Changing inlet stem on a Micromatic PremiumPlus regulator

I’m looking to add a nitrogen stout tap to the keezer.  As a result I need to add another gas cylinder to the setup – a 30/70 blend of CO2 to nitrogen.

In Australia we have a couple of different cylinder threads.  Standard CO2 comes in a cylinder with a Type 30 connection.  The new blend I will be using has a Type 50 connection.

I bought another Micromatic regulator to go with the new cylinder.  The original model that I bought is no longer locally available and the PremiumPlus model has taken its place.  This model comes standard with a Type 30 connector so I need to swap out the inlet stem with one compatible with Type 50.

Older model Micromatic regs use right-hand threads on the low pressure side and left-hand threads on the high pressure side.  This would be a massive problem because all commercially available inlet stems I’ve seen are for right-hand threads (left-hand threads seem to be a Micromatic idiosyncrasy).  I was really hoping that left-hand threads wouldn’t be applicable to the PremiumPlus, otherwise my options would be down to a custom fabrication or buy yet another regulator from different manufacturer.  Having emailed Micromatic about this I can say that, in my experience, as a company you should not expect any sort of reply – I certainly didn’t get one.  Not even an acknowledgement.  So I thought I would document my findings here.

The first thing to note is that all the fittings are sealed with thread-lock and assembled by sumo wrestlers wielding spanners.  They are not easy to get off and due to the limited purchase on the body of the reg you have to be very careful not to damage dials, etc.  You really have to build a jig like I have below.

Grab a sturdy off-cut of wood, drill a hole in it so that the regulator can sit flush against the surface.  The low pressure dial and outlet treads are held in place by coat hanger wire that is twisted tight on the back side.  You will also need to cut a notch so that the captive nut of the existing inlet stem can drop down exposing the hexagonal end of the stem.  You will also need to pry off the nylon washer that sits on the end that seals with the cylinder.

Grab the appropriate sized socket (metric) and you’ll need a long length of pipe to turn the spanner into a large breaker-bar.  I used a 1m length of cast iron gas pipe.  The thread on the inlet stem is right-hand (yay!) so apply controlled gradual anticlockwise pressure until the thread-lock loosens.  It’ll take a fair amount of torque.  I also recommend getting a friend to hold the regulator and be ready to catch it should the jig snap to stop it all crashing to the floor.