The Art of Connecting Stainless Steel Fittings and Nipples

The Art of Connecting Stainless Steel Fittings and Nipples

As the components of a piping system that join the sections of pipe together, no plumbing system would be complete without the proper fitting to bring it to life – and stainless steel fittings and nipples can be the ideal fit. Not only is this material corrosion resistant but stainless steel is also known for its durability, strength-to-weight advantage, and aesthetic appeal. However, the trick to getting such quality results starts with the techniques utilized upon connection.

When connecting one stainless steel part to another stainless steel part that will require future disassembly, a thread sealant that is designed for stainless steel must be used. Due to the fact that this material galls (binds) easily, the application of the incorrect sealant can make the connection next to impossible to disassemble. In addition, PTFE (polytetrafluoroethylene) tape should be wrapped with the thread, with the process shown to the left.

Stainless steel is much harder than standard brass because of the elimination of the lead. Therefore, the sealing process is different. Follow these steps for the best results:

1. Apply gray PTFE tape with nickel to the male threads of the fitting
2. Apply a quality pipe thread on top of the PTFE tape
3. Thread the two pieces together and hand tighten plus one half to one full turn at the most. Do not overtighten as it will cause a leak. The more you tighten, the more it will leak. If overtightened a lot, you may not be able to use the fittings again.
   • If there is a leak, it may be necessary to add more thread sealant or a second layer of gray PTFE tape with nickel

While commonly found in many industrial, architectural, chemical, and consumer applications, stainless steel fittings have been a popular choice for over half a century. To learn even more about the topic, enroll in our ‘Techniques for Connecting Stainless Steel Fittings and Nipples’ AYU course, call our Customer Service Department at 1-800-292-2737, or fill out a contact form on AYMcDonald.com.

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:

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 3000 lb high pressure.

316 stainless steel NPT fittings include:

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:

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:

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:

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.

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 5130 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 1000Psi 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

 For more information on stainless steel fittings, please contact our stainless steel experts online today!