Flange Facing Types
One end of the flex joint is a flat face to match the pump face and the other end is raised face to match the flange.
- Flat Face (FF) – Typically these flanges are used on pump facings or on fiberglass flanges where the torque of compressing the gasket will damage the flange body. They are found in 150# and 300# ratings. Their principal use is to make connections with 125# and 250# cast iron flanges, respectively.
- Raised Face (RF) – The raised face is the most common used flange face. It is called raised face because the gasket is raised 1/16″ and 1/4″ above the bolt circle face: 1/16″ for 300 lb. and less, 1/4″ for 400 lb. and more. The flange facings are machine finished toANSI/ASME B16.5 requirements.
- Ring Type Joint (RTJ) (Class 300 and larger) – This flange is normally used for high pressure gas pipe work. Ring type gaskets must be used on this type of flange.
- Tongue and Groove (T&G)
- Small Tongue and Groove
- Large Tongue and Groove
- Small Male and Female
- Large Male and Female
The flange face finish is determined by the standard used and measured as an Arithmetical Average Roughness Height (AARH). An example would be ANSI B16.5 which specifies face finishes within a range 125AARH – 500AARH (3.2 Ra to 12.5 Ra).
- Cold Water – It has a mirror like finish. This is made with a wide tool at a high speed which gives a finished surface much like a ground surface. When a surface has this type of finish it is normally used metal to metal, not with a gasket. It is seldom used in the oil, chemical or related industries.
- Concentric Serrated – A 90 degree inclined angle tool is used to make the grove. It makes a grove 1/64″ deep and 1/32″ apart in a concentric circle.
- Smooth – This can be made with several different types of tool shapes. No tool markings will appear to the naked eye on the surface. The roughness of the finish is from 125-250 microinch.
- Spiral Serrated – This is similar to a stock finish but the difference between them is the way the grove is made. A 90 degree inclined angle tool is used to make the grove. It makes a grove 1/64″ deep and the feed is 1/32″.
- Stock – The surface is created by a continuous spiral groove. The roughness of the finish is from 125 to 500 microinches and is cut with a tool with an approximately 0.06 inches or larger radius.
Pressure equipment and gas appliances
Pressure Equipment Directive (PED):
The Pressure Equipment Directive (97/23/EC) was adopted by the European Parliament and the European Council in May 1997. It has initially come into force on 29 November 1999. From that date until 29 May 2002 manufacturers had a choice between applying the pressure equipment directive or continuing with the application of the existing national legislation. From 30 May 2002 the pressure equipment directive is obligatory throughout the EU.
The directive provides, together with the directives related to simple pressure vessels (2009/105/EC), transportable pressure equipment (99/36/EC) and Aerosol Dispensers (75/324/EEC), for an adequate legislative framework on European level for equipment subject to a pressure hazard.
The PED Directive arises from the European Community’s Programme for the elimination of technical barriers to trade and is formulated under the “New Approach to Technical Harmonisation and Standards”. Its purpose is to harmonise national laws of Member States regarding the design, manufacture, testing and conformity assessment of pressure equipment and assemblies of pressure equipment. It therefore aims to ensure the free placing on the market and putting into service of the equipment within the European Union and the European Economic Area. Formulated under the New Approach the directive provides for a flexible regulatory environment that does not impose any detailed technical solution. This approach allows European industry to develop new techniques thereby increasing international competitiveness. The pressure equipment directive is one of a series of technical harmonisation directives for machinery, electrical equipment, medical devices, simple pressure vessels, gas appliances etc.
The Directive concerns items such as vessels, pressurised storage containers, heat exchangers, steam generators, boilers, industrial piping, safety devices and pressure accessories. Such pressure equipment is widely used in the process industries (oil & gas, chemical, pharmaceutical, plastics and rubber and the food and beverage industry), high temperature process industry (glass, paper and board), energy production and in the supply of utilities, heating, air conditioning and gas storage and transportation.
Under the Community regime of the Directive, pressure equipment and assemblies above specified pressure and/or volume thresholds must:
- be safe;
- meet essential safety requirements covering design, manufacture and testing;
- satisfy appropriate conformity assessment procedures; and
- carry the CE marking and other information.
Pressure equipment and assemblies below the specified pressure / volume thresholds must:
- be safe;
- be designed and manufactured in accordance with the sound engineering practice of a Member State; and
- bear specified markings (but not the CE marking).
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