Posted to News on 20th Oct 2015, 14:55
Twiflex puts the brakes on offshore winches
Designing components that will provide reliable operation for marine and offshore applications requires considerable expertise, especially when manufacturing vessel mooring winches designed to bring two ships alongside each other. When such an application was being designed for a pipe-laying vessel, Twiflex Ltd. was approached to support the project with its many years' experience in supplying the marine industry with brake products.
The initial consultation began with Intertech B.V., which is the official distributor for Twiflex products in the Netherlands. As a technical trading company, it specialises in power transmission and motion control products, with particular focus on the petrochemical, power generation and marine sectors and has over 15 years' experience developing Twiflex products for use in the offshore industry.
In this instance the OEM responsible for the vessel mooring system on the pipe-laying vessel approached Intertech for advice on caliper braking options for its new range of hydraulic haul back winches. Intertech was quick to suggest the Twiflex range thanks to its reputation for delivering reliable products into marine and offshore applications, as well as offering the largest range of industrial disc brakes in the world.
Alexander Kuhne, Managing Director at Intertech, comments: "Our experienced engineers have long appreciated the benefits that Twiflex designs can bring to our projects. The technical knowledge and support enables us to work closely with the client and deliver a bespoke package tailored to the specific requirements of each application."
The purpose of this particular winch was to allow two vessels to be brought alongside each other using the cable to pull them together. However, the action of the waves between the two vessels can greatly increase the tension in the cable. This required a braking system that would allow the cable to be gradually released in order to protect the winch system when the tension exceeded 30 tonnes.
Twiflex was selected as the first choice for this project for a number of reasons, including the compact dimensions of the VKSD-FL and its "parked-off' feature which increases the ease of adjustment and maintenance.
Once the initial design specifications had been provided, the Twiflex engineers formulated a braking design that would enable a 30 tonne holding force to be maintained on the winch drum. Working with the starting point of a 660mm drum, the designers selected a 1500mm diameter brake disc and three VKSD-FL spring-applied caliper brake modules to ensure the complete system would have sufficient braking torque.
The VKSD-FL is a single-spring brake module that is well suited to applications such as this, where space can be at a premium. This range also includes the "parked off' feature, which addresses the risk of brakes clamping shut unexpectedly during maintenance.
Maintenance work
Normally when spring applied brakes are powered down for maintenance work the brake is shut tight against the disc and as a result the springs need to be compressed by mechanical means to remove the pads. This process makes maintenance more time consuming and, due to the stored energy in the spring, leaves the brake prone to unexpected closure in the event of component failure.
The Twiflex "parked off' feature is different to other approaches in that it actively removes the spring force from the brake while its powered off, meaning there is no force acting on the pad.
With hydraulic pressure applied, maintenance engineers can unwind an adjusting spindle, which releases the spring pack. When the hydraulic pressure is removed the springs have the freedom to extend without acting on the brake. At this point the spring load and hydraulic pressure are both zero and the brake has no stored energy.
The "parked off' feature has a number of benefits. First, basic maintenance such as brake pad replacement can be carried out quickly and with a reduced risk of unexpected closure when compared with conventional brake designs. Second, the brake force can be easily adjusted by setting the brake to "parked off' and adjusting the number of shims from the end cover. Finally, installation is made easier and the brake can be installed without the need for hydraulic pressure.
For this project two winches were manufactured, each fitted with three Twiflex brake calipers to produce a combined braking capacity of 234 kNm. Each module is designed for over 2 million cycles which deliver excellent durability and spring fatigue life. The brakes were supplied for marine use and painted to ISO 12944-5: 2007, C5 to meet the client's specifications.
Alexander Kuhne concludes: "This demonstrates the ability of Intertech and Twiflex to deliver bespoke solutions that are designed to meet very specific requirements while also adhering to the specifications of marine design dictated by the regulatory bodies such as Lloyds Register."
To learn more about the company's brake products for the marine and offshore industry go to www.twiflex.com.
