Hygenic piping Guidelines

 

Hygenic piping Guidelines in Large scale Industries

"This guideline has been developed to help you with systems design for food and beverage industrial manufacturing, no matter it is a new installation, replace an existing one, process upgrade, or factory production increase."

Sri Pumps has created a checklist to guide you through the entire process, from design to installation and testing. It's crucial to consider the appropriate cleaning system for the production process. The piping system should be built to withstand the chosen cleaning system, such as Clean-in-Place (CIP) or Steam-in-Place (SIP).

In sanitary processing plants, the surface finishing is of utmost importance. It must meet certain criteria to ensure it is smooth enough to prevent any dirt or particles from sticking to the processing product. If the system does accumulate dirt or particles, it needs to be cleaned using the CIP or SIP system.

Food equipment surfaces could be subdivided into two categories:

1. Food product contact surfaces.

2. non-product contact surfaces.

Food product contact surface: is defined as a surface in "direct contact with food residue, or where food residue can drip, drain, diffuse, or be drawn". For sanitary design, all food contact surfaces should be:

• smooth;
• impervious;
• free of cracks and crevices;
• nonporous;
• non-absorbent;
• non-contaminating;
• inert;
• corrosion resistant;
• durable and maintenance-free;
• nontoxic; and
• cleanable

If the surface of the equipment is covered with any type of coating, whether it's a metal alloy or non-metal material like ceramics, plastic, or rubber, it needs to meet the previously mentioned requirements. According to 3A Standards, these coatings should have good corrosion resistance and should not show any signs of surface pitting, flaking, chipping, blistering, or distortion when used as intended.

It's important to pay attention to all the parts of the equipment that don't come into direct contact with the product, such as legs, supports, and housings. Even though these surfaces don't directly touch the product, they can still become a source of contamination. Therefore, it's necessary to consider their sanitary design and ensure they are properly designed and maintained to prevent indirect product contamination. 

Materials:

Different materials are used to make equipment for food and beverage applications, and each material has different properties that affect how it can be used.

Metals:

Stainless steel: This is the best metal for surfaces that come into contact with food and beverages. The properties of stainless steel depend on the levels of chromium and nickel in the alloy. The more chromium it has, the better its resistance to corrosion, and the more nickel it has, the stronger it is. Low carbon content is preferred for welding.

Titanium It is highly durable and resistant to corrosion, especially in acidic environments. However, it is expensive and used mainly in stainless steel alloys for processing highly acidic or salty food products.

Platinum:  It is an excellent corrosion-resistant material, but it is too expensive to be practical for widespread use.

Gold: In certain cases, gold is approved for use in food contact surfaces according to sanitary standards. It is used for soldering optical sensors into stainless steel fittings due to its abrasion resistance and compatibility with glass.

Other metals are limited by application as follows:

Copper: is primarily used for the equipment used in the brewing industry, with some use for cheese vats in Swiss cheese manufacture, due to tradition. Care should be used with copper equipment when processing acid products, as copper residues can leach into the product.

Aluminum: is used in certain parts and components where lighter weight is desired. However, aluminum has poor corrosion resistance and can become pitted and cracked with continued use. Care should take when cleaning and sanitizing aluminum components as oxidizing chemicals can accelerate the pitting of the metal. In most food contact applications, aluminum must be coated with an acceptable material. Plastic coatings such as polytetrafluorethylene (PTFE or Teflon) are common.

Carbon steel: and cast iron are only used for frying and cooking surfaces, and similar applications in food service

Galvanized iron: should be avoided as a food contact surface because it is highly reactive with acids. (Folkmar Andersen & A/S, 2006)

Non-metals:

Various non-metal materials are used in specific applications, such as probes, gaskets, and membranes. These materials should meet sanitary design and cleanliness requirements similar to metals. However, they are generally less resistant to corrosion and less durable, so regular inspections and replacement may be necessary.

Non-metal materials used in food contact surfaces include:

• Plastics, rubber, and rubber-like materials that should be food grade and should meet the requirements designated under 3A Sanitary Standards (18-03and 20-20). Multi-use plastics, rubber, and rubber-like materials may also be considered indirect food additives under FDA regulations.

• Ceramics are used primarily in membrane filtration systems. They may also be used in other limited applications if wear resistance is necessary.

• Glass may be used as a food contact surface. These applications are limited due to the potential for breakage. Specially formulated glass materials such as Pyrex® have proven successful. When glass is used, it must be durable, break-resistant, or heat-resistant glass. Some applications where glass is used are light and sight openings into vessels and in very limited glass piping applications.

• Paper has been used over the years as a gasket material in piping systems designed for daily disassembly. Paper is considered a single-use material.

• Wood, which is highly porous and difficult to clean, should be avoided as a food contact surface. Wood is restricted in food service applications by most regulatory agencies, with the exception of hardwood cutting boards and tight grain butcher blocks.

Surface Texture and/or Finish:

If any surface is ground, polished, or textured, it should be smooth, durable, and free of cracks and crevices to meet sanitary design requirements.

Piping Design:

Before discussing piping design, it's important to understand two terms:

Cleanability: The ability to clean surfaces easily and without damage. All surfaces should be accessible for cleaning solutions to establish and determine the effectiveness of the cleaning process. Surface imperfections should be eliminated whenever possible.

Drainability: The ability of the system to drain by gravity. Gravity drainage is effective for sterilization and cleaning. Piping should be designed with the appropriate slope to facilitate drainage.

Pipework:

The material and roughness of pipes should meet the minimum requirements specified by international standards for each industry.

• When working with the inside surface of an object, it's important to treat it properly. This can be done by passivating, pickling, or electropolishing it. Passivation protects the surface from corrosion, pickling removes impurities, and electropolishing makes it smooth and shiny. However, when welding surfaces that have been electropolished or made shiny through processes like grinding or electropolishing, extra caution is needed. These surfaces require improved gas protection during welding. Therefore, it's important to take special measures to ensure a safe and effective welding process, such as using the right gas shielding techniques.

•The product side of the steel should be in perfect condition with no scratches, holes, porosity, or any other surface defects. It is important to have a smooth and flawless surface on the product side of the steel.

• When delivering pipes, it is important to ensure that they are free from any defects and are clean both on the inside and outside. This means there should be no imperfections or damage on the surfaces of the pipes. Additionally, the ends of the pipes should be securely plugged, and the pipes should be properly wrapped for protection during transport.

• When it comes to delivering fittings, it is crucial to ensure that they are in perfect condition, without any flaws or defects. This applies to both the exterior and interior surfaces of the fittings. Additionally, the fittings should be thoroughly cleaned to remove any dirt or debris. To protect them during transportation, it is important to wrap the fittings appropriately.

• 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 standard (DS, DIN, 3A, SMS, or other). (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). (Folkmar Andersen & A/S, 2006)

Piping Layout:

Process piping would be installed to meet with standards:

• Continuous slope for correct drain ability-. The pipe layout must be designed to reduce pressure loss as low as possible using a few elbows, branch tees, etc.

• Dead pockets/blind ends are not allowed.

• To avoid undrainable pockets, for horizontal pipelines use eccentric reducers to change pipe diameter. For vertical pipes use of a concentric reducer is allowed. Change of pipe diameter is not allowed without the use of proper sanitary reducers.

• For pipe expansion due to temperature changes insert a lyre or an expansion joint. Stainless steel expands by more than 1 mm per meter per 100°C heat increase. For correct slope:

• Adequate spacing of supports to avoid liquids traps

Tubing

A tube, or tubing, is a long hollow cylinder used for moving fluids (liquids or gases). Stainless steel tubing for the Brewery, Food, Dairy, and Pharmaceutical Industries must be manufactured in 304L & 316L polished on the ID from 32u-­in to 20u-­ in Ra;

Sanitary Gaskets

Thousands of gaskets are used daily throughout food and beverage processing plants at every hygienic union. They are inserted between two flanges and connected using a Clamp and or threaded Nut. Biopharmaceutical processes usually require one or more Steam-­In-­Place (SIP) cycles per production batch. Depending on the requirements and the location in the process, the number of SIP exposures that a seal may be subjected to may be as high as 20 to 30 SIPs per production batch. In the Food and Beverage Industry, automated Clean-­In-­Place (CIP) operations are more common place today. One cleaning per production batch is typically required, and cleaning cycles usually consist of weak caustic acid and/or bleach solutions at elevated temperatures.

Most common sanitary gaskets are elastomer materials

Buna-­N (NBR): Will handle most food, dairy, beverage, and sanitary services. It is the backbone of the food and edibles processing industries and has excellent resistance tocompression set, tear, and abrasion. It has good acid and milk-alkali resistance and is good for vegetable oil service. Rated at -­40° F to 225° F.

EPDM: Excellent for hot water and steam service up to 275°F. EPDM is very abrasion resistant and has excellent resistance to ozone, sunlight or weather, and de-­ionized water. EPDM also has good tensile strength and good resistance to mild acids, alkalis, and alcohol. Rated at -­55° F to 275° F (short term to 400° F).

Silicone: (VMQ): Known for its standard of purity and non-­leaching characteristics. Its ability to withstand many chemicals and combinations of chemicals is the reason it is so popular with the pharmaceutical industry. Silicone has excellent low-temperature flexibility -­ to -­100°F in dry heat;; 400°F is the maximum for continuous duty with 600°F possible for short periods of time. Rated at -­80° F to 400° F (short term to 600° F).

Teflon PTFE: The material of choice whenever low-temperature flexibility or hygienic seal memory is not required (not recommended where large temperature variations occur frequently, leakage can occur). PTFE has almost not extractable, has a low absorption rate, and excellent resistance to process fluids. It can remain in service for longer periods of time in both water and steam for continuous use, high pressure clamps are recommended to prevent leakage resulting from temperature variations.

A PTFE envelope hygienic seal with an FKM Fluoroelastomer inner core should be used if slight misalignment is observed. 

Envelope: Almost universal chemical inertness. This gasket is a composite construction being a PTFE outer case, in contact with the media, and an FPM. Filler that provides elasticity. Temperature range from -­ 20°F to 400°F

Sanitary Fittings

One of the elements on the piping systems are fittings, let's say elbows, branch tees & branch yees, concentric & eccentric reducers, etc.

Following a different international standard as DIN, ASME, ISO, SMS, 3A,

Fittings are made in different dimensional standards, metric or inches, take care that pipe dimensions and thickness match with the fittings you choose to avoid problems in the welding development.

Following we will try to illustrate some of the most used fittings for hygienic piping systems:

Equal Tee Reduced Short Tee Concentric Reducer Eccentric Reducer

Sanitary Valves

Valves are process components that provide dynamic seals within the process. Is a device that regulates, directs, or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings

but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. They also provide seals between the process and the atmosphere. (ASME-­BPE, 2014)

Ball Valves:

This popular valve is a form of the quarter-­turn valve which uses a hollow, perforated and pivoting ball (called a "floating ball") to control flow through it. It is open when the ball's hole is in line with the flow and closed when it is pivoted 90-­degrees by the valve handle.

Butterfly Valve:

It is from a family of valves called quarter-­turn valves. In operation, the valve is fully open or closed when the disc is rotated a quarter turn. The "butterfly" is a metal disc mounted on a rod. (unknown, Wikipedia article butterfly valves, 2015) The seal creates a dynamic seal when the disc is rotated into the closed position the same seat also forms the primary stem seal to prevent sealing through the stem journal. (ASME-­BPE, 2014)

Relief valve:

The relief valve (RV) is a type of valve used to control or limit the pressure in a system or vessel which can build up for a process upset, or instrument or equipment failure. Vacuum safety valves (or combined pressure/vacuum safety valves) are used to prevent a tank from collapsing while it is being emptied, or when cold rinse water is used after hot CIP (clean-­in-­place) or SIP (sterilization­in-­place) procedures. When sizing a vacuum safety valve, the calculation method is not defined in any norm, particularly in the hot CIP / cold water scenario, but some manufacturers have developed sizing simulations. (Unknown, 2015)

Check Valves:

A non-­return valve or one-­way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. The valve seat is closed either by mechanical means of spring or by process fluid that the flow stream is blocked. (Unknown, Wikipedia Article Check Valves, 2015) The body cavity may be sealed by a static seal. The seat can be sealed by an O-ring seal. (ASME-­BPE, 2014)

Material receiving & Inspection:

Material Reception

• Check the following points carefully when the material arrives:
• Material has been delivered in the agreed quality, and make sure mill certificate numbers match with heat numbers engraved on pipes and fittings.
• Fittings and pipes are wrapped according to the specifications.
• Longitudinal welding in pipes and fittings does not show any discoloration on the inside.

Material Storage:

Once the receiving inspection has been completed, pipes and fittings must be resealed to avoid impurities and/or small insects coming into the pipe and fittings. All materials (Sheets, Pipes, Valves, and Fittings) must be stored in a dry, dust-free room (Folkmar Andersen & A/S, 2006)

Welding:

In every project, it is necessary to have a clear welding specification that outlines the requirements for how the welding should be done, how it will be controlled, and how the final job will be inspected. If the completed job doesn't pass the inspection or doesn't meet the quality standards set, the inspection should be made more thorough than initially planned. Any defects found during the inspection must be fixed. It's important to note that only certified welders should be entrusted with the task of welding product pipes. This ensures that the welding work is carried out by skilled professionals who have the necessary qualifications.

Welding Roughness

The normal roughness of a well-­performed weld will be approx. 1.6 to 4 μm. The maximum roughness accepted on the product side is 6 μm.

Shielding

• During stainless steel welding, shielding gas must be used at all times, both on the front and on the backside of the weld zone. The purpose of the shielding gas is to prevent the access of oxygen to the weld area.
• Insufficient shielding will become in the oxidation of the heat-­affected weld zone. This will reduce stainless chemical properties.
• Often, argon is used in the welding gun and as gas protection inside pipes

Equipment required for welding

The following equipment is expected to be required:

• TIG welding unit with pulse box. (Manual and/or Orbital)

• Oxygen meter to check residual oxygen content at the shielding.

• Flow meter to control the inert gas supply. For welding guns and for pipe shielding

• Shielding gas Argon and Pickling paste to passivate stainless after the welding procedure.

• Orbital pipe cutter. (Folkmar Andersen & A/S, 2006)

Welding Preparation

For piping installations, observe the following guidelines:

• All pipe fitting materials (couplings, unions, valves, etc.) must be at the mounting side temperature to prevent condensation inside the pipes, which may cause welding defects Joint design for hygienic tubing and fittings shall be square butt joints.
• The tubing and fittings shall have ends prepared by machining or facing to provide square ends.
• The butt weld joints shall be properly cleaned within 1” (25mm) of the joint area on the inside and outside surfaces prior to welding.
• Welding on the tube will be done using an orbital welding machine, except where the size or space will not permit In that case, manual welding can be performed.
• Pipe ends must be free of burrs.
• Pipe ends to be welded must have identical inside and outside diameters. In case of any difference, the smallest pipe must be expanded to the big inside diameter.
• When using fit-­up clamps for pipe ends, the contact face must be stainless.

After Welding

• Weld piping systems must be inspected by endoscopy.

• The weld is pickled on the outside with pickling paste. When possible, it is also pickled on the inside. (Folkmar Andersen & A/S, 2006)

Installation:

Proper Slope for correct Drainability

Pipes must be mounted so as to be fully drainable (minimum incline of 0.29°).

If the location prevents drainability problems, valves must be built in at all low points of the installation.

Slope measurements should be taken with a calibrated digital level or protractor per ASME Bends, Branch tees, and other fittings to guarantee correct drainability. (ASME-­ BPE, 2014)

Recommended Mounting Practices

Supports and hangers must be installed in close proximity to each change in direction of piping, with consideration of pipe movement due to thermal expansion and the use of anchor and guide inserts to facilitate intended pipe movements.

Supports and hangers will be installed as close as possible to any concentrated loads, such as valves, instrumentation, and other process components. It may be necessary to install on both sides of certain loads to reduce deflection and ensure proper continuous slope for drainability.

• Anchoring systems should be designed to accommodate piping motion including thermal expansion. (Folkmar Andersen & A/S, 2006)

Spacing of Pipe Hangers

Hangers and/or supports shall be spaced as far apart as economically possible, with due consideration to assure that the sag of the pipe between supports is within limits that will permit drainage and also avoid excessive bending stresses from concentrated loads such as valves and in-­line equipment.
The contractor shall use the maximum recommended spacing between pipe support specified below.
Additional hangers may be necessary to adequately support concentrated loads such as valves, flanges, or instruments.

Installation inspection:

Welding Inspection

1.-­Verify all welding tests and reports approved by the Quality Assurance team from welders who carry out welding operations during installation.

2.-­ A minimum of 5 percent of all pipe welds must be endoscopies welds and must subsequently be individually identifiable and recorded.

3.-­ If defects are detected, an extended endoscopy inspection is made on 10 of the welder’s latest welds. If further defects are found,

the welder in question must have his certificate renewed. Before the welder can perform welding operations on installations again, he must perform three supervised, error-­free welds on setups selected by Quality Assurance Team.

4.-­ If defects are detected during 2.-­, further endoscopy inspection must be carried out on 5 percent of the other welds that were not referred to under 3.-­.

5.-­ Endoscopy must be carried out regularly – weekly – and a video copy hereof must be sent to Quality Assurance Team, as the inspections are performed.

6.-­ The customer reserves the right to carry out his own endoscopy to an extent chosen by him, and documented defects must be subject to the procedures in steps 2.-­, 3.-­, and 4.-­. (Folkmar Andersen & A/S, 2006)

Pipework Inspection

The layout of the mounted pipe runs is sensible and according to the project specifications.

the selected pipe dimensions, valves, and other equipment are sensible to mounting requirements and guidelines have been observed.

If a plant inspection shows inside discolorations from welding, and there is no root defect in the welds, the discolorations can be removed by pickling.

The pickling procedure must ensure:

• Rubber gaskets pump mechanical seals and similar materials are not damaged

• pickling does not represent any kind of danger or hazard to persons and the environment

• No valves and measurement equipment is damaged

• The pickling procedure must be approved by the customer and his safety representative before it can be implemented! (Folkmar Andersen & A/S, 2006)