Hi -

I did a few searches and came up blank so I'm hoping someone here can help.

I have an Isomac Tea with a gauge issue. When pulling a shot, the pressure head gauge has a very high frequency chatter - When it 1st started I suspected air in the system, as it was much worse after the machine had gotten hot. Now it oscillates constantly.. The shots seem to be okay, and the average pressure still ends up at approx 9bar.

Any suggestions on repair? I suspect the pump check valve....

Thanks!

Jim

Set your OPV down to 9 bar -- do a google site search here or on CG to get the instructions

Another Jim -

I just gave your suggestion a shot - I went ahead and disassembled the OVP flushed it out and put it back together...

Sadly -no change



No matter what I try the pressure head gauge oscillates at very high frequency over about a 2-4 bar range. In fact is so fast the needle is blurred!!

At start of the shot the gauge reads about 4 bar (average) with a +- 3 bar chatter. By the time the pressure climbs to 9bar the shaking calms down a little, maybe +-1.5 bar.

Any additional suggestions would be greatly appreciated!

Please refresh my memory. Doesn't the Isomac Tea use a capillary tube to dampen the vibration from the pump (recent discussion excerpted below)?

HB wrote:Question: Is there a way to damp out the vibration to the gauge (this IS a vibe pump, after all)?

Answer: All the machines I've seen have dry gauges and eliminate flutter by coiling very thin 1/8" OD tubing several times to act as dampeners. Manufacturers install the tee further downstream to reduce the effects of the vibration pump's pulses and the thin tubing dissipates heat that would otherwise be transmitted to the gauge.


Brew pressure gauge tee on the Andreja Premium at the heat exchanger exit

Alternatively you can install a snubber and wet gauge for good measure. I had a dry gauge and snubber on hand for this installation. The gauge buzzes a little, but it's a fast install and temporary (i.e., I install a temporary brew gauge if the evaluation machine doesn't have one, e.g., the Cimbali Junior, Giotto Premium, etc.).

Yes, there's a very long coiled capillary that damps out even real chatter. On vibe pumps, you'll see chatter at 11 bar plus on pf mounted gauges, but the OPV will damp them out once they are set down to 9 bar and diverting water (which is why I suggested it).

My next guess is that there's a fault in the gauge itself -- even with no opv on the line, a vibe pump shouldn't chatter at 4 bar. If you are seeing anything peculiar in the espresso flow when you make shots, it may indicate a pump problem, otherwise I'd suspect the gauge. Perhaps a loose connection?

Can you post a picture of the coiled capillary? My Andreja had the same issue but replacing the original capillary with one that was slightly longer and with twice the number of coils cured the problem. This is the first time I've heard of the problem on an Isomac Tea, though...

Br,
Teme

I added an aftermarket pressure gauge to my millennium. I originally used a piece of ¼ inch copper but the flutter was as bad as you describe. I replaced it with a much longer and smaller peace of copper. I coiled it around the handle of a screwdriver to keep the shape. I believe that is about three feet of tube in the coil.

Thanks to everyone for the suggestions.

I pulled the system apart this weekend with the intent of adding a second gauge to monitor the stability of the OEM unit...Unfortunately the fittings I had available were all 1/8" and not the metric stuff used on the machine.

I've decided to increase the length of the capillary and replace the gauge since I can just sweat in new bits..I'm too lazy to look for fittings right now ...

So I have a couple more questions...

Is the capillary only filled with air?

Other than being irritating - are the vibrations seen in the gauge going to hurt anything?


Teme - I don't have a pic of the OEM capillary setup right now, it currently has about 4 loops. I'll try and post before and after pics.

-jim

Jim,

If there are only four loops in the capillary, I suspect that is the problem. The pic posted by Dave above looks like mine - more loops help dampen the vibrations of the pump.

The capillary is filled with brew water when in situ.

Br,
Teme

The excessive pulsing will blow out the membrane in the gauge, so yes, letting it run that way will eventually damage it.

The gauges you have are 1/8 NPT, what you need is a 1/8 BSPT male to 1/8 NPT female adapter. McMaster-Carr (http://www.mcmaster.com) is about the best place. I looked everywhere for some fittings just a few weeks ago. They have a very easy to navigate page. You want 'Pipe and Pipe Fittings' under the Pipe, Tubing, Hose and Fittings section. Then drill down, 'brass pipe fittings and pipe', 'adapter', 'female x male adapter', 'BSPT male x NPT female' then 1/8 inch. $3.91 each. That adapter would screw onto the gauge end of copper, then onto your NPT gauge.

I am using an oil filled gauge to help dampen the vibration, but with a large enough capillary you would not need the oil filled.