Steam Heating (2)

After some pretty hectic weeks, I have most of the sub assemblies ready to fit. Rapid progress has been made possible by Amanda and Rob at South West Engineering Supplies at Bumpers Farm industrial estate near my home in Chippenham. Without them, I'd have been struggling to obtain all the bits and pieces in a short time and they have given me ready access to trial and error items. So a big thank you to them.

Following on from 'Steam Heating (1)', this is how it's developed.

What equipment is needed?

1. High pressure pipework and an isolating valve able to withstand the Sentinel boiler temperature & pressure (212DegC & 275psi).

High Pressure Pipe Fittings and Valve

In the photo above, the steel 'T' fitting's leg links to a 3000psi stainless steel union and thence to a taper threaded hex nipple which will screw into the boiler orifice. This union allows the angle of the 'T' to be set after securely fixing the nipple into the boiler orifice. The plug at the top of the 'T' fitting is to provide another steam outlet for future use.

The second union below the 'T' fitting allows the valve to be orientated appropriately. The valve is a three-part ball valve made by Valtac. I've written about these before. The hex nipple below the valve will connect to flexible braided hose to take the steam down to the buffer beam. Although the nipple in the photo is a steel type, I will be using a parallel threaded hydraulic fitting machined to take a copper washer sealed mating connector.

2. Pipework to carry the boiler pressure steam to the buffer beam apparatus.

Purists might criticise me for using modern flexible stainless steel braided hose instead of copper pipe with braized end fittings. I can order and receive the flexible hose with welded end fittings and a pressure test certificate within a week and be confident in the result. Using copper pipe, I cannot do this. (In fact, the hose arrived in four days!).

I've covered this before in detail here.

3. A pressure reducing valve to take the boiler pressure down to the carriage requirements (about 40psi).

Blue Pressure Reducing Valve (centre) (and one assistant)

Blue Pressure Reducing Valve (and other assistant)

The blue Spirax Sarco PRV is a 1/2" BRV2S with a Green Spring to allow a range of 20-60psi.

Arguably, to reduce the length of high pressure hose, I could have put the pressure reducing valve below the ball valve instead of behind the buffer beam. However the PRV needs to be mounted upright and would have taken up too much space in the cab.

4. A safety valve to prevent exceeding the carriage maximum pressure.

Gunmetal Safety Valve

The safety valve is a 1/2" ART 642 type made by Albion.

Safety Valve Detail including 3 bar setting.

5. A pressure gauge to allow the carriage pressure setting.

3" Steam Pressure gauge

The safety valve has been delivered certified to 45psi (3 bar) so 100psi full-scale is fine. I purchased it new from "thegaugeman61" on Ebay".

6. Heavy duty bracketry to fix the pipework and standard buffer beam equipment to the buffer beam itself.

Flange made to fit the standard buffer beam equipment to the buffer beam

The flange's central hole is tapped to 1.25" BSPT (tapered) to take a 1.25" section of pipe. The pipe section is then held by a Stauff clamp with an additional supporting bar screwed to the bottom edge of the buffer beam. A third bolt fixes the flange through the buffer beam. It is pretty strong and intended to survive heavy handling.

The flange 3-point mounting to the rear buffer beam

The Complete Assembly

I've pre-assembled the 'flat-pack' version of the equipment to show it all together before it disappears out of sight in and under Joyce's metalwork.

Complete 'flat-pack' and assistants

The boiler fitting is at the top. It passes steam via a 'T' fitting to a ball valve and thence to the braided flexible hose. The hose links to the blue PRV which passes lower pressure steam to the safety valve and pressure gauge pipe. Finally the pipe connects to the back of the flange and to the standard buffer beam equipment.

Now all I have to do is fit the kit and test it. Initial fitting will be quite quick for test purposes. I'll clamp the pipework properly when I'm happy it performs satisfactorily. The assistants will not be allowed on site at Midsomer Norton as they haven't passed their Personal Trackside Safety exam (honest!).