Maintaining Safety Valve Control on Gas Pipelines
Pipelines carrying products including natural gas from Asian countries traverse Turkey en-route for export to final destinations or for domestic consumption. Compressor stations along the route are designed to preserve the pressure level in the networks and transfer the gas for local area consumption. These are among the pipeline locations where Rotork valve actuation technologies are widely used.
The compressor station on the natural gas pipeline at Erzincan in eastern Turkey, serving the country’s Anatolian area, is a typical example. Here, Rotork’s agent has supplied, installed, and commissioned actuators for operational and safety-related duties.
The Erzincan station consists of four turbine/compressor units maintaining a pipeline flow rate of between 1.6 and 2 million standard cubic meters per hour, which helps to increase the network’s overall transportation capacity. Rotork valve actuators are integrated into an ABB automation system that controls the compressor station and other processes, including a high integrity safety system for emergency shutdown, instrumentation and other electrical equipment.
Gas-Over-Oil Actuators
The safety-related valve duties are performed by Rotork GO Range gas-over-oil actuators operating ISO Class 600 ball and plug valves in 16 and 48 in. sizes. The GO Range uses the pipeline gas as the motive power source. The gas is delivered to oil tanks that convert the gas into hydraulic pressure and this pressurized hydraulic oil is used to drive Rotork scotch-yoke quarter-turn or linear valve actuators.
Using pressurized oil as the driving force provides powerful, smooth actuator control and isolates the cylinder from the pipeline gas. This prevents contaminants from entering the hydraulic cylinder, eliminating corrosion and seal deterioration and extending actuator life.
At the center of the gas-over-oil system, the multifunction manifold block integrates gas control functions to facilitate a wide range of valve control options. Standard gas control systems are complemented with optional equipment for functions including line break, low pressure close, high differential inhibit, and emergency shutdown (ESD). The manifold has the facility for a high-flow hand pump, pressure relief, and a locking handle for safe commissioning. High pressure and low pressure control logic designs are also available, together with torque limiting devices for valve and drive train protection.
Rotork GO actuators are IP66M/67M third party certified and approved for environmental protection, together with CE and ATEX hazardous area certification. The standard working operating pressure range is 10 to 105 barg, enabling a quarter-turn operating torque of up to 600,000 Nm and linear thrust of 5,000,000 N to suit pipeline valves of virtually all sizes and description.
Solid-State Electronics Offer Benefits
Operational isolating duties at Erzincan are performed by Rotork IQ intelligent valve actuators with secondary gearboxes, operating ISO Class 600 ball valves in 24, 28, and 48 in. sizes. The benefits of IP68 watertight and ATEX certified Rotork IQ actuator technologies are widely recognized for isolating and regulating valve duties in the oil, gas, and pipeline industries. The use of solid-state electronics as an alternative to switch mechanisms and counter limiting devices, combined with programmable microprocessor-based control and instrumentation functionality, offers many proven benefits.
These include ‘nonintrusive’ configuration and data transfer by means of a handheld instrument via a secure, bidirectional link. This system is used to perform all switch setting and commissioning functions that were traditionally only achieved by removing electrical covers. Using the multilingual menu on the actuator display screen, it is quick and easy to commission the valve, with or without mains power connected.
The same instrument is used to download operating information from the actuator’s data logger. The inclusion of a data logger enables an event-by-event history of valve activity, including torque profiles produced during each opening and closing. Using Rotork’s IQ-Insight2 software, these can be compared with the valve torque signature profile logged during the commissioning process to identify the trend of valve operating wear or isolate tight spots and other problems. Analysis of this data improves asset management through fault diagnostics and preventive maintenance.
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