How are the flange dimensions for DN350 PN420 determined?
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The valves purchased from two different companies have now arrived; both require a DN350 PN420 specification. However, the flange dimensions of the valves from these two companies differ significantly, whether it is in terms of outer diameter, bolt hole size, or flange thickness. Upon checking HG/T 20592~20635-2009 and ASME B16.5-2013, no corresponding dimensions were found. Does anyone know what standards can be used to determine the flange dimensions for this model?
The standard does not specify this; it should be determined by the manufacturer themselves. It’s indeed a hassle; the two are different, and there was no prior communication. Generally, it needs to be calculated using the Walter method.
Are they all domestically produced? Standard or non-standard?
They are all domestically produced; at that time, a tender was issued for procurement, and both bids specified ASME as the standard to be followed.
One manufacturer claims that their products are made in accordance with ASME DN300 standards, while another manufacturer’s flanges are significantly smaller in size; not to mention, their thickness is much lower. The steel grade indicated on the shell is PN250, but they say this was a mistake – they can’t provide any evidence for it. However, if we want to refuse to accept the goods, we need to have some proof as well. Therefore, we would like to know how the dimensions of flanges of this type are determined, as we are not involved in design work.
Your supplier is really amazing; since it’s marked PN250 on the housing, the valve must be capable of withstanding 250 kilograms of pressure. This is clearly forced selling. It’s better not to work with such suppliers; even though we try to be polite and humble, we still can’t get any orders from them
Sigh. . . Yes, the problem is that the person who was in charge of procurement here has left, and the person who took over either accepted bribes or wanted to be a good guy by constantly helping that valve factory, which has resulted in the project being partially halted
There should be a technical specification sheet in the design
Contact the suppliers directly and ask them to provide the compliance standards for their valve flanges, then check whether the dimensions of those flanges match the standards. If the actual product does not match the specified standards, such suppliers must be held accountable, and their responsibilities shall be pursued.
You can also ask them to provide the matching flanges and supply them together.