Xylem Pumps Provide Complete Solution for Dutch Mussel Farm

Faced with the need to pump a combination of salt and fresh water to clean, cool and package a range of shellfish, the engineers of Prins & Dingemanse, a Dutch mussel supplier, turned to Xylem to address all of their needs.

Prins & Dingemanse (P&D) is the largest mussel provider in The Netherlands and market leader in the Benelux market. P&D brings to market over three million pounds (1.5 million kilos) of mus- sels, oysters and other shellfish a year.

The culturing of mussels and oysters for the company takes place in the Oosterschelde, an almost 100,000 acre (37,000 hectare) tidal wetland that is part of the North Sea. The Oosterschelde is the largest national park in the Netherlands and an important fishing ground for mussels, oysters, flatfish and crabs. The tides and flora of the park create water that is rich in nutrients, and that gives an intense, desirable flavor to the mussels.

Mussels and this marine environment are particularly well suited to each other. Mussels are bilalve molluscs that filter diffuse plankton from the water. As efficient primary consumers in the food chain, mussels grow relatively quickly and profusely, making them ideal for marine culture in this environment.

Reducing Operating Costs With a Single Vendor

Up until about 8 years ago, P&D used pumps from a variety of suppliers. Reliability and maintenance created constant challenges for the company. The variable production cycles of the pumps, which was dependent on the flow of shellfish from ships to the processing lines, meant there were periods of time where the pumps sat idle. During these periods, the harbour water, which is rich in microscopic marine life, would cause the pumps to foul and require cleaning.

At that time, Xylem introduced a plan to replace P&D’s existing pumps with all Xylem Lowara brand pumps. Their cast iron duplex impellers and shafts eliminated the problems caused by bronze and stainless steel components in the earlier pumps, making them much more suitable for use in these challenging conditions.

Three Xylem Vogel brand LS pumps with cast iron duplex impellers and shafts are used for rinsing the mussles and replaced six existing pumps while maintaining similar performance curves. Two Xylem Vogel brand LM series pumps are used to keep the mussels bathed in constantly circulating cold water

Using a single brand of pumps simplified the sup- ply and maintenance situation for P&D. The Xylem Lowara brand pumps were also equipped with Xylem’s Hydrovar® “smart pump” control technology, which improved efficiency and reduced operating costs.

A Wide Range of Applications

After the mussels are fished out of the farming beds, they need to be carefully rinsed for five to 24 hours to remove all sand before packaging. The production process includes separation of the mussels from other items, such as crabs, stones, empty shells, etc. This is done in large metal containers that sit in flushing platforms that capture and filter the rinse water for re-use. Here, P&D now uses three Xylem Vogel brand LS 15kW pumps that replaced six existing pumps while maintaining similar performance curves. Each pump sup- plies 550 M/3 per hour.

Once the washing cycle is complete, the mussels are bathed in constantly circulating cold water – maintained at 10 degrees Celsius – to keep them fresh until they are packaged and transferred to refrigerated and frozen storage facilities. P&D uses Xylem Vogel brand model LM and Lowara brand model SH pumps in the production lines to keep the mussels cool and properly aerated.

Two Xylem Lowara brand FH series pumps are controlled by Hydrovar units for a test plant flushing process with oysters in stackable containers.

Oysters are processed in much the same way, but in smaller tanks that are stacked for the washing process. P&D is currently refining a cleaning process that uses two Lowara brand model FH series pumps controlled by Xylem’s Hydrovar technology to vary the flow of water from 0-100% of capacity, based upon the amount of product in each tank. This will further improve energy efficiency and pump maintenance costs over and above the use of the pumps alone.

Hydrovar Control Systems Proven to Improve Pump Efficiencies

Hydrovar is a patented Xylem smart pump technology that monitors and controls pump operations according to customer specifications. The Hydrovar control system monitors both the supply and demand pressures of a pump or multiple pump installation. Based upon the customer- specified performance curves, the Hydrovar controllers signal the pump motor to start, stop, increase speed or decrease speed as installation parameters vary with operations. Customers find a number of important advantages to using Hydrovar:

• Reduced Operating Costs – Pump duty cycles and operating speeds are dynamically optimized to the application requirements that may vary over time, reducing pump motor energy consumption.
• Reduced Implementation Costs – Since a pump can only operate along its engineered performance curve, constant pressure systems always require additional components in order to regulate the supply of liquid to the application.
• Reduced Maintenance Costs – By reducing the necessary component count, maintenance costs are lower. Similar maintenance cost reductions result from the reduction of duty cycles, running pumps at lower speeds, and starting and stop- ping motors gradually rather than abruptly.
• Enhanced Performance Levels – Component reduction, reduced wear and tear on components, and improved monitoring and control all contribute to overall performance level improvements by minimizing down time and out-of-spec operations; all at reduced overall implementation and operating costs.

A Complete Solution From One Vendor

The process of seed harvesting from the “crop” of mature mussels is currently undergoing significant changes. P&D is experimenting with using a crane to drop an Xylem Flygt brand pump into the water next to the ship, to use it like a vacuum cleaner to suck up the mussel “seeds” from 100 meter long nets before the mussels are stripped from the nets and forwarded to the washing process.

Whatever the water-handling application – water supply, cleaning shellfish, cooling, seed harvesting or packaging – today, all of the approximately 35 pumps used in this P&D facility are supplied by Xylem brands including Lowara, Vogel, Flygt and Hydrovar.