Besides regular maintenance, there is a direct link between the skills of the operators in relation to the ship unloader capacity. In other words: when the operators are not skilled, it will influence the unloaders performance.
Basically there are 2 different types of pneumatic ship unloading systems: fully-automatic or semi-automatic.
This type of equipment is capable of unloading the ship fully-automatic by means of a PLC/HMI, valves, instrumentation and a logic on the needed valve sequences allowing to collect and convey the dry material from A to B. This equipment is better known as shore Stationary or Dock mounted Pneumatic Ship Unloaders whereas the ship itself is equipped with the needed floor & piping onboard. Allowing the cargo to be collected by the unloader onshore through a flexible hose connected to the piping onboard. As this system is now fully air tide and all piping is fixed, it can run the PLC according the needed sequences and gain maximum performance with minimum on dust. However the ship is a dedicated cement barge/carrier with its own fluidized floor, piping and valves. The unloader has intermediate tanks for temporarily collecting the material through a vacuum and use the compressor for the conveying again towards the storage facility onshore. Due to this automation, a continues high capacity is reached without influence of the operator skills limitations.
This type of equipment is capable of unloading the ship semi-automatic by means of a PLC/HMI, valves, instrumentation, a logic on the needed valve sequences in combination of a manipulator arm, allowing to collect and convey the dry material from A to B. This equipment is better known as open top barge/carrier unloaders and able to unload regular cargo/bulk vessel as its using a manipulator arm with an integrated vacuum system. Basically a big industrial vacuum cleaner allowing to reach each corner of the vessel hold floors. As there is an interaction between the vacuum system (manipulator arm) and the cargo awaiting to be collected, the skills of the operator becomes all important now. For reaching a high unloading capacity it is needed to maintain a “deep” vacuum in the vacuum system and her cargo, let’s say minus 650mbar (G). The difficult part here is that the manipulator arm needs to moved, rotated, angled into multiple direction during the whole process until the dry material is fully collected and hold bottom is reached. Same like a vacuum clearer at home, when “false” air is collected it will reduce the vacuum and negatively effect of the overall capacity.
Now that we have a common sense on the different types of pneumatic unloaders in relation it the operator influences, we are frequently asked “how efficient the unloader will perform on an average, in the clients own local circumstances”? As for the fully-automatic unloaders we can closely calculate such capacity based on piping route, piping diameters, material specifications, amount of piping bends, internal resistances, etc. However there is no clear answer to such question on the semi-automatic unloaders.
Let us explain why:
All the material and equipment variables are able to determine, but the limitation lies with the ambient conditions, cleaning-up procedures and operator skills on moving the manipulator arm in the correct direction for keeping the piping (nozzle) submerged in the dry material, maintaining a solid “seal” and her corresponding vacuum.
The ambient conditions like rain influence the continuation of the unloading, as the holds need to be closed by hatches/covers during rain allowing the cargo to be protected.
The operator skills are not able to quantify in a number or percentage on how it will negatively influence the unloader capacity. The fact is: when the vacuum is dropped, less cargo will be collected. Meaning, in case the operator moves the manipulator arm slightly out of cargo reach, false air will add and lower the vacuum.
Once to cargo is reached the hold bottom, maintaining a “deep” vacuum is difficult and not achievable any longer. At this stage cleaning-up is needed which could be undertaken with varies tactics.
To come back to the question of the customer: “how fast the unloader will perform on an average in the clients own local circumstances”? This is the one million dollar question which nobody could indicate or predict.
A nice comparison on such question could be found in the F1. The performance of the engine is calculated by the engineers, the quality of the tires is set, the length of the track is known, same as for the weather conditions, but limited to the drivers skills and his influence.
Easy to forecast and calculate the F1 car’s maximum speed on the straight, but no way what the average speed and time would be around the track in advance. After a couple of rounds, different tracks, multiple drivers, variety of weather conditions, tire and compound changes, an experience is build and will be every time closer to reality in predicting such average “speed” in advance.
Once the car is set for optimum conditions, equipped with the best tires and weather conditions are its finest, we are replacing the F1 driver for a regular person and tell him what to do…can you guess in advance what the track time would be?
All in all, unloading an open top barge/carrier is like playing chess. When you play the game you can move several chess pieces, such as the bishop, tower or the queen. Every chess piece has its own characteristics and its own type of move. With every move you are thinking of winning the game and to use all the pieces as efficient as possible. You would like to move the correct piece at the correct moment, within the minimum required time. It will take a balance of using time and making the right move. Just one wrong move and you will end-up “losing time”, to compensate your earlier (wrong) move or worse losing the game. Open top barge unloading has several unloading factors (chess pieces), which the operator will choose. But is your operator been able to make the correct moves, so he/she can operate the unloader efficient to end up the winner?
Based on more than 50 years of experience in pneumatic conveying, Lion Bulk Handling is able to train your crew and operators via our Bulk Academy in-house or on-site for getting most out of your pneumatic ship unloader. Book your training here: http://www.lionbulkhandling.com/services/