Diminishing functionality of combustion turbine components due to aging parts is a concern for plant and maintenance managers. The harmonization of each individual part of a machine is crucial to efficient operation, and that is especially true in aging 7E, 7F and 9F combustion turbines. The valves, which were originally branded as Dana-Gresen and distributed by Tri-Line Automation, have been supported and manufactured by Parker for many years. As the parts continue to age, there is increased potential for inefficiency and performance issues. So, when is the best time to take a deeper look at your vintage turbine valves?
The answer is yesterday. It’s never too early to have a replacement on hand or get your current valves serviced. If you’re too late in responding to the potential issues, your production, efficiency, and uptime will all suffer. Find out why right now is the time to inspect your turbine valves.
Plan to register for our upcoming webinar, Parker Legacy Valve Service: How to Maintain the Future of Your 7E/7F Turbine Valves.
There are three combustion turbine control valves that all plant and maintenance managers should keep on their radar:
- Gauge Selector Valves
- Fuel Oil Isolation Valves
- Water Staging/Isolation Valves
Each valve has a different purpose, but if any of the aging valves are overlooked, they may cause issues or even unplanned shutdowns.
Gauge Selector Valves
This valve allows for fuel pressure measurement of each supply line feeding the combustion cans. With 20 to 30 years of wear and tear from stagnant fluids or heavy cycling, the condition of this valve should be closely monitored.
There are many potential issues that may occur. First, the gauge selector handle may become hard to move. An even bigger concern involves fuel oil pressure leaking into the common port connecting the fuel pressure gauge. This type of leakage would result in the gauge always showing some amount of fuel pressure, regardless of the selector handle position. As with most elastomeric type seals, thermal and process exposure contribute to a limited seal lifespan.
Fuel Isolation Valves
This large multi-port “check valve” delivers fuel to the primary and secondary ports on each combustor can, only permitting fuel flow when actuated. Fuel isolation valves are actuated by a single-piston to ensure each combustor can get fuel at the same time. This eliminates the risks of turbine cold spots and avoids startup or fuel transfer issues. This valve also has zero internal leakage and has a limit switch to confirm the valve operation.
While there is no internal leakage to a fully functional valve, there is likely internal wear and damage due to old, dirty, and stagnant fluids, which could eventually lead to corrosion and leaking.
A new fuel isolation valve offers protection against the risk of cold spots. Contamination can cause restrictions that create an increased pressure drop across the valve, resulting in less than the desired amount of fuel being delivered to the engine. Contamination, corrosion/erosion, and heavy cycling can also cause internal leakage across the check valves and in extreme cases, external leakage.
Water Staging/Isolation Valves
The water staging/isolation valves control water that is used for NOx reduction and combustion temperature control. They also have the same number of ports as the gas turbine has combustion cans.
The potential issues for water staging/isolation valves are identical to the fuel isolation valves. Valves with 20 to 30 years of wear are more likely to experience pressure spikes, leakage, and control issues. The longer a valve has been in service, the greater the possibility of internal wear, corrosion, and seal degradation.
Why now?
Based on the vintage of the turbines and valves and a recent spike in requests for service and overhaul, it is crucial to understand the condition of the valves at your power plant. Parker has developed a Valve Service Plan for the replacement or refurbishment of these valves scheduled around your planned outages, minimizing disruption to plant operations.
Plant and maintenance managers should begin thinking about replacing these aging valves prior to planned spring or fall outages, avoiding downtime during the year. The inspection of these valves is important to the performance of 7E, 7F and 9F combustion turbines, and the age of the valves is enough reason to assess them immediately.
What should you do next?
The next step is to rely on Parker. We have been an experienced and trusted partner in the industry for decades, and our goal is to help you minimize downtime, create efficiencies, and increase plant output. Inspect your valves and schedule a call to discuss Parker’s Valve Service Plan with the Energy, Oil & Gas Team. Learn more on our turbine valves website.
If nothing is wrong with your valves, that’s great! But it is never a bad idea to have a known support path, contacts within Parker’s manufacturing operations, experienced field-based engineers, and spare parts on the shelf!
If you just want to learn more about the valves in your combustion turbine and the importance of their maintenance, register for our webinar: How to Maintain the Future of Your 7E/7F Turbine Valves, which takes place at 11 a.m. ET March 18.
Article contributed by James Hoke, capital projects manager, Parker Hannifin’s Energy Team, and
Mitch Eichler, business development manager, Parker Hannifin Hydraulic Valve Division
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