Robot pressure gauge water path repair

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drgary
Team HB

#1: Post by drgary » Oct 30, 2018, 7:08 pm

What if the pressure gauge (manometer) on your Barista Robot develops a leak? That happened to me the other day, and Paul Pratt told me that I'm the only one who's experienced this so far. So with thanks to Murphy's Law, here's how I met the challenge of repairing it. Murphy was still at it, so during the repair I replicated an issue another user developed with a crimped tube. I had cut the replacement tube slightly too long and it pinched between the lever arm and the case but still seems unbroken and functional. I can only speculate that the tubing on my Robot may have been cut slightly too short, so that it was straining at the bottom of the pull.

How did I discover the leak? During a pull the pressure failed and I heard a gurgling sound. I hadn't done anything I know to bring this about, and Paul assures me the pressure gauge and fittings are built to take up to 20 bars pressure. I'm not strong enough to exert that much force! The piston gasket had been working perfectly and was still correctly installed, so that wasn't the problem.

In the unlikely event that the Robot's pressure gauge develops a leak, here is how you can find and fix it. As Paul writes in the user manual, pages 17 and 18, "you would see water drops or hear air hissing from somewhere along the tube." I have an additional pressurized basket, so I filled it partly with water and heard some gurgling but no air hissing near the manometer. It is common to have water travel up the 2 mm PTFE tube, but it wasn't leaking water there either. That told me that the leak was either at the tube insertion or the fitting seal where it attaches to the piston. To rule out a leak around the fitting itself, turn a 2.5 mm hex key clockwise to make sure it's hand-tight. If you still have a leak the tube may have become dislodged from the bottom fitting.

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I didn't want to disturb the tube insertion near the manometer, so I disconnected the fitting using a 13 mm wrench. The fitting and the manometer both are 13 mm, and you may want to hold the manometer nut in place while loosening the fitting. Otherwise you can misalign the manometer on its bracket. From this angle the fitting hex keys loosens to the right. Alternatively you could press the compression tab toward the fitting and also press the tube toward the fitting, see if it releases and pull it out. Freeing up the tubing at the top allows you to remove the piston and inspect the inside.

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To remove the piston, lower the arms so you have access to the piston screw. Turn a 5 mm hex key counter-clockwise to unscrew it. This will take about 9 turns.

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Grab the screw and pull it out. This disengages the piston from the arms, although it is still connected to the manometer tubing.

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If you've kept the top fitting attached to the tube, raise the Robot's arms out of the way so you can thread the fitting through the top case. That will release the piston. Take care not to drop the piston on the base, which could scratch the finish. I kept the silicone pad in place to prevent that.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#2: Post by drgary » Oct 30, 2018, 7:35 pm

Here's the fitting inside the piston. It has a similar compression ring to the top fitting. Inspect the tubing by pressing the compression ring and tubing downward and see if the tubing releases. If the end of the tubing looks undamaged, press it back into the fitting all the way until it stops. Pull at it very gently to make sure the compression ring has gripped it. (Pulling too hard can damage the tubing.)

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When I inspected the tubing I found it damaged. During assembly my tubing may have been cut just a bit too short, creating strain on the tubing that started a leak. When the leak was at its worst and I tried a pull with water partly filling the pressurized basket, water splashed through the top of the case. I snipped off the end and reattached the tubing. Then I reassembled the Robot and found the tubing was too short to reach the manometer fitting. I disassembled it and cut some spare 2 mm PTFE tubing to size (this is a part not provided with the Robot). Here's the snipped end, showing the damage. But as I worked out this repair I discovered that the length of the tubing is critical, as you'll soon see. First, let's look at reassembling the Robot.

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I found this next part a bit fiddly, so there may be a better way to do it. To reattach the piston, lay the Robot on a clean, soft towel with the front side up. Look through the piston hole and align the arms so the fastening holes catch the piston screw. This only works if the piston screw hole is close to the case. Be careful not to scratch the case by overlapping its bottom edge with the upper rim of the screw hole. To get the bottom of the arms to align, I had to tilt the Robot upward while peering through the hole. Then I carefully lowered it onto the towel. I inserted the screw, tested the arms to make sure the fastening hole was attached for both. Then I reattached the tubing and fitting up top. I did a successful pull. Then I saw that the tubing had crimped between the left arm and the case. This replicated an issue reported by another user.

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The tubing was still intact and usable, so I cut the tubing a bit shorter, and now it neatly threads between the two arms and reaches the manometer. I'm back in business. Since I got it working I didn't want to take everything apart to measure the tubing length. If you need a replacement tube, contact Cafelat, and they can provide you with a piece of correct length.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!