Bespoke trim designs optimise compressor Anti-Surge valves for the specific application demands of the LNG plant where they’re installed.

Internal components of a valve that come into contract with process media is collectively known as the trim. They are critical to its reliable operation. This is especially true of Control Valves that protect centrifugal compressors from surge events on LNG liquefaction trains.

Compressor Anti-Surge Control Valves are often exposed to high flow velocities. Severn’s Repair Intelligence data (based on our engineers’ analysis of historic OEM valve products) shows this can lead to severe operational issues including high noise levels, vibration, erosion, and premature failure. These problems bring the risk of safety issues, production loss, and unscheduled shutdowns. Spiralling costs can be incurred too, due to frequent maintenance and replacement of damaged parts.

Since process conditions vary considerably between LNG projects, tailoring compressor Anti-Surge Valve trims to handle specific gas flow characteristics is highly advantageous. As well as facilitating precise and reliable control, this enhances valves’ ability to endure the operating conditions, improving longevity and reducing potential maintenance and safety concerns.

Customising Compressor Anti – Surge Valves for Endurance and Performance

To enable the release of process gas, Anti-Surge Valves are sized (as per specification) to have 1.8-2.2 times the required capacity for the process conditions. This ensures enough gas is supplied to the compressor to prevent surge and avoid a trip situation. Due to the high velocities created by the process, the gas must be carefully controlled, and the trim fulfils two main duties. The first is to enable the controlled release of the process gas that can cause the compressor to go into surge. The second is to control the velocity of the gas passing through the valve.

As well as having potential to cause erosion, the velocity of the gas can result in high aerodynamic noise levels which may exceed acceptable plant limits. High noise levels are also indicative of vibration within the trim which may affect the valve and downstream equipment, potentially inducing various modes of failure. Lagging the pipework is often seen as a solution, but this does not address the root cause. It is more effective to optimise the valve trim for the process conditions.

Severn’s bespoke trims optimise surge gas control

Severn’s Anti-Surge Control Valves benefit from engineered solutions to address the high capacity and velocity control requirements of the application. Trim components that benefit most from engineer-led customisation are the plug and the cage.

Precision engineering of cage geometry, informed by Severn’s expert analysis of flow conditions and Repair Intelligence insights, improves valve responsiveness and overall control. For instance, the 3D flow path of the cage can be engineered to reduce deadband and improve controllability. Our Multi Labyrinth Trim (MLT) can handle up to 48 stages of velocity reduction and our 1CC trim offers a high-capacity option which maximises throughput. To balance the need for high capacity and precise velocity control, we have also developed the Vari-Stage Trim which can be configured to meet end users’ exact process requirements.

A valve’s cage helps to balance pressure and reduce turbulence as the plug lifts and surge gas enters. Even so, there can be a delay in the equalisation of pressure in the area above the plug with the changes below it. This can lead to severe vibration and instability if the system does not respond in adequate time.

Severn’s Repair Intelligence has identified that process forces acting on a valve plug can severely detract from valve performance in operation. To combat this, we have developed a ‘Waggon Wheel’ plug design, in addition to our standard options, which can be implemented where conditions dictate. The design ensures process forces are equalised across the plug allowing for rapid movement and accurate control.

All these solutions are designed and engineered using Severn’s robust sizing and selection process, technical expertise, and years of Repair Intelligence.

Valve engineering expertise

Severn’s Anti-Surge Control Valve Technology is rooted in an adaptive design process led by experienced engineers. Applying our valve engineering expertise to compressor Anti-Surge challenges on an application-by-application basis results in durable, highly functional valves which ensure reliability, efficiency and safety.

Contact us to find out more.

Compressor anti-surge control valves for FPSO North Sea Client delivered three days ahead of schedule

Compressor anti-surge control valves for FPSO North Sea Client delivered three days ahead of schedule

Compressor Anti-surge Control Valves delivered three days ahead of schedule

Industry : Oil & Gas FPSO

Location: UK Central North Sea

Project: Two anti-surge control valves to be delivered within a tight time frame for UK Central North Sea Client

The Challenge:

A North Sea operator needed a solution for a technically challenging anti-surge application, required on a very short delivery schedule of 16 weeks, the initial requirement was for one valve to be delivered and the second valve to be delivered 10 days later.

Finding a solution:

The Severn team made initial engagement with the client to full understand the application and performance requirements that the customer needed.

A swift coordinated approach internally by Severn’s application and engineering team was needed and the teams worked closely together as it was imperative that the issue was identified quickly so a solution could be provided, manufactured and delivered within the 16-week delivery schedule.

The product:

After identifying the clients requirements, the engineering team designed and manufactured two off 4” Cass 1500 RTJ Fig 5413 LTCS Body, SS/FC Trim, 14 Turn CCD, PC1N Pneumatic actuator with a Neles Positioner.

The positioner was revised mid order as per clients added operational requirements, the team was seamless in reacting to this change with no impact on the design or delivery schedule.

The outcome:

The contracts department managed the scope of the job and the challenges it brought professionally and with complete transparency; the client was kept fully informed throughout the production and delivery process.

The collaboration between the different departments and the constant engagement and the feedback with the client ultimately led to both valves being delivered three days in advance of the 16-week schedule, this was appreciated by the client.

The valve performed significantly well within the anti-surge required by the client for this application, especially on small step changes. This was a major issue with the clients previous valve, and an issue our team overcame with flying colours.

Severn requested to provide engineering support offshore on the asset, firstly with the installation and then subsequent valve commissioning activity.

” I want to take this opportunity to personally thank the entire Severn team for their continued focus and support during this project and more importantly, for getting both valves ready for shipping ahead of an already tight schedule.

Getting two high spec anti surge valves designed, assembled , and fully tested in less than 16 weeks is definitely an achievement” – Client representative