Of the cranes operating today in terminals, harbours and on- board ships, many were commissioned one or perhaps even several decades ago. If properly maintained, a crane can remain in operation for several years. At some point, however, normal maintenance is no longer sufficient or even possible. The crane has become ripe for refurbishment.
A further motivation for taking a more radical step may be to benefit from the advances in technology that have been made since the crane was built. Generally, control and information technology has developed faster than basic mechanical crane technology, and a crane is likely to employ at least two electrical control systems during its operational life.
This article will focus on aspects of refurbishing a crane’s electrical control system in a wider sense – when it is necessary, and what you need to keep in mind when planning refurbishment.
Life cycle plans
The electrical control system of a crane is made up of components such as motors, drives, relays and in most cases a PLC. The power handling components of the system – i.e. transformers, power distribution gear, motors, etc. – can usually be kept in good shape through normal maintenance. Should components fail, compatible replacements can usually be found.
Electronics, however, are a different story. Basically, electronics can be defined as components integrated in one way or the other. Some components, such as power components (thyristors, IGBTs, etc.) may be discretely fitted, but most components are integrated into circuit boards. In principle, repair and maintenance are possible
as long as the respective components are available as spare parts. In practice though, complete spare circuit boards must be on hand for repairs in order to keep downtime due to failures at an acceptable level. Since a circuit board can only be produced if its components are available, the supply of circuit boards eventually dwindles. To inform users of a product or system concerning the evolvement of availability of support and service over time, ABB uses the concept of life cycle plans.
The envisioned life cycle of a product is divided into four phases: active, classic, limited and obsolete. During these phases, available support and service gradually change. For each product, the current life cycle phase is continually updated and pertinent information published together with the scheduled transfer date to the next phase. This enables users to plan maintenance and refurbishment activities in good order and well in advance of transfer. The same principle can be used regardless of the original supplier. Although life cycle plans may not be published for a system, the basic method of determining the need for refurbishment is the same:
• Inventory the products and systems installed in the crane
• Find out if spare parts are available, for how long and at what prices
But be prepared; the results may come as a shock.
Service skills
Another factor that may indicate the need for refurbishing is the availability of service skills, or rather the lack of them. Most work on a system is carried out in the early phases of delivery, i.e. design, start-up, etc. The system may later operate for years with very little need for attention, and the people involved move on with their lives. This is also reflected in the supply of and demand for service skills for the system in question. Since demand is limited, so is supply. Generally, support and service
options tend to be easier to find for currently produced and supplied (active and classic) system generations.
Alternative to new crane
As mentioned previously, development of control technology has moved faster than that of the basic mechanics. In fact, an old crane may be well designed and mechanically sound but difficult to operate and unreliable due to an outdated control system. In such case, refurbishment may well be a financially viable alternative to purchasing a new crane.
