Sensing technology at the heart of major PTA upgrade success
Formed in 2000 when DuPont’s polyester business became part of Turkish company Sabanci, Advansa now manufactures and sells polyester intermediates, fibres and polyester polymer solutions across the European, Middle East and African regions. It also carries out product R&D and provides technology and product solutions based on the company’s experience of how to run operations safely, efficiently and in an environmentally-friendly manner. Its products are used in many end-use markets, including apparel, technical textiles and home textiles.
As part of this growth, Wilton-based Advansa UK has evolved into a major European manufacturer of pure terephthalic acid (PTA) and polyester resin products (Fig.1).
Substantial investment has recently been made in the Wilton facility in the form of the T8 revitalisation project. As a result of this upgrade, annual production of PTA has increased by around 100 000 tonnes to over 500 000 tonnes.
In order to maintain safety with this substantially increased throughput, the company has installed a Servomex2200 series process oxygen analyser as part of a functional safety instrumented system.
A significant part of the upgrade project involved installing new equipment to enrich the process air fed to the reactor with oxygen; using oxygen-enriched air in the reactor increases the conversion rate in proportion to the additional oxygen. However, care must be taken to ensure that the oxygen level is not too high, otherwise a potentially explosive atmosphere could form.
A safety instrumented system (SIS) was therefore preferred with a safety integrity level of 2 (SIL2) in accordance with EN61511. This standard covers the functional safety of safety instrumented systems for the process industry sector.
To assist in the safety justification, Servomex provided a failure mode and effects analysis report to the system’s engineers, which was generated by an independent specialist in functional safety. This report demonstrates that the Servomex2200 transmitter safe failure fraction is suitable for operation at SIL2. Servomex is now actively considering functional safety requirements for all future product development.
Advansa UK has been using various Servomex paramagnetic oxygen analysers at the Wilton site for over 30 years.
Servomex has extensive experience of supplying gas analysis equipment for PTA plants worldwide, for both oxygen and infrared measurements. Having discussed the system requirements and studied the specification, the Servomex engineers recommended using a 2200 series transmitter and control unit in a sampling system using a GRP cabinet. The transmitters utilise fast, rugged, non-depleting paramagnetic sensor cells, which means that zero drift is extremely low and frequent calibration is not required, which helps to minimise the operating cost. An auto-calibration facility also reduces the cost-of-ownership, and the unit’s intuitive, multi-language text interface requires almost no training to use.
