Valuing Valves

Valves enable operators to shut down their plant quickly and safely. However, they should not be the cause of a shutdown. This can happen when the wrong valve is inserted into an application it was not designed for, or when valves are not properly maintained.

Valves are not a set-and-forget solution. At a minimum, they need to be partially opened and closed – although, ideally, they should be fully opened or closed – at regular service intervals to ensure they are in working order when needed.

It is not unusual for a valve to remain open for, say, 12 months. If it has not been checked in that time, there is a chance that corrosion has formed and, as a result, when the operator goes to close it, it jams.

Valves are meant to improve maintenance efficiency, rather than become a maintenance item.

Valve selection

There is a range of things to consider when selecting valves – pressure, temperature, and the actual media going through the valves, for instance. However, perhaps most importantly, working through a process with an experienced OEM, one that is able to draw on an extensive installed base, is the best way to ensure the right valve is selected for the right application.

Selecting the ideal material is critical and requires considering what the slurry needs. For example, if it is acidic, a super duplex material, or even a titanium, might be needed.

There are other factors that may seem less consequential, but which actually have a significant impact of the actuation required. For instance, if the slurry has a high percentage of solids, depending on the valve’s orientation, it can impact the closing and opening of the valve.

Similarly, operators often overlook the extent to which velocity causes wear in valves. Weir recommends that operators ensure the slurry velocity does not exceed 3.5 m/s, as it can wear out the valves prematurely.

However, there are obviously other factors that influence slurry velocity. One such factor is that an operator might upgrade their pumps or change something in their process that affects flow rates, without considering how these changes will impact their valves.

These are all things that can be worked through, but if there are plans to change the process or increase capacity, these should be factored in when selecting valves.

There are also external factors, like the climate, that need to be considered. As a case in point, a standard silicon grease that is designed to work optimally at 20°C will have a dramatically different viscosity when it is being used on a valve in the Pilbara, where the grease might reach temperatures of 50 or 60°C. Conversely, at some sites in Mongolia, temperatures can drop as low as -45°C, so the operator might need to put a heat blanket or heat tape over the valve to make sure it can operate optimally.

One of the other things that operators have to consider is the type of actuation. This is often a site and/or application-based decision, and, from Weir’s perspective, it is important that it can offer its customers a wide range of actuations – pneumatic, hydraulic, electric, etc. – to suit their particular needs.

For instance, tailings pipelines are typically quite long, and while the main tailings valves are near the tailings pump, there are instances in which valves need to be installed on pipelines a long way from the site. As a result, they might not have electricity available to operate the actuator, and therefore need to opt for an alternative system.

 

This is a preview of an article that was originally published in the April 2025 issue of Global Mining Review.

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Read the article online at: https://www.globalminingreview.com/special-reports/25042025/valuing-valves/