The objective of AGLs initiative was to develop the SIL rated Safety Instrumented System (SIS) for the compressors and generators at Wallumbilla. The compressors are in a Zone II hazardous area and the generators and control cabinets are outside the hazardous area. Working with Drivetrain, Parasyn’s scope of services included Hazardous Area Electrical Design, Controls Systems Development, Hazardous Area installation, and Project Management Services. Type B compliance is a requirement for gas powered engines that ensures they are purged of gas at the commencement of each starting cycle.

Parasyn’s specific responsibilities included design of the safety control system, construct a control panel based on the Hazardous Area design requirements and the HAZOP report, configure software, test the system (and obtain external peer review and acceptance of the design prior to the site installation), install the system and commission the SIS panel and functionality against the requirements and functional specifications in support of the type B compliance across three compressors and three generators.

Having worked on other AGL sites before, and understanding the critical nature of operational knowledge, Parasyn on this occasion opted to engage Instrument Installation Services, already known to AGL, to support the installation activities on site.


AGL’s Wallumbilla LPG plant North West of Dalby Queensland is over 400km from Brisbane.


The LPG Plant includes various plant items for the processing and ultimately compression of Natural Gas for transportation by road.  The major items of plant at the site that support this process are;

  • 2 x Superior Engine powered Gas Compressors
  • 1 x Waukesha Engine powered Gas Compressors
  • 3 x CAT 3306 gas engine powered Electricity Generators
  • Oil Heater Gas Burner
  • Salt Bath Heater


Our Primary Requirements

Much can be said about fail to plan and you have planned to fail. With many parties involved bringing this all together, Parasyn’s execution plan led by a dedicated project manager was critical to a good outcome. Some of the activities, common as they may seem to projects of this nature, are absolutely essential for timely and commercially sound outcomes for all stakeholders.

What were our primary activities?


Site audits to assess installation and connectivity requirements

Design Services

Based on the P&ID’s, an SIS design (including control panel) was required for safe start-up of the engines and compressors. The SIS design was based on the functional requirements provided for each Safety Instrumented Function (SIF) which is a combination of the logic solver, sensor and final element. This included development of Functional Specifications to achieve the controls requirements in support of the overall type B compliance.

HAZOP & Design Meetings

Participate in the HAZOP and Design Meetings in relation to the Control System, Electrical Design, Operation and Safety Instrumented Functions. Parasyn managed the design verification provided by an independent third party to meet the regulatory requirements for Electrical Equipment installed in a hazardous area.


Procurement, Fabrication, Assembly & Testing of an SIS Panel based on the outcomes of the accepted design.

Management Services

Provide management services for the project, reporting of progress, resource management, coordination with other parties including design reviewers, AGL operations and maintenance, Drivetrain Project Manager etc. Develop and manage the project’s planning requirements including safety, execution, design, development, construction, installation and testing.

Engineering Configuration and testing

Based on the agreed functional and technical specifications developed for the design develop suitable test procedures. Configured the PLC control system and then tested against the test procedures.


Install and Commission the system

Install the hardware including installation of cable assemblies and local devices according to the site implementation plan, wire and pre-test the installation, perform commissioning with the local operations staff and be available for inspections.

Our Challenges getting it done

In terms of access to industry and local supply of equipment, Wallumbilla like many other upstream gas infrastructure in Queensland is isolated. This called for good collaboration between AGL, Drivetrain, AMEC and Parasyn. The aged existing plant had not been operational for a number of years so it was difficult to ascertain the integrity of some elements of the plant prior to commission, despite efforts to audit the existing equipment and facilities. There was limited information on the existing generator and compressor control systems. A number of design changes were required to cater for the specific equipment and the final operational requirements for the plant.


The result

After all the collaboration, design, development and implementation was over, AGL’s plant was left with;

  • A SIL rated control system consisting of three PLC’s and additional instrumentation.
  • The previous control system for Compressors which was pneumatic including shut off and vent valves were changed to pneumatically actuated valves with an internal Ex-i intrinsically safe solenoid valve.
  • The previous control system for Generators was electrically controlled using solenoid valves which were replaced with new units interlocked by the new PLC control system.
  • High and low pressure switches were installed on the gas supply to each engine to provide additional plant protection
  • The ignition control of the spark plugs of each engine was interlocked to the new PLC control system.
  • Additional sensors on each engine were installed to ensure engines are rotating during the purging process and also to detect the engine stopped condition.

Benefits to AGL

The AGL Wallumbilla facility located 12kms south of the Wallumbilla township primarily consists of an LPG processing plant and contains three gas compressors and three electrical generators. The gas compressors and electrical generators are of a significant age to the point where the gas engines needed changes to comply with AS 3814 – 2009 specifically Type B compliance. By implementing a suitable PLC control system and instrumentation to a SIL rated system compliance with the Type B legal requirement and ensuring the integrity of the Programmable Electronic System (PES). Ultimately this translates to “safer plant operation”.


To see more about intelligent gas management solutions and intrinsically safe system solutions see: