Posts by JASC Controls

JASC was featured in Power Engineering’s April 2014 publication, discussing innovative applications and design modifications that have lead to improvements in actuator technology, reducing costs and providing better performance for high-pressure steam bypass, turbine bypass, and other critical power plant operations.

Read the full article here.

Read JASC’s contribution to the article below.

Over time, there may not be another auxiliary system more maligned than that of a back-up liquid fuel system on a dual fuel gas turbine. The hardware shortcomings responsible for the inability to start on liquid fuel or transfer from gas to liquid fuel, check valve failures, flow divider failures, fuel system evacuation, exhaust temperature spreads, and related turbine trips have all been addressed by designs developed by JASC Controls. Water cooled check valves, which prevent carbonization, metal to metal sealed water injection check valves rated for service at 750 degrees “F”, multiple use crush gasket technology which replace o-rings with a 1000 degree “F” rating at 2000 psi and a Zero Emissions Equipment design which allows a turbine owner to test the readiness of the liquid fuel system without firing on oil are examples of the JASC’s unique technology.

These system specific products have two common design goals. First, they provide reliable operation for at least 32,000 hours or until a scheduled turbine service interval is reached. This provides the optimal timing for returning the valves to the JASC facility for refurbishment after three or four years of use.

Second, the valves must maintain an ANSI Class 6 sealing capability from installation until removal for refurbishment. Elimination of reverse flow results in separation between the turbine combustion process and auxiliary systems such as liquid fuel, purge air, and water injection. With no reverse flow of combustion gasses into these systems, back-up fuel system availability and reliability typically exceed 98 percent.

Finally, JASC’s solutions are configured to be interchangeable with the turbines existing hardware. This characteristic both minimizes the cost and reduces the time associated with performing fuel system upgrades on a turbine of any age.

Gas turbine engine owners can experience fuel transfer success rates of 98% or greater when employing water cooled valve technology. JASC’s water-cooled liquid fuel check valve has shown that gas turbine owners can operate liquid fuel systems reliably for extended periods of time. This is due to a water-cooled jacket that helps maintain check valve internal temperatures well below the coking threshold. Additionally, through the prevention of coke formation, valves can maintain their ANSI Class 6 seal, which prevents evacuation and fuel leakage into fuel nozzles.

To learn more about the causes of liquid fuel transfer failures and JASC’s revolutionary solution, read below.

Click here to learn more about JASC’s Water Cooled Liquid Fuel Check Valve.

Liquid fuel check valve operation in dual fuel gas turbine applications is exceptionally severe. The impact of both system and related environmental anomalies on liquid fuel check valves lead to both premature failures of the valve and other fuel system components.

Check valve coking, high-frequency oscillation, hydraulic hammer, tubing stress fatigue related failure, flow divider corrosion, fuel nozzle coking, fuel pump failure, magnetic clutch failure, and fuel system evacuation are all problems which result from liquid fuel check valve failures. The resulting reliability issues significantly increase the cost of ownership due to increased maintenance and valve replacement intervals.

Check valve coking is the first phenomena which will be discussed. The term coking is used to describe carbonization of diesel fuel on the check valve internal components when the turbine is operating on gaseous fuel. During this time, the liquid fuel system is idle and the diesel is stagnant in the check valve. Temperatures of 250 degrees F are typically enough to start the process and are easily achieved in the turbine compartment where the check valves are positioned.

Unfortunately, as diesel fuel becomes older and more unstable, the temperature threshold at which coke forms decreases. An essential characteristic of coke is that once it forms, short of soaking the component in a strong solvent, it does not dissolve. At this point, crack pressure and sealing capability are significantly compromised.

Cracking pressure is defined as the point where check valves are designed to open and allow fuel flow to begin. Sealing ability both prevents diesel fuel from leaking downstream into the combustor and combustion gasses from traveling upstream through the valve into the fuel system. Coke formation inside of the check valve degrades both of these critical parameters.

As it relates to gas turbine operation, fuel system integrity suffers significantly from the partial or complete evacuation of liquid fuel when leakage exceeds an ANSI Class 6 standard. Symptoms of check valve leakage related failure include but are not limited to: multiple attempts required to achieve turbine ignition on liquid fuel, high exhaust temperature spreads both at start-up or when transferring from turbine operation on gaseous to liquid fuel.

Finally, data collected from gas turbine sites worldwide during the past several years has demonstrated that there is a solution available which mitigates the risk of check valve related failures. The development and use of water-cooled liquid fuel check valves has shown that gas turbine owners can operate liquid fuel systems reliably for extended periods of time.

The benefit is that by maintaining check valve internal temperatures well below the coking threshold, liquid fuel check valve failure is all but eliminated. The ability to prevent coke formation
allows the valve to maintain an ANSI Class 6 seal. This seal prevents fuel system evacuation and fuel leakage past the check valve into the fuel nozzles.

Maintaining a primed liquid fuel system allows all check valves to open at pressures which adhere to specification. The uniform opening of all liquid fuel check valves allows consistent fuel flow to the fuel nozzles. Thus, high exhaust temperature spread related system failures are avoided during turbine ignition on liquid fuel and during fuel transfers. Fuel transfer success rates nominally approach 100% on gas turbines which have implemented water cooled valve technology.

To download this article, please click here.

August 2012—JASC has launched its facility expansion project. The company is building out its Tempe, AZ headquarters and will provide an additional 8,400 sq. ft. of usable space to the existing 20,000 sq. ft. already in use. The new area will feature engineering development labs, high-pressure pneumatic capability, fuel testing, shock and vibration testing, and an expanded aircraft component assembly space, offering better organization and production workflow.

Equipment is being moved into the new space as the buildout moves toward completion.

Matt Caspermeyer of JASC and Bill Heatley of O’Miller Associates attended the 3rd NASA GRC PCD Workshop held February 28-March 1, 2012 at the Ohio Aerospace Institute, Cleveland, OH. The workshop covered various aspects of propulsion controls including Enhanced Engine Control, Model-Based Control and Diagnostics, Distributed Engine Control, Industry Perspectives on Propulsion Control Diagnostic Research, Active Combustion Control, and High-Speed Propulsion Modeling and Control.

Matt (on the left) and Bill also participated in a poster presentation describing the JASC Active Combustion Control Valve concept that is currently in a Phase II SBIR. The High-Frequency Proportional Rotary Fuel Valve is designed to mitigate combustion instabilities at higher frequencies than have been previously achieved (~1000Hz) allowing gas turbines to run at operating points that produce lower emissions and higher performance.