Sanitary Fittings and Tubing for Food Processors

Introduction

Sanitary tubing and fitting types (referred to collectively as “piping”) and the standards that regulate their use have evolved over the years by trial and improvement. Consequently, a great variety of sanitary piping and standards are in use today. This fact sheet briefly explains the most common sanitary piping and standards and how they are applied. A section with sources of sanitary piping materials is also included.

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Materials

Stainless steel is the most common material used in sanitary piping. This metal has the advantage of cost, corrosion resistance and durability, relative to other materials. Table 1 shows some of the grades of stainless steel and their description. In general, the higher the grade, the better the corrosion resistance. Price increases with grade.

Table 1. Selected grades of stainless steel with brief descriptions.

Surface finish

Description of surface finish of stainless steel components is often confusing, since different reference scales are commonly used, depending upon industry and custom. Two of the most important scales used to measure surface roughness are: Ra and grit. Ra is the “roughness average” specified in the ANSI/ASME standard B46.1 -. The Ra value relates to an arithmetic average of the surface roughness as measured by the stylus motion of an instrument. For comparative purposes, an Ra of 4 corresponds to a “mirror” finish. In the dairy and food industry, surface finishes have traditionally been measured by grit. Grit is the number of abrasive grains per given area. The higher the grit number, the smoother the finish (similar to traditional sand-paper). Table 2 gives a guide for comparison of Ra and grit finish measurements. Comparison of grit to Ra finish is not exact and requires consideration of variable elements such as polishing equipment, materials and technique.

Table 2. Guide to comparison of grit finish and Ra (micro-inch) measurements.

Electro-polishing is a finishing technique that results in a smooth surface due to a chemical-electrical treatment that is most often applied after mechanical polishing steps. Electro-polished piping usually carries the initials “EP” and has a superior, mirror-like finish.

Product piping is polished on the inside, as a minimum, since the product-contact surface should be smooth to prevent attachment of soils and microorganisms. Polished finishes on the outside of piping are normally specified for appearance or to facilitate cleaning. Piping surfaces that are covered with insulation are often specified as unpolished. Industrial grade (mill finish) piping is frequently used for potable water, cleaning solutions or other applications where soil residues and microbial levels are low. Table 3 describes industry standard finish numbers commonly used for food and dairy tubing.

Table 3. Finish number and description for sanitary tubing.

Sanitary Tubing 

Fortunately, the wide acceptance of seamless stainless steel tubing and standardization within the metals fabrication industry has simplified tube selection. Outside diameter and gage is used to specify sanitary tubing. Sixteen-gage tubing is used for the vast majority of applications, except those with large-diameter and/or higher product pressures. Specifications for sanitary tubing are shown in table 4. Tubing is manufactured according to ASTM A270 “Specification for Seamless and Welded Austenitic Steel Sanitary Tubing.”

Table 4. Specifications of sanitary tubing.

Sanitary Pipeline Fittings are manufactured by a long list of companies utilizing a number of joint styles and sealing techniques including (in no particular order): Tri-Clamp or “clamp,” Butt-weld, Bevel Seat, DC, H-Line, HDI-Line, John Perry, S-Line, and I-line. Fitting types have been developed specifically for certain industries, manufacturers and user groups. Adaptors to connect different types of fittings are sometimes available, as well as adaptors to connect fittings to non-sanitary piping such as flanges, pipe thread, pipe OD (compression fitting) and other items. The system designer must select carefully, especially when mating new piping to existing piping and equipment.

In Oklahoma, clamp (figure 1) and bevel seat (figure 2) fittings are the most common for systems that require frequent disassembly. Butt-weld fittings (figure 3) are used for permanent piping systems. Hygienic design and sanitation standards for sanitary fittings and pipeline have been developed by and are available from the 3-A Sanitary Standards Institute (McLean, Va.). Fittings that have been manufactured according to the 3-A specifications and standards bear the 3-A symbol and are accepted nationwide by health inspectors. Sanitary fittings conform to an identification system based on numbers, with examples given in table 5.

Figure 1a. Disassembled clamp fitting, clamp and gasket

Figure 1b. Disassembled clamps

Figure 2. Bevel seat fittings

Figure 3. Butt-weld fittings

Table 5. Selected identification numbers of sanitary fittings.

Food-Grade Gasket Materials

As specified by the 3-A standards, food-grade rubber and plastic material can be used for gaskets in sanitary joints. Table 6 lists selected 3-A approved commercial gasket materials and their working temperature range.

Table 6. Selected list of approved gasket materials and their operating temperature range.

Pipeline Installation

Extreme care and planning must be considered before installation of sanitary pipelines. Professional help should be employed when possible. Installed cost of stainless piping can run from $30 to more than $300 per foot, depending upon many factors. Orbital welding techniques are used to join pipe fittings to tubes or equipment as necessary. Inert gas is employed to prevent weld contamination. Subsequent polishing steps may be necessary, depending upon welding methods selected. Pipeline installation mistakes and rework are costly. Some installation tips follow:

• Begin your project with a drawing (three-dimensional if possible) and include clearance areas for operations, cleaning and maintenance activities.
• Design to minimize piping, valves, joints and fittings.
• Slope lines to facilitate self-draining.
• Support piping at ample locations, considering thermal expansion and dynamic product loads.
• Potable water lines connected directly to sanitary tubing are a violation of plumbing code; lines must be isolated with a physical “air gap.”
• Use check valves and vacuum breakers in steam lines connected to sanitary tubing or cook vessels to prevent product “suck-back.”
• Eliminate dead legs that contain stagnant product in process lines.
• Use flexible connections (hose) at pumps, tanks and other devices that may be moved or frequently disconnected.
• Install quick-release fittings to facilitate cleaning and inspection.
• Insulate only when necessary to prevent operator injury or to protect product.
• Costs of installed piping systems can be dramatically reduced by prefabrication at an outside shop. Use of clamp fittings will facilitate shipping and eliminate or reduce the number of costly on-site welds needed. Warning–precise dimensions and specifications are required!

Summary

Sanitary piping systems are an important part of many food processing operations. When designed, fabricated and installed correctly, they require minimal attention and help to maintain product quality and integrity. Awareness of the great variety of fittings, materials, type and sizes of components available will help during the selection and installation of any sanitary piping system.

Select Sources of Sanitary Tubing and Fittings

National distributors/manufacturers

Alfa Laval

104th Street

Pleasant  Prairie, WI

800-558-

www.alfalaval.us 

Robert-James Sales, Inc.

PO Box

Walden Ave.

Buffalo, NY

800-666-

www.rjsales.com 

Top Line Process Equipment

P.O. Box 264

Bradford, PA

800-458-

www.toplineonline.com 

Waukesha Cherry-Burrell

611 Sugar Creek Road

Delavan, WI 

800-252-

www.gowcb.com 

SwageLock

Tulsa Valve & Fitting Co.

West Detroit

Broken Arrow, OK

918-258-

www.swagelok.com

Local food equipment supplier:

Crouch Supply Company, Inc.

413 Northwest 5th Street

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Oklahoma City, OK

405-235-

Local and mail-order dairy equipment suppliers

Double H Dairy Supply

Pryor, OK

918-825-

Farm Supply Inc.

Chickasha, OK

405-224-

Parts Dept

45 Lynwood Drive

Trumbull  CT 

800-245-

www.partsdeptonline.com 

Meltec Dairy Supplies

Country Farm Drive

Naperville, IL

877-973-

www.meltec.net 

References

3-A Sanitary Standards, Inc., Dolly Madison Boulevard, Suite 210, McLean, VA, -. website: www.3-a.org. 

ASTM (American Society for Testing and Materials), 100 Barr Harbor Drive, West Conshohocken, PA -. website: www.astm.org.

Tim Bowser
FAPC Food Process Engineer

Many industries use stainless steel fittings with tube / pipe lines to transfer liquids and other product around their plant facilities. These industries include food and pharmaceutical sectors or building and construction.

• Stainless steel fittings are critical for the food and pharmaceutical industries as they are non-toxic, stain resistant, easy to clean and provide excellent life cycle costing. 
• Stainless steel fittings are critical for the building and construction industries as they are corrosion resistant and able to withstand high pressure. 
• Stainless steel balustrading is now common place and serves as a stunning and cost-effective alternative to other materials.

Detailed below are several types of stainless steel fittings.

Stainless Steel BSP Fittings

BSP is an acronym for British Standard Pipe and is a common pipe thread in Australia. Commonly stocked stainless steel BSP Fittings are BSPT (tapered. Also known as an R thread) male fittings and BSPP (parallel. Also known as a G thread) female fittings. When these two thread forms are screwed together with thread tape as a sealant they will bind and seal across only one or two threads for a leak proof connection.

There are many fittings available and here is a list of commonly stocked items:

• Sockets
• Hex Nipples
• Reducing Nipples
• Barrel Nipples
• FF Elbows
• MF Elbows
• Tees
• Toe Nipples
• Tube Toe Nipples
• Male Hose Barbs
• Barrel Unions
• Reducing Bushes
• Reducing Nipples
• Reducing Sockets
• Hex Plugs
• Locknuts
• Nut & tails
• Crosses
• Hex Caps
• All Thread
• Thread Tape

Stainless Steel NPT Pipe Fittings

NPT is short for National Pipe Thread / Taper an American standard for pipe threads. NPT pipe fittings are similar to BSP but with a 5 degree difference in the thread angle.  Also the male and female fittings are tapered to prevent the different threads being readily interchangeable. The NPT Pipe Fittings generally stocked are lb high pressure.

316 stainless steel NPT fittings include:

• Hex Nipples
• Toe Nipples
• Barrel Nipples
• Cross Over Nipples  (NPT to BSP male adaptors)
• Hex Plugs
• Hex Caps
• Elbows
• Barrel Union
• Reducing Bushes
• Reducing Nipples
• Couplings (or sockets , but referred to as couplings in NPT as the internal thread is not continuous throughout the fitting)

Stainless Steel Sanitary Fittings

There are many types of stainless steel sanitary / hygienic fittings. Below are some of the more common fittings used in Australia.

• BSM Unions– BSM stands for British Standard Milk (originating from the milk industry). These consist of a BSM Male, Liner, Nut and O-Ring. The hexagon nut holds the male with the O ring and liner together. The unit is tightened with a special BSM spanner. BSM blank caps and BSM blank nuts are available to blank off a male at the end a of line.

• Triclover Unions – or Tri Clamp Unions or Ferrule Fittings are referred to as a sanitary fitting due to their clean nature and lack of thread. They have 2 body halves (Triclover ferrules) which have a butt-weld end to suit tube, and a face side which accommodates a seal and is then brought together with a finger nut clamp. Triclover Blank caps are used to blank off a ferrule at the end of a line. There are many different seal materials, including EPDM, Silicon, Teflon, Viton & Buna. (Buna AKA Nitrile Rubber)

• DIN Unions – A DIN union comprises a male, nut, seal and liner. They typically have a D profile EPDM seal and a four slot nut. Australia is seeing an increase in the use of DIN fittings as more equipment is imported from Germany. The acronym D.I.N translates from German as Deutsche Industrie Normale. Just as we have A.S. for the Australian Standard and B.S for the British Standard, this is the German Standards institute prefix.
• Wine Unions – originated in Australia for the wine industry, and consist of a Wine male, liner, seal and nut. The brass wing nuts are unique to this union. The seal sits over the liner. The wine nuts are available in stainless steel wing and slotted configurations. A robust plastic wing nut is available in 2” only. Blank caps and blank nuts are available to blank off the males at the end of a line.

Keystone and Dixon Valves

Hygienic Keystone F250 Butterfly valves are used throughout the food and beverage industry as an isolation or ‘modulating’ valve. The Keystone F264J Check Valve is a hygienic one way /  Non Return Valve. The Dixon brand has a similar product range of hygienic butterfly valves and check valves.

All end connections are standard tube butt-weld. This allows them to be fitted with specific process connections such as the sanitary fittings detailed above.

Stainless Steel Butt Weld Pipe Fittings

Stainless Steel Pipe fittings (as opposed to Tube fittings) are a butt weld fitting for direct welding onto pipe. They are produced in different  ‘schedules’. The schedule determines the wall thickness according to the nominal bore pipe size. Schedule 10 and 40 are commonly available but schedules 80 and 160 are also produced.

The range comprises of:

• Long Radius 90 degree Elbows
• Long Radius 45 degree Elbows
• Short Radius 90 degree Elbows
• Tees
• Reducing Tees
• Concentric Reducers
• Eccentric Reducers
• Caps

Stainless Steel Clamps

When installing tube / pipe lines then stainless steel clamps and saddles may be required to attach them to walls, ceilings or beams. The tube clamps are a T Slot hinge one side and bolt/nut/washer the other. These are made of stainless steel 304 material. Some larger sizes of tube clamps are made as a double bolted tube clamp, having bolts/nuts on each end of a ‘saddle’ style clamp. For smaller tubing a saddle or Stauff Clamp (plastic 2 piece body with stainless top and bottom plates) can be used.           

Pipe clamps are also a 2 piece double bolted saddle style clamp suitable for clamping pipe in place. These are made from heavier stainless steel 304 flat bar for heavier duty industrial applications.

Stainless Steel Compression Fittings

Twin ferrule stainless steel compression fittings are a unique way of crimping fittings onto stainless steel cold drawn seamless tubing without special tools. The two ferrules are swaged onto the tube via rotation of the nut, and once installed correctly will give you a leak-tight high-pressure seal.

 Stainless steel compression fitting come in the following types (and more) to suit all applications:

• Tube Unions
• Reducing Tube Unions
• Tube Union Elbows
• Tube Bulkhead Unions
• Tube Union Tees
• Male Connectors
• Female Connectors
• Male Elbows
• Female Elbows
• Male Bulkhead Connectors
• Female Male Bulkhead Connectors
• Male Adaptors
• Male Branch Tees
• Female Branch Tees
• Ferrule Sets

Stainless Steel Camlock Fittings

Camlock Fittings (also known as Cam & Groove fittings) are a simple male and female coupling. The male fitting slides into the female fitting, then the cam levers on the female fitting are pulled down to lock into place. To un-couple, just lift the levers up.

Both the Male and Female configurations are available to BSP Male, BSP Female, Hosetail, and as a plug or cap. Additionally there is a male to butt-weld end to suit tube.

Camlocks are widely used on tankers and in any industry that relies on fluid conveyance through hoses.

Stainless Steel Tube Fittings

Stainless steel tube fittings are all the connecting fittings that butt weld to tube. These fittings are measured on the outside diameter of the tube and are available in grades 304 or 316 stainless. The main forms are:

• Tube bends in 45 degree, 90 degree, 180 degree and 1x Diameter short radius 90 degree
• Tube concentric and eccentric reducers
• Tube tees in equal, reducing, swept and 45 degree branches
• Tube crosses
• Tube Y pieces
• Tube dome caps
• Tube end discs
• Tube hose tails
• Tube sealing flanges

Stainless Steel Flanges

Stainless Steel flanges are used to connect pipe, tube, valves, pumps and other engineering products. They can be welded or screwed onto pipe or tube and then bolted to the mating flange. A flange gasket between the two mating flanges will seal the joint. There are numerous ‘standards’ of flanges with specifications originating from many different countries. Below are some of the more commonly used in Australia.

• Table D SOW Tube
• Table D SOW Pipe
• Table D Blind
• Table E SOW Tube
• Table E SOW Pipe
• Table E Blind
• Table E BSP Threaded
• ANSI 150lb SOW Tube
• ANSI 150lb SOW Pipe
• ANSI 150lb Blind
• ANSI 150lb BSP Threaded
• ANSI 300lb SOW Pipe
• ANSI 300lb Blind
• DIN PN16 SOW Tube
• DIN PN16 SOW Pipe
• DIN PN16 Blind

Flange Gaskets

A flange gasket between the two mating flanges will seal the joint. The gaskets are made to the dimensions of the flanges and there are many different materials available to suit different applications. Below are a few commonly used types.

• Natural Rubber Insertion Flange Gaskets reinforced with cotton have good mechanical properties. These are suitable for general applications like water and air at lower pressures. They are not suitable for use with oils and solvents and high pressure applications.
• GraphTek  Flange Gaskets have graphite in the composition, making them ideal for temperature and pressure applications such as steam.
• Spiral Wound Flange ‘composite’ Gaskets are made from metal strip of various grades sandwiched between layers of non-metallic filler such as graphite or PTFE.

Applications range from cryogenic to super-heated steam at pressures that match the pressure class of the specified flanges.

Pressure Gauges

Pressure gauges are widely used to indicate the pressure in the line and/or equipment. A visual scale / unit of measure (Kpa / Psi) with a needle gives you a reading of the pressure. Gauges are mounted via a thread, flange or clamped fitting to the pipework/equipment. Glycerine filling promotes gauge longevity. Face / Dial size, mounting process connection, pressure range and scale as well as materials of construction are varied to suit your application.

Ball Valves

Ball valves are a quarter turn, isolation valve commonly used in many industries. The ball valve is made up of a body, a ball with a hole through the middle which allows for flow, and a handle to operate. Ball valves can be made as a one piece reduced bore, a two or three piece full bore that are all rated to Psi for water oil & gas at ambient temperature. Standard end connections are BSP Female, however other end connections and configurations such as 3 way L & T port are also available.

Butterfly Valves & Check Valves

Butterfly valves are widely used for air, liquids, dry powders and some slurries in applications that require on/off or modulating control. They give tight shut off due to a resilient seat and are operated by a lever or gear operator for larger sizes. Butterfly valves consist of a cast or ductile iron painted body, stainless steel disc & stem and choice of seat such as EPDM or nitrile. For ease of installation the seats sit proud of the valve body to provide the seal onto the flange.

• Wafer butterfly valves are installed by sandwiching between two flanges using the locating holes on the valve as a guide for the bolts that run through the mating flanges.
• Lugged butterfly valves have drilled & tapped mounting holes which allows for end of line applications and servicing of pipe work that needs to be disassembled without emptying upstream lines.
• Check valves / Non-Return valves are one-way valves that allows flow only in one direction. This makes them suitable for services where you do not want back pressure flows into a pump or vessel. Commonly stocked wafer check valves have a stainless steel dual flap in a cast iron painted body with EPDM / nitrile seals which is sandwiched between flanges.Being a wafer style valve, they are a universal fit for nearly all flange specifications.

Stainless Steel Balustrade Fittings

Architects and builders are now using stainless steel balustrade fittings in both domestic and commercial building projects. This is due to the appeal of stainless steel in terms of both its aesthetics, mechanical strength and corrosion resistance.

There is a vast range of complimentary stainless steel 316 fittings available.

Included in the range are

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• 180 deg handrail returns (or candy canes) knock in end caps
• base plate and cover sets
• dome caps, rail converters
• wall bracket & cover sets
• Flush joiners
• Flush 90 degree corner joiners
• Oblong base plates.