Challenging Conditions demand new valve philosophy
Companies need to step away from simple valve classification
On most production and process plants the majority of valves, up to 90% of the population, can be considered a commodity.
But a top tier of severe service valves deals with harsh conditions that have a high likelihood of causing valve problems and unplanned maintenance. They are typically linked to around 80% of valve-related unplanned shutdown incidents, so represent a critical asset that requires skilled engineering.
Ever-increasing pressure on production, in the Middle East and worldwide, is exacerbating process conditions that expose service control valves to applications likely to cause operational problems and possible failure.
Extreme environments, the increase in High Pressure High Temperature wells and problems such as sand and black powder erosion are bringing a new wave of technical challenges.
In many cases, severe service valves are now dealing with the most demanding conditions ever encountered by the industry. And some engineers are calling for a new top tier valve classification of ‘special’ service in addition to the traditional general and severe service categories.
Whatever definition you use, we are clearly in the throes of a shift towards more intelligent, high-integrity valve engineering to underpin innovative approaches for enhanced production efficiencies.
Sophisticated control valve classification methodologies drawing on historic failure data play an important role in this progressive trend. By identifying a specific application’s propensity to cause failure, valves can be specified and engineered more precisely to ensure better operation and reliability. This represents a positive step towards higher production and efficiency.
A valve’s classification is usually determined by contractors’ instrumentation engineers. However, lack of access to a good depth and breadth of historical valve performance data makes it difficult to draw on a wider context when addressing this vital decision.
The reality is that we need to step away from simple categorisation of valves, which suggests there can be a defined, off-the shelf solution.
In order to truly improve performance of valves that are critical to efficient operation, the emphasis needs to be on the distinct characteristics of actual applications.
Article continues on next page ...
A broad-brush approach which puts all valves of one type into the same category misses the opportunity to develop customised solutions that can make a significant, positive impact on the performance of individual valves and the plant as a whole. Instead we need to look at delivering better, more proactive management of valves and focus on long-term performance improvement.
This approach can dramatically increase the cost-effectiveness of operations and overall production rates. Improving valve performance in the face of growing technical challenges requires breakthrough solutions to deal with situations that are likely to cause failure.
This can be achieved with the support of an intelligence-led approach focused on solving complex production problems, such as the presence of particulates where solids interfere with valve performance through erosion or blockage.
Analysing performance data against historical resources enables patterns to be identified, facilitating better risk-based decision making.
Traditional parameters for a severe service valve consider factors such as pressure differentials across the valve, potential for cavitation and sand or solid contamination. They also cover issues linked to a high potential for excessive noise, erosion or corrosion damage.
However, use of repair intelligence data indicates that in practice many more variables combine to cause the level of extreme severe service duty that is increasingly common today.
These include factors such as high ‘control rangeability’ requirements, wide variations in upstream and downstream pressures during start-up and low-flow, extreme operating temperatures and fast stroking times.
Historic review of actual valve performance data signifies that the number of possible combinations of these factors and operating scenarios that define a valve duty as ‘severe service’ are almost infinite.
It follows that, in order to maximise reliability, a detailed evaluation of a valve’s actual performance should be overlaid with historic information about valves in similar conditions.
This is the soundest way to predict propensity to fail and determine the best course of action in terms of materials selection and design features. Drawing on long-term operational intelligence, including failure mode and failure effect information, facilitates individually specified solutions selected to provide long-term reliability and performance.
Traditionally, valve product development has relied upon design philosophy and prototype testing. Marrying this with long-term operational intelligence differentiates the reliable value of delivered products.
It’s about finding ways to leverage historic knowledge of plant conditions, valve performance and process impact then couple that with an understanding of how to use developing materials, technologies and flow dynamics to enhance performance.
Evaluation of valve performance shows that using ‘nearest fit’ catalogued products for duties correctly defined as extreme or special service are rarely successful.
In the face of evolving production demands, advanced custom engineering rooted in historic valve intelligence is the only feasible solution. Technical challenges are set to escalate further over the coming decades, and failure to address emergent needs now risks exposure to significant technology gaps.