Newsletter, No. 1 - 2014
There is bronze and then there is “Van Voorden bronze” The bronze Van Voorden propellers meet the highest quality standards of classification companies such as Lloyds Register, Bureau Veritas, Germanischer Lloyd, Rina, RMRS or ABS for decades. “There is nothing left to do” is easily said, but nothing could be further from the truth. Van Voorden is always searching for better design and production methods in order to improve quality and efficiency.
Pure alloy is the basis The allowed variations in the composition of nickelaluminium-bronze which classification companies require, are too broad according to us. The strict composition prescriptions that Van Voorden allow, guarantee far better mechanical properties of the propeller. Because of this, the required hardness and tensile strength have significantly improved. And not only an improvement on design and quality of the propeller, it also gives you a superior reparability. Before casting, the composition of every melt is being checked through a spectrometer to make sure that the quality requirements of Van Voorden are met. Simultaneously with the propeller, test rods are cast in order to check and ensure the excellent mechanical properties of the alloy being used.
What is left to improve? In our induction furnaces, the metals copper, nickel and aluminium are blended in the prescribed composition. At the melts temperature of 1250째C, environmental moisture separates in oxygen and hydrogen. The oxygen reacts with the aluminium to aluminium-oxide and very small hydrogen gas bubbles remain in the melt. When these tiny gas bubbles are not extracted, it can cause intrusions in the propeller after cooling down. This would of course have a negative impact on the quality of the propeller. The bubbles, as well as the aluminium oxide, need to be removed from the melt beforehand.
The new rotor-degassing unit; kill three birds with one stone A huge heat resistant blender is lowered into the melt and will start mixing the bronze. Whilst mixing the bronze, Argon gas is blown into the melt through the rotating head of the blender. The Argon gas bubbles absorb the hydrogen bubbles and will float towards the surface of the melt. The gas evaporates from the melt, hence no gas intrusions will occur in the propeller. The bubbling upstream in the melt will meanwhile bring the aluminium oxides and other impurities to the surface. Prior to casting, this slag can be skimmed off easily.
The advantages Purity The propeller is being cast from an extremely pure melt. The thorough degassing and desoxidation process, guarantee a propeller without intrusions or porosity (see Figure 1). Van Voorden reaffirms herewith its leading position in the design and production of only the best quality ship propellers. Energy saving The use of the rotor-degassing unit limits the temperature loss during the casting process. As the degassing of bronze takes place inside the furnace, casting the propeller can take place very quickly after the bronze is poured out of the furnace. Consequently, temperature loss is very limited and a lot of energy is being saved.
Cost reducing The melt is kept in motion by the turbulence caused by the Argon gas injection. This motion causes less sticking of material to the furnace wall. Also the pouring pan shows less sticking. Because of this, both the furnace as well as the pouring pan require less renewal of refractory lining.
Van Voorden Castings: Top quality & competitive pricing go hand in hand! Made in Holland Made in Zaltbommel Figure 1) A dye check confirms that the Van Voorden bronze consists of a better material quality
The team Jochem Goldschmidt Sales Manager Propulsion
Ralph Moolenaar Propulsion Engineer
“We observe the start of market recovery, both nationally as well as in export. It seems an excellent moment to inform our customers that we have not just been waiting passively, but that we are constantly looking for quality improvements and cost reductions. These are the main factors of our success as the sole Dutch propeller foundry. We are part of Andus Group, a strong group of companies. This enables us also in difficult circumstances to develop our capabilities and to invest in our future.”
“For over 100 years our customers appreciate the top quality in design and production of our ship propellers. The propeller is more and more envisioned as an integrated part of the ship. With help of Computational Fluid Dynamics (CFD) studies, it is possible to simulate the flow along the ship in high detail. These results can then be used to fine tune and optimize the propeller design, resulting in a more efficient propeller together with more comfort. Supplying our clients with this kind of knowledge becomes more and more important.
Van Voorden Castings Van Voorden Castings is part of Andus Group. “Serving the industry” is the motto of the fifteen companies within Andus Group with its approx. 1.000 employees. Andus Group is a strong and reliable industry partner with an annual turnover of € 220 million. Leading concerns all over the world are served with complex projects and innovative products. Andus Group prove that “Made in Holland” has a solid future.
Van Voorden Castings BV Bossekamp 6, 5301 LZ Zaltbommel NL T +31 (0)418 - 57 12 00 E castings@vanvoorden.nl
PO Box 67, 5300 AB Zaltbommel NL F +31 (0)418 - 51 57 90 I www.vanvoorden.nl