries at Charleville and Sochaux (France).
The results have always been satisfactory and the installed machines have always demonstrated their reliability, asking for very low maintenance.
At the beginning of 2006, on the occasion of the choice of the supplier for the line 3 sand cooling system, PSA Peugeot Citroen technicians chose SPACE, thanks to the positive experience made on the first installation.
The system proposed by Space was not only a simple cooling system, but it was based on the following principle:
- Return sand contains a not burnt bentonite percentage that has to be reactivated by adding water.
- The better way to obtain this reactivation is to store the sand for at least one hour into the sand storage silos having suitable temperature and moisture (36 to 38 °C and 2 to 2,2%); during such time bentonite slowly absorbs the water, swelling in a proper way. Then, into the mixers, only the little quantity of water and additions is required to reach the exact characteristics for good moulding
- The sand obtained in such a way has much better flowability, better moldability, has no free water and can grant therefore sound castings with better surfaces.
The system is composed by the following:
- Surge hopper under the screen, able to absorb the production peaks and the short stops of the moulding line.
- Sand drawing-off with weighing device.
- Pre-mixer cooler where the water is introduced, accurately dosed according to the return sand weight, moisture and temperature, and according to the required moisture content. Moreover, the air produced by a centrifugal fan is blown into the mixing pan, cooling the sand.
- A very reliable control system compares the outlet moisture and temperature values with the required ones and automatically adapts the water calculation, to obtain the ideal sand characteristics.
- Then sand is sent to the silos, where bentonite swells.
- After this treatment the sand goes out from the silos almost prepared and asks in the mixer only the little quantity of water and additions required to reach the exact characteristics for moulding.
In partnership with JML Industrie the Space cooler and his control system has been assembled during summer holidays in August and started without problems in September, immediately reaching the required performances.
Now, after several months of operation, Sept-Fons foundry can affirm that all objectives required in the specifications are respected and, consequently:
- Castings quality is considerably improved
- Scraps percentage is reduced
- The sand quality increase (better flowability and moldability) has allowed to reduce its weight into the moulds
- The transports of prehumidified and cooled sand, together with an efficient dedusting system, grant an important improvement of the working conditions.
Translation of the article issued in Hommes et Fonderie – May 2007