I'm upgrading my old Silvia with the new adjustable OPV and want to install a pressure gauge at the same time. To keep things simple, I'm planning on tee-ing it into the tubing between the pump and OPV. From what I've read, this is 4mm x 6mm teflon tubing. It's attached with compression fittings (at least at the OPV end--I haven't yet looked at the pump side). Has anyone sourced a compatible tee fitting for this tubing? What about an adaptor to the 1/4" NPT end of the gauge?

I've checked McMaster but didn't find what I was looking for there, though they do sell the tubing itself by the foot. Would a barbed tee + clamps handle the pressure, and if so, which clamps?

I've read about using John Guest tubing instead, and I guess I could go that route.

Thanks for any tips,
Jack

The Techno is entirely plumbed with instant tube fittings and Teflon tubing. While from the factory the larger tube, of the size you're describing, is used with a brass ferrule inside, I've used it without the ferrule and it hasn't caused any problems. Something like this item from McMaster should be fine for you.

Best,
David

DavidMLewis wrote:Something like this item from McMaster should be fine for you.

Looks interesting! I see the o-rings, but I'm unclear what holds the tubing on under pressure. "Push to connect" fittings are new to me, but I guess I still expect the tubing to be captured between an inner and outer sleeve/ferule/etc. Is there another part that I'm not seeing?

erics wrote:I would opt for some Swagelok fittings, in particular a B-6MO-3, described here: http://www.swagelok.com/search/fi...B-6MO-3&PG=0&RPR=5 and a straight connector, B-6MO-7-3, described here: http://www.swagelok.com/search/fi...6MO-7-4&PG=0&RPR=5 . I would also opt for a brass plug, P/N B-6MO-P described here: http://www.swagelok.com/search/pr....aspx?part=B-6M0-P

These look great too. Is there an online vendor for these individual pieces? My "local" Swagelok place isn't exactly local.

erics wrote:The straight connector will thread onto your glycerin-filled pressure gage that has a 1/4" NPT male stub. You did buy a glycerin-filled gage, didn't you?

Yep: This one.

erics wrote:The plug will allow you to temporarily stop your pressure measuring adventure and continue on with espresso production

Does this imply that the gauge will somehow interfere with my espresso production? I'm sure my attention would be better focused on perfecting my distribution through analysis of naked pours. But a gauge is cool, if nothing else. (I'm easily amused, but also easily distracted.)

erics wrote:BUT, in lieu of all this, I would design and build a high quality portafilter pressure gage having a fixed or variable orifice that will allow you to measure YOUR pressure at YOUR desired flowrate.

I might get there eventually, and I don't doubt the above is a better mechanism for improving my shots, but my current project seems a much better fit with my limited skill set. I'm still learning. BTW, I greatly appreciate the WDT needle you sent along with the thermocouple adaptor!

Jack (aka Chris J)

Hi Jack,

Push-to-connect fittings are designed so that the pressure that's trying to push the tubing out of the fitting causes an O-ring to tighten against the outside surface. The John Guest fittings are an example, but not the only one. The only thing I've ever found tricky about them is that they tend to be sensitive to dirt or nicks on the outer surface of the tube. I usually try to use a little extra tubing, because I find it saves hassle if I can cut a fresh end when I remove and replace the tubing. Eric's suggestion is, of course, good too. Note that McMaster-Carr has a number of different kinds of Teflon tubing. Make sure you get something rated for the temperature and pressure you're going to see.

Best,
David