Joe,

My associate (who's been working on espresso machines since the mid 60's) today tells me that boilers have to pass the same tests as water heaters and in fact water heaters work under more pressure, which is true. As to whether they have a similar construction, I don't know. The figure he quoted me when I asked how much pressure before the boilers explode was 300 psi. A figure I'm inclined to believe.

Sorry to swipe the thread from you.

Hello Norm,

Thank you and everyone else for the review and comments. It has been most helpful.

With respect to boiler testing, I remember growing up near Nela Park, Ohio where GE made light bulbs. That was where I learned the term "destructive testing". The only way to know how long a light bulb will burn is to turn it on and wait. I hope to never find out where my boiler will pop- but I am not going to pressurize it beyond 30psi.

Time to get some work done! Off to the garage-

I am off to drill and tap for pressure and temperature sensing on the backs of my groups in position 3 shown in the following post. When I reassemble the group, I believe that I will leave out the gliceur, as I think it will only complicate estimation of puck pressure.

NEXT POSTING IN SERIES:

Playa Espresso Cart 4: Where to Measure Pressure and Temperature?

PRIOR POSTING IN SERIES:

Playa Espresso Cart 2- Thermoregulation

After reading this Thread I am thinking that a lever machine might just be the way to go! There was a wealth of info in this Thread and the videos of the Levers in action reminded me of my month in Italy, but at the time I was not thinking machines but just good espresso.

Maybe I should ditch my Rocket and get a good Lever machine Any suggestions??

I know I've mentioned this before on (I think) a different thread but if anyone wants to add a final, as fool proof as can be, pressure relief a blow-out plug can be added. These come in many sizes, metric and inch and many temperature ratings. It is a fitting with a plug of alloy that will melt at a precise temp and dump all the pressure. They can be had with threads on the exhaust end so the steam/water can be piped to the drain. One nice thing about them is they are real cheap: I've seen them as low as $3.
KDM