Hansen Industrial Transmissions (HIT) recently introduced a hydraulic brake system (patent pending) for its M4 ACC (Air Cooled Condenser) industrial gearboxes, which allows the user to safely slow down the gear unit and condenser fan and keep them at standstill during maintenance activities in dry cooling towers. The Machinery Directive 2006/42/EC, applicable to machinery on the EU market, aims at ensuring a high level of protection of the health and safety of people and the environment. The Directive states that "machinery must be designed and constructed so that it is fitted for its function, and can be operated, adjusted and maintained without putting persons at risk".
With this hydraulic brake system, Hansen gearboxes can now be equipped with a tool that avoids the risk of maintenance personnel being injured due to ‘wind milling' (an idle fan which starts rotating due to airflow and thus driving the gear unit). The new hydraulic brake system is unique in that the braking force not only holds the fan and gear unit when at standstill, but is capable of decelerating it to a safe stop within a limited braking time (max. motor speed to be confirmed by HIT per project). It consists of two hydraulic brake cylinders with brake shoes and a hand pump with hose. The brake cylinders are built onto the motor lantern and brake on the coupling between the motor and the gear unit. Due to the fact that it is a mobile solution the investment is kept limited, since a single brake kit can serve a whole batch of fan drives. In case the customer/end-user prefers a stationary solution, two hydraulic brake cylinders with brake shoes are assembled to each gear unit. This avoids having to uninstall these on-site and allows keeping several gear units at standstill at the same time. The number of hand pumps can be chosen freely.
The system also allows demounting of the motor during maintenance activities, because the brake shoes only work on the bottom half of the coupling. Additional safety is obtained due to the mechanical locking mechanism on each brake cylinder. As an option, limit switches can be installed on the hydraulic brake cylinders to detect their position. The signal can be used to prevent the drive from being started while the brake is engaged.