Bespoke pressure regulation solution helps Peruvian gas distributor
22 March 2016
When Peruvian gas company Contugas decided to expand its residential pipeline services into cities including Ica, Nazca and Marcona, the company approached IMI Critical Engineering for a bespoke and innovative valve solution. In order to extend supply coverage, a new facility, the Humay City Gate Station, had to be built.
Contugas City Gate plant
A city gate is a delivery stage where natural gas is transferred from a pipeline and into the local gas utility. At this point, the transmission rate of the natural gas must be reduced to one more suitable for consumer applications.
The project presented several major challenges. However, IMI Critical Engineering’s IMI CCI business worked closely with Contugas throughout, providing both expertise and a custom-made pressure regulation valve solution.
Initially, the Humay city gate design was particularly challenging because it called for 11 pressure regulation systems that would operate across a range of pressures, between 1,450 and 2,175psig. The client also specified that pipeline gas should be used for actuation.
However, if standard applications were to be used in the Humay context, it was likely that noise and temperature problems, including frozen actuators and accessories, would result due to the effects of kinetic energy. A bespoke pressure regulation valve which would eliminate these problems therefore had to be created. Furthermore, the solution had to have enough flexibility and scalability built in to allow Contugas to grow its services in the future.
The key requirements involved were the need for high rangeability with travel operation between 10 and 90%, while maintaining low noise levels and low kinetic energy within the application. The valves had to have natural gas-operated actuators and gas conditioning units that could reduce the natural gas pipeline pressure from within a range of 1,450-2,175psig to 100 psig for the actuator, while the system needed to include a means of preventing the freezing of accessories that would normally result (via the Joule-Thompson effect) from such high pressure drops. All of this had to be achieved within a very tight timetable of less than six months from agreement to delivery.
Clean gas regulator
The team from IMI CCI worked with Contugas to clearly define the operating conditions involved in the project, and in particular the split range and redundant conditions, for which the client had only incomplete definitions. This allowed IMI CCI to provide expert advice on the size and type of solution required, and ultimately to produce appropriately-sized hardware that could handle the required rangeability for both the low flow and high flow valves.
The IMI CCI solution was to use a split valve approach, whereby one valve handles low flow conditions while another deals with high flow, with smooth transition between the two functions ensured by high levels of valve control. Noise is not an issue because IMI CCI has designed the application in light of the client's specifications concerning noise, using ISA sizing criteria for severe service applications and restricting kinetic energy to a limit of 480kPa (70psig). The resulting valves can handle high pressure drops without generating excessive noise and/or vibration.
A heater is installed for each valve, to stop the actuator from freezing. Furthermore, each pressure regulation station has a backup system to prevent interruption of the gas supply.
Although many design reviews were needed, in the end IMI CCI delivered the system ahead of the already very demanding deadline. The system itself is, by design, easy to maintain and highly efficient. In designing and producing this custom-made application, IMI CCI has delivered a unique, bespoke solution that provides multi-stage, multi-path pressure let down to reduce noise and vibration in the system, as well as ongoing technical support and advice.
The system has delivered instant savings on installation and space costs, since IMI CCI used two valves per pressure regulation station, in contrast to the three valves generally used by other providers. Cost reductions have also been achieved on maintenance and replacement costs for both actuators and accessories, which tend to freeze in more conventional systems, while downtime has been reduced as a result of the integral back-up system. This in turn saves the customer paying penalties to the Peruvian Government which become due if the gas supply is interrupted.
The highly innovative pressure regulation valve solution that IMI CCI has designed for Contugas represents the first time that IMI CCI valves have been used in city gates in this region, but is just one element of the established and productive relationship that IMI CCI has with this client. Contugas and IMI CCI are now working together on a range of other severe service applications.
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