Internationally accepted specifications for manufacturing forged flanges dictate what materials can be used in their production; how big (dimensional aspects) they can be; how much pressure they will hold (pressure rating); what testing procedures must be performed to measure performance; etc. Examples of common specifications that should be referenced when producing forged flanges include: ASME B16.5 covers pipe flanges – from 0 to 24 inch; and ASME B16.47 covers large diameter flanges. Many forged flanges contain ASTM A105/A182/A350 carbon/alloy steel. With regards to Europe, the EN1092-1 and DIN specifications are also generally utilized; as are various ISO specifications that exist internationally. All of these standards were developed to provide same-size products that can be interchanged and that have met their specified industry requirements with regards to the range of pressure, temperature and end use of forged flanges in an industry such as petroleum, electric power and process chemical.
How are bolt holes drilled in forged flanges?
After forging, the size and spacing of bolt holes on a forged flange are accurately drilled or machined in order to meet dimensionally accurate and correctly aligned standards. CNC and radial drill machines are generally used for drilling the evenly spaced holes into forged flanges based on industry standards, such as ASME, EN or DIN. To meet the correct fit for mating flanges, the drilling process consists of exact pitch circle diameters and hole sizes according to a predetermined requirement. The drilled holes are then deburred prior to inspection to remove sharp edges, ensure smooth insertion of bolts, and maintain the integrity of the forged flanges during installation.
What tests are performed on forged flanges?
All forged flanges must undergo a variety of tests to ensure they comply with SOP (Standard Operating Procedure), the engineering standards applicable to the product and the conditions for which they are used. Typical tests performed on a forged flange are:
- To determine the material grade used by conducting a chemical composition analysis.
- To measure the strength and toughness of the forged flange using tensile tests and impact tests.
- To verify that the forged flange was properly manufactured (heat treated) with a hardness test.
Nondestructive testing methods such as ultrasound testing and depending on the requirements, magnetic particle or dye-penetrant testing, will be performed to identify any defects in the forged flanges (e.g. internal or external defects).Inspections are also performed for dimensional accuracy and visual appearance. All results from testing will be recorded on a material test certificate so that there is a complete record of the operations and traceability of the forged flanges.
Where are forged flanges commonly used?
Industries needing high tensile strength, pressure resistance, and long-term reliability with their piping systems rely heavily on forged flanges as a material choice. Great examples of this include oil and gas pipelines, refineries, petrochemical and chemical processing plants, power generation facilities, and other offshore/marine infrastructures. Additionally, forged flanges can be found in water treatment plants, ship building and heavy engineering sectors where it is essential to have leak-proof joints and structural integrity. As forged flanges are made from forged steel and therefore able to withstand high pressure, high temperature, and chemicals, they are ideal for both onshore and offshore applications because of their reliable performance.
Conclusion
In summary, forged flanges are designed and produced within a set of internationally accepted requirements, having been developed through machining techniques that are customized to meet exact specifications, and are subject to multiple quality assurance and performance testing procedures prior to being released into service. In all cases, the dimensions and materials of forged flanges must conform with internationally accepted specifications, and the accurate drilling of the holes used to connect flanges to pipes will provide the correct fit and a leak-free joint when all parts of the system are in use. The mechanical and non-destructive testing that occurs during the manufacturing of flange parts has been used to verify the strength, integrity, and reliability of forged flanges for many years. These various manufacturing methods of a controlled nature and quality assurance inspections performed on each part have led to wide acceptance of forged flanges within many of the key industries (i.e. oil & gas, power generation, chemical, marine) for creating safe and reliable connections for the transmission of fluids through pipes.
