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Energy converters prove most reliable for Gazprom.

One of the most serious problems which has confronted Gazprom's pipeline projects has been the need for reliable power for unattended stations in the severe environments under which these pipelines must continuously operate (temperatures as low as -60 [degrees] C (-76 [degrees] F) in the winter). Moreover the pipeline telecommunications. protection and control stations cannot be reached by maintenance technicians for months at a time.

Another important consideration is that to ensure the pipeline operational integrity, the telecommunication and electronic equipment installed at these stations at intervals along thousands of kilometers of pipelines must be kept at temperatures between 0 [degrees] C and +45 [degrees] C (+32 [degrees] F and 113 [degrees] F), regardless of the outside ambient conditions. Heating of the equipment shelter cannot be practically accomplished by either combustion-type space heaters, (which pose a safety problem), or by electric heaters, (which require high power).

Selection Of Ormat Energy Converters As Power Source

After extensively applying and studying available power options in the range of 400 to 5,000 watts, including reciprocating engine generators (EGs), thermoelectric generators (TEGs), wind generators (WGs), photovoltaic cells (PVCs) and Ormat Energy Converters, which are closed-cycle vapor turbogenerators (CCVTs), Gazprom selected the Ormat CCVT as the most reliable and best suitable for unattended remote pipeline power stations.

The selection criteria, which is summarized in the accompanying table was based mainly on the following issues:

* Reciprocating Engine Generators (EGs) regardless of fuel used, required periodic maintenance and under severe arctic winters could not be kept running reliably.

* Thermoelectric Generators (TEGs) were found to be unsuitable because of (a) frequent flame-outs, (b) low power output. (c) lack of multiple and dual-fuel capability, (d) lack of non-electric or non-combustion shelter heating capability, (e) high fuel consumption, which exceeded manufacturer's specifications and was constant even with low load and (e) low reliability and dependability.

* Wind Generators (WGs) were found to be unsuitable due to unpredictability of winds and need for a large station battery.

* Photovoltaic Cells (PVCs) were unsuitable due to arctic environment with long periods with no sunlight.

The Ormat arctic-type CCVT and its associated non-electric closed-loop convection heating system was selected and has provided power systems that incorporate high reliability with maintenance requirements reduced to a visit only once every six to 12 months, as well as a solution to the equipment shelter internal temperature stabilization problem.

Since 1972, Gazprom has placed more than 600 CCVTs in operation and has found them to be field-proven as dependable and cost-effective, both in terms of fuel consumption, (which is in accordance with the manufacturer's specifications as well as proportional to power output) and maintenance expenses.

The CCVTs selected operate at their nominal power under ambient temperatures from-60 [degrees] C to +45 [degrees] C (-76 [degrees] F to+113 [degrees] F) and with wind velocities to 160 km/hr continuous [TABULAR DATA OMITTED] and gusts as high as 200 km/hr. The CCVTs' multiple-fuel capability has allowed the use of either natural gas in the pipeline as fuel or locally available fuels such as arctic kerosene or diesel fuel. In addition. with dual-fuel CCVTs. microwave telecommunication stations have been powered by external fuel until the gas pipeline has been commissioned, with the fuel then switched to natural gas.

Closed Cycle Vapor Turbogenerator

The Closed Cycle Vapor Turbogenerator is shown schematically in Fig. 1. The fuel is fed to the external burner which heats the organic fluid in the boiler, where this fluid is vaporized. The vapors generated drive the special turbine, which is on the same shaft as a brushless generator. The spent vapors are condensed in an air-cooled condenser and are gravity-fed back to lubricate the hydrodynamic bearings of the turbogenerator, and then to the boiler to repeat the cycle. The generator output is rectified and regulated for use by the station loads.

The CCVTs on the pipeline operate either singly, for standby to mains or non-critical applications, or as dual units in hot standby to each other, with each at 50 percent load, for ultra-high reliability.

The CCVT power unit, other than the burner and controls, is sealed for life in a stainless steel "envelope", which does not require any periodic maintenance or overhaul.

The CCVTs are supplied fully assembled and factory-tested so that installation and commissioning on site takes only a matter of a few days. Installation is quite rapid and simple, consisting of bolting the CCVT to a concrete or prefabricated base, connecting the fuel supply and connecting the load and alarm circuits.

Special features have been incorporated on some projects, including CCVTs which h integrate directly with the equipment shelter and Cathodic Protection Voltage Control Modules.

Non-Electric Equipment Shelter Heating

One of the most important problems to be solved in the design of an integrated remote telecommunications system in the arctic regions is maintaining the temperature of the electronic equipment installed in the shelters at levels between O [degrees]C and +45 [degrees] C, to ensure correct operation in winter and summer.

Heating the shelters in wintertime cannot be accomplished cost-effectively by electrical heaters due to the need for as much as 2,000 watts for this purpose alone. In addition, the use of gas heaters is prohibited for safety reasons.

To accomplish this task the Ormat CCVT incorporates a non-electric "cogeneration" system which uses thermal energy from the heat generated in the CCVT boiler (vapor generator), and delivers this energy in the form of heat directly into the equipment shelter.

The heating system uses Fluorinert FC-72, a non-chlorofluorocarbon, as the heat transfer medium in a closed loop cycle. Each loop of the heating system is capable of delivering 1,000 kcal/hr to maintain a minimum temperature of +5 [degrees] C in the equipment room during unattended operation in wintertime.

Projects Using Closed Cycle Vapor Turbogenerators

Gazprom is the largest natural gas production and transmission company in the world, with over 30,000 kilometers of existing pipeline stretching from Siberia into Europe and thousands of additional kilometers of pipelines under development, as shown in the map below. These pipelines pass through arctic regions subject to the most severe environmental conditions. The use of the highly dependable CCVTs for powering the many unattended and remotely located telecommunications control and protection systems has enhanced the reliability and operational integrity of the entire pipeline network.

Here, we describe some of the projects in Russia which use CCVTs.

* Urengoy-Uzhgorod Telecommunications and Cathodic Protection Systems

The 4,500-kilometer-long Urengoy-Uzhgorod Telecommunications and Cathodic Protection Systems were installed in 1983-85 by Alcatel of France. This project utilizes 85 dual CCVT stations for telecommunications (170 units total) rated at either 400, 600, 800, or 1,200 watts, and fueled by kerosene or natural gas and 36 single natural gas-fired CCVTs rated 2,000 watts for cathodic protection. (See Photo 1)

Initially, the CCVTs for telecommunications all operated in hot standby to produce autonomous power, or where mains existed, these mains were so unreliable that the units were operated in hot standby to these mains. With the connection of the project to more reliable mains, 19 CCVTs were relocated in the Yakutia and Krasnoiarsk regions.

Some of the sites are inaccessible in wintertime except by special conVoys and only by helicopter in the summertime. Therefore, the supply of fuel and the routine maintenance is conducted only once every six months. To accommodate the project's fuel constraints, the CCVTs have dual fuel capability, enabling full interchangeability between kerosene and gas burners.

* Other Gas Pipeline Projects

With 200 Ormat CCVTs supplied in 1993, the total number of such units operating on Gazprom projects exceeded 600. These units power such important radio relay links as Nadym-Ukhta, Nadym-Yamburg, Nyuksenitsa-Archangelsk and Yugorsk-Pripolyarnaya. The total length of these radio links is more than 5,000 kms. (See Photo 2)

These CCVTs are rated at 1,200 watts and are equipped for dual fuel operation from either natural gas or arctic diesel fuel. The ambient temperatures range from -55 [degrees] C to +45 [degrees] C, and all stations have an equipment shelter with a non-electric heating System. The radio equipment is either manufactured by Harris (U.S.) or Alcatel (France).

Recently, 28 additional Ormat CCVTs have been ordered for the telecommunications system along the Tiumen-Surgut-Novyi Urengoy gas pipelines. The CCVTs for this project will be used for standby to mains. When the mains' voltage drops below 180V, a control module automatically starts the CCVT, which will provide the necessary power to the system until the mains are restored.

Conclusions

More than 600 CCVTs are operating in Russia with a high degree of reliability, many since 1973, in various telecommunications and gas pipeline cathodic protection and control applications. Typically, these units experience yearly down time,(from all causes) averaging from approximately five hours on older projects to less than a half-hour on newer projects. This means that the CCVTs have availability factors ranging from 0.999 to 0.9999.

With this record, Gazprom feels that the selection of the Ormat CCVT as the power source for remote unattended stations and inaccessible sites has been justified by field-proven reliability and dependability.
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Author:Belousenko, I.V.
Publication:Pipeline & Gas Journal
Date:Mar 1, 1997
Words:1510
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