Wood’s new software eliminates production constraints and increases design flow by 20%
The integrity of process piping on aging assets is a common concern for operators. Failures caused by ongoing issues such as vibration-induced fatigue can have devastating and costly effects.
An Omani-based customer had been operating its three-train LNG plant at reduced production rates because of concerns around the integrity of the main process piping. Operations personnel had reported the risk of vibration induced fatigue failure and were worried about the ongoing condition of the piping systems. A new gas field was also planned to come on stream to supplement the existing feed, so it was imperative that future production constraints were avoided.
We started the project by working closely with our customer’s site integrity team to assess the vibration integrity of the hydrocarbon process piping and identify any areas at risk of vibration induced failure.
Our initial office-based investigations were conducted with Veridian, our digital, risk-based vibration screening tool.
We considered all typical vibration sources for the assessment, including flow-induced turbulence and pulsation, mechanical (machinery) vibration, pulsation due to reciprocating gas compressors, transient forces due to fast-acting valves, and rapidly changing fluid flows.
Changes to the existing piping system were planned, assessed and implemented prior to introduction of the new gas stream: with remaining (low-risk) anomalies identified and ranked using the software’s anomaly manager feature.
Our Veridian software saved the customer hundreds of hours by accurately screening, calculating and pinpointing the areas of piping for further investigation. This enabled the operator to remove the production restrictions on the current feed gas and extend the design flow by up to 20%.
Over 2,000 main process flow lines were assessed and more than 400 had a potential vibration integrity concern that required a more detailed investigation. In addition, the customer identified specific flowlines of concern due to slugging and multiphase flow, liquid flashing, and high flow velocity vibration.
Due to the significant gas inventory associated with an LNG plant, a relatively large number of flare system gas valves were highlighted as a potential concern, requiring a more detailed integrity assessment of the flare piping. Noise control measures had been included in the original plant design, however, specific design features were identified as being a long-term integrity risk. Wood’s vibration engineers worked to identify short- and long-term control measures, assessing the flare system for the risk of acoustic-induced vibration (AIV).
To more accurately quantify the vibration risk, onsite visual inspections and vibration and dynamic stress measurements were conducted on all the accessible main lines identified in the screening study, as well as the lines previously identified by our customer. The results were used to update the Veridian database and the areas of concern were included in an online anomaly tracker.
To determine whether the piping stresses were acceptable for the current and future operating ranges, detailed finite element analysis was carried out for the main flowlines with significant vibration concern. Where necessary, vibration control measures were evaluated using our computer models, and once a satisfactory solution was agreed with the customer, we provided specialist engineering support to implement the change.
Our vibration and acoustic mitigation methods ensured the continued safety, integrity and commercial viability of the plant’s piping systems.
This approach was highly regarded by the customer, and discussions are already ongoing for using Veridian to predict and manage the integrity of future plant developments.
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