Vacuum Systems

[LabTech09]

Does anyone know if decreasing the ID of the vacuum tubing leading from the pump into a chamber will significantly change the negative pressure inside the chamber?

[hairygrape]

This is no different to the basic concept in physics about water flowing through a hose. Does the volume of water from a hose increase or decrease when the hose diameter is iincreased or decreased given that the water pressure remains the same ie the tap is not turned on more or less.

In your case, the pump must be set to continue to shift the same amount of air per minute in litres regardless of the pipe diameter.

[richtee]

Hi LabTech,
Don't want to get into any arguments with the "scientists" on this site regarding the absolute theory of vacuum flows etc., but my experience is with industrial food vacuum packing and sealing machines. There are other factors than gas flows/pipe diameters to consider- if you are vacuuming wet products (meat etc), it takes longer to pull down the vacuum within the chamber than with dry products. My best rule of thumbs are- don't use smaller pipe than the pump inlet and the chamber outlet connections, keep the pipe run as short as possible, with minimum bends, and make sure you have no leaks.
Using smaller diameter pipe than suggested will reduce flow and increase the time taken to reach required vacuum in my experience.
Hope this helps.