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Automation Articles
Case Study: CitectSCADA for reliable monitoring and control
[2008-11-12]

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Read on below to discover how both Electrogas and Metrogas are able to monitor and control hundreds of kilometers of pipelines easily and reliably thanks to CitectSCADA. CitectSCADA’s true hot standby of control and monitoring prevents any loss of data in the event of a failure and automatically backfills data to the host system.
 
Chilean Natural Gas Pipelines
Electrogas and Metrogas both choose CitectSCADA for reliable monitoring and control of their pipelines

 

Project Overview
In Chile, almost all natural gas comes from Argentina via pipelines running through rugged terrain. Only the Magallenes Region in the southern part of the country contains natural gas resources.
 
The Challenge
The Gas Andes pipeline runs 460 kilometers from Argentina to central Chile. The 149 kilometers that runs through Chile crosses the border from Argentina near the Maipo volcano at an altitude of 3,400 meters. There are valves controlling flow, pressure and gas temperatures every 30 kilometers that are controlled remotely by a supervisory control and data acquisition (SCADA) system.

The pipelines have a 24 inch diameter and are buried 3 meters underground. There are 39 points where the pipeline must be buried as a deep as 10 meters underground when it crosses water channels. In addition to the pipeline, a fiber optic line permits uninterrupted communication between La Mora station and the City Gates stations in Santiago.

In this rugged geography it is imperative to have a secure, reliable SCADA system monitoring the length of the pipeline at all times. It is also imperative to have real-time data from each station along the pipeline to remotely monitor and assess field issues.

 

The Solution


Electrogas, Chile
Electrogas monitors and controls the pipelines from Argentina to Santiago.
Fluor Daniel Williams Brothers contracted PSI to provide engineering and system integration for the SCADA system on the pipeline running from Quillota to Santiago.

 

The project had severe time constraints, and CitectSCADA’s exceptional flexibility meant that engineering time would be minimal. PSI also selected CitectSCADA for the project over competitors because CitectSCADA is exceptionally reliable. Its built-in redundancy enables the system to withstand any single point of failure – hardware or communications – without impacting operations.
Another important factor in selecting CitectSCADA was its true hot standby architecture for the control and monitoring functions that are so vital to the safe functioning of the pipeline. Unlike other SCADA systems in which the localized data collection will stop completely or go offline and later have to be backfilled by the controller, CitectSCADA’s true hot standby architecture means localized data collection will keep functioning as normal even if the host system fails. There is neither data loss nor the need for an engineer to backfill data at a later period.

 

The CitectSCADA solution also helped lower operating costs by increasing the level of computer control and monitoring. By allowing users to view information and take corrective actions from any location on the network, CitectSCADA reduced the need to travel to individual sites.


Metrogas, Chile
The largest natural gas distributor in Chile, Metrogas serves the Metropolitan Region of Santiago. Metrogas serves over 300,000 residents and businesses in the capital with over 4,000 kilometers of network.

 

Metrogas also chose CitectSCADA to monitor and control its network because it needed a high-performance SCADA system that can reliably manage huge quantities of data. With such a large network, it can take over 45 minutes to complete one circuit of its remote sites and Metrogas needed SCADA software that could provide reliable monitoring of its numerous RTUs without having to wait 45 minutes or more to collect data.
All RTUs are polled by a master radio. This radio has a buffer cache that is checked by CitectSCADA when it sees that data is ready. CitectSCADA software reads the packet, deciphers the information, and writes values to the corresponding disk tag. CitectSCADA then backfills the data to the trend system at a time predetermined by a timestamp that is part of the packet data. Then a handshake occurs between CitectSCADA and the master radio to inform it that the data has been read. After CitectSCADA receives the information has been read, it clears the item from the cache and prepares the next piece of information.
 
Like Electrogas, Metrogas selected Citect for its ability to efficiently handle the large quantities of data required to monitor the pipeline. Its report by exception capability advantage preserves bandwidth by only sending data that differs from the last data reported. Instead of data being polled constantly and sent over the network regardless if the information has changed, data is sent automatically only when a change occurs. When a disturbance or change occurs, the data is then sent to the operator or an alarm goes off at the control center.

 

 

Pipeline monitoring generates vast amounts of data each milli-seconds, far too quickly for a human to see small changes in the operations. CitectSCADA allows data to be collected and time-stamped in the milli-seconds. Operators can then review the time-stamped data to establish trends.

 

CitectSCADA also provides great ease in interfacing with other systems as a resulting from its truly open architecture and offering the largest number of native drivers completely free of charge. Metrogas had a hardware and original system configuration using a Modbus driver. Citect simply had to replace a mode of a behavior/feature to the Modbus driver that had been removed to enable a new version of CitectSCADA to work with an old Modbus driver.

Electrogas chose Citect because of its reliability and flexibility:

  • True hot standby support of control and monitoring functions
  • Able to support report by exception from the field
  • Minimal engineering time required; no re-engineering needed to original installation when additional I/O points are added

 

Hardware overview
the current hardware platforms include:

  • Modicon PLCs
  • OMNI flow computers
  • ABB multi-loop controllers
  • Ethernet LAN

© 2008 Citect Pty Ltd ABN 88 001 158 854







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