Schaffhausen, April 2008
Piping systems for conveying, measuring and controlling high purity media
Even though the specifications for pure and ultra pure media diverge considerably from one industry to another, they are similar in one respect: Contamination of the medium from the materials, pipes, fittings and valves through which it is conveyed is not tolerated. If this should occur, exorbitant sums of up to several million euros might have to be paid for rejected goods or product liability. High purity media are used today, for instance, in microelectronics, in power plants for boiler feed, in the life science industry, hospitals and research laboratories. They are used as a cleansing agent, an additive or a process medium. The specifications for pure or ultra pure media are of major importance, since these define specifically the degree of permissible contamination as well as any additional conditions which need to be fulfilled.
In the chemical industry and in the food and beverage industry, the formulation, the pH value and most notably the particle count are often specified, while in medicine, the pharmaceutical industry and in biotechnology, the conductance, the TOC (Total Organic Carbon) and the number of microorganisms play a decisive role. The semiconductor industry is furthermore interested in the maximum permissible contamination for anions, cations and specific elements, such as O2 (oxygen), SiO2 (silicon oxide), NH4+ (ammonium) and B (boron).
Varied requirements
The technical product features alone do not constitute the quality of a piping system or the corresponding measurement and control systems for conveying high purity media. More important is the interaction of the various parameters that are present: basic structure and the purity of the raw material, production and production environment, scientific procedures, installation and operating conditions. Only when all these factors are in equilibrium can we speak of “quality“.
This very brief look at the different application areas suffices to illustrate the complexity of selecting an ultra pure media system including valves. Comprehensive know-how is an absolute must if errors in the evaluation, design and planning phases are to be avoided.
High purity applications
High purity media have one thing in common: they are treated in a series of process steps in order to remove all objectionable solid or solvent impurities, ions and organic content. Depending on the application, a different treatment profile is modeled.
Water is the medium most frequently used for high purity applications. It is the ideal process medium because of its “neutrality”. Different purity levels are derived from drinking water (especially for life science applications) or treated surface water. These are related directly to the legal or normative body of regulations and the specifications derived thereof for process management and control for the operation of such systems. The various levels of quality for treated water and their key properties are illustrated in the water pyramid (Fig. 1). In order to better understand how the term “high purity“ is quantified, we can look at the following comparison: From a microbiological point of view, the maximum concentration of microbes is equally precisely specified for water for injection (WFI) as for drinking water. Albeit, the total microbial count differs, from a simplified perspective, by a factor of 3000. In contrast, the concentration of ions in WFI and in ultra pure water for microelectronics is another significant parameter. In simple terms the permissible concentration is a factor 1000 lower in microelectronics than in the pharmaceutical industry.
Pure or ultra pure water is used to clean containers (for example reaction vessels), to feed boilers or steam generators, or alternatively to rinse wafers in chip manufacturing. Influential quality parameters in conveying high purity fluids are, in addition to the original purity of the water, consistency and upholding of the purity values at the place of treatment and the point of use (POU). Traditionally, stainless steel pipes have been used for this, plastic piping has, however, become an established alternative in recent years.
The two polymers polypropylene (PP) and polyvinylidene fluoride High Purity (PVDF HP) are primarily used for pure and ultra pure applications today. The choice of material depends first and foremost on the required degree of purity for the medium. Other decisive criteria are temperature and pressure range, selected method of disinfection, the available know-how and the budget.
System concept
Within the framework of the given conditions, quality can only be realized with an integrated system. Each link in the chain of a pure/ultra pure water project must meet the purity specifications and legal requirements and continue to meet them on a sustained basis. So besides the physical properties of the product, all the other parameters must be considered, the scope of their influence analyzed and assessed, registered and evaluated as a basis for statistical process control. Furthermore, the trend and long-term data are very important indicators for the above mentioned consistency in quality. The complete chain, from raw material to the final approved installation, is subject to the same logic.
Valves – indispensable elements in a piping system
In a complete piping system, valves play a major role since it is these which ultimately enable checking the flow, distributing and controlling the transported media. PW quality (pure water) or WFI is the most important raw material in the pharmaceutical industry and in biotechnology for the production of active ingredients and drugs. It is distributed through complex piping systems that can stretch over several kilometers, depending on the plant size. The water is generally tapped at the POU via diaphragm valves, in particular outlet valves, such as T-valves or zero static (diaphragm) valves. The manufacture of such valves, as for all components in ultra pure systems, should therefore correspond to the respective applications. For extremely stringent requirements, clean room segments, in which the production conditions are clearly defined, have proven to be the best solution.
Pipes, fittings and especially valves, which have been manufactured in this manner, exhibit consistently high quality and purity, which precludes a possible contamination from the production process and at the same time offers optimal conditions for installation.
Materials which have proven ideal for ultra pure media systems and the respective valves, are the high-performance polymer PVDF in high purity quality and for extremely demanding specifications PFA (perfluoroalkoxylalkane). These materials, which belong to the group of fluorocarbon polymers, exhibit ideal properties for ultra pure media distribution systems and have been used successfully in diverse branches of industry for over 20 years.
Jointing technology
Besides the valve design, the integration of the valves in the actual piping system is crucial in ultra pure applications and naturally in the pharmaceutical industry as well. As jointing technique, the pharmaceutical industry tends to prefer permanent connections, i.e. fusion jointing, instead of removable connections, such as unions, clamps, etc.
Flange connections. Generally, the only connections which are permitted are those free of gaps, undercuts and dead legs as these are the spots in which microorganisms can grow.
Predestined for use in PW and WFI systems is the BCF fusion technology (bead and crevice-free), which enables optimal joining of PVDF and PP pipes because, for instance, the fusion technology satisfies the specified criteria and produces excellent surface quality Ra _ 0.25 µm in relation to SYGEF PVDF HP.
The BCF fusion technology offers another major advantage over other fusion methods for metal piping systems: BCF welds can be inspected with a light source from the outside. Endoscopy, X-ray examination or the conventional passivation used for stainless steel systems are not necessary, which represents a huge cost savings in PW and WFI projects.
From raw material to product
Using the example of high purity manufacturing of PVDF products, the entire production process can be demonstrated from the viewpoint of contamination minimization. During production, impurities in however minute quantities can have a negative impact on the medium to be transported. These could potentially wash out into the system and must be ruled out unconditionally. Starting with the raw material and ending with components manufacturing, the purity-relevant parameters are the subject of continual inspection and monitoring. The high purity chain comprises diverse elements in the production of high purity piping components.
Raw material testing:
Stringent materials testing on the PVDF-HP granulate, prior to release for production
Production in the clean room segment:
Injection molding of valve bodies in class 10,000; machining, if necessary, in class 100
Cleaning the components:
UPW (Ultra Pure Water), specified resistance 18.2 M_/cm, TOC < 15 ppb, particles < 100 particles/l, size 0.2 µm
Packaging:
Double bagged, pipes also sealed with end caps
Transport:
In cardboard boxes with bubble plastic wrap
Installation:
Fusion technology corresponding to the HP piping components, such as BCF, IR (infrared).
Production itself takes place in the clean room, where constantly monitored conditions prevail. The process logic dictates various categories of clean room. The closer the process is to the end product, the higher the category of clean room and the more intensive the monitoring. In the final manufacturing phase, the products are rinsed with ultra pure water.
The quality of the clean room production is ultimately judged on the basis of the product itself. The purity values per customer specifications or norms are determined in comparative testing. The test points are metal leach-out values, organic elutriation (TOC) and inner surface roughness. Leach-out measurements are additionally conducted in periodic and statistical form at EMPA (Swiss Federal Laboratories for Materials Testing and Research) in Dubendorf (Switzerland). The tests conducted over years enable continually optimizing the process and guarantee high process stability.
Consistent product performance in life science sector
Traditionally, the pharmaceutical industry has used stainless steels in quality 1.4404 or 1.4435, but corrosion, rouging and the costs of components and system qualification have led to the high-performance plastic PVDF in high-purity quality often being preferred over stainless steel.
Water in PW or WFI quality is the most important raw material in the life science industry for production of active ingredients and drugs. It is transported through complex piping systems that can stretch over many kilometers.
Georg Fischer piping systems are tested in scientific analyses for their application suitability and requirement congruency. Particularly in the life science sector, the legislation for production or processing of pharmaceutical products is extremely rigorous and is scrutinized closely. For example, in an effort to protect consumers and patients, all the process steps in the complete production chain are subject to testing for high and consistent microbiological purity. These parameters ensure that the medicines produced in each batch are of the same high quality and possess the same properties.
In addition to conventional hydraulic and mechanical testing, other internal purity-related tests are standardized in the manufacturing plant. Decisive parameters of quality for plastic piping, such as leach-out and inner surface roughness, when studied over years, supply relevant basic data. Additionally, a scanning electron microscope (SEM) is frequently used to collect data on the surface structure as well as pore size and number. This becomes manifest when the inner surfaces of PVDF-HP pipes are examined immediately after production and then compared with results from pipes after two years of use in a pharmaceutical production facility with the medium pure water at room temperature.
The respective tests at GF Piping Systems are periodically supplemented with updated pharmaceutical-specific microbiological specifications and field data from plants in active use. The consistency of the collected data and the perceived process mastery are the requisite basis from which concrete customer benefit can be drawn.
Specifications, requirements and customized solutions
A great deal of effort is put into supplying high purity, uncontaminated piping components for a variety of industries – piping components which often contribute to industrial advancements. A discussion on the subject of pure or ultra pure media should always include explicit specifications, clearly defining the intrinsic values and the tolerance range. Attention should be given to the corresponding guidelines of authorities, such as the FDA (US Food and Drug Association) in the pharmaceutical industry and the respective guidelines, regulations or the technical literature specific to an industry, which reflect the current state of the art.
Furthermore, it is important to consider the general requirement profile for the entire planned piping system including valves because today many sectors require a system solution from one source instead of a component solution from various suppliers. Regarding the valves in an ultra pure media system, attention should be given not only to the design and flow characteristics, but also the connection options, dimension range, surface quality, leach-out behavior, cleaning and automation possibilities. Naturally, the varied ambient conditions, as well as the price for the actual valve and maintenance and repair, should be taken into consideration in the planning.
Author:
Christina Granacher, Head of Global Market Development & Innovation,
Georg Fischer Piping Systems, Schweiz
Georg Fischer – Adding Quality to People`s Lives
GF Piping Systems is one of the three core businesses of the Georg Fischer Corporation and a leading supplier of piping systems in plastic and metal with global market presence. Connecting technology, fittings, valves, measuring devices and pipes are used for water conveyance and treatment as well as the transport of liquids and gases for industrial purposes. GF Piping Systems provides innovative, engineered solutions for the segments building technology, chemical process industry, cooling, life science, microelectronics, ship building, water and gas utilities and water treatment. Sales companies in more than 25 countries and representatives in another 80 countries ensure customer support 24 hours a day. Production sites in Europe, Asia and the US are near the customers and meet local requirements. The Georg Fischer headquarters is based since its foundation in 1802 in Schaffhausen, Switzerland.
Key figures GF Piping Systems 2008
More than 4’700 employees worldwide (per 31 December 2008)
1224 MCHF sales
122 MCHF EBIT
Further information is available at www.piping.georgfischer.com
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