They Run and Run and Run…

Injection Valves with Unusually High Service Life

As part of the company's 40th anniversary, Flowserve Essen took a project-specific retrospective look. Among other things the review focused on an installation that could be considered as quite unusual. This particular installation was a special development of injection valves from 1989 and 1990 supplied to Bayer Materialscience, and today these valves are still equal to the material and technical demands placed on them.

Bayer Materialscience is one of the world's largest manufacturers of polymers and high-quality plastics. Its innovative developments are used in coating, painting, insulation and sealing materials, as well as in polycarbonates and polyurethanes. These developments contribute to a higher quality of life — particularly in the automotive, construction, electrical, electronics, household, sport and leisure areas.

Today the Flowserve injection valves for precipitation processes used in extracting additives for paints and plastics are still fully integrated in the production processes of Bayer Materialsciences. This begs the question as to whether these implemented valves might even satisfy the functional safety requirements in accordance with the safety integrity level (SIL), due to their high and sustainable reliability. Now on one hand the SIL requirements catalog did not yet exist at the time the valves were deve-loped, and on the other hand these valves represent specific applications and are not standard products, such as are offered on the market in high volumes. The requisite effort to verify the safety classification of products with high production volumes in accordance with SIL is usually feasible for manufacturers, and it is a sensible undertaking for technical and competitive reasons. High-quality and reliable equipment and devices make a significant contribution to increased safety, longer trouble-free production periods, longer inspection intervals, and improved product quality. However these criteria should also be satisfied from the user's side for special solutions, or special designs.

Valve Design
Flowserve Kämmer control valves are used in precipitation reactors that are used to extract chlorinated rubber.

The product is precipitated with an excess pressure of 8 bar, and for technical process reasons it must be ensured that the minimum precipitation temperature is maintained. Hence the reactors are operated around the clock by a team that works in five shifts. Feed is executed through a small annular gap in the gate valve. This was the locus of the specifications at that time. The objective was to develop an injection valve with an adjustable nozzle for the precipitation process that would ensure a precise media mix ratio. Development and planning of the design of this valve type was handled jointly by experts from Bayer and Flowserve. These successful efforts resulted in a joint patent.

Although the preliminary stage tanks were "only" leaded, it was clear from the outset that with media containing chlorine, and with the high temperatures involved, stainless steel designs deviating from those otherwise employed in this application case were required, and hastelloy got the nod. However, after a relatively short time it was evident that due to the high temperature in the valve interior so-called cracking occurred. In other words deposits formed obstructions. Impairments to processes and extensive cleaning and rework tasks were the consequence. In simple terms the solution consisted of introducing a ceramic sleeve into the critical section where the temperatures range from +145°C to +195°C. After these ceramic sleeves were integrated, the service life of these valves appeared to be unlimited. It is clear that the ceramic sleeves have proven their utility.

These sleeves are taken out when the valve is overhauled and adjusted. If product sits between the housing wall and sleeve then it can be assumed that the ceramic will break. In this respect the utmost caution is required for cleaning work and also when installing and dismantling the valves. The ceramic sleeves are neither simple nor are they standardized. They represent a certain investment because these elements are manufactured individually and have a delivery time of 12 to 14 weeks. Years of experience has shown that up to this point, in the actual operating phase, nothing has happened — which is a great comfort to the customer.

Through the precipitation process in water, chlorinated rubber is precipitated in the form of flakes. The residual moisture is then removed from this material and the material is processed into fine particle powder. The additive that is thus produced is offered by Bayer Materialscience in various forms under the trade name Pergut. These products are used as additives for paints and adhesives. Depending on the particular characteristic they influence adhesion and viscosity of the paint and adhesives. For example, the adhesion of different types of foil in the packaging industry or the achievable higher strength of adhesives in the furniture industry is increased. In general the substances contribute to high strength and resistance characteristics of the bond and to good adhesion on different materials. Moreover they are characterized by high flexibility even at very low temperatures.

Tailor-made Products
Worldwide Flowserve produces high-quality control valves and control drives for special implementations and standard implementations in a wide variety of designs - wholly in accordance with customer specifications. Flowserve Kämmer valves satisfy many implementation conditions, even in the standard version. Operating pressures range from vacuum to 4,000 bar and temperatures range from -269°C to +400°C. The casings can be made from all standard stainless steels, plastics or special alloys. The valves are used in process plants in more than 30 countries. Since the company was founded in 1966 Flowserve has concentrated its design and manufacturing competence on the production of control valves for special applications. More than half of the Flowserve Kämmer valves that have ever shipped are order-specific special designs.

Authors

Contact

Flowserve Essen GmbH
Manderscheidtstr. 19
45141 Essen
Germany
Phone: +49 201 8919 5
Telefax: +49 201 8919 666

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