The importance of loading spouts is superbly encapsulated by the perceptive CEO of one of the world’s largest copper producers, as he peered down a ‘tiny’ 600 mm diameter spout and remarked ‘Our entire cash-flow depends upon, and will pass through, this tiny spout on its way to the world markets’. For a brief moment, it seemed as though the success of this multi-billion dollar development hung on the end of the shiploader boom. Of course, the same is equally true for each of the myriad of non-redundant items between the mine and the port, but this paper addresses the very last link in the chain, the loading spout fixed to the end of the shiploader or barge loader boom.
Traditional shiploading spouts
There are numerous spout designs available to meet specific shiploading needs, but there are none that will meet all needs of all the products all of the time. At the one end of the scale is the ‘no-spout’ approach. In this case, material is discharged off the end of the conveyor belt directly into the ship or barge. In many cases, a curved hood may be used to collect the discharged material and direct it vertically downward into the hold, but sometimes the trajectory of the discharged material is used to gain additional outreach.
This ‘no-spout’ option is the cheapest, most reliable solution, and should be chosen whenever conditions permit. The biggest advantages of this option are: zero maintenance, zero risk, and zero ‘plugged chute’ load. For really dusty, free flowing commodities such as potash, dustfree loading spouts are ideal. These spouts are usually telescopic surrounded by a telescopic dust skirt, they gently lower the material down their centres. The biggest draw-back of these spouts is that they may not be suitable for really sticky materials like metal concentrates.
For less dusty, sticky materials, telescopic spouts with retractable spoons are often specified. For free-flowing materials such as coal, spouts with trimmers are an option. For both of these cases, the banana spout, described herein, may offer significant advantages, and is becoming an increasingly popular choice.
Considerations for spout selection
When selecting a spout the operating conditions must be clearly defined and generally boil down to the following key parameters:
• Characteristics of product/s to be handled
• Dynamic flow properties
• Density function
• Compatibility with other products and materials
• Loading rate
• Trimming requirements (IMO regulations)
• Vessel characteristics (air draft light and loaded, beam, hold dimensions, ship’s gear, log stanchions, type of hatch covers, etc)
• Tidal range
• Shiploader characteristics
The criteria used for evaluating each option should consider, at least, the following points:
• Ease, duration and cost of maintenance
• Potential for damage due to:
• Spout hitting hatch coaming
• Ship surging
• Chute plugging
• Dust containment
• Trimming versus peak loading rates
The most important variable is obviously the product, or range of products, that must be handled.
The banana spout was initially developed to increase the capacity and outreach of a copper concentrate shiploader operating in Chile. In that case, an outreach of 6 m from the centre of the discharge point was required. The only two viable options were a motorised trimmer (sometimes called a flinger) or a spout with an appropriately designed spoon. While flingers work extremely well with some materials, such as wood chips, they were considered inappropriate for copper concentrate. With the conventional chute and spoon approach, it was only possible to achieve an effective radius of about 4 m.