Economic projections point toward a gradual recovery of industrial production activity in Mexico in the next few years. A prerequisite for this growth, however, is the timely availability of energy supplies for the production units.
This prerequisite acknowledges the advantages of using natural gas to produce electric power, because of its reduced environmental impacts compared with other fuels and the efficiencies now available with combined-cycle technology.
The combination of favorable expectations in economic growth and the environmental advantages of using natural gas will result in a considerable increase in demand for gas, projected at a growth rate of more than 15%/year for the next 6 years (Fig. 1). This outlook requires a fast-paced upgrade of the country's pipeline network.
In view of this, Pemex Gas Pipelines (PGP), the gas pipeline arm of the state company Petroleos Mexicanos SA, is readying itself to face new operating conditions. These include the two-way handling of natural gas, moving it from north to south and vice-versa, in response to either an increase in the production of dry gas in the north of Mexico or to an increase in necessary imports to meet domestic industrial demand. These efforts must also be accomplished with the pipeline system now in an open-access configuration with growing competition among gas distribution companies.
As part of the upgrading program, in 1996 Pemex initiated a far-reaching instrumentation process in its security, health, and environmental protection program-an effort that has placed the Mexican state company among the world leaders in this category. As a result of this program, PGP was able to reduce the number of accidents from 45 in 1966 to zero in 1999 and 2001 (Fig. 2).
At the same time, Pemex initiated a technology plan that has allowed the incorporation and assimilation of advanced international inspection and rehabilitation practices by means of preventive and predictive maintenance, which enables full capacity operation in order to maximize profitability.
Part of this plan was to replace conventional pneumatic instrumentation with the most advanced automatic control and monitoring technologies to operate an existing 9,043 km of natural gas pipelines and 1,787 km of LPG pipelines, along with 3 compression and 5 pumping stations.
To this end, PGP proceeded to establish the world's most ambitious supervisory control and data acquisition (SCADA) system, which would automate, in one single effort, 11,000 km of pipelines crisscrossing 20 states in Mexico (Fig. 3).
SCADA system
In order to control and monitor, in real time, natural gas pressures, flows, and temperatures and LPG pipeline operating conditions, the SCADA system was considered to offer the best means to help regulate transportation capacity, remote control of the facilities, and quick emergency response and to configure operational data bases, all of which will help improve customer relations and make optimal use of the transportation infrastructure.
In October 1997, an international call for bids for the project integrator was launched. Four international companies responded, and the Spanish company Soc. Anónima de Control won.
Project integration included engineering, procurement, and construction coordination, in which highly qualified firms participated-including, among others, the Canadian firm Valmet Automation Ltd., in the development of software; US companies such as Hughes Network Systems for satellite communications, Rotork Controls Inc. for the activators, and Woodward Governor Co. for turbine control systems; and the Mexican company Bicyc for power, mechanical work, and civil construction on 420 work fronts, all of which required complex logistical coordination.
The SCADA system enables the remote operation of the gas compression stations at Cárdenas, Chinameca, and Lerdo, each with two 55,000 hp turbines; and the LPG pumping stations at San Mart!n Texmelucan, Arroyo Moreno, Maltrata, Mendoza, and Zapoapita, with 260,000 b/d pumping capacity along 1,787 km of the world's longest LPG pipeline.
The system controls practically every injection and extraction operation in PGP's pipeline network. The operation required adding more than 6,000 new actuators, which include 588 strategic valves installed before and after river crossings and, in urban areas, nearly 1,000 pressure and temperature data transmitters, 440 natural gas actuators, fire and physical protection systems, and grounding and lightning rods to ensure the operational and personal safety in a project of such magnitude.
SCADA central control facilities are at PGP's main offices in Mexico City (Fig. 4) and are supported by a duplicate center outside Mexico City, which would automatically take over in any catastrophic event that could affect operations in the main control unit.
Both control centers receive information from 17 remote stations located wherever the national pipeline system has operations offices.
This type of infrastructure makes it possible to operate in real-time remote company facilities in case of an emergency, opening or shutting down valves anywhere in the country, in only 4 sec.
It is also possible to pinpoint any pipeline section, thus avoiding leak propagation and its effect on the population and the environment.
Internet interface
In addition, the SCADA system enables PGP to better approach its clients via internet interfaces that enable the main consumers to instantly access their consumption data, so that they may inquire about the quality of the gas that is being delivered and other particulars (Fig. 5).
PGP's SCADA system is equipped with an internet exit module that enables clients to ask, in real time, their consumption, the quality of the gas being delivered, and pipeline operating conditions-pressures, temperature, flow-of their respective stations.
This information is very valuable for the industrial and commercial clients of Pemex Gas in their decision-making process.
This is especially important to establish the basis of their participation in B2C (business to customer) operations, and placing Pemex Gas among the leading pipeline transportation firms in this area.
The internet exit module is backed by technological advances that ensure a secure operation, because it is designed so that third parties can access only authorized information. All the safety checks are in place to prevent unauthorized parties from accessing databases and infringing upon operations.
The SCADA system allows clients to access their information 24 hr/day year-round, avoiding reprocessing of information and reducing errors by voice commands.
Operational data determine what financial strategies will be most beneficial to the clients and are an early indicator of the client's productivity.
Thus SCADA offers advantages that translate into considerable financial benefits by allowing pipelines to operate at maximum allowable pressures, optimizing investments and improving business profitability.
This project allows the continuous improvement of the financial indicators of the gas business. This will translate into larger transportation volumes per worker, more capacity utilization generated per employee, and in greater asset values handled by each company segment, thus achieving a greater aggregate value of its operations.
Project details
The SCADA project was completed at a cost of $120 million, which included engineering, procurement, and construction.
SCADA instrumentation required an expansion of the existing telecommunications infrastructure. This consists of a digital microwave network that required durable connection equipment and systems that could handle the considerable distance between contact points. This required the use of various new technological advances, among them:
- Expansion of the multiplex section in the existing digital microwave system.
- An on-land satellite station within the central control station.
- Interconnection of microwave stations to SPCs via cable and modems
- A UHF digital multipoint system.
- A satellite communication system set to the Ku band.
Backed by this advanced technology, SCADA data are permanently updated, thus maintaining an operational database that improves service to clients by keeping an accurate electronic record of their consumption free of errors or subjective evaluation elements.
The integration of SCADA in PGP's network represents a technological "leap" that places the company within the highest echelon of the international gas pipeline industry. This tool allows an intensive utilization of the company assets by operating its infrastructure at maximum efficiency and safety.
It also prepares Pemex Gas to participate in a competitive market with open access to natural gas businesses, enabling electronic commerce, and providing better service to its clients in North America's increasingly competitive energy market.
