Here, Derek Vanek, technical manager at SIFCO looks into how the marine industry can decrease costs and reduce downtime using selective plating methods as an alternative to disassembling components for repair.
Day in, day out, marine equipment is subject to extreme conditions including, salt water, high temperatures, wear, corrosion and fatigue. The problem which comes with these conditions is the length of downtime needed to repair key marine components and equipment.
Every second a vessel spends in the shipyard is one where it’s not creating value or safeguarding national security. In the USA alone, investment in shipbuilding has grown steadily, with gross output in 2013 topping $28 billion. With these figures, it’s crucial to minimise downtime.
Typical component problems and issues can include: fretting or wear on bearings and flanges due to continuous vibration, extensive wear on bearing cap faces and saddle areas, corrosion on various components such as compressed air valves and parts exposed to sea water, steam cuts on high pressure turbine castings, worn Babbitt coatings on bearing shells, as well as out of tolerance or mis-machined shafts, housings and bearings.
Traditional plating
You may ask yourself why is an alternative plating method needed if the traditional method of tank plating is safe and still creates proven results? Every second of downtime counts, as costs can mount up very quickly. The use of this traditional method can hinder the process and increase downtime further due to the need to disassemble components, the time it takes to transport from shipyard to plating facility and the reinstallation ahead of re-entering service.
Tank plating involves the use of large tanks of preparatory and plating solutions and often requires extensive masking. The procedure is not portable, meaning the overall process, by nature, is rigid and not suited to components which need plating particularly fast.
Selective plating is a well-established and reliable process which has already been written into shipbuilding specifications. It is a portable method of electroplating localised areas of metal surfaces for OEM components, permanent repairs and salvaging worn or mis-machined parts; providing a fast, efficient and targeted solution to corrosion, wear, galling, solderability and brazing. It is carried out by skilled technicians to repair or maintain critical parts.
The main benefit is portability. Only four elements are required; a power pack, plating tools, plating solutions and a trained operator. Unlike tank plating, selective plating can be performed in situ - the part or component does not need to be removed and transported to an external site. It can be brought into the shipyard, aboard vessels, or anywhere it’s needed to enhance or repair components, by any team member – certified technicians and engineers can take on the role after training, while the portable equipment facilitates machine shops at the point of repair.
The process not only exceeds the fundamental requirements of shipbuilding manufacturing, and repair and maintenance processes, it also provides a full circle of benefits, including quality, durability, cost saving and time saving.
Take the SIFCO Process. Carrying approvals from the American Bureau of Shipping, Mil-STD 2197(SH) and NAVSEA, the process uses significantly smaller volumes of plating solution than tank plating, using only the required material. There may be no need for disassembly or transportation, and minimal masking and post-machining; just a quick process that extends maintenance intervals and service life.
What’s more, through the ASTM C633-79 Standard Test Method for Adhesion or Cohesive Strength of Flame Sprayed Coatings, the SIFCO Process also established that the cohesive strength of the deposit exceeds that of the bonding cement. For example, the minimum tensile strength value established (at the point of cement failure during testing) for Nickel High Speed is 22,803 kPa (11,200psi) on a SAE 4130 steel base material. Additional qualitative tests, as described in AMS-QQ-N-290 were also conducted in which the plated areas were subjected to high stresses and strains. These results also showed excellent adhesion.
Protection in port
Remanufacturing is an alternative option to replacing or re-engineering equipment, and is worth considering in the marine industry with bigger components which can be especially costly.
Sitting at the heart of the remanufacturing decision is the used part that is at the end of its service life. According to a study on Remanufacturing Inspection Models by a PhD student at Exeter University, UK there are four main strategies applied in the decision making process for remanufacturing, each of which comes down to value and type of component.
It states: “If cores [end of service life components] are relatively cheap, disposal is an effective way of increasing the reliability of the population as a whole. If cores are expensive they must be processed almost regardless of cost. In the case of low value cores there is often a new alternative that can be purchased in its place.”
Remanufacturing of a component should be assessed on a case-by-case basis. Different processes, like selective plating, might be used in the remanufacturing process than were used in manufacturing the original equipment or part. Due to the high cost of marine equipment combined with the lead time required to purchase new equipment, remanufacturing with selective plating should always remain an option.
Fully automating the process
When a ship is in port, multiple repairs may be needed. Depending on the application, selective plating can be mechanised or fully-automated. Mechanising the process minimises the direct contact the operator has with the tooling and chemicals by using a computer program to control the rectifier performing all of the pre-treatment and plating steps, providing consistent control of the process. While fully-automating the process removes the operator - and the variability - from the entire operation.
The main benefit of customised, fully-automated systems is that they require minimal need for operator intervention. Various pumps, flow systems, and cleaning agents work together to change, catch, and circulate solution; while a robotic arm holds, oscillates, and changes the anodes needed throughout an entire plating operation.
By automating the selective plating process using a programmable logic controller, operators can review data captured through the human-machine interface to determine if the operation was completed correctly. If any errors do occur, or quality standards are not met, operators can review the data and trace the error to its source and assign the appropriate corrective action, preventing the errors from being repeated – effectively improving traceability and repeatability within the process. Additionally, automation reduces the ergonomic risk to the operator, and also increases the available capacity by allowing skilled operators to focus on the core business processes.
Naval forces of the US, UK and Japan have all adopted the SIFCO Process to keep their vessels moving. Now, however, more commercial shipyards are opening up to selective plating for minimising downtime, getting vessels back out there – and keeping them protected.
