La Pavoni + PID = better temperature control? - Page 2

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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RayJohns (original poster)

#11: Post by RayJohns (original poster) »

Ordered this PID controller: ... ucts_id=14

Also ordered the RTD sensor mentioned above.


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RayJohns (original poster)

#12: Post by RayJohns (original poster) »

Here's the latest:

The PID controller and RTD sensor is on order. Should be here this week. Now I'm trying to figure out how to attach a gauge (for pressure readings) and some sort of inlet port (to provide additional pressure to the boiler).

Searching for some sort of suitable adapter on this thread:

La Pavoni OE gauge adapter fitting information?

And all that talk of adapters got me thinking...

Maybe I can find some sort of M12x1.00 adapter that is tall enough to squeeze a banjo fitting between it and the La Pavoni bracket on the side of the boiler (the top fitting that the glass tube goes up into). My thinking is that if I find a fitting which has 1/8 NPT on the top, but it longer, then I can catch a banjo fitting (with an inlet pipe) under it. This would allow me to mount a gauge on the machine, and then introduce compressed air (via a hand pump) through the banjo fitting.

I think with a brash bushing and a couple of crush washers, this can be done. I'm taking some measurements right now...


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RayJohns (original poster)

#13: Post by RayJohns (original poster) »

Okay.. here is a quick drawing (not 100% to scale, but you get the basic idea), that shows the area of the La Pavoni where the adapter goes. I've taken some measurements, while trying to sort out how to rig up both a gauge and also pressure inlet:


As you can see here, this is a sketch of the boiler and the block at the top of the glass sight tube (where the gauge adapter threads in). I've included measurements of the area (noted in green).

So my basic train of thought here is this:

buy a brass or bronze bushing that is 18 mm with a 12 or 13 mm hole in the middle - one which is about 4 or 5 mm in height. This would sit down into that area where the "I don't have a gauge" screw goes. From there, I could install some sort of threaded adapter (M12x1.00) with a 1/8 NPT on top. Then I should be able to find a banjo fitting that could then be pinched between the top of the brass bushing and the bottom of the M12x1.00 adapter. This would provide a sort of "low profile" way to install a gauge, as well as an inlet port (which, again, will be used with a manual pump in order to provide a little pressure into the boiler - since the soon-to-be-PID-controlled water temp will more than likely be below boiling (thus no steam pressure)).

Let me see if I can find any specs on banjo fittings (or any fittings) and a bushing. If I can find them, then I'll do another drawing showing how it will all fit together.

In the meantime, behold the hand pump:

The pump will probably require some sort of one-way check valve and/or some sort of more heavy duty tubing running to the inlet.

Stay tuned...


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#14: Post by okmed »

CAUTION! You will be lucky if you can hand pump to a pressure of 25 psi (less than 2 bar) with that tool. I've used those hand asperaetors to stroke pneumatic actuators and over 20 psi is hard, slow work. Also you will probably blow the bulb if the check valve leaks at all. I wouldn't want a little high pressure steam hose flailing around.


#15: Post by Richard »

This thread from 2007 documents PID'ing a Cremina and using an air pump to pressurize the boiler.
-- Richard

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RayJohns (original poster)

#16: Post by RayJohns (original poster) »

okmed wrote:CAUTION! You will be lucky if you can hand pump to a pressure of 25 psi (less than 2 bar) with that tool. I've used those hand asperaetors to stroke pneumatic actuators and over 20 psi is hard, slow work. Also you will probably blow the bulb if the check valve leaks at all. I wouldn't want a little high pressure steam hose flailing around.
Thanks for the information. 1 bar should be plenty in the boiler (as far as pushing the water up into the siphon tube) I think.


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RayJohns (original poster)

#17: Post by RayJohns (original poster) »

I've been searching all over the internet, looking for parts, all day. I'm still not sure which adapter to use, but I think I have come up with a workable solution. It basically goes like this:

1. Use a 12mm stainless banjo fitting

2. Pinch that between the La Pavoni and a M12 x 1.00 adapter that has a 1/8 NPT hole in the top

3. Fabricate a bronze bushing (to fill up the recessed area where the gauge adapter normally sits)

4. Seal everything with copper washers

I'm still hunting around for the perfect brass adapter, but there are a few possible candidates. Another possibility is to buy a 12 mm x 1.00 mm pitch Banjo bolt and then drill into the top and tap it for 1/8 NPT myself. Anyway, that's still a little up in the air. In the meantime, here's a rough drawing I did showing how everything would more or less look and go together. It's not to scale, but you can sort of get the idea.


I noticed quite a few of the Banjo fittings come with a threaded end (e.g. AN3 or AN4). It might be possible to rig up a short distance of braided SS line or something (over to the hand pump). I'll have to wait until everything arrives to see how it will all go together.

Unless I have over looked something, I think this should come out pretty nice. The only question marks right now relate to which adapter to use and also the fitting of the Banjo fitting itself. The clearance between the banjo fitting and the edge of the boiler might also be tight, but I think I have found some slimmer banjo fittings that might just clear (or clear with a tiny bit of grinding).

The bushing will have to be cut down (luckily my neighbor has a lathe). I may also need to turn down part of the threaded area and/or drill and tap a 1/8 NPT thread (as mentioned above) to accept a 0-30 psi gauge.

So that's where everything stands now.


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RayJohns (original poster)

#18: Post by RayJohns (original poster) »

Here are the two current front runners as far as the adapter goes:

Both are for brake lines. They both have a 1/4 in hole in them, which is 0.250" The drill hole for a 1/8 NPT is .332", so it will just be a matter of drilling the hole out a bit, then running a tap down it. The body is M12 x 1.00 mm.

Here is one. This one is nice, because it's made from Brass and can be easily machined, drilled, tapped, etc. Part # in the UK appears to be "HU9" (for the 3/16 size) or "HU15" (for the 1/4 size). It's an M12x1.00 fitting for 3/16 or 1/4 size brake lines. Here's a photo of the HU15, even though both look the same (just different size through holes): ... anguage=en ... _4990.html

And here is the other. This one is made of steel, however. As such, if there was too much machining, it could open it up to rusting down the road and/or requiring the need for chrome plating or bluing, etc.

This one is also a contender, but it's stainless steel and would need to be drilled and tapped (and drilling and tapping stainless is no joke). In order to accomplish that properly, I would probably (ideally) need to use a lathe to bore a hole and then very carefully (and slowly) tap it out to 1/8 NPT:

Another possibility is to find the same M12x1.00 banjo fitting, only in steel (which would be easier to drill). However, there again, that brings into question the issue of surface rust and oxidation down the road.

Still searching around, but the ones above look pretty decent. I've also found several very nice stainless steel 12 mm banjo fittings as well.


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RayJohns (original poster)

#19: Post by RayJohns (original poster) »

Okay, just purchased 4 of the HU9 adapters (M12 x 1.00 with 3/16th hole) from Total cost was $12 and change via paypal. They will no doubt require a little modification to work, but I think the extent of it will be drilling the top of the hole and tapping it for 1/8 NPT and then maybe turning down some threads and/or drilling a little hole on the side (to make it into like a banjo fitting).

Next on the list is the Stainless Banjo fitting in 12mm size. I'm thinking I may use a 90 degree one. Just not sure about using an -3 or -4 AN size yet, as I don't have the hand pump.

BTW, for anyone interested in Aircraft hose sizing, here's are a couple of handy links:

I also ran across a helpful video on YouTube, which shows how to make up your own Teflon hoses:
So to connect from the Banjo fitting to the little hand pump, I'm thinking I will just make up a 2 or 3 inch little section of Teflon hose or something.

I may also be able to rig up my own "home brew" check valve right into the Banjo fitting. I'm not sure, but my thinking is that I may be able to drop a little stainless steel ball bearing into the inlet of the Banjo fitting and then stick a spring in there. I'll have to see, but it seems like it could be possible (and this would keep the pressure from getting into the little hand pump).

For now, the M12 x 1.00 brass adapters are on order.


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RayJohns (original poster)

#20: Post by RayJohns (original poster) »

Well, the PID controller and the RTD sensor arrived today.

I have to say, the quality of the PID controller is simply outstanding. It's even nicer than I expected (especially considering the very low cost). Below are a couple of photos:

Auber PID controller:

RTD sensor:

Now that the PID and RTD are here, I'll be ordering a few more parts. However, things are on hold for a bit, while I await delivery of my new Taig mini lathe. I finally became sick and tired of not having at least a small lathe around the garage (in order to turn down parts, work on projects, etc). As soon as I have the lathe here and setup (next week hopefully), I'm going to order more parts for the PID project and then start putting everything together. On top of everything else, I'm also in the midst of restoring my Dad's 35 year old drill press, so that might delay things a bit also.

As far as the M12 x 1.00 mm brass adapter, it's coming from the UK; so that may hold up the show for a couple of weeks no matter what.

Still deciding on how to go with the pump. I'm thinking either the squeeze bulb route or perhaps a little brass piston pump. If I do the brass piston pump, I was contemplating cutting into the boiler knob and then silver soldering the pump into it.

Does anyone happen to have a spare (broken?) La Pavoni boiler cap around, that they want to part with? I only need the threads, so if it's broken, that's fine.

[EDIT: disregard the request above (for a boiler cap). I decided it wouldn't allow any place to rest your hand, while pulling a shot, so I am going with the original bulb pump idea]

Anyway, more to come soon...