System downtime due to equipment wear and failure is costly to mine operators, costing millions of dollars in lost production each year.In fact, maintenance typically accounts for more than 30-50% of a mine’s total operating costs.
For mining operations that rely on Knife Gate Valves (KGVs), valve replacement is particularly expensive, as inspection and repairs require isolating the line and removing the valve completely from the piping system.Operating budgets are further constrained by spare parts and storage costs: To reduce downtime during changeovers, mines often maintain a full inventory of replacement valves.So while KGVs are very common, they also present several pain points for mining operations.
In this article, we describe common KGV maintenance procedures and highlight the processes and benefits behind a new “on-line” technology that has changed the way mines approach and maintain budgets.
For decades, mines have used flanged disc or lug KGVs to control the flow of extremely abrasive slurry as it is piped through various equipment to processing plants.KGVs wear out during operation, so regular maintenance is required to reduce the risk of sudden valve failure and unplanned system downtime.This maintenance interval depends on the particle size flowing through the system, the percentage of solids contained in the fluid and its flow rate.
When the KGV needs to be repaired or replaced, the entire valve must be removed from the piping system for inspection.This process usually takes several hours per valve.For large maintenance projects, replacement inevitably results in days of system downtime and reduced productivity.
But before the inspection process can begin, the ductwork must be shut down and isolated through proper tagout/lockout procedures in accordance with mandatory provincial health and safety regulations.Any electrical or air connections to the valve actuator must be disconnected, and depending on the size and weight of the valve, assembly equipment may be required to separate them from the system.It may also be necessary to cut the pipe or remove the coupling due to corrosion of the flange bolts due to slurry leakage or discharge from the bottom of the valve.
After removing the old valve, a new valve needs to be installed in its place.To avoid maintenance delays, many mines invest in on-site replacement valve inventories, which often means stocking one replacement for each valve in their piping system.However, considering the hundreds of valves in a single mine system, the investment in valve replacement and storage nearly equals the inventory cost of heavy equipment used to excavate the material.Especially for producers of gold and other high-value minerals, the opportunity cost of traditional valve maintenance can be significant.
For years, mine operators have called for lighter and cheaper alternatives to conventional KGVs.In theory, a lightweight and affordable valve would make maintenance easier and less dangerous for workers without breaking operating budgets.However, this tiny improvement to fundamentally outdated valve technology fails to address the most costly consequence of valve maintenance: constant downtime and diversion of resources from profitable tasks to repairs.
Then, in 2017, a new KGV technology was developed specifically for the mining industry to provide what mine operators really want – increased productivity.With a new “in-line” design that keeps the valve installed throughout the maintenance cycle, users experience up to 95% less maintenance downtime, while saving up to 60% in annual valve maintenance costs.
The valve’s wear parts – including stainless steel knives, polyurethane seats, packing glands, knife seals and other hardware – are encapsulated in a single-seat valve cartridge kit, greatly simplifying repairs.Maintenance personnel simply isolate the line, remove the consumable filter element, and replace it with a new filter element—while the valve remains installed in-line.
This approach to KGV maintenance provides benefits on several levels.There is no need to remove the entire valve from the piping system, eliminating significant downtime.Unlike maintaining a single conventional valve which typically takes hours, the consumable filter element of the new KGV can be removed and replaced in just a few simple steps in as little as 12 minutes.
In addition, online KGV also reduces maintenance risks for workers.Replacing only one lightweight component – the cartridge – significantly reduces the need for rigging with heavy chains and pulleys that swing over the maintainer’s head.
This unique maintenance process eliminates the need to put a second valve on standby.In fact, the investment in spare inventory can be greatly reduced and often almost eliminated.
In addition to this improved maintenance process, it has also been recognized that further productivity gains can be achieved by extending the overall wear life of the valve and, ultimately, the time between maintenance cycles.To this end, the wear-resistant spool is designed with a polyurethane seat (10 times higher than rubber) and a tool that is nearly four times thicker than conventional valves, providing significantly improved wear resistance and service life compared to conventional designs.
In all use cases, valve maintenance that once required hours of downtime can be reduced to minutes by using in-line valve technology.For mines with pipeline systems containing hundreds of valves, the annual safety and cost-effectiveness of in-line KGV technology can be considerable.
Opportunities for in-line KGVs exist wherever piping systems are designed for grinding services, including slurries, flotation cells, cyclones and tailings.
As slurry systems continue to evolve to handle higher levels of solids content, flow rates and pressures, KGVs are an increasingly important component of the operating system.Mining operators using online KGV can minimize the incidence and cost of valve wear and maintenance.
Canadian Mining Magazine provides information on new Canadian mining and exploration trends, technologies, mining operations, corporate developments and industry events.
Post time: Jan-14-2022
