Cost Affective Dockside Crane Retrofit Barry W. Wiles Industry Manager Crane Systems Avtron Manufacturing Inc. 7900 E. Pleasant Valley Rd. Independence, OH 44131 Phone: (216) 642-1230 FAX: (216) 642-6037 bwiles@avtron.com Key words: SCR Firing, DC Drive Upgrade, Dockside Crane, Retrofit INTRODUCTION Electrical equipment obsolescence can be a major problem on dockside cranes. Mergers and acquisitions throughout the industry have caused product lines to go obsolete or unsupported. Operating facilities can find obsolescence issues as short as a year after the original equipment has been installed. Once initial warranty periods are over, equipment issues can cause dockside operators large sums of downtime. Problem Maryland Port Administration s Dundalk Terminal operates several dockside cranes for the loading and unloading of containers from ships. Cranes No.7 and 8 were originally installed in 1977 by IHI with GE controls, then the cranes were upgraded in 1996/97 by Square D using Telemechanique controls. The electrical equipment supplied by the manufacturer was becoming obsolete and causing problems with the crane operation. Down-time was increasing and there was limited diagnostic capabilities for troubleshooting. MPA was also told by the manufacturer of the DC drives that they were no longer supported and parts were unavailable. MPA was at risk of losing one of these vital cranes for a large period of time if a major malfunction of the system should occur. MPA recognized that something had to be done before a major problem shut down one of the cranes for an extended period of time. A project was put together that would eliminate the risk of product support and also installed a system that required less time to maintain and diagnose. Project goals included: 1. Eliminate the Telemecanique Rectivar 4 Electronics system. 2. Replace the existing Telemecanique PLC. 3. Provide new operator controls for better crane performance. 4. Install a state-of-the-art diagnostic system with remote monitoring capabilities 5. Eliminate the exposure of the port to downtime due to obsolete electrical parts. 6. Minimize the downtime exposure to operations for installation of the project. 7. Provide on site troubleshooting training on the new system. Solution MPA put a budget together for the retrofit of the two cranes. Several different solution approaches were reviewed. Avtron presented a retrofit package where the Hoist/Gantry DC drive SCR s would be left in place and fired by Avtron Manufacturing s proven Advance Firing Module (AFM) technology. Due to the Trolley/Boom drive size, economics dictated that this drive would be replaced completely. A new PLC was also proposed that would be well supported for years to come. Page No. 1
BACKGROUND Maryland Port Administration cranes No.7 and 8 were originally Built and installed in 1977 at the Dundalk Marine terminal. Originally built by IHI, the cranes were equipped with GE S21 DMG Controller and hardwired controls. The cranes were upgraded by Square D in 1996/97 and was provided with Telemechanique DC drives and programmable logic controller. (PLC). MPA have been notified that the Rectivar 4 series DC drives were no longer available and that spare parts would also be discontinued and the PLC spare parts obsoleted and were becoming hard to get support. This left the port exposed to lost production should a major malfunction occur. The crane control system was configured so that Hoist/Gantry motions were controlled by one DC drive and the Trolley/Boom motions controlled by another. Control was performed by a PLC through local and remote inputs and outputs. Service issues were on the rise causing concern by both maintenance and management. Although the drive control boards, electronics and associated hardware were obsolete, the power components such as SCR s were still commercially available from several sources. Figure 1 Dockside Crane for Maryland Port Authority Page No. 2
PROJECT SCOPE MPA solicited bids for the electrical upgrade of both cranes. Each supplier was asked to present the most economical solution available. In many cases, vendors proposed the complete removal of both DC drives PLC system and associated hardware. Installation schedules were also long and required 14 or more days to complete. Avtron presented a solution that kept the large DC drive power components on the Gantry/Hoist section and replaced the smaller drive on the Trolley/Boom. By not replacing the Hoist drive, Avtron could save time during installation and provide a 7-10 day total schedule for the implementation of the project. Avtron also demonstrated to the customer that its hardware could be used on any type of DC drive for retrofitting and provided several successful references of similar projects. System Layout The crane controls were located in a control room that is part of the equipment house. Two DC drives provided power conversion for the crane for the following functions: Drive No.1 = Hoist/Gantry, Drive No.2 = Trolley/Boom. Motor and drive ratings are listed below: Section Name HP VDC ADC Motor RPM Hoist Motor No.1 250 HP 250 800 942/2260 RPM Hoist Motor No.2 250 HP 250 800 942/2260 RPM Gantry Motor No.1 20 HP 240 69 1750 RPM Gantry Motor No.2 20 HP 240 69 1750 RPM Gantry Motor No.3 20 HP 240 69 1750 RPM Gantry Motor No.4 20 HP 240 69 1750 RPM Gantry Motor No.5 20 HP 240 69 1750 RPM Gantry Motor No.6 20 HP 240 69 1750 RPM Gantry Motor No.7 20 HP 240 69 1750 RPM Gantry Motor No.8 20 HP 240 69 1750 RPM Trolley No.1 60 HP 500 95.6 1424 RPM Trolley No.2 60 HP 500 95.6 1424 RPM Boom Hoist 100 HP 500 160 1750 RPM Table I Motor Specifications The motors were powered from the two DC drives with the following arrangements Rated ADC Rated VDC Overload Rating Drive Name Hoist/Gantry 1750 500 200% Trolley/Boom 280 500 220% Table II Drive Specifications Page No. 3
Drive Retrofit Solution Many factors go into determining whether a section is a candidate for retrofitting the SCR s or not. A typical rule of thumb is that sections rated 250HP and above can typically be upgraded economically. Key factors in this decision include: 1. Drive size and complexity. Drive HP size is a key factor in determining a retrofit path. If the HP is small, it is generally easier to replace the drive with a new unit. Cabling is typically small and easy to replace along with associated hardware. Experience has shown that 250HP is typically a breaking point depending on the situation and complexity of the system. Typical crane applications utilize drives for multiple motions and are generally more complicated systems. 2. Are the SCR s still commercially available? In most cases, the semiconductor devices will still be available for a particular drive. Manufacturers have used standard sizes over the years which are still produced and supported. In most cases, SCR s are installed in a heat sink assembly and are readily accessible. Avtron generally will survey the drives prior to a solution proposal to determine the best upgrade path. 3. SCR firing type. Almost all crane drive systems use a picket-fence type firing circuit for the SCR s. Modern day SCR s are designed to fire by this approach. Most drives that are retrofit candidates are less than 20 years old. There are some types of older technology where SCR s are fired by a single hard pulse which is known as Hard Pulse firing. Avtron Manufacturing can work with either system by supplying a different firing board. 4. Drive Location and accessibility Another key issue in retrofitting an existing DC drive is its location and accessibility. In most cases, it is easier to retrofit the SCR s than replace the entire drive. Removing the entire drive unit may require additional wiring because the power terminals are not in the same location. It will generally also require large amounts of re-wiring to existing components that support the drive. Manufacturers will typically provide entire new panels with the support devices included which adds cost and installation time. 5. Customers goals and objectives A final review is with the customer to determine their goals and objectives. In most cases, the customer is looking to eliminate obsolete equipment with newer equipment that will be maintained and supported for several years. Schedule is also important and can dictate a solution path. If the schedule is aggressive, retrofitting the SCR s takes less time and can get the crane back into operation quicker. Economics also proves that retrofitting the SCR s is less costly than replacing entire units. 6. Staggered Upgrades If the customer schedule precludes a longer downtime then a staggered Upgrade approach can be done by doing each part of the system singly. Page No. 4
After reviewing all of these factors for the MPA project, Avtron determined that its best proposed solution would be a combination retrofit. Key issues in determining this included: 1. The Hoist/Gantry drive was rated at 1750 ADC which is a strong candidate for retrofits. 2. Trolley/Boom drive was rated at 280 ADC which was small and could easily be replaced by a stand-alone drive. 3. SCR s for the Hoist/Gantry drive were still readily available and cost affective to obtain. 4. Customer wanted a 7-10 day outage window which required the most time affective solution which was retrofitting the drive. Figure No.1 shows the drive system layout for the project. Figure No.1 Drive System One-Line Page No. 5
Hoist/Gantry Drive Retrofit Details Avtron retrofit solutions offer a flexible approach to firing existing SCR s. Hardware includes the Avtron Firing Module (AFM), sense module and bridge firing module. Experience has allowed Avtron to invent firing solutions that can be applied to almost every manufacturer of drive. A typical configuration is shown in the following figure: Figure 2 Typical retrofit system diagram Page No. 6
Hoist/Gantry Retrofit Details MPA s hoist drive is rated for 1750 ADC in both the forward and reverse direction. The existing DC hoist was broken into two separate components. SCR s were enclosed in a unit that sat by itself on a panel. A second panel housed the control modules and firing controls along with a stand alone field supply for the gantry, which is controlled from the ADDvantage-32 unit to ensure tight coordination of the drive and field control loops. Avtron s solution replaced the entire control modules with an AFM module with integrated field supply for optimum control of the Hoist. A second field supply used for the Gantry motor fields. Figures 3 shows the system prior to the retrofit, figure 4 shows the retrofitted panel. Figure 3 Original DC Hoist controller and field supply (Left), SCR assembly (Right) Figure 4 Panel before retrofit (Left), panel after retrofit (Right) Most DC contactors and associated hardware were left in place due to the fact that they were still in working order and well supported. In order to reduce the rework of this section, Avtrons firing control module was placed in the same location as the original controls.. This created a minimum impact for installation that allowed Avtron to complete the system rework inside the outage window. Trolley/Boom Retrofit Details Due to its smaller size, the Trolley/Boom drive was replaced in its entirety. Original system layout included a stand-alone DC drive with controls and two external power supplies for the fields. Each field supply was single phase. The original contactors and switching relays were kept along with the existing process controller to switch motor configurations for the Trolley and Boom motors. Avtron replaced the entire drive with an ADDvantege-32 DC drive with integrated field supply. This eliminated the Trolley motor field supply unit. The field supply for the boom was replaced, which is controlled from the ADDvantage-32 unit to ensure tight coordination of the drive and field control loops. Page No. 7
Figure 5 Trolley/Boom Drive before (Left), Trolley/Boom after (Right) Avtron s ADDvantage-32 product line incorporates Smart Drive technology. A preconfigured software block package resides in the firmware of the drive that performs all crane functions for a particular section. Most competitive solutions require a mill master or Programmable Logic controller in addition to the drive equipment to operate the crane. This makes upgrade more expensive and harder to do. With Avtron s ability to perform all crane functionality in the drive equipment, upgrades can be performed at a reduced cost and in multiple steps if desired. In many situations, Avtron can replace section at a time and integrate the equipment into the existing PLC or hardwired relays. If a PLC is supplied, it is used to provide the basic logical operation of the crane control so that hardwired relays are not required. Page No. 8
Programmable Logic Controller Replacement MPA decided to replace the programmable logic control system because of support and spare parts issues. System I/O was distributed throughout the crane which required a new racks in the drive control room, remote I/O for the drives, remote I/O for the Boom and Engine, remote I/O in the operators cab, remote I/O Gantry landside and Gantry waterside. Due to the aggressive schedule, the I/O system replacement was considered the largest challenge. This required the most amount of rework and could only be accomplished by individual electricians due to confined work areas. A detailed plan was put together to carry out this phase of the project. Figure 6 PLC System One-line Avtron s communication flexibility allows it to connect to most major brands of PLC s. MPA had a preference for a SLC-500 PLC s because many of their electricians were already trained in its use. It is also a well supported product that would offer the ports years of service. New I/O was installed in the same locations as the original to reduce the amount of re-work and allow the use of the existing field wiring. With the PLC and drive systems being unique systems, Avtron service engineers were able to split these two systems so that each was commissioned on its own. This cut-down on the amount of time required for the start-up of the crane and fit the project into the projected outage window. Page No. 9
Figure 7 Original PLC system (Left), new system (right) Figure 8 Operators CAB remote I/O before and after retrofit. The original PLC and drives communicated over a copper information link that was susceptible to noise. Avtron proposed its proven Ethernet communication technology that allows all devices to communicate over a high speed connection. Fiber optic cabling was utilized to connect the new drives, PLC and diagnostic computer. The original PLC remote I/O communicated to the operators cab and boom I/O using Fiber optics, this was retained. The Gantry Landside and Waterside communications was upgraded to use a high flex blue hose shielded twisted pair copper cables run separately to all other wiring. Fiber-optic networks are less susceptible to noise and installation issues unlike proprietary copper networks. CONCLUSION Maryland Port Authority reviewed several different upgrade solutions for dockside cranes No.7 and No.8. Avtron reviewed the customers expectations, existing DC drives sizes, commercial availability of the parts and existing drive packaging to offer the best solution fit possible. Analysis of this data concluded that MPA would benefit from an SCR retrofit solution over a complete drive change-out. After two successful short outages, MPA is now Page No. 10
experiencing the benefits of the upgrade. System reliability has increased helping improve the productivity of the cranes. Troubleshooting time has been reduced with the new diagnostic system and the port is no longer exposed to obsolete parts and potential downtime on the crane. Avtron SCR retrofit packages are a very cost affective upgrade path to existing cranes. In many applications, the existing relay logic or I/O can be reused to save time and costs. Flexibility and Smart Drive technology allow Avtron products to be implemented in almost any situation to meet the customers need. Page No. 11
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