This guideline provides general advice on the design of piping systems in the food industry. The focus will be on the design and installation of stainless pipes in closed hygienic (CIP cleanable) systems. The guideline is divided into chapters that can be read independently of each other. If read in its entirety, the guideline will contain repetitions, which is a deliberate choice. The guideline is prepared by the flow component task group under the auspices of the competence centre of the Danish steel industry. Guideline no. 1: Cabling and electrical cabinets – with focus on hygiene Guideline no. 2: Check list for the purchasesale of production equipment – with focus on hygiene Guideline no. 3: Conveyors – with focus on hygiene Guideline no. 4: Stainless steel in the food industry – an introduction Guideline no. 5: Design of piping systems for the food processing industry – with focus on hygiene Guideline no. 6: Installation of components in closed processing plants for the food processing industry – with focus on hygiene
Guideline no Design of piping systems for the food processing industry – with focus on hygiene Authors: Folkmar Andersen, Jens; Alfa Laval Kolding A/S Boye Busk Jensen, Bo; BioCentrum – DTU Boye-Møller, Anne R.; Danish Technological Institute Dahl, Michael; Danish Technological Institute Jepsen, Elisabeth; APV Nordic A/S Jensen, Erik-Ole; Arla Foods amba Nilsson, Bo; Senmatic A/S Olsen, Bjarne; Tuchenhagen GmbH Thomsen, Willy; Royal Unibrew A/S Prepared by the flow components task group under the auspices of the competence centre of the Danish stainless steel industry 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no Den Rustfri Stålindustris Kompetencecenter c/o Teknologisk Institut Holbergsvej 10 DK-6000 Kolding Tel.: +45 72 20 19 00 Fax: +45 72 20 19 19 info@staalcentrum.dk www.staalcentrum.dk This guideline is developed with the support of the Danish Ministry of Science, Technology and Innovation Published for the Centre by: Holbergsvej 10 DK-6000 Kolding www.teknologisk.dk © Danish Technological Institute ISBN: 87-7756-750-1 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no Introduction This guideline provides general advice on the design of piping systems in the food industry The focus will be on the design and installation of stainless pipes in closed hygienic (CIP cleanable) systems The guideline is divided into chapters that can be read independently of each other If read in its entirety, the guideline will contain repetitions, which is a deliberate choice The guideline is prepared by the flow component task group under the auspices of the competence centre of the Danish steel industry Guideline no 1: Cabling and electrical cabinets – with focus on hygiene Guideline no 2: Check list for the purchase/sale of production equipment – with focus on hygiene Guideline no 3: Conveyors – with focus on hygiene Guideline no 4: Stainless steel in the food industry – an introduction Guideline no 5: Design of piping systems for the food processing industry – with focus on hygiene Guideline no 6: Installation of components in closed processing plants for the food processing industry – with focus on hygiene Enjoy! Key words Piping systems, pipe runs, food industry, steel quality, hygiene design, requirements, welding, fittings, receiving inspection, mounting, inspection, flow, installation, construction, check list, plant layout 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no Contents Domain 1.1 1.2 Limitations Definition and use of guidelines Choice of steel quality 2.1 Recommended material selection for the food industry Design of piping systems 3.1 Drainability or not? Requirements for pipes and fittings Receiving inspection 10 5.1 Analyses for the inspection of deliveries 10 Storage 11 Welding of stainless steel pipes and fittings 13 7.1 7.2 7.3 7.4 7.5 Choice of material to be welded 13 Filler material 13 Welding from a product hygiene perspective 13 General welding requirements 14 Shielding gas 15 Welding requirements 18 8.1 8.2 8.3 8.4 Equipment 19 Welding preparation 19 Pipe welding 20 After welding 23 Mounting 24 9.1 9.2 9.3 9.4 9.5 9.6 10 Drainability 24 Pipe dimensions 24 Pipe layout 24 Seals at pipe joints 25 Pipe supports 25 Production stoppage precautions 25 Inspection of completed work 26 10.1 10.2 Weld inspection for deliveries 26 Installation inspection 27 11 Overview of other guidelines about piping, etc 27 12 Applied methods 29 13 Further information and literature 29 14 Change protocol 29 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no Domain This guideline provides general advice on the design of piping systems in the food industry Special attention points will be illustrated by drawings/photographs 1.1 Limitations The focus will be on the design and installation of stainless pipes in closed hygienic (CIP/SIP cleanable) systems for the food industry 1.2 Definition and use of guidelines The guideline can be used by construction engineers in connection with the design of new and the renovation of old plants It can also be used by chief installation engineers as a check list to prevent unsuitable installation Furthermore, the guideline contains knowledge for production supervisors of correct handling and storage of the supplied material It can also be used by purchasing officers when deciding on the specification of plant layout and parts Finally, the guideline can be used as a communication tool between purchasing officers and suppliers when coordinating their expectations for the delivery It is not the purpose of the guideline to recommend certain types of solutions or suppliers Choice of steel quality Stainless steel of varying quality is the most used material in the food industry for the construction of machines and processing equipment This is due to the ability of steel of forming a chromium oxide layer on the surface, which will appear smooth and whole, and have good mechanical properties, without the steel corroding When the chromium oxide layer disintegrates, the steel will corrode Basically, stainless steel is not a precious metal but a material which is more or less inactive to most environments Despite the many good properties of stainless steel, it is a complex material in which corrosion problems may arise due to wrong use or treatment This can lead to the premature replacement of processing equipment or machines For an introduction to stainless steel, please refer to Guideline no 4: Stainless steel in the food industry – an introduction 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no 2.1 Recommended material selection for the food industry Generally, the quality of steel should be selected according to the environment to which is will be exposed A change to a more corrosive environment (e.g changes in the product or detergent/cleaning procedure) may lead to serious corrosion attacks on the plant In the food industry, stainless steel grades below the following requirements should not be used (see the reason for this limit below and in section 7.1): Carbon content (C) max 0.05% Molybdenum content (Mo) 2.0% When using grades like AISI 304 and AISI 316, special attention should be paid to the carbon content This can be as high as 0.08%, which is too high if the steel is to be welded Table shows the most frequently used steel grades in the food industry, including the contents of the most important alloy constituents When choosing stainless steel for welding operations, a low carbon content is crucial to prevent the formation of chromium carbide The greater the material thickness, the longer the workpiece will take to heat during welding, and the lower the carbon content has to be 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no Table Stainless steels in various standards, grouped according to grade with a 2004 price index As prices of stainless steel are very dependent on the alloy constituents, the price index will fluctuate over time Steel grade C % Cr % NI % Mo % P % S % N % Price index (relative scale) Common stainless steel (austenitic) AISI 304 AISI 304 L EN 1.4306 SS 2333 EN 1.4301 Acid-resistant stainless steel (austenitic steel containing molybdenum) AISI 316 AISI 316 L EN 1.4404 SS 2347 SS 2343 EN 1.4401 EN 1.4436 Duplex steel (austenitic-ferritic steel) AISI 904 L AV 254 SMO SAF 2304 SAF 2205 (EN 1.4462) SAF 2507 max max max max max max max max max max 0.08 18.0 20.0 8.0 10.5 - 0.045 0.030 0.03 18.0 20.0 8.0 10.5 - 0.045 0.030 0.05 17.0 19.0 8.0 11.0 - 0.045 0.030 0.07 17.0 19.0 8.5 10.5 - 0.045 0.030 0.08 16.0 18.0 10.0 14.0 2.0 3.0 0.045 0.030 0.03 16.0 18.0 10.0 14.0 2.0 3.0 0.045 0.030 0.05 16.5 18.5 10.5 14.0 2.0 2.5 0.045 0.030 0.05 16.5 18.5 10.5 14.0 2.5 3.0 0.045 0.030 0.07 16.5 18.5 10.5 13.5 2.0 2.5 0.045 0.030 0.07 16.5 18.5 11.0 14.0 2.5 3.0 0.045 0.030 25.0 18.0 4.0 5.5 4.5 6.1 - - 0.03 20.0 20.0 22.0 23.5 21.0 23.0 4.5 6.5 2.5 3.5 0.14 0.03 24.0 26.0 6.0 8.0 3.0 5.0 0.30 0.03 0.01 0.01 max max max 100 130 300 400 0.10 170 190 400 Please note that although AISI 304 and EN 1.4301 are often regarded as identical, there may be small differences in the carbon content 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no Design of piping systems The design of piping systems must ensure a good future-enabled pipe layout by using the fewest possible components, and at the same time ensure optimal functioning of the plant There are many possible solutions for a pipe run Often, far more elbows than necessary are used because the designer did not give the layout enough thought An elbow too much means: • • • costs for the purchase of an elbow costs for the installation increased energy costs for the entire lifetime of the plant due to pressure loss It is therefore important to think everything through during the design phase! Figure Example of more elbows than necessary being used, which leads to increased costs During replacement of existing piping systems, the existing piping systems are often not dismounted while the new system is being built The existing piping system will often constitute an obstacle for the new system Therefore, the existing piping system has to be taken into consideration, and consequently the new system turns out to be less than optimal The focus should be on optimising the new piping installation It is better to change the old installation temporarily than to mount new pipes around it, with a poor outcome When planning the pipe layout, it will be useful to use 3D drawings or perspective drawings to illustrate the pipings It will be easier for the customer and the supplier to troubleshoot, avoid misunderstandings and find the optimal pipe layout together, before the final mounting is initiated This will facilitate the mounting process considerably 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no 3.1 Drainability or not? Two different operating situations are predominant in the processing industry: The first is that the plant must be emptied every time production has taken place, i.e it is very important that it can be drained of everything before the plant is left The second, and most widespread in recent years, is that the plant must be liquidfilled at all times This means that when a process has ended, a sterile liquid is fed to the plant and left there until the next process is started, when the sterile liquid will be displaced by the process liquids Regardless of the chosen solution, the plant must be designed so that it can be drained This is done by constructing the plant with a highest point and falls on both sides in the process piping system and by incorporating drains to ensure that the plant can be emptied of air, product and CIP-liquids It is highly unlike that the plant will never have to be emptied at some point Requirements for pipes and fittings • • • • • • • • The choice of steel quality must match the load and the environment to which it is exposed A sensible choice might be EN 1.4401, however with a maximum carbon content of 0.05% (see Table 1) Pipes must be round, and fittings must have round branch pipes There must be no oval cross sections at the ends of neither pipes nor fittings Special attention should be paid to elbows and plungings The inside surface roughness is industry dependent The typical requirement in the food industry is Ra < 0.8 µm Please note that according to international norms, there is a difference between specifying a “max value” and an ”upper value” (and similarly for a ”min value” and a ”lower value”) If e.g an "upper Ra value” of 0.8 is specified, it means that 16 per cent of the measurements can be higher than this value If, on the contrary, a ”max Ra value” of 0.8 is specified, no measurements can be higher than this value Measurements must 1) be based on sufficient statistical data (a sufficient number of measurements) and 2) be carried out on uniform flawless surfaces that are inside the basis of the estimate The inside surface should be passivated, pickled or electropolished Special care should be taken when welding electropolished surfaces as a far better gas protection is required for welding of surfaces which have been made “shiny” – e.g through grinding, electropolishing, etc There must be no scratches, holes, porosity or other surface defects on the product side of the steel Pipes must be delivered free of defects and clean on the inside as well as on the outside The pipes must be plugged at the ends and wrapped Fittings must be delivered flawless and clean on the outside as well as on the inside, and they must be wrapped, see figure All pipes and fittings belonging to the same mounting operation should have identical pipe diameters and material thickness, i.e be delivered in the same 2006-06-27 Version 1.0 In replacement of New Page of 29 Guideline no standard (DS, DIN, SS and similar) (Later a DIN pipe can, however, be welded onto a DS pipe It only requires that the pipe with the smallest diameter be milled to the same diameter as the other pipe) Receiving inspection Receiving inspection should ensure: • • • • • • • • • • That the delivered material contains no visible defects and impurities This may later on cause problems in the processing equipment where these impurities might accumulate That the material has been delivered in the agreed quality, and that the material comes with certificates verifying this That the supplied pipes are plugged at the ends and dry on the inside That the cross section is not oval in the material as this can cause root defects when welded Often the case in fittings That fittings are delivered in the right degrees/angles that were ordered That the inside surface roughness of pipes and fittings complies with the agreed requirements (often Ra < 0.8 µm) That pipes as well as fittings are pickled and passivated on the inside Special attention should be paid to welds That the longitudinal welding in pipes and fittings did not cause discoloration on the inside, see figure That fittings and pipes are wrapped That surfaces which come into contact with the product are free of scratches, holes, porosity and other defects that appear as cavities in the surface Figure Recently delivered pipes with discoloration in the longitudinal weld The pipe is a reject (A mirror is inserted into the pipe The picture shows the reflection) 5.1 Analyses for the inspection of deliveries The following techniques can be used for the inspection of received material and documentation of surface treatment and finish 2006-06-27 Version 1.0 In replacement of New Page 10 of 29 Guideline no A well-performed weld will not require any form of grinding but, in so far as possible, it should be pickled both on the inside and outside of the pipe This will increase the corrosion stability Pickling piping on the inside is difficult, and normally it is not done This makes it even more important to be meticulous with the gas protection in the pipe welds that cannot be pickled In general, it should be avoided to mix pipes of different standards (DIN/DS/EN ) as they may vary in terms of diameter as well as material thickness Should it become necessary to weld pipes with slightly different diameters, the smallest of the pipes must be milled to reduce the diameter difference between the pipes to < 20% of the material thickness Likewise, none of the pipes must be oval or out of flush with each other (eccentric), and the deviation must be < 20% of the material thickness (see figure 6, 3) All pipes and surfaces that are to be welded must be straight, and to ensure perpendicular cuts, mechanical cutting devices should always be used for cutting pipes The distance between workpieces to be welded must be [...]... welding • • • • • After welding, the welder must perform a visual check of the welds on the inside as well as on the outside of the pipe Internal inspection of piping systems is performed by endoscopy The inspection of the welds must show no signs of oxidation and weld splatter around the concavity/convexity of the weld as shown in figure 12 The weld is pickled on the outside with pickling paste When... receipt of the video In matters of dispute, an impartial party will be chosen as arbiter The losing party shall bear the costs for said impartial party The supplier shall bear the costs for any of the above endoscopies, videos etc performed by the supplier The customer shall bear the costs for any of the above endoscopies, videos etc performed by the customer as control inspections Requirements for weld... assessment of the hygienic design of equipment The guideline can be bought at EHEDG: http://www.ehedg.org EHEDG Doc 10, 1992: Hygienic design of closed equipment for the processing of liquid food The guideline deals with specific examples of good and poor design of different components and piping systems in closed processing equipment Some these are: gaskets and couplings, shaft insertions and dead pockets The. .. lifetime of the installation This means that if there is corrosion over time in a weld, but not in the base material, it will be deemed as failure on part of the supplier of the plant Therefore, the supplier must also provide a warranty for weld stability Such warranty should not be less than 5 years Should there be corrosion in the welds (the weld zone), but not in the pipes, the supplier of the plant,... plant, the client (the food manufacturer) selects the steel grade based on the anticipated environmental strains the steel will be exposed to Once the steel grade is selected, the requirement will be that the welding of the plant does not reduce the quality of the installation With respect to corrosion, the welds must in principle withstand the same environmental strain as the base material throughout the. .. pickled on the inside Any subsequent internal inspection of piping systems is performed by endoscopy The supplier of the plant must prepare a welding specification describing how the requirements for the welding procedure are met and how compliance with the procedures is checked regularly during the entire construction phase The client determines the procedure for control and inspection of the finished... always be used for cutting pipes The distance between workpieces to be welded must be