Direct Gas Actuator
Actuation on gas transmission pipelines
Direct gas is a simpler variation of the gas-hydraulic actuator. All gas controls used on the actuators are routing pipeline gas directly to the actuator cylinder. Gas filtration is a primary element for achieving long and reliable service for gas powered actuators. Solid particle and moisture content of pipeline gas are addressed to insure trouble free operation. Filtration systems to suit any customer application, such as sour gas, is available upon request.
Manual override is an optional actuator feature. The design incorporates a separate cylinder for hydraulicoverride to ensure complete separation of high pressure pipeline gas from the hydraulic fl uid. The use of an independent override cylinder allows replacement of power cylinder seals without removal of the actuator from the valve and will even allow for manual operation while the power cylinder is disassembled.
Direct gas actuators are built to provide long and efficient service with a minimum of maintenance. The design, engineering and materials used in the construction ensure optimum performance even under severe environmental conditions. Remote control of the actuator is accomplished by the use of solenoid valves, configured to operate with a wide variety of voltages. Remote position monitoring device can be adapted per end users requirements.
Actuator Key Features
The stainless steel and lockable cabinet is designed to enclose all controls and equipment, including solenoids, gas regulator, speed control, remote/local isolation valves, and pressure gauges. The enclosure will provide proper ingress protection to allow installation of control system even under severe climatic conditions as well as defence against unattended and non-authorized operation and vandalism.
All items which vent will have common exhaust port outside of the cabinet. Vents will exhaust vertically upwards at a minimum high of 0,5m above the top of cabinet. Such vent pipe will be fitted with vent flaps.
Vent pipes shall be adequately supported. The equipment will be designed that individual items of control system can be removed via the cabinet door without removal of other equipment. Equipment is grouped together to form removable modules. Piping
within the cabinet is reduced to a minimum. Modular block design provides easy interchangeability.
Electrical interlock by door switch is provided such, that if cabinet door is open, operability to control is only given to local staff. Remote control shall not be possible to ensure workers safety during local operation or service activities.
Flow control valves for both directions can allow independent
adjustable opening and closing times for actuator.
Under low temperature conditions, cabinet is optional available with an explosion proof heating system.
Drawing of control system with part list, gas-schematic and electric diagram is laminated and affi xed to the inside of the door. Labels specifying the operating instructions are provided on or adjacent to the equipment.
Basic Control System
The Main Panel
All direct gas operated actuators are supplied as standard with a basic control system that provides local open and close valve control using power gas. Manual hydraulic override by hand wheel or hydraulic hand pump is available as an option. Control packages utilise standardised, integrated manifolds to minimise control piping and improve reliability.
- Junction box
- Inlet Block Valve
- Dirt indicator
- Power Gas Filter
- Pressure Regulator
- Speed control valves
- Manual ‘Close’ Relay
- Manual ‘Open’ Relay
- ‘Open’ Solenoid Valve
- ‘Close’ Solenoid Valve
Direct Gas Control
Modular Block Design
The modular control design provides fast and easy access to the components during on site service and maintenance activities
Pneumatic and Electronic Line Break detection system is available for monitoring safe operation of the pipeline. The design is based upon comparison of a reference adjustable rate of pressure drop to pipeline pressure. The system utilises a pressure balance vessel and adjustable bleed orifice to develop the reference rate of pressure drop.
High and Low acting pilot valves, with pressure sensing and manual rest function are optionally available. Upon either pressure increasing or decreasing at a predetermined set point, the actuator can be confi gured for automatic operation into defi ned fail safe position. Additionally a manual reset valve may be fi tted which requires manual intervention (reset) after sensor trip, before putting the actuator into operation again.
A gas storage tank assembled on the actuator ensures proper power supply in case pipeline pressure falls below critical value. Gas storage tank sizing and design depend on client‘s specifi cation and will be individual foreseen. Inlet block valve provides coupling device for connection with Nitrogen bottle, often required during commissioning phase when pipeline is not pressurized yet, but hydraulic pipeline pressure testing requires actuator operation.