Actuation on gas transmission pipelines

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Philosophy

 

  • Gas/Hydraulic actuators are most normally used for automating valves located in gas transmission pipelines.
  • These pipelines typically run hundreds of miles through inhospitable and undeveloped areas where no low pressure pneumatic instrument air or high pressure hydraulic supply lines are available.
  • Since gas transmissions pipelines carry gas under high pressure (typically up to 1440 psig) this is a potential supply source for the actuators.
  • Gas/Hydraulic actuators use the pressurized gas in the pipeline as their power source since gas under pressure is a potential source of explosion, Gas/Hydraulic Operators use an oil barrier to ensure that clean, non-explosive hydraulic fluid is used to drive the a actuator rather than using the high pressure gas directly.

 

Application

 

  • Power gas supply is from the pipeline in which the actuated valve is located
  • Power gas supply is taken from both upstream and
    downstream of the valve
  • The highest gas supply pressure is always used to power the actuator

 

Result

 

  • The power gas supply pressure to the actuator is always equal to or greater than the differential pressure across the valve.

 

 

 

 

 

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, pressure gauges and hand pump with lever.
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.


Construction of the cabinet back plate is of reinforced
material with 10mm thickness to ensure rigid position
of cabinet during hand pump operation with lever.


All items which vent will have common exhaust port
outside of the cabinet. Vents from gas-hydraulic system
will vent vertically upwards at a minimum high of 0,5m above the top of cabinet. Such vent pipe shall be fitted with vent fl aps. Vent pipes shall be adequately supported.


Mechanical interlock will be provided to ensure that
when the cabinet door are shut, all controls will be in
the correct position for remote control. Suitable interfering
devices, mounted on the door, is provided.

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.

Gas and hydraulic pressure is indicated by pressure
gauges independently within the cabinet.

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-hydraulic
schematic and electric diagram is laminated and affixed 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 Gas/Hydraulic actuators are supplied as standard with a basic control system that provides local open and close valve control using power gas as well as a hydraulic hand pump for emergency control.

 

 

1. Manual ‘Close’ Relay 5. ‘Close’ Speed Control Valve 9. ‘Open’ Handpump Selector Valve
2. ‘Close’ Handpump Selector Valve 6. ‘Open’ Speed Control Valve 10. Manual ‘Open’ Relay
3. Power Gas Filter / Regulator 7. Hand pump 11. Solenoid to ‘Close‘
4. Inlet Block Valve 8. Handpump Safety Valve 12. Solenoid to ‘Open‘

 

 

Gas-Hydraulic Control

Modular Block Design

 

The modular control design provides fast and easy access to the components during on site service and maintenance activities.

 

Due to the modular design, the basic Control can be optional equipped with either:

 

1. Pneumatic Line Break Valve

2. High or Low Acting Pilot Valve

3. Manual Reset Valve

 

 

 

 

 

 

 

On Site Installations