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[derekwarner]

mmmmm.... another trial by trial & error.......the following is self explanatory.......however has generated little comment when previously raised..........Derek___________________________________________________________________________________________________________________________   Hi PD's.....not to be baulked with this and after ZERO response from Miniature Gauges UK  .........I have discovered

1. the lower tapping in the rear of these miniature brass cased gauges is in fact a 10 BA jacking screw tapping
2. by screwing a 10 BA brass screw impinges or contacts the inner face of the gauge dial
3. by continued rotation of the 10 BA screw the case bezel is displaced however it may have caused further damage to the burden tube hair spring
4. it also pops the needle pointer off the spindle 

To cut a long storey short......I have stripped two gauges, marked the RED line & reassembled them.......

5. now to see if they still work....... ......Derek                     
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« Last Edit: Today at 01:52:52 PM by derekwarner_decoy »                      Report to moderator                                                    121.218.169.182                      derekwarner_decoy ...Wollongong Australia
                                                   derekwarner_decoy                     

Marking of Steam Pressure Gauges                             « Reply #1 on: Today at 01:40:26 PM »                          08.11.2013.....from another thread
_______________________________________________________________

RGY....thanks ..I understand the relief valve construction  ...

1. what is the intended steam relief valve setting?
2. is this governed or dictated by the discussions you held with the boiler inspector...prior to construction?
3. do you use the manual water pump to hydrostatically set the relief valve?
4. are you going to place the RED line on the boiler pressure gauge?

The reason I ask this last question is that I damaged a 1" pressure gauge ....[I think beyond repair  ] in my attempt to remove the gauge outer bezel to inscribe the 45 PSI RED line marking......Derek                     
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[steam up]

Why not indicate the red line with a red line (nail varnish) on the outside?

[mrsgoggins]

Parallax?

[hammer]

Derek, Do they still read correctly??? I have answered your question on PDs I am sure you has seen it. Geoff

[derekwarner]

Geoff...I should be able to test them hydrostatically early next week when my manual boiler feed pump arrives.....I considered steaming....but the water test will be far more reliable....Derek 

[MickK]

Hi Derek
I also had to put a red mark onto the FACE of my pressure gague.
It's too easy!!
 
The outer casing is a push fit onto the body of the gauge. Just wiggle it off. A small screwdriver or the end of a sharp knife helps to ease it over a small nipple on the body.
Use paint for the red line, as I originally used a red marker pen and it faded,
 
I also broke the glass when I put it together, got it replaced at my local glazier, cost $5
 
Mick
 
 

[southsteyne2]

Hi all Iwas always led to believe these gauges were for steam only and not for hydro pressures testing 
John.

[derekwarner]

sorry John...... when I mentioned 'hydrostatic test'...........I simply meant filling the boiler to 100% with water & pressurise to check the function of the gauge as connected.....
Water or steam pressures @ these conditions are essentially the same.......
This method will also enable testing of three individual pressure gauges & comparing readings to the pre set relief valve setting etc...........Derek

[ooyah/2]

Why not indicate the red line with a red line (nail varnish) on the outside?

Hi Mark,
This isn't acceptable as it can easily come of the glass face.
George.

[ooyah/2]

sorry John...... when I mentioned 'hydrostatic test'...........I simply meant filling the boiler to 100% with water & pressurise to check the function of the gauge as connected.....
Water or steam pressures @ these conditions are essentially the same.......
This method will also enable testing of three individual pressure gauges & comparing readings to the pre set relief valve setting etc...........Derek

Derek,
Pressure gauges can only be tested against the calibrated test gauge, see rule( see rule 11.3 )  that is if you want it Certificated for insurance purpose.

I would suggest that you do not hydraulic test them against a pressure relief valve as valves are inclined to start lifting before Pw is reached under steam and it's about the same under hydraulic and you can have a false reading.
If you do this and mark the gauge Pw + 10% you will have a different reading when you eventually have your boiler and gauge tested by a Boiler inspector who will fail your gauge, why not leave them until it's time to have them tested for insurance purposes.

To take the bezel of the gauge grip the square base in protected vice jaws and with a brass drift gently tap with a small hammer around the circumference of the bezel and it will come of in stages.
This will save you ruining another gauge,
George. 

[AlexC]

 
 
Hi Guy's,
 
I should point out that the redline marking of pressure gauges should be performed by the boiler inspector with reference to the STANDARD pressure gauge being used (this would be a certified gauge).
Any marking by the owner would be disregarded during a pressure test, since the  reference would be an unknown.
 
Hope this clears things up a little.
 
Derek... I thought I taught you better than to mark your own... naughty boy
 
Best regards.
 
AlexC aka SandyC.

[derekwarner]

Thanks George & Sandy...... .....Derek

[derekwarner]

mmmmm there is clear confusion in OZ as to who is responsible for the inscribing of the RED line
I have re-tested both gauges and confirm that they indicate relative or closely to the boiler relief valve setting and to a third gauge as further comparison
I do also understand the accuracy for  these style of gauges is +/- 10%....but the words missed so often is on FSD [full scale deflection] ...so between my two gauges I could have as a worst case +15 PSI and -8 PSI [or 23 PSI differential]
The RED line on the 3/4" boiler gauge has been removed & gauge returned to the boiler. I will use the 1"gauge complete with the marking either on the engine or on makeup water service after the pump...so this gauge will not be subject to boiler certification
Hammer....from this exercise....clearly I have wasted time & potential cost  & certainly will not go down a similar path again.....
southsteyne2.....when your boiler was recently certified....was it at St George?....and did the inspector inscribe the gauge?....... Derek

[hammer]

We all have to pay to learn DEREK. AND DON'T I KNOW IT. 

[southsteyne2]

Hi all "Derek I joined St George model boat club and had my boiler tested by their inspector ,yes Red line is put on by the inspector.but I must say the safe working pressure is determined by the inspector in regards to the construction and design as many model boilers including mine were inspected before silver soldering and again for hydro and final steam test then registration .
I have a copy of the Australian model boiler code that you are most welcome to borrow (highly recommended as it will give you most ofl the answers you need
Cheers
John