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DRY BULK AND SPECIALIST CARGO HANDLING

PRODUCT PROFILE

PT27- 28/3

New developments in continuous ship unloading (CSU)

New drive control applications in pneumatic ship unloading: The use of frequency inverters

Tomas Kisslinger, NEUERO Industrietechnik, GmbH, Melle, Germany

The Garant Feed Mills group, who since 1999, have had extensive experience working with a Flexiport unloader at their mill in Pöchlarn, Austria, on the Danube River, decided to install the same unloader type at another of their mills; in Aschach, Austria. The new Flexiport, which has been incorporated with the latest technical developments, was delivered to Aschach, also on the Danube, and installed at the beginning of 2005 (see Figure 1). The new unloader replaced an older system which used a cutting head nozzle (Figure 1). The old nozzle, like many other similar systems, made large holes, but was not very effective in handling non-free flowing materials. Normally, only a short boom is needed for unloading ships between 400 and 1,500 dwt. In this particular situation, a 20m trellis work boom was designed to overcome the distance between the ships (tied to a floating pontoon) and the unloader itself mounted on top of an existing conveyor bridge, which had previously carried the old unloading system (Figure 2). The structure was reinforced and optimised. For smooth operation, the drives of the winches and slewing have a speed control, with a start and stop ramp.

Controlling air flow

The traditional way of controlling air flow on turbo blowers is by using a butterfly valve (throttle valve). It reduces the load at the motors together with a second mechanically operating flap valve (Figure 4) that changes the position of the flap according to the air pressure (air speed) in the conveying system. With this simple system, it is possible to set a certain required air speed, but it is limited to one setting at a time. This is done by adjusting the counterweight of the valve. This control method is used in small pneumatic mobile conveyors (GSD) and has been traditionally used in ship unloaders.

Figure 1. A 20m trellis work boom was designed to overcome the distance between the ships.

New features

The new unloader reduces unloading time in half and is equipped with effective sound insulation and dust suppression. This was one of the main requirements of the client in respect to the unloaders environmental influence, especially as the mill's location is in close proximity to a very touristy area near a famous cycling path along the Danube. A further interesting aspect of the new installation is its new drive control, which uses FI frequency inverters. The pneumatic system has two turbo blowers, each 110 kW. They are started and controlled via frequency inverters; the system is also able to work with one blower, achieving a capacity of approx. 50 per cent. The blowers, the hydraulic package, and the electric panels are separated inside a machinery house in container form. The electric and hydraulic settings are set by the manufacturer, facilitating the site assembly. Instead of a cutting nozzle, the Flexiport uses a rotating feeder (Figure 3) that is moved against the material. A swivel and kick in arrangement at the nozzle makes it possible to reach material inside the hatch and under the hatch wings. This is very beneficial when unloading older ship types that have inside reinforcements. The nozzle also has a remote adjustable nozzle air entrance, which allows one to get the best air to product ratio.

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Figure 2. The older system used a cutting head nozzle.

Figure 3. The Flexiport uses a rotating feeder.

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PT27- 28/3

PRODUCT PROFILE

DRYBULK AND SPECIALST CARGO HANDLING

Figure 4. Mechanical system with starting valve below and air flow regulator.

Figure 5. FI valve below and vacuum breaker.

Figure 6. FI drive with vacuum breaker (no air flow regulator).

The use of programmable logic control (PLC) has opened the way for new control methods. The second method of regulating air flow is by using a frequency inverter (FI) and control software on the PLC. One flap (Figure 5) does the work of both, like the traditional mechanical variation. The air flow regulator can be set at different points using the motor current. This makes the system more flexible (compared with the traditional mechanical system) to operate the unloading system for different goods, and saves space and energy because only one valve is used in the air flow. It is not as flexible as the speed control of the blowers though, as described in the third method of control below. The third method, successfully applied, is to directly control the blower drives using the FI technology. With this method, startup can be programmed with no valve (Figure 6) at all in the

pneumatic line, and is only limited by the motor current. The main advantages of this system are: · Less energy consumption · Flow control at any unloading situation ­ partial load · Capacity settings for different products, such as wheat or sun flower seeds The energy is saved because the blowers do not run at full speed all of the time, but rather at a lower speed during idle operation, as well as during partial load operation. This is especially useful for systems handling different types of materials or when needing to maintain the same capacity during different operation situations, therefore avoiding big fluctuations in the material flow. Operation is quite simple: The settings can be adjusted from the operator's touch panel, as shown in Figure 7.

Results

This system was introduced on the Flexiport unloader (for nonfree flowing materials) at Garant Feed Mills in Aschach. The tests were successful and the client was especially satisfied with the solution of flow control, because his existing conveyors and scales could not handle lighter products at higher capacity rates. The new settings allow continuous work, while reducing downtime caused by overflowing conveyors or scales. The air flow control in connection with the PLC and the use of FI in pneumatic conveying system, especially in ship unloading, offers a wide range of controlling methods in relation to the air speed in the system and to the unloading rate. With prices coming down, using FIs at the main drives to control air is becoming an attractive option, as it is making ship unloading equipment more flexible, and is reducing overall operating costs.

ABOUT THE COMPANY

NEUERO is manufacturer of mobile pneumatic conveyors, grain vacs and ship unloader/loaders for transport of bulk materials such as bulk grain, meals, plastics and alumina. NEUERO started in pneumatic grain conveying over 80 years ago with the manufacture of small agricultural machines. Since then the company has delivered equipment in the 20 t/h to 2000 t/h range to many installations around the world. NEUERO has two companies with sales, engineering, manufacturing and service facilities in Germany and in the US. Tel: +49 5422 9503 20 Fax: +49 5422 9503 50 E-mail: [email protected] Web site: www.neuero.de

Figure 7. Touch panel blower speed settings.

ABOUT THE AUTHOR

Tomas Kisslinger has twenty years experience in bulk handling, especially in grain related areas. Since 1992, he has been Managing Director of NEUERO Industrietechnik.

ENQUIRIES

Tomas Kisslinger NEUERO Industrietechnik Neuerostr. 1 49324 Melle Germany

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