6. MSM Boilers - General Description
All MSM boilers incorporate a “center flue” design. This means that the heating gases generated
by the burner pass through the centre of the boiler which has a central tube fitted with a spiral
of cross tubes carrying boiler water that gives a maximum opportunity for the heat energy in the
burner flame to be transferred to the water to generate steam.
Not shown in the pictures above is the gas pipe following .
This has a knurled nut on one end to connect to the gas tank and the gas jet holder on the other. This slides into the gas tube on the burner to allow adjustment of air entry in the process of “calibrating” the burner flame. See Library Guide 11. Setting up the Burner. When calibrated,
the burner is inserted into the center flue and is retained there by simple friction and the proper
adjustment to the burner pipe shape to provide inward pressure on the burner. The outer part
of the burner that fits onto the center flue is called the “burner shroud”.
The “banjo” is the pipe fitting that connects the boiler to the pressure gauge. It’s purpose is to
retain a column of water between the boiler and the pressure gauge so that the pressure can
be indicated to the gauge without allowing steam into the gauge internals.
The “check valve port” is a 1/4” x 40 tpi fitting that is delivered with a blanking nut fitted. It is provided
to allow for easy connection of a boiler feedwater pump or as part of a gas regulator installation.
As noted in the table below this is not fitted to the 2” boilers.
The “steam vent pipe” is intended to be a stylish way of venting the steam from the safety valve
when it releases.
Safety valves and their setting is detailed in Library Guide 12,Safety Valves.
The steam cock is only fitted to boilers bought individually or on steam plants with slide valve
engines. The steam cock for steam plants using oscillator engines is usually integral to the displacement
Separate water filling ports are fitted to all boilers and should be obvious - except for the 3” & "Econo" vertical
boilers where the top cone has to be lifted to access it.
The water level sight glass is important for maintaining proper operation of the boiler. When operating
the boiler a water level should show at all times. See Library Guide 9. Filling & Maintenance.
The above pictures and the annotations typify what could be shown for all our boilers—with the
following variations. (Extract from Guide 12. Safety Valves)
One other variation is the 2” Special Vertical Boiler pictured below, has it’s burner built into the
base for the boiler. It is still a center flue boiler with all the other features.