The grease-free ThorPlas-Blue bearings Thordon supplied and installed to a Mississippi River line haul boat recently have helped reduce the vessel’s operating costs while creating a safer working environment for the crew.
When this 180 ft (54.9m) triple screw work boat recently docked for repairs, the ThorPlas-Blue bearings previously retrofitted to the vessel’s tiller and jockey bars by precision field machining company Mactech On-Site showed no signs of wear, despite two years operating in the abrasive, low draught waters of the Mississippi River in the U.S.A.
In response to the customer’s request for grease and corrosion-free tiller linkage capable of withstanding greater vertical movement of tiller pins, Thordon’s grease-free ThorPlas-Blue bearings were retrofitted to the triple screw towboat in 2016 with Mactech replacing the bronze bushings in the vessel’s steering.
Thordon Bearings’ Business Development Manager, USA, Jason Perry, stated: “It is typical of these Mississippi workhorses to drydock frequently to replace their greased sleeve type bushings. These types of bearings are unable to tolerate angular misalignments resulting from deflection or improper mounting, which can place considerable stresses on the steering system, causing high levels of vibration, corrosion and, in some cases, pollution.
The nature of the work done by these vessels and the environments in which they operate also means that metal-on-metal bearings are more susceptible to damage and rapid rates of wear, which can increase operational costs.”
At various times during the past two years’ the vessel’s steering gear was spot checked by pulling the tiller pins and measuring the internal diameter of the bushings. Based on measurements taken by Mactech and the customer, the bearings had experienced “no measurable wear.”
“The commercial benefits of no longer having to replace metal-on-metal bearings every one or two years or purchase, store and apply lubricating greases are obvious, but the crew has also remarked that the tiller flat is a cleaner, safer working environment. The linkage system is completely grease free, so there’s no chance of slipping on greasy decks.”
Based on the results and performance of the Thordon bearings on this vessel, the customer has now opted to retrofit ThorPlas-Blue to 10 additional workboats.
Commenting on the retrofit process, Mactech Operations Manager Monty Glisson explained: “To create a completely grease-free steering system, a ThorPlas retrofit typically involves replacing hydraulic power units and cylinders, and carrying out quadrant modifications, as well as machining all quadrant and jockey bar bushings. Thordon and Mactech have the proper tools, experience, and processes to complete the job without removing all the steering components. We have a complete understanding of what the customer is trying to accomplish.”
Prior to any retrofit project, Thordon and its partners will measure and record all as-found bushing data before creating a mock-up steering linkage. After this, new bushings are machined to size and clearance before fitting to quadrants and jockey bars. New wear plates are then manufactured for each pin joint and the steering system is reassembled with new pin retainers.
“The ease of machining allows the bushings to be finished quickly so that repairs and retrofits can be completed on time and without costly drydocking,” said Glisson.
ThorPlas-Blue is a homogeneous, self-lubricating polymer bearing with a low dry coefficient of friction, high strength, and low creep.