Ensuring Reliability And Safety Of Your Process Cranes
Marilyn | March 1, 2008
Are you investing too much, too little or too late in your crane maintenance efforts? An in-depth reliability survey can be invaluable in helping determine what level of this maintenance is optimal for your operations.
It’s widely known that investing effectively in crane maintenance can help reduce the risk of safety and environmental incidents, breakdowns, loss of production and premature equipment failure. Unfortunately, what level of investment is “optimal” is not as well known. There are various levels of crane maintenance that dictate what value, benefits and return a company can expect on their investment. The optimal level must not only remediate risk factors but also demonstrate a measurable return on investment.
Cranes represent a substantial investment for a company. Thus, determining the right level of maintenance required to maximize that investment should be a high priority. This is especially important for companies that depend on cranes as a part of their process.
When a crane becomes an integral part of a production process, it is called a “process crane.” Since process cranes are designed for round-the-clock use, they call for maximum reliability. They must be able to answer the most stringent performance requirements, including: automation, highly demanding duty cycles, difficult operating environments, high operating speeds and special control systems. The cost of downtime for a process crane can easily exceed $1 million US per day. Repairing the equipment after it breaks (i.e., corrective maintenance) is simply not enough. The optimal solution is to prevent the breakdown from occurring in the first place.
Optimal maintenance of process cranes can significantly reduce overall operating costs associated with downtime, etc., while boosting productivity. This is considered a proactive maintenance approach. In order to truly develop a proactive maintenance strategy, companies must conduct an in-depth crane reliability survey to gain the insights needed to develop their plans. Systematic and exhaustive surveys of this type will provide the facts needed to develop a smart strategy. In-depth crane reliability surveys also generate the information needed to enhance safety and mitigate issues, improve performance and reliability and extend the service life of a company’s process cranes.
Enhancing safety and mitigating issues
An in-depth crane reliability survey relies on the use of advanced diagnostic tools that penetrate deep into equipment and uncover problems that are undetectable by standard equipment inspections. Addressing those problems in advance prevents injuries from occurring and presents tremendous savings in injury-related costs.
Improving performance and reliability
A crane reliability survey provides a roadmap for improving equipment performance and reliability. Knowing what repairs are needed in advance allows a company to prioritize its maintenance activities and schedule the work so as to maximize productivity and increase uptime over the life cycle of its equipment. This not only helps prevent unnecessary production downtime— it saves money.
Extending equipment service life
A crane reliability survey also can help extend the service life of equipment by providing a guide for preventive maintenance, which, in turn, helps reduce capital investment costs. Knowing when to anticipate repairs allows a company to forecast expenses and put them into its budget for improved cash flow. This will help to avoid the unpleasant surprise of a sudden breakdown and the unexpected expense of the repair or replacement of their crane, which could lead to a loss in production revenue.
Conducting a crane reliability survey
A crane reliability survey is a very sophisticated undertaking. Every crane is different. Therefore, it’s important to study documentation, interview users and conduct in-depth analyses using advanced instruments that detect potential problems other inspections miss. A crane reliability survey should include four key modules: the CORE inspection, structures and working conditions, components and the maintenance assessment.
CORE inspection and analysis…
The aim of the CORE Inspection is to calculate the crane’s Safe Working Period—a time period assessed in which the operating characteristics of the crane (running speeds, acceleration, and deceleration) are suitable to the current use of the crane. During this phase, all crane information should be collected. It is important to become familiar with the crane through a review of all available documentation—reports and notes from past inspections and photographs of the crane and its parts. It also is important to gather information regarding the service history and current condition of the crane.
Next, it is important to conduct interviews to fully understand the usage and performance of the device. Any machine is best known by its primary operators. In some cases, the operator may need to adjust usage behavior and habits in order to extend the service life of the machine. Lastly, a detailed inspection is required. A field inspection should include gathering information on the overall crane condition. The crane should be inspected and the service life analyzed.
Structures and working conditions…
This study provides an overall analysis of the crane’s condition by evaluating the operating environment, the present state of the power supply, the alignment of the crane structure, its associated runways and the steel structures of the equipment. A series of four exhaustive analyses should be performed.
- An ambient conditions analysis ascertains the operating conditions of the equipment, in which temperature, humidity and dust of operating equipment are analyzed. In addition, it is important to define the corrosive effects of the environment, using both tests and visual inspections.
- A power supply analysis can detect potential problems related to the supply voltage of a crane. Common problems may include: a too high or too low voltage level, voltage dips, swells or interrupts.
- It also is essential to conduct a geometric analysis to study the runway where the equipment is located. The condition of the runway strongly influences how well a crane moves on its rails, affecting the usability and lifetime of the traveling machinery units. It’s important to inspect the permitted geometrical tolerances: measuring, visually inspecting the rails and their fixings and comparing them to original installation drawings.
- During the final stage in this phase, it is crucial to conduct a steel structure analysis to scrutinize each individual part for deficiencies in physical condition and assess structural safety.
The component analysis is a specific, detailed assessment of the present condition of the crane’s electrical components— all motors, gearboxes, hook block assemblies and the wire rope and its revving component. It is important to evaluate the risks that can lead to production loss due to component failure and explore options to minimize such occurrences.
An electrical component analysis will help to determine the condition of crane electrification. To improve reliability, there are many objects in the electrification that require monitoring. Furthermore, a motor analysis is necessary to determine the current condition of the motors on the crane.
The wire rope is one of the most critical parts of the hoisting machinery. The rope is stressed by tension, compression and bending during lifting cycles. Along with visual inspection, it is imperative to perform an advanced, non-destructive assessment with a rope tester.
Determining the condition of the crane’s hoisting and traveling gear is critical. Gears are normally designed so that the gear surfaces wear clearly and the load-carrying capacity is not lost—assuming that the gear case is maintained correctly. The purpose of the gear analysis is to define the current status of the gear in order to reduce the risk of gear failure.
Based on international standards, the hook and hook block also should be examined. The hook is used during every lift cycle and can be subjected to conditions that will produce mechanical stresses.
Maintenance and reliability…
During this phase, evaluate the overall maintenance of the crane by analyzing the reliability of the crane. The purpose of this analysis is to define the reliability of the crane and identify the most critical components that could cause downtime.
The reliability analysis should include a Life Cycle Assessment (LCA) environmental impact analysis, a spare parts analysis, and a cost analysis. The Life Cycle Assessment (LCA) determines the total environmental impact the crane will produce during its operating lifetime. This analysis includes emissions to air and water.
Spare part availability can cause an increased threat to productivity. The purpose of the spare parts analysis is to determine the parts that are critical and that should be readily available. The analysis also considers the suitable requirements of a storage location and estimates the value of the inventory of spare parts.
Next, evaluate all costs associated with the operation of the crane in a cost analysis. This analysis documents the company losses—time and monetary—as a result of inefficient equipment. Examine maintenance and operation records from a two-year span to determine the duration and frequency of a crane’s downtime and its overall impact on the production line. During this phase, analyze maintenance costs, production and quality losses. Moreover, a complete audit of the current maintenance situation of the company’s material handling equipment is recommended.
A company can perform its own crane reliability surveys or obtain them through outside sources (see Sidebar). Whatever approach you take, the point is to help you determine that “optimal” level of maintenance that will keep your process cranes up and running as scheduled—safely, reliably and cost-effectively. MT
Mike Williams is vice president of Service with Konecranes Americas. Telephone: (937) 525-5560; e-mail: mike.williams@ us.konecranes.com
Products and services backed by 80+ years of experience
Konecranes designs, manufactures and services standard and heavy lifting equipment for multiple industries around the globe. Operating in 41 countries, it maintains more lifting equipment than any other company in the world. It also is a leader in the development of specific industry requirements and regulations for reliability and safety of overhead lifting equipment.
Konecranes is able to assemble highly-experienced teams to conduct Crane Reliability Surveys (CRS) on all makes and models of cranes. Each Konecranes CRS team is composed of technicians and specialists. CRS results are presented in a comprehensive, yet easy-to-read report that includes recommendations for future action. After the CRS, the company will understand the crane’s current operating capacity, know how to plan ahead and be able to forecast expenses in order to better manage its maintenance budget.