I don’t know. Can’t think of anything where a differential of more than minus 5 PSI is “safe” compared to zero differental. It it was mmH2O it might have been a fume cabinet or similar where you don’t want something leaking out…

Robert.

Hi, Testing advance and retard on petrol engine also brake bleeding on cars using hand held vacuum pump .Look on eBay .

Maurice

Looks a bit too cheap to be medical; have you had a new windscreen fitted?

Bill

That was good fun.

I wouldn’t complain if it became a regular Sunday quiz 🙂

Ches

Hi, where I used to work many years ago, they had a 20 foot in diameter table, with perforated slots upon which woven Nylon cloths were were fitted, washed industrial sand was then pumped onto a selected area, as the table was turning at less than walking pace. Below the table were four 12″ diameter steel pipes, which were connected to four separated sections of and interface section to the table, The four pipes were connected together and lead to a large round chamber, which was connected to another chamber of the same size in series, which was on the same floor as the table, and this one was connected to a large very powerful vacuum pump. As the table was turning, the Vacuum pump would suck the water from the sand to an extent to be just moist. The second chamber had a vacuum gauge connected near its outlet, but this one had markings up 32 inch’s. If I remember correct, this system would turn up to about 80 Tonnes of really wet sand an hour into moist sand for storage, some of which would be kilned bone dry.

Regards Nick.