Just as any other temperature control would, with the obvious difference being the deadband.RuiReis wrote: ... how the machine behaves with a presso and i don't have how to attach the probe internally...
Sirai pressurestats are practically indestructible but quite noisy and a repair kit is what is usually done when the diaphgram stretches.
It is industrial duty equipment and the noise it can make goes unnoticed when (for example) a 5 HP compressor starts up.
Unfortunately, the price the repair kits go for is also usually high in relation to what a new unit costs but not always, it pays to shop around.
That said, I do not think the new Sirais are the same quality as they were 35 years ago and maybe a repair kit is worth it.
But I don't think you'll need a PID, I'd say a good quality temperature control with an adjustable deadband will do fine.
When I first set it up, my ca. 2000 Cimbali D/1 (on a timer in a small appartment) would wake me up and then keep me up ...
So I added a PID, which at the time was the thing to do on an HX and the clack-clack went away.
But I kept the OEM Sirai set just below 2.0 bar as a back-up safety measure just in case.
My guess is that you may be able to use your Sirai to the same end after a good refurb/clean-up.
Check this post to see how I fitted the temperature probe.
Cimbali Junior D/1 temperature probe
You basically need to find a place where you can slip in a 'T' to access the boiler at steam level with a stainless well to hold the thermocouple ie: above water level.
You'll probably be able to do this the same way I did with my D/1: at the point of exit where the tube going from the boiler to the pressurestat is located.
Just make sure it is far from the element.
BTW: a must see is Paul Pratt's page on pressurestats: