Pipeline valve actuators for safety-related duties

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Courtesy of Rotork

  • Sectors: Oil & Gas
  • Category: Failsafe Valve Actuation
  • Products: HPG, GO, Electro-Hydraulic (SI)

Introduction

Pipelines present a number of operational requirements demanding specialised actuation solutions. These include actuation of valves in remote areas, where mains power sources are not available, and actuators to provide vital failsafe and safety shutdown duties, which are often in remote locations.

For 60 years Rotork has manufactured electric and fluid power actuators for pipeline flow control in areas with and without mains power availability. Rotork has also developed innovative and reliable actuator designs to meet specific pipeline safety and shutdown duties in the most demanding environments. This article will focus on these actuators.

Fig 1 (Front cover & above) – Rotork ElectroHydraulic SI pipeline valve actuator providing failsafe Emergency Shutdown (ESD) protection

Safety-related actuator designs

The technologies fall into three categories - High Pressure Gas (HPG), Gas-over-Oil (GO) and Electro-Hydraulic (SI). All three have low power consumption requirements, providing suitability for renewable energy power sources in remote environments.

HPG and GO actuators use the pressure of the pipeline gas as the motive power source. The HPG design uses the gas directly, whilst GO actuators convert the gas into hydraulic pressure to operate the valve.

These 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. Higher torque and thrust outputs can also be provided for.

At the centre of the actuators’ control system, a multi-function manifold block integrates gas control functions to facilitate a full range of selectable failsafe and Emergency Shutdown

(ESD) options for pipeline events including Line Break, Low Pressure Close and High Differential Inhibit. These can also include altering the speed of valve travel to enable very fast operation during an emergency, with much slower operation to prevent damage to the pipeline during routine operations or partial stroking testing.

Electro-Hydraulic SI actuators combine the simplicity of electrical operation with the precision of hydraulic positional control and a programmable ESD failsafe function, utilising Rotork’s non-intrusive setting, commissioning and data communication technologies. A hand held, intrinsically safe, setting tool enables safe and rapid commissioning by means of easy to follow ‘point and shoot’ menus. The same setting tool also enables actuator configuration and data logger files to be transferred from the field to the control centre for diagnostics and asset management.

Electro-Hydraulic actuators are certified to the requirements of IEC61508-2:2010 for use in safety systems performing safety functions up to SIL2 and SIL3, including partial stroke testing capabilities.

Designed to enhance the functionality of these products, the Rotork Electronic Line Break (ELB) is a robust, self-contained instrument that combines pipeline pressure monitoring with intelligent valve control. The ELB can also collect detailed operational data for optimising performance and enhancing pipeline safety. The ELB continuously monitors upstream and downstream pipeline pressures to provide early detection of pipeline breaks and initiate automatic valve actuator movement to an emergency position, based on user-defined parameters. Actuator control - selectable as fail close, fail open or stay put - is based on Rate-ofDrop (RoD) and Rate-of-Rise (RoR) as well as high and low pressure limits.

A remote Process Shutdown (PSD) input with the option to override all functions is also available to drive the valve to the fail position.

Fig 2 – Shown here attached to a GO actuator, the Rotork ELB continuously monitors upstream and downstream pipeline pressure dynamics to provide early detection of pipeline breaks and initiate automatic valve actuator movement to an emergency position.

Recent Case Studies

Pipelines carrying products including natural gas from Asian countries traverse Turkey en-route to other destinations or as a source of energy for domestic consumption. Compressor stations along the route preserve the pressure level in the networks and transfer the gas for local area consumption.

The station at Erzincan on the Baku-Tbilisi-Ceyhan Pipeline is a typical example. Here, safety-related valve duties are performed by Rotork GO actuators operating ISO Class 600 ball and plug valves in 16 inch and 48 inch sizes. The 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. At the same site, isolating duties at are performed by Rotork IQ intelligent electric valve actuators operating ISO Class 600 ball valves in 24, 28 and 48 inch sizes. In Chile, Rotork HPG and GO actuators have been installed at a major LNG importing and distribution project that meets 40% of the demand for gas in the country. The actuators have been supplied for safety-related duties on a new 28 kilometre pipeline which links the LNG import complex at Quintero to a terminal at Quillota for integration with the existing gas network and for supplying combined cycle power plants.

In China, Rotork Electro-Hydraulic actuators have been ordered for increased safety duties on two new oil pipelines. Owned by the China National Petroleum Corporation, the Mahui and Yunnan Pipelines are attached to the network bringing oil and gas to China from offshore fields in the Bay of Bengal.

The Electro-Hydraulic actuators are installed in automated and unmanned valve chambers at pump stations, where they provide isolating and failsafe ESD functions. The actuators operate Remote Operated Shut-off Valves (ROSOV) valves, which are designed to isolate sections of the pipelines in the event of a potential emergency. By providing quick and accurate valve movement in one direction and very reliable mechanical spring return movement in the failsafe direction, Rotork’s self-contained Electro-Hydraulic actuator design successfully performs this critical application.

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