Article About Pid On Steam Boilers
I came across this article PID and Steaming - Coffeetime whilst researching double boiler machines for my next purchase.
I thought it was interesting and wondered what other peoples opinions on the subject were.
Too many generalisations in that piece FG...
Like he says right at the start, PID Control of the Steam Boiler/HX works just fine if implemented properly and if you stick with the major players, they all know how to do this...
I think he does have a valid point for a pure steam only boiler, take your average sirai p/stat thats rated at 0.15 bar differential but in reality probably controls over a 0.2 bar differential or even a bit more depending on the condition of the membrane. For dry saturated steam 1.5 bar = 127.6°C drop that to 1.3 bar 124.9°C as you steam some milk and the pressure stat cuts back in it's only a 2.7°C drop. Unless your temp sensor for your PID is very fast acting and directly sensing the steam boiler liquid temp, the good old fashioned pressure stat is going to do the same thing for a lot less cost/complication.
Yep, in general terms I agree...
However, there are commercial p/stats around that operate within a much tighter band than the Sirai unit for decent HX machine designs. I was referring only to his take on the the use of PID Controllers for what ever use the target is....