Hoisting system design specifications

With increasing corporate focus on risk management, best practices in hoist plants are a high priority. Implementation of these best practices for the specification and selection of components for a hoist plant can present challenges with the overall hoist system design. 

The benefits of AFE PWM variable frequency drives coupled to mine hoists indicates that this will be the preferred application for the foreseeable future. When powered by off-grid diesel generation systems, particular attention paid to design specifications of drive transformer or input reactors, generators, load banks, harmonic filter banks, and power system controls can avoid potential power system problems and ensure a successful system implementation. Individual equipment manufacturers need to have an understanding of overall system design... 

As a result of this visit, the GFN team were able to confirm their decision, and provide valuable feedback during the subsequent design and risk assessment exercises. Specific examples of similarities and differences between the Telfer and GFN hoisting systems are provided in the subsequent text. 

Thyristors have been replacing saturable reactors they are small, efficient, and easily controlled by a wide variety of control systems. A modern crane control drive uses fixed secondary resistors and two sets of primaiy thyristors (one set for hoist, one for lower). With tachometer feedback for speed sensing, the control for the motor provides speed regulation and torque hmiting in both directions, all with static-devices. A wide variety of control systems is possible the control should be designed for the specific application. 

To minimize the effects of voltage distortion on weak AC systems introduced by VFD s applied on hoisting equipment, care should be taken during the specification phases of the VFD s and generation equipment procurement to ensure compatibflity and a trouble-free design. Also, the ratings of harmonic filtering equipment should be verified by a full harmonic study of the system. 

Since the release of EN 61508 in 1998, several related standards such as EN 62061 and EN ISO 13849-1 have been developed to provide designers of mechanical equipment with specific guidance as to the application of this general standard. New hoist control systems are often required to comply with these standards. 

Since the release of EN 61508, there have been rafts of other standards developed that address specific industries and other disciplines. Two standards that are commonly asked to comply with in designing hoisting are EN 62061 Safety of machinery Functional safety of electrical, electronic and programmable electronic control systems, and EN ISO 13849-1 Safety of machinery Safety-related parts of control systems. The latter standard caters for design of safety systems irrespective of the technology used, whether it is electrical, mechanical, hydraulic, pneumatic etc. 

AECOM Australia was awarded the task of completing the installation design of the structures and facilities to allow the hoist to be integrated into the GFN materials handling system and meet the site-specific design requirements. Several of these are described in the following text. 

---