Bolts & stud bolts for flanges: grades 8.8, 10.9, A2 and A4
A flange connection is only as good as its bolting. Stud bolts, nuts and washers must suit the pressure rating, temperature and medium.
Strength classes for steel
For steel bolts, the strength class provides information about tensile strength and yield strength. Common grades are 8.8 for standard connections and 10.9 for higher loads. The first number stands for the tensile strength, the second for the ratio of yield strength to tensile strength.
Stainless steel: A2 and A4
Corrosion-resistant connections use stainless bolts. A2 (corresponds to 1.4301) is the standard stainless steel, A4 (1.4401/1.4404, molybdenum-alloyed) is additionally resistant to chlorides – for example in outdoor and seawater environments.
Stud bolts for flanges
Stud bolts (double-ended bolts) with two nuts are frequently used for flange connections. They can be tightened evenly and are easier to loosen during maintenance than through-bolts.
Everything from a single source
We supply the complete bolting to match the flange and gasket – so the entire connection is coordinated.
Frequently Asked Questions
What do the numbers 8.8 and 10.9 mean on bolts?
They indicate the strength class: the first number stands for the tensile strength, the second for the ratio of yield strength to tensile strength. 10.9 can bear higher loads than 8.8.
What is the difference between A2 and A4?
A2 (1.4301) is standard stainless steel; A4 (1.4401/1.4404) is additionally molybdenum-alloyed and more resistant to chlorides, e.g. in seawater environments.
Do you need exactly these parts?
Grade, size, pressure rating and quantity are enough – you usually receive your quote the same day, with an inspection certificate 3.1 on request.
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