The Leap to Real Time

When the manual inventories, extra mobile clerks, and frustrated CRT operators are either too expensive or are physically unable to bring the inventory errors under control, two changes can be made which will eliminate the errors:

• Reduce the time lag between when an inventory error is detected, and subsequently corrected in the computer. There are two methods to reduce the lag:
  1. Provide the gang supervisor with a CRT connected to the computer [see Figure 6]. Usually the gang supervisor is in voice radio contact with the equipment operator. When an inventory error is detected, a verbal discussion is held between the equipment operator and the supervisor at the CRT to immediately correct the inventory in the computer.
  2. Provide computer CRTs in the handling equipment which will allow the equipment operator to receive information directly from the computer. This eliminates voice radio contact and calls in to question the need for the gang supervisor.
  If it is inappropriate for the equipment operator to update the computer when an inventory error is detected, a mobile clerk in a vehicle which also has a CRT installed can perform a spot inventory of the area in question. When the time lag is eliminated in this manner, not only is the accuracy of the inventory improved, but there are several other positive side effects:
  • The operation has more flexibility; changes in the work list are instantly relayed to the equipment operator either directly, or indirectly through the gang supervisor.
  • The planning improves dramatically because now the computer model of the yard accurately reflects the actual location of the containers.
  • The planning lead time required is lowered. No longer must a full shift of work be preplanned ahead of time for each gang, only an hour or so. This improves the planning and its flexibility.
• Eliminate the key errors and unreported container moves. In order to correct this problem, the handling equipment must be instrumented so that the machine can determine its location in the marine terminal. If the machine has location instrumentation, it can report its position directly to the computer without any human intervention. In this case, unreported container moves are eliminated because the machine routinely and automatically sends pick-and-deck messages directly to the computer so that the inventory is always accurate.

  The most successful attempts at location instrumentation on handling equipment has occurred on rail-mounted cranes and rubber-tyred gantries which move in fairly fixed paths.

Which CRT communication method and whether location instrumentation will be selected will depend on the quality of the labor available at the facility. If the labor quality is good, and the labor contract allows, there is little economic incentive for the additional expense of providing location instrumentation on the handling equipment. The CRT and location instrumentation installed in the handling equipment are usually connected to the computer with some variation of a digital radio system, although other methods have been successfully employed [reference 5].

The Benefits

For marine terminals installing a computer system, the following beneficial effects were reported by at least 50% of the marine terminals responding to a recent survey [reference 6]:

• The dwell time for import containers was reduced.
• The necessary sorting, checking, and forwarding of documentation was easier.
• Overall administrative costs were lower.
• The available space in the container yard was used more efficiently.
• The turn round time for equivalent sized vessels was reduced.
• The average waiting time for vehicles to be serviced at the import/export grid was reduced.

The End Result

Although passive-tracking was instituted to solve the access problem inherent in the paper system, the end result of the passive-tracking phase is to achieve accurate inventory control. The accurate recording of inventory by passive-tracking is a basic building block if the computer is to participate in the management chores of the container terminal. To understand this requirement, the yard board model should again be pictured inside the computer. Updates to the yard board are received by the passive-tracking system. Just as the accuracy of the yard board model affected the planner in the paper system, its accuracy inside the computer affects the quality of any directions issued by the computer.

Since accurate passive-tracking is the first basic building block for a computer-directed operation, it is often the most difficult to achieve. Some operations personnel take pride in managing a chaotic operation, instead of bringing it under control.