But, as many plant managers are now finding, systems designed for regular 24-hour operation are exposed to greater operational stresses when having to stop and restart or fluctuate between loads of 50%-100%.

Cracking is a common outcome of this type of operation, particularly wherever water is injected into the steam flow to control temperature. Attemperators, desuperheaters and turbine bypass systems are all particularly vulnerable to cracking, with subsequent maintenance of these assets often running into six figures or more. And that’s before counting the cost of unplanned downtime.

Yet even where cracks do not lead to unplanned shutdowns, their development can still impact plant performance and contribute to inefficiencies. As such, there is a growing need to examine, monitor and implement strategies that optimise plant performance in an age of irregular cycling.

We need better analysis, not more data

The solution to these issues has tended to rely on the increased use of invasive sensors, collecting growing volumes of data as part of a preventative maintenance plan (PMP).

Yet such an enormous volume of data is of limited value without useful insights that can be applied ‘on the ground.’ There will always be a gap between what is shown on screen and what is actually happening in the plant.

In many cases, if not most, better interpretation of existing data is required. This is where IMI Insyt comes into play. Rather than the costly installation of additional sensors, IMI Insyt is focused on extracting useful insights from the latent operational data already available in many combined cycle facilities.

Analysis conducted by IMI Insyt can help identify data signatures that lead to structural integrity issues, such as cracks and leaks. It can also be used to identify component issues that impede system performance. This analysis can then be used to fix plant control logic issues that create the massive thermal stresses that can cause severe disruption.

US plants using IMI Insyt are benefiting from a proactive approach to failure prevention through improved plant reliability, improved maintenance planning and scheduling, large data being batch processed by industry experts, reduced accidents, and near-misses, as well as savings on time and money, while enjoying increased ROI.

IMI Insyt has previously only been available in the US market but is now being introduced across Europe, bringing significant benefits for plant engineers focused on efficiency, safety, and reliability.

Waste-to-energy

A crucial difference between the US and European markets is that irregular cycling is much more common in Europe because of a greater reliance on renewables. The first plant in the UK to benefit from IMI Insyt was waste-to-energy plant in London.

The facility was experiencing severe water hammer issues, which caused the control valve’s stem to shear in half. This happened twice in two years before IMI Insyt could identify and fix the issue.

The plant’s original valve saw spray water entering through the bonnet and mixing within the trim. Following recommendations from IMI Insyt, an upgraded IMI valve was installed using an outlet diffuser and spray ring, thus taking the cooling away from the valve trim.

The IMI Insyt team also found the controllers for the DCS were never calibrated, creating anomalies on the spray valve that caused it to open 100% before the steam valve was ready. The mix of gas and fluid, and the consequent expansion, caused a significant water hammer effect downstream.

A second plant is now being built next door and IMI is already discussing implementing a similar approach. This is a testament to IMI Insyt’s diagnostic powers, which are already beginning to influence overall plant design in Europe despite having only been used in a limited capacity to date.

Cracking is a problem that may never be avoidable, as spraying cold water into hot steam is a constant feature in Combined Cycle operations. Coupled with the increasing complexity of new plant design, unforeseen issues with cracking are likely, if not expected. IMI Insyt ultimately offers plants a valuable and cost-effective tool to manage remedial work better and avoid instances of unplanned downtime long term.

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