mhoy wrote:Anyone know what pressure the safety release valve is suppose to let go at?

Usually around 1.6 bar, though some may not crack open until the pressure approaches 2.0 bar. Occasionally new espresso machines will include the factory's boiler pressure test results; IIRC, they test it to 2.0 bar.

Yeow, so it was very close to where it should have released. I guess I could run it to 2.2 it doesn't do the right thing get a new one at $42...why couldn't they just put a regular pressure safety valve in the top!

Mark

mhoy wrote:I tried to remove the pressure stat tube by unscrewing the compression fitting on the bottom of the boiler. I was able to move the tube about 1/4" and then it stopped.

Let me save someone from trying this, it won't work because the pressure stat tubing has a funky bend inside the boiler to avoid the heating coils. Instead hold the pressure stat with a pair of pliers and unscrew the compression fitting connected to it.



The older pressure stat itself comes part easily with just two flat head bolts. I had a look at Stefano's site and I couldn't find a replacement for the pressure-stat membrane. Mine seems to be made of rubber on one side and cloth on the other side. I'm guessing it's not as flexible as it once was.



I'll clean this up and lubricate the sliding piston part with a tiny bit of Dow 111.

Mark

Cleaned it up with some citric acid and tsp. Lightly polished some of the parts that rub on each other with some 600 grit emery cloth.



Put a small bit of Dow 111 on the edge of the rubber part of the seal, also put some on the spring and sliding contact areas of the pressure piston. Tightened the two flat head screws in, then the cap that compresses the spring. Clipped the brass frame on that holds the micro-switch in place. Held the pressure stat with some pliers as I tightened the compression fitting.

Pulled out the piston (thanks Dan) by applying a bit more force than before. It slowly slid out and looked to be in pretty good shape. The rubber one the two rings are in fine shape! Wheee. Cleaned off the old lubricant, soaked it in tsp and some citric acid for a bit and washed clean. Not looking too bad at all. The piston just fit in place and gently slid down into place, no force required.




Filled her up with some water and checked for leaks. OK so far. Figured out a way of adjusting the pressure without having to hold things up. Placed Elektra where two of my counters connect at 90 degrees. Here is a view looking up at the pstat.



Mark

Shoot, I'll have to take the pstat apart again, it leaks at 1+ bar. I hope I can get a new gasket. At least it works now, seems to be at the far end of the throw for the piston. I'm guessing the gasket has lost elasticity, heck it's probably only 20 years old.



Might as well pull a shot now that everything is cleaned up.



I'll drain the water while I await news on getting a new gasket.
=-=-
Mark

Very nice work indeed. Nothing like clean brass parts, but that leak? If you can't get the part, or if it is too spendy, McMaster's Carr has rubber sheeting for almost every purpose, with good description of properties etc, but stick with inch measurements rather than metric, since the types of rubber are limited with metric. Sounds like some fabric backed rubber, which makes sense for a bit more rigidity than plain rubber or viton, though as I said, I cut a disc of 1/16" viton to fix an identical pstat and it works fine. Since you have the old diaphragm for a pattern and a minimum of half a square foot to order, you should be able to get a perfect disc cut with material to spare for your next project. Just look through the rubber sheeting options, and get something with good heat stability and a fairly high durometer rating and that should do it.
Doug

I can get the entire pressure stat part replaced, however I'd rather just replace the seal. I'll browse McMaster's Carr and see what I come up with.

Mark

They appear to have 1 square foot available at McMaster-Carr, at these prices I might as well just get new CEMA or Mater pressure switch for $44.

McCarr wrote:9473K61 $31.89 - 12" x 12"
Viton— Has better chemical resistance than other rubbers. Resists grease, oil, detergents, and some acids. Durometer hardness is A75. Temperature range is -20° to +400° F for Viton. Maximum pressure is 1000 psi for Viton.

8525T41 $15.36 - 12" x 12"
Silicone— A broad temperature range of -70° to +500° F makes silicone great for use in high-temperature applications. Also resists alkalies, acids, detergents, and steam. Maximum pressure is 1000 psi. Durometer hardness is A60.

Mark

Ah yes, the high cost of rubbers. Tell me about it as you multiply that one type and thickness by a lot of different applications and it does add up. You've got the old rubber and I've got the sheet rubber.....send us the part and I'll make you one ( and save $$$$$not buying the similar Elektra on ebay this week). Actually, we just need the diameter of the piece. The viton diaphragm replacement in our club machine did turn out to be nicely sensitive, though of course I do not know just how flexible the OEM rubber is designed to be. If you do get a new pstat, have any plans for the old one?

Doug

Thanks to Doug, I'm going to try rebuilding the diaphragm.

mark