High-reliability solution for Du Pont nylon plant

Citation

(2000), "High-reliability solution for Du Pont nylon plant", Anti-Corrosion Methods and Materials, Vol. 47 No. 3. https://doi.org/10.1108/acmm.2000.12847cab.005

High-reliability solution for Du Pont nylon plant

Keywords Du Pont, Tubing, Parker Hannifin

Du Pont UK Ltd reports that it has standardised on Parker CPI tube fittings for a major upgrade to its nylon plant in Middlesbrough. The company is installing around 14,000 fittings on the advanced DCS-controlled instrumentation network, because of the way CPI's single-ferrule design has been shown to combat corrosion, leakages and problems stemming from mis-assembly.

The choice of CPI for this major upgrade project follows extensive experience with this type of fitting. The Du Pont nylon plant has specified CPI tube fittings exclusively for the last six years, because of corrosion and incompatibility problems encountered with previously-used brands. The ferrules inside some of these fittings had corroded, because of material problems, and the acidic media used in Du Pont's nylon processes.

A planned changeover to metric tubing in 1994 provided the opportunity to rectify the situation, and Du Pont decided to standardise on a single brand of tube fitting. Staff evaluated Parker's CPI range after a recommendation from colleagues in a sister oil and gas company, which used Parker fittings for offshore installations because of their special protection against corrosion.

Parker informs us that, following vendor assessment and tests, the final decision to adopt CPI was taken on the superior integrity of connection, and proven interchangeability with leading brands of fittings. The plan was to convert existing plant as refurbishments took place - a process which, in practice, was greatly simplified by the fact that CPI stainless steel fittings have distinctive black nuts, giving a visible identification of the work done.

"Tube fitting integrity has improved dramatically since standardising on Parker CPI. From personal experience, Parker fittings have proved to be 100 per cent reliable", says Tony Marr, instrument and electrical engineer at the nylon plant. "The single ferrule design is extremely reliable and I feel it will make a significant contribution to the operational, safety and environmental goals of the new plant."

A key technical factor in Du Pont's decision was resistance to corrosion. Du Pont knew from experience that ferrules are not always fabricated from the same stainless steel material as the fitting's body, and had suffered leaks because of ferrule corrosion following exposure to adipic acid.

The intrinsic resistance of Parker's CPI fitting is said to stem from the fact that its single ferrule is "suparcased" - a treatment which provides the hardening necessary to bite into the tubing to effect a reliable seal, without opening up an avenue for corrosion. In Parker's opinion all competitive commonly-used ferrule hardening techniques - chrome plating, work hardening, or chemical edge treatment - weaken a metal's corrosion resistance in some fashion. "Suparcase" is an infusion which penetrates for a few microns only and does not affect the underlying molecular structure of the base material.

Parker distributor SES Instrumentation is the supply point for the contract, holding stocks at its Cleveland plant for a responsive local service during installation and for routine maintenance.

"The supply chain is crucial for a large project like this" says Ian Moore, of SES. "We hold stock levels geared to the construction schedule of the upgrade project, plus a buffer to accommodate any emergency and maintenance requests."

CPI is claimed to be the only instrumentation-grade tube fitting on the market which makes its seal via a single rather than twin ferrule arrangement. This halves the number of potential leak paths in the connection, dramatically boosting safety, reliability and integrity, and also simplifying assembly and maintenance.

The fact that CPI fittings need only a single ferrule has also eliminated the mis-assembly problems to which conventional twin-ferrule tube fitting designs are prone. "There is no possibility of mismatch with this design", adds Tony Marr. "CPI tube fittings are very simple to use and work well."

Chemical Petroleum Industries (CPI) tube fittings are available in metric and imperial sizes, for outside diameter tubing from 3mm to 25mm or ¹/16in. to 2in.

Parker offers a wide choice of body styles for simple and efficient tubing system design, including straight unions, reducing unions, elbow joints, cross and tee connections, and adaptors for interfacing to threaded pipework.

As standard, stainless steel CPI nuts are coated with molybdenum disulphide, which leaves them coloured black for easy identification. This coating also acts as a lubrication, so that assembly requires only a similar torque level to conventional twin ferrule fittings.

Parker tube fittings support integrity of Sellafield Dry Pack project

In a second major project Parker's instrumentation division is supplying all the tube fittings and valves for the fluid instrumentation systems currently being installed as part of BNFL's Sellafield Dry Pack project. The project reportedly, as with Du Pont, standardised on Parker components because of their technical performance - in particular, the integrity and long life provided by the fittings' corrosion-resistant "Suparcase" ferrules - and the company's responsive supply network.

The £450 million Sellafield Dry Pack (SDP) project provides a long-term solution for storing intermediate level nuclear waste. It treats liquid and sludge waste products by drying, compressing and encapsulation. Parker's fittings, valves and manifolds are employed in this process to implement the wide variety of instrumentation that controls parameters such as level, flow and pressure.

The SDP plant has been designed and specified by BEL Engineering Ltd. It chose Parker as its instrumentation products supplier following an extensive technical appraisal, which included destructive tests on a burst pressure rig, and an assessment of the company's quality control and supply chain. Parker's north-west UK distributor, Heap and Partners of Liverpool, provides the supply point for the contract, holding extensive stocks for a responsive local service during the build cycle, and throughout its operational life.

The instrumentation on SDP has been designed to have a minimum operational life expectancy of ten to 15 years, so high-integrity components are essential. BEL specified tube fittings with ferrules treated using Parker's "Suparcase" process. Standardising on a single vendor has helped to keep this ambitious project on track, notes BEL's design engineer Dave Armitage, who has been involved from the initial stages of SDP. Following selection on technical and quality grounds, equipment suppliers are chosen for their ability to provide engineering back-up and maintenance. In Parker's case, this included the provision of hands-on training on fittings assembly for the site's installation contractors, and the manufacture of non-standard fittings to simplify the instrumentation architecture.

"Corporate standardisation agreements give us the flexibility to add real value for our customers", says Andy Baxter of Parker. "We are free to invest in the relationship too, with services such as training and a special local stock depot, to help ensure that the project runs smoothly and to schedule".

Details available from: Parker Hannifin Instrumentation Products Division. Tel: +44 (0) 1271 313131; Fax: +44 (0) 1271 373636; E-mail: ipd@parker.com and Parker Hannifin, Middle East Office. Tel: +971 2 788587; Fax: +971 2 793812; E-mail: mamin@pmail.emirates.net.ae