Since the Industrial Revolution, overhead cranes have been put to use in a variety of diverse applications to move heavy and oversized objects that other material handling methods cannot. As your business changes with the introduction of new products or processes, so do your material handling requirements, and your existing overhead equipment may not be able to meet these demands. From the slow speeds and limited ratings of early cranes, we now find hoisting speeds of over 300 FPM, bridge speeds as high as 1,000 FPM, handling loads from 10 pounds to over 1,000 tons.
Three options exist for equipment improvement – buy a new crane, refurbish a used crane, or upgrade the present crane. There are several reasons why it is safer, more efficient, productive, and cost-effective to upgrade your existing crane.
Increased production requirements may demand more capacity, faster operating speeds, better controls, or automation. Reliability may have deteriorated resulting in unscheduled shutdowns and increased production costs. Parts may be obsolete, resulting in high spare parts costs and long lead times. Inspections may show excessive wear or non-compliance with current safety standards or practices.
The original equipment manufacturers designed the structural components of their cranes to withstand mechanical forces far in excess of those encountered in normal, everyday operations, and it is not uncommon to find overhead cranes that are more than 80 years old still in operation today. Rather than scrap an outdated crane, which is still structurally sound, it is often more cost-effective to upgrade and modify the unit to meet current operational needs.
Since the structural life of an overhead crane normally is in excess of 30 years, increasing the capacity of the crane and runway or moving the crane to another location and either stretching or shortening the span are options worth considering.
Older trolleys with their large cast iron frames, drums, gear cases, and other heavy components can be replaced with modern compact trolley-hoists, and in many cases, permit an increase in the capacity of the crane due to the reduction in trolley weight alone.
The useful life of mechanical parts such as wheels, gears, bearings, etc. is in excess of 20 years. However, even the availability of spare parts after 10 to 15 years can be problematic. Upgrading old, worn parts with modern and improved counterparts is just one advantage to modernization.
Technological advancements in engineering can extend the life of a modernized crane. For example, modern precision gearing with much closer tolerances can result in reduced vibration, less gear wear, lower maintenance, and notably quieter operation than gears common in older cranes.
Utilizing modern Flux Vector Control and eliminating high-maintenance, inefficient hoist mechanical load brakes can improve performance, reduce wear on brake discs or pads, and allow gearing to run cooler.
One of the most important crane modernization, retrofit, or repair considerations is the replacement of outdated or unserviceable crane brakes with current modern industrial braking technology.
Brake performance has improved, and brake linings last longer especially when brakes operate in conjunction with AC adjustable frequency controls or digital DC controls.
In many cases, journal bearings in pivot arms have been replaced with self-lubricating composite bearings which are shock resistant, unaffected by dirt or other contaminants, and can operate in corrosive environments. Newer brake designs include features such as automatic adjustment that compensates for lining wear and automatic equalization, which provides balanced braking and assures equal brake pad wear. These features go a long way in reducing maintenance costs and prolonging brake life.
Old hydraulic brake systems tend to leak and create maintenance and environmental issues. They can be replaced with modern “brake-by-wire” packages with foot pedal operated AC Thruster Brakes that address these issues while still providing operators with the same “feel” they had with hydraulic brakes.
Complete modern-design “drop-in” brakes are available, which meet the performance and dimension characteristics of the original equipment brakes — often at a cost less than that of a replacement component — with significantly shorter lead times. They can operate with existing brake wheels and avoid costly brake-support modifications.
Heavy Duty Caliper Disc Brakes with ratings from 50 to 30,000 ft-lbs are available as replacements for existing brakes in high duty cycle, high speed, or high torque stopping AC or DC applications.
Low cost AC Thruster Brakes are often used to replace aging DC drum brakes. These brakes eliminate the need for AC-DC rectifier panels, and have optional features, such as stepless externally adjustable time delays for both brake setting and release; external torque springs to permit maintenance personnel to “dial-in” just the right amount of stopping torque for traverse motions; and automatic adjustment and automatic equalization to reduce maintenance costs.
Motor-mounted brake-support bases can also be furnished — greatly simplifying retrofits and avoiding costly brake-support modifications.
Emergency Caliper Disc Brakes for Container CraneIn addition to upgrading your high-speed side brakes using thruster drum and disc brakes, you will dramatically improve the safety of your crane by adding Emergency Caliper Disc Brakes to the low-speed side of your crane. These brakes are typically packaged with a disc mounted to the flange, and Air, Magnetic, or Hydraulic Released Caliper Disc Brakes (fail safe) are selected that will provide sufficient torque to overcome full motor torque with sufficient safety factor which ultimately stops a falling load and thus precludes a major catastrophe from occurring. The emergency disc brakes are synchronized with either a PLC or Encoder which monitors the pulses of the drum and triggers the brakes to apply when the RPM reaches a predetermined amount and the brakes apply.
Crane Rail BrakesStorm and Parking Brakes enhance the safety of outdoor cranes, protecting it from high winds and environmental conditions that can have an adverse effect on the crane such as a Runaway Crane from occurring. Our Rail Clamps, Rail Brakes, and Wheel Clamps will hold your crane down during harsh weather conditions and ensure safety.
Crane specific software, drive support tools, and serial communication with various peripheral devices provide valuable monitoring, status, performance, and diagnostic information. Features, such as Reverse Plug Simulation, Stall Prevention, Inching Control, Micro-Positioning Control, and “Static Stepless Simulation”, are built-in and individually selectable, further enhancing the crane’s performance.
No two applications are the same. Variable Frequency Drives provide the crane or hoist user with a variety of operating modes and a wide range of options.
Most single-speed squirrel cage motors can be controlled by VFDs, including conical-rotor motors used by many European hoist manufacturers. Multiple control modes (two, three, and five step or infinitely variable speed) allow for changing the operation to suit the needs of specific applications or the desires of individual operators. A wider range of selectable speed choices (up to 1000:1) are available to the user compared to the fixed speed ratios provided by typical two-speed motors (2:1, 3:1, or 4:1) or micro-drives (10:1)
Safety is built into modern Variable Frequency Drives. They include features, which reduce the possibility of lifting an over capacity load, minimize or eliminate dangerous load swing, prevent overheating of the motor, and provide safeguards that limit unauthorized modification of drive parameters or programming unsafe parameters.
Simple, innovative, low-cost, application-specific software options can be added to many VFDs to meet unique application requirements and enhance performance, safety, and production throughput including Sway and Bucket Control, Drive Synchronization, and Footbrake/Static Stepless Simulation.
Sway Control improves the accuracy of load placement and reduces material damage caused by incidental contact of swinging loads without the need for external Programmable Logic Controllers (PLCs) or costly height measurement devices.
Bucket Control lets you control the various motions of a multi-line clamshell or grapple bucket that utilize two independent open/closing line hoists without the need for a PLC or master/ slave arrangement. Features such as “Bucket Position Indication”, provide the operator with the open/close status of the bucket while dredging (underwater) or when the bucket just isn’t visible; “Speed Matching” maintains the bucket in the open position while lowering; and “Torque Sharing” keeps a full bucket closed while raising.
Many find themselves today with aging overhead cranes, originally designed to perform and survive in the tough environments of steel and manufacturing plants but operating with the previous generation of high-maintenance DC motors and controls. There are some 3,000 active cranes running in North Amerika with traditional DC controls that could be retrofitted over time. Most of these older cranes rely on traditional electromechanical DC Constant Potential (DCCP) systems which use contactors to switch regenerative load currents to resistor banks in order to dissipate the energy. DCCP systems are maintenance intensive due to their many moving and wearing parts which must operate under severe duty and in harsh environments. Rather than scrap an outdated crane, which is still structurally and mechanically sound, it is more economical to upgrade or modernize these cranes with state-of-the art electronic controls, designed to meet current operational needs.
AC is becoming the power source of choice, especially for new installations in paper mills, steel mills, bulk materials handling, shipyards, and many more areas. However, DC motors are both efficient and robust and offer year upon year of service, providing acceptable performance for the most demanding applications. Retaining an existing DC motor and upgrading the crane with solid-state controls is more environmentally friendly and – from a commercial perspective – provides an opportunity to enhance overall system performance and reliability while minimizing the risk to production and the required capital investment, an attractive proposal in today’s economic environment.
Retain existing power source, DC-motors and control wiring and replace traditional contactor control or obsolete static controls with Digital DC Controls.
While pendant push button stations suspended from the hoist or on a separate festoon track bring the crane operator closer to the load and eliminate the need for a separate person to “hitch” or “signal”, they are often in the wrong place for safe or efficient operation, forcing the crane operator to dodge obstacles or untangle cords. Remote wireless control solves these problems.
Remote wireless control of overhead cranes and hoists has been around for over 50 years, and technology has changed significantly in recent years, allowing kontrol jarak jauh manufacturers to bring products to market that are safer, more reliable, ergonomically designed, extremely versatile and flexible, and now affordable for even the smallest crane or hoist application.
Remote control can be transmitted by either Radio Frequency (RF) signals or by infrared light. The use of RF signals is the decidedly more popular option in the U.S., where it accounts for approximately 98% of remote control transmissions. Infrared systems, which are similar to those used for TV remote controls, have inherent problems, such as short operating ranges; frequent line-of-sight dropouts and interference from dust, bright light, and sunshine; and relegation by the leading US manufacturers to down-load/up-load functions.
Modern Radio Remote Controls employ state-of-the-art technologies such as Graphic Displays and various types of wireless communication including Synthesized Frequencies, Time Multiple Sharing and Frequency Hopping Spread Spectrum (FHSS).
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