Header sizing can be assessed by putting a vacuum gauge at both ends of it. If there is a significant difference between the readings as the pumps are chugging away, then yes, it needs to be increased in diameter.

However, the vacuum level at any moment is related to the boiling temperatures of the fluids in the autoclave chests. If the material were only water, then the vacuum level at, say 90degC would be a lot lower than the vacuum level at, say 15degC. The actual figures can be gleaned from a set of Steam Tables, an essential tool in the process engineer's toolbox.

What is wrong with disconnecting the vacuum pumps from the header and running each chest to its own vacuum pump? At least this would improve operational flexibility, thereby improving throughput, and would give an indication as to whether there is a problem with one particular autoclave chest, or with all of them. If it is one, then it could be a maintenance issue; the thing might have a leak. If it is all of them then it could be a process design issue; the equipment isn't capable of doing what is being asked of it in that configuration. In either case, it is difficult to see from here.

Why all the vacuum pumps are connected in series in the diagram is a complete mystery, and may indeed be the process bottleneck. Please try reconfiguring them in parallel, and then report back to the forum on the changes.

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