Key points
Process Control Valves are a crucial element in any system where fluid flow must be monitored and controlled. Andrew Prew – Market Development Manager at Spirax Sarco outlines the benefits of modern control valves and explains why a failing valve can actually be an opportunity to save costs.
The onus is on steam plant owners and operators to run their plant as efficiently and cost effectively as possible in order to safeguard plant uptime, reduce maintenance costs, maintain process control and save energy by accurate temperature control. That means ensuring all components of the steam system work as efficiently as possible – and that includes control valves.
Process control valves are crucial elements in any system where fluid flow must be monitored and controlled. They are integral to many critical processes, from delivering a reliable and consistent supply of hot water for cleaning-in-place applications, to providing the right quality of steam to support processing facilities.
Choosing the right process control valve
It is estimated that more than 70% of existing valves are over-sized because steam load has either reduced since their installation or been overestimated. Arguably, it’s probably pretty easy to ignore this ‘problem’ if it doesn’t actually seem to be causing any difficulties.
After all, if it isn’t broken, don’t fix it, right? Well, not really. The reality is that failing to take action contributes to higher costs, energy inefficiency and poor process control. And it certainly won’t help your organisation to achieve its sustainability targets.
Over-sized valves cost more to buy and install than smaller units and are also more expensive to run. Over-sizing will also ultimately lead to accelerated wear of the valve trim as the plug operates close to the seat for extended periods during valve operation, increasing maintenance costs.
There are other important considerations that also need to be taken into account regarding the selection and installation of control valves.
Control valves are some of the hardest working plant within a steam system, often throttling energy several million times per year to maintain productivity.
So it’s hardly surprising that even with the most stringent preventative maintenance procedures in place, problems can occur. And when they do, downtime, lost production and procurement costs can mount.
Many conventional valves feature screw-in seats that often seize in place, meaning that if maintenance is required it is often necessary to remove the entire valve assembly from the pipeline, risking a further lengthy plant shutdown and associated costs.
Steam plant operators and owners face a similar challenge when it comes to changing the duty of existing valves in response to changing system demands. Again, most valves have to be removed from pipework to have their capacity changed, leading to plant downtime and reduced productivity.
Taking control of Process Control Valves
Replacing a failing valve with a modern, correctly-sized unit, whether as an emergency measure or during planned maintenance, will enable your organisation to save money, reduce energy consumption, improve system control and reduce lifetime cost of ownership.
If replacing an oversized unit, a correctly-sized valve will not only be cheaper to buy and install, it will also be cheaper to run. An over-sized value will accelerate wear on the unit, increasing maintenance costs.
Installing a control valve that is perfectly sized to match your process will also enable you to safeguard process control and maintain plant uptime. Fluid flow through control valves inevitably causes valves to vibrate. If a valve is over-sized, the vibrations tend to be greater and can even alter the valve’s position. Even a small change can have a large effect on flow, resulting in poor control performance.
Modern control valves offer other benefits, too. Advanced models feature quick-change ‘clamp-in-place’ seats that enable the duty to be altered to match changing plant conditions while the valve is in situ, rather than the entire valve being replaced.
The self-aligning ‘clamp-in-place’ seat also simplifies maintenance so no special tools are required and there is no need to take the valve out of the pipeline.
Immediate savings with the correctly sized process control valve
All steam-using organisations could benefit from reappraising the process control valves in their current system to ensure they are correctly sized and also offer the greatest advantages in terms of process manageability, energy efficiency and cost savings.
Today’s process control valves are designed to be easy to install and easy to use. Many models can be supplied ready-commissioned, enabling ‘plug and play’ functionality.
Fast delivery and installation is particularly crucial to avoid the disruption of a lengthy shutdown that can result from a failing unit, so look for a vendor that can guarantee to deliver a control valve perfectly matched to your system within 48-hours.
Once in place, steam users will start to reap the benefits immediately. So, the next time your organisation is due to upgrade its process control valves, or if a control valve starts to fail, don’t think of it as a nuisance. Think of it as an opportunity to improve process control and save money.
