Ex-proof AirLINE Ex 8650 system chosen for North Sea project

Jiskoot, part of Cameron's Measurement Systems Division, designs, manufactures and supplies customised turnkey sampling systems to the global oil and gas sector. The company's success is evidenced by the fact that over 60 per cent of the world's crude oil is either valued on the basis of, or handled by, Jiskoot equipment.

In one of Jiskoot's recent projects, the company required an electro-pneumatic actuation system for a sophisticated and compact gas sampling system that it was manufacturing. The skid was for controlling three gas samplers in a highly automated system on an oil rig in the North Sea. Maintainability and space were premium requirements.

The skid's control system was required to interface and communicate with a Profibus DP network and be suitable for use within an ATEX Zone 1 Area. This meant that Jiskoot needed a single supplier to provide the control system, in the form of an integrated system in a stainless steel control panel, which would then be certified for use in the hazardous area.

This requirement for single-source responsibility was also important due to the location of the oil platform in a remote area of the North Sea. This placed a premium on equipment conformity and reliability, as getting spares and/or personnel to site could be difficult, depending upon the prevailing weather conditions.

New technology

Until recently, Jiskoot's requirement for a control cabinet that combined electrical and pneumatic devices for use in Zone 1/21 could not have been satisfied. This was due to the risk of corrosion of electrical parts, which could subsequently cause an explosion. However, Burkert's development of its AirLINE Ex 8650 system meant that a new alternative was available to Jiskoot. The AirLINE Ex 8650 system delivers substantial reductions in cabinet space, wiring, documentation and validation by combining EExia solenoid valves with modules from the intrinsically safe Siemens Simatic ET 200iSPTM system, together with fieldbus communications, to provide customers with a complete ATEX-certified unit for use in zone 1/21.

Burkert's EX 8650-based system enabled Jiskoot to collect all of the control signals generated on the sampling skid in one place within the hazardous area, and then communicate this information back to a Siemens S7 315 PLC located in a safe area. The use of a pneumatic manifold with integrated I/O reduced the amount of wiring required and tubing on the skid; and because the PLC and remote I/O were from the same manufacturer, this ensured that there were no communication problems between the hazardous location panel and main control centre.

The AirLine Ex 8650 system is housed in a stainless steel control panel with the ET200iSP distributed I/O system consisting of 17 3/2 solenoid pilot valves, 32 channels of digital input (from proximity switches) and 11 channels of 4-20mA Hart input for two-wire transmitters.

In operation, the control panel collects the digital signals generated from position feedback switches on process valves, analogue input control signals generated by external pressure transmitters, temperature transmitter signals, and position transmitters located on the sample collection cylinders to provide performance feedback and alarming and for the valve position confirmation, as well as sending pneumatic signals to the 17 process valves located on the skid. These signals are then fed back to a Siemens S7 315 PLC that is sited in a safe area and acts as the Profibus DP system master. The S7 315 communicates with the ET200iSP module on the front end of the 8650 Valve + I/O assembly and also the Stahl ET316 touchscreen located in the door of the Jiskoot panel.

Tony Brennan of Burkert UK comments: "We are delighted that such a prestigious project has allowed us to demonstrate the benefits that our integrated AirLINE EX 8560 system can provide in harsh, hazardous offshore applications; the integration provided a more dependable, maintainable and compact design that saved considerably on labour during design and building of this system. In many applications offshore, customers go for traditional solutions, but we have demonstrated with this application, the real cost-saving advantages of adopting new technologies that are fit for purpose."