The inherentoxidation resistanceand elevatedtemperaturestrength of stainless steel

Flange Fittings Pipe China Supplier www.wilsonpipeline.com

The inherent oxidation resistance and elevated temperature strength of stainless steel finds useful application in buildings and structures where fire resistance is very important. The most useful family of stainless steel for these applications is theaustenitic, but the short-term nature of fire means that embrittlement should not be practical issue and so the ferritic andduplex families can also be considered.

As materials, stainless steel, do not have an intrinsic ‘fire rating’. Tests to assess fire resistance are done on specific fabrications under precise conditions. This is covered by BS476 parts 20, 21 (load-bearing elements) and 22 (non-load-bearing elements).

Design software which automatically calculate the behaviour of loaded stainless steel sections in a fire can be accessed at Stainless Steel in Construction.

Fire testing
BS 476 covers fire testing on building material and structures. Many of the parts of this standard are not directly relevant to stainless steel. 
Parts 4, 6,7, 11, 12, 13, 15 in particular are not appropriate to stainless steel as these deal with tests such as:
combustibility (ignitability from flame impingement or thermal irradiance)
fire propagation
surface spread of flames
heat emission at 750°C

Stainless steel are not ignitable and will also not assist in the propagation of fires by flame spread. The surface of stainless steel is normally inert and stable in oxidizing conditions, such as those found in most flames and heat sources

However to satisfy the requirements of BS476 and similar fire testing standards, tests need to be done on specific fabricated components. Stainless steel, as a material, does not carry a ‘fire rating’.

Results of fire testing on stainless steel components

Tests done for Stewart Fraser Ltd. on their fire resistant 316 type doors and frames to BS467 part 22 showed that after 60minutes, the temperature on the ‘safe’ side of the door only reached 98°C. (These doors have a 316 frame and contain an insulating non-combustible board filling.)
The test was terminated after 2 hours 10minutes with the doors and frames fully in tact.
The only damage was due to thermal distortion and some discoloration of the steel on the ‘safe’ side. The fire on the ‘attack’ side was fully contained by the doors for over two hours.

Tests done on 1.4362 (2304) type duplex, supplied for testing by Avesta AB 1991, and fabricated into a clad ships bulkhead, also demonstrates the fire resistance of stainless steels.
The fabricated bulkhead with a 1.5mm thick 1.4362 corrugated profile skin and ceramic wool insulating filler performed satisfactorily under a simulated hydrocarbon fuel fire. The ‘attack’ temperature reached 1100°C and radiated a bright orange colour after only 15 minutes. Some distortion and attendant insulation smoke were recorded during the tests, but after 40minutes the temperature on the ‘safe’ face was still below 30°C. This surface temperature had risen to around 110°C after 60 minutes.
After 120 minutes it was noted that the test unit was continuing to satisfy the criterion (International Maritime Organisation ResolutionA517 (XIII)) for resistance to smoke and hot gases penetration.

Manufacturers of products and components for fire resisting applications should be consulted at an early stage to avoid costly design changes at a later stage.

Heat resisting properties of stainless steel

Most stainless steel grades that would be considered for building applications ie the 304 (1.4301) and 316 (1.4401) types have useful, long-term oxidation resistance at temperatures over 800°C and do not begin to melt until temperatures of over 1375°C are reached. It is unlikely that uniform, sustained high temperatures like these would be reached in short term ‘transient’ fire conditions.

The short term tensile strength, elastic (Young’s) modulus and physical properties of thermal expansion and conductivity are of interest in assessing stainless steels for fire resistance.
The 304 and 316 austenitic types loose strength to about 55% of their ambient temperature levels at 700°C, the 0.2% proof strengths being around 225 to 308 Mpa (N/mm2) at ambient to 95 to 131 Mpa (N/mm2) at 700°C. The modulus, typically around 200KN/mm2 at ambient temperatures, falls to around 144 KN/mm2 at 700 °C for type 304. This is significantly different from carbon steels, where the modulus at 800 °C can be as low as only 9% of the ambient value.

The higher thermal expansion rates for the austenitic stainless steels means that physical distortion can be a problem in transient fire conditions where thermal gradients are likely to be large.
The thermal conductivity of the austenitic family is lower than ferritics and although this may be useful in containing heat flow through a structure, it may contribute to thermal distortion.
Allowances for distortion and seizing of items like fire doors should be considered.

Source: Zhejiang wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Flange Fittings Pipe China Supplier www.wilsonpipeline.com

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A Plug Valve is an industrial purpose valve which is used to control the flow of fluid in pipelines or into any processing units.

 They are a kind of rotational motion valves which are used to stop or start fluid flow. They are so called because of the shape of the disk, which resembles a plug.

A Plug Valve is an industrial purpose valve which is used to control the flow of fluid in pipelines or into any processing units. These valves consist of plugs which are either conical or cylindrical tapered and can be rotated inside the valve body either with the help of a hand wheel or motor actuated.

Materials used:

• Stainless steel
• Aluminum
• Bronze
• Brass
• Copper
• Nickel
• Cast iron
• Steel
• Plastic
• Rubber etc.

Buying Tips Certain features to look for are as follows: Body Options Port Options End Connections Sizes Material of construction Types Durability Corrosion resistant

Types of Plug Valves:

Plug valves are made with tapered and cylindrical plugs and are available in various types like given below:

• Nonlubricated plug valve: This is the earliest form of plug valve. A nonlubricated plug valve may use a tapered plug having a mechanical lifting device, which unseats the plug before it is turned to reduce the operating torque required. It may also have an elastomeric sleeve or plug coating with a low coefficient of rubbing friction. Though this design is still in use, the problems with galling and sticking limit their usefulness.
• Lubricated plug valve: The lubricated plug valves were developed to overcome the difficulties of non-lubricated plug valves. In this type of plug valve, the lubricant is forced into the valve under pressure. The lubricant prevents leakage between the plug and body. The lubricant also reduces friction and wear between the surfaces when the plug is turned. The use of lubricant between the plug face and the seat eliminates most of the problems of nonlubricated valves.
• 2-port valve: This kind of plug valve has two positions—one which is open to allow flow, and the other to shut or close to stop flow. Ports are openings through which fluid can enter or leave in the valve body.
• 3-way plug valve: In this type of plug valve, there are three ports and flow from one port could be directed to either the second or third port. A 3-way plug valve can also be designed in such a way to shift flow between ports 1 and 2, 2 and 3, or 1 and 3. They can also connect all three ports together.

Parts of plug valves:

The body of the plug valve comprises three parts:

• Body
• Cover
• Plug

The plug is a cylindrical, tapered or cone-shape mechanism that can raise or lower within the seat to restrict, maintain or completely shut off flow. The plug valve is opened by rotation and the plug is the only element that is capable of movement.

A diagrammatic representation of plug valve is given below.
The body of a plug valve is designed to receive the tapered or cylindrical plug.

Uses of plug valves:

• Plug valves are high capacity valves that are found widely in-
  • low-pressure sanitary applications and
  • industrial applications, like petroleum pipelines, chemical processing and related fields, and power plants.
• They are extremely versatile valves that can be used for directional flow control.
• They can be used even in moderate vacuum systems.
• Plug valves can efficiently handle gas and liquid fuel.
• They can safely handle extreme temperature flow, such as boiler feed water, condensate, and other such elements.
• Plug valves can be used to regulate the flow of liquids containing suspended solids, for example, slurries.

Industries Using Plug Valves:

• Air Conveying
• Automobile plants
• Atomic Energy Installations
• Bakeries
• Chemical industry
• Dairies
• Fertilizer plants
• Iron and steel industry
• Testing laboratories etc.  

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Piping standards imply application design and construction rules and requirements for pipe fittings like adapters, flanges, sleeves, elbows, union, tees, valves etc.

 

The integrity of pipe fittings and flanges in the piping system depends on various principles used in design, construction and maintenance of the entire system. The components of pipe fittings are made in different materials, in a variety of types and sizes and hence should be manufactured according to common national standards or according to manufacturers’ proprietary item. Some manufacturers also use their own internal piping standards based upon national and industry sector standards.With the rapid expansion in the global trade, standardization of various products has become an essential requirement. The standards given to various products significantly contributes towards increasing international trade which in turn bridges the quality gap between the manufacturers, producers and buyers of different nations. In pipe fittings as well, standards play a vital role. The manufacture and installation of pipe fittings is tightly regulated by various standards and codes.

Difference between “Standard” and “Codes”:

Piping codes imply the requirements of design, fabrication, use of materials, tests and inspection of various pipe and piping system. It has a limited jurisdiction defined by the code. On the other hand, piping standards imply application design and construction rules and requirements for pipe fittings like adapters, flanges, sleeves, elbows, union, tees, valves etc. Like a code, it also has a limited scope defined by the standard.

Factors affecting standards:

“Standards” on pipe fittings are based on certain factors like as follows:

• Pressure-temperature ratings
• Size
• Design
• Coatings
• Materials
• Marking
• End connections
• Dimensions and tolerances
• Threading
• Pattern taper etc.

Types of pipe fitting standards:

Some widely used pipe fitting standards are as follows:

1. ANSI: The American National Standards Institute
   ANSI is a private, non-profit organization. Its main function is to administer and coordinate the U.S. voluntary standardization and conformity assessment system. It provides a forum for development of American national standards. ANSI assigns “schedule numbers”. These numbers classify wall thicknesses for different pressure uses.
2. ASME: American Society for Mechanical Engineers
   This is one of the reputed organizations in the world developing codes and standards. The schedule number for pipe fitting starts from ASME/ANSI B16. The various classifications of ASME/ANSI B16 standards for different pipe fittings are as follows:
   • ASME/ANSI B16.1 – 1998 – Cast Iron Pipe Flanges and Flanged Fittings
   • ASME/ANSI B16.3 – 1998 – Malleable Iron Threaded Fittings
   • ASME/ANSI B16.4 – 1998 – Cast Iron Threaded Fittings
   • ASME/ANSI B16.5 – 1996 – Pipe Flanges and Flanged Fittings
   • ASME/ANSI B16.11 – 2001 – Forged Steel Fittings, Socket-Welding and Threaded
   • ASME/ANSI B16.14 – 1991 – Ferrous Pipe Plugs, Bushings and Locknuts with Pipe Threads
   • ASME/ANSI B16.15 – 1985 (R1994) – Cast Bronze Threaded Fittings
   • ASME/ANSI B16.25 – 1997 – Buttwelding Ends
   • ASME/ANSI B16.36 – 1996 – Orifice Flanges etc.
3. ASTM International: American Society for Testing and Materials
   This is one of the largest voluntary standards development organizations in the world. It was originally known as the American Society for Testing and Materials (ASTM). This is a reputed scientific and technical organization that develops and publishes voluntary standards on the basis of materials, products, systems and services. This is a trusted name for standards. The standards covered by this organization covers various types of pipes, tubes and fittings, especially made of metal, for high-temperature service, ordinary use and special applications like fire protection. The ASTM standards are published in 16 sections consisting of 67 volumes.
4. AN: Here, “A” stands for Army and “N” stands for Navy
   The AN standard was originally designed for the U.S. Military. Whenever, a pipe fitting is AN fittings, it means that the fittings are measured on the outside diameter of the fittings, that is, in 1/16 inch increments. For example, an AN 4 fitting means a fitting with an external diameter of approximately 4/16″ or ¼”. It is to be noted that approximation is important because AN external diameter is not a direct fit with an equivalent NPT thread.
5. BSP: British Standard Pipe
   BSP is the U.K. standard for pipe fittings. This refers to a family of standard screw thread types for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. This has been adopted internationally. It is also known as British Standard Pipe Taper threads (BSPT )or British Standard Pipe Parallel (Straight) threads (BSPP ). While the BSPT achieves pressure tight joints by the threads alone, the BSPP requires a sealing ring.
6. DIN: Deutsches Institut für Normung
   This refers to the industrial pipe, tube and fittings standards and specifications from the DIN, Deutsches Institut für Normung which in English means the German Institute for Standardization. DIN is the German national organization for standardization and is ISO member body for that country.
   DIN standard designation
   The designation of a DIN standard shows its origin where # symbolizes a number:
   • DIN # : Used for German standards having mainly domestic significance or designed as the primary step toward international status.
   • DIN EN # : Used for the German edition of European standards.
   • DIN ISO # : Used for the German edition of ISO standards.
   • DIN EN ISO # : Used if the standard has also been adopted as a European standard.
7. Dash (-) size
   Dash size is the standard used to refer to the inside diameter of a hose. This indicates the size by a two digit number which represents the relative ID in sixteenths of an inch. This is also used interchangeably with AN fittings. For example, a Dash “8” fitting means an AN 8 fitting. A standard hose guide is given below:

Hose Size In	Nominal ID Inch Dash Size	Standard Dash Size
1/4	3/16	-04
3/8	5/16	-06
1/2	13/32	-08
3/4	5/8	-12
1	7/8	-16
1 ½	–	–
1 ¼	1 1/8	-20

Flanges: Ratings in Classes and Pressure Numbers (PN)

Flange Class	150	300	600	900	1500	2500
Flange Pressure Number, PN	20	50	100	150	250	420

ISO: International Organization for Standardization
ISO is the industrial pipe, tube and fittings standards and specifications from the International Organization for Standardization. ISO standards are numbered. They have format as follows:
“ISO[/IEC] [IS] nnnnn[:yyyy] Title” where
nnnnn: standard number
yyyy: year published, and
Title: describes the subject

JIS: Japanese Industrial Standards
This is the Japanese industrial standards or the standards used for industrial activities in Japan for pipe, tube and fittings and published through Japanese Standards Associations.

NPT: National Pipe Thread
National Pipe Thread is a U.S. standard straight (NPS) threads or for tapered (NPT) threads. This is the most popular US standard for pipe fittings. NPT fittings are based on the internal diameter (ID) of the pipe fitting. 

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A 90 degree elbow is also called a “90 bend” or “90 ell”.

 

Materials used:

A 90 degree elbow is also called a “90 bend” or “90 ell”. It is a fitting which is bent in such a way to produce 90 degree change in the direction of flow in the pipe. It used to change the direction in piping and is also sometimes called a “quarter bend”. A 90 degree elbow attaches readily to plastic, copper, cast iron, steel and lead. It can also attach to rubber with stainless steel clamps. It is available in many materials like silicone, rubber compounds, galvanized steel, etc. The main application of an elbow (90 degree) is to connect hoses to valves, water pressure pumps, and deck drains. These elbows can be made from tough nylon material or NPT thread.

Materials used in 90° elbow is as follows:

• PVC
• Rubber
• Copper
• Cast iron
• Brass
• Stainless steel
• Bronze
• Galvanized steel
• Aluminum etc.

Types of 90° elbows:

90° elbows are manufactured as SR (Short Radius) elbows and LR (Long Radius) elbows:

SR (Short Radius) Elbows: These elbows have a Center-to-Face dimension of 1.0 X diameter. They are typically used in tight areas where clearance is the main issue.

LR (Long Radius) Elbows: These elbows have a Center-to-Face dimension of 1.5 X diameter. They are the most common type of elbow and used when space is available and flow is more critical.

Size and Dimension:

90° elbows are available in various sizes. To get the actual size, just take the measurements of A and B as shown in the figure.

Buyer’s guide

What should buyers look for bulk purchase of 90° elbows?

The buyers should always consider for maximum assurance of reliable performance, such as high pressure, impulse, vibration, vacuum and temperature. Some specifications to look for are:

• Light weight, convenient to transport and handle
• High strength
• Less resistance
• Corrosion resistance
• No pipe furring
• Sound insulation
• Easy to install
• Long lifespan
• Low cost
• Recyclable (optional)
• Color
• For water pipes, healthy and non-toxic, bacterial neutral, conforming to drinking water standards
• Resistant to high temperatures (110°C)
• Reliable installation
• Good heat preservation
• Excellent design which ensures suitability for both exposed and hidden installation etc.

Application of 90° elbows:

The main application area of a 90° elbow is to connect hoses to valves, water pressure pumps, and deck drains. 90° elbows help to make dust hose take that quick turn at the corner. These elbows can be used on instrumentation, process and control systems and equipment employed in chemical, petroleum, fluid power, electronic and pulp and paper plants.

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