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[Bunkerbarge]

The one I have mounted directly on the boiler I set to about 35 psi and it seems to be OK at that. 

The trouble is with a boiler with a working pressure of 45 psi the safety valve has to be set less than that so mine is set at 40 psi.  You then want to set the valve to less than that so I went with 35 psi but of course this all depends on your own boiler and engine configuration.

I'm glad though that you seem to be getting to grips with the valve and learning a bit more about it.  I would suggest that you give Forest Classics a call as they are very helpful and always interested in feedback as regards how the valves are performing.

[red_noir]

35 psi seems like a better alternative to 40psi.  At 40psi my safety valve starts to act up.

I ordered a PPS whistle today from pm research, I cant wait to get it on this project !

[benjaml1]

Just my humble opinion...

With all diaphragms there are several conditions at play. The main ones being hysteresis & repeatability... A higher working pressure will often narrow the hysterisis ( linearity) band but repeatability is a condition of uniform temperature &/or material science (stability.) Thermal shock is the main bugaboo for repeatability hence my recommendation for isolating with a condensate trap. Not only a possible problem with material science, just good engineering practice. My credentials ? Control instrumentation design & application, a career over 40 years.. I am considered by many to be a boiler/steam controls expert...

No matter what the vendor says, isolate with a condensate trap. Tens of 1000's of instrumentation engineers can't all be wrong....

[derekwarner]

Well Mayhem members...we have comment here from benjaml1 .... "I am considered by many to be a boiler/steam controls expert"  ...& is certainly modest at that 

We have a number of qualified marine engineers [both steam & motor] 
We have an electronic GURU in computing & control for flash steam 

So having said all this   benjaml1   gets my vote as an appropriately qualified specialist in the area of steam control where we can use full scale rules & relate down to model steam engineeing... - Derek

[Bernhard]

Hi...i have one from Forrest to,,set to 60psi,,,and work ok............and i have one from Anton in France,,,set to 50 psi,,,,the did told me...if the gastank get more pressur than 45 psi..3 bar...i scut use a valve before the regulator....
i have that valve to,,,,,,,,,,,

Regards Bernhard

[benjaml1]

Apologies for being a little "cockey", remind me not to post after a few pints down the pub... 

[derekwarner]

Hullo Bernhard..........if my memory serves me correctly.... ...you also had two gas regulators from an alternate British manufacturer that were non functional & were returned

You also have a German manufactured duplex [twin] yellow cast body gas regulator that you advised was totally functional 

I think your ANTON unit is the same V71 that I have ......but mounted with the adjustment screw vertically down 

Hullo benjaml1.........don't be embarrassed ....sometimes the best thoughts are after a few pints down the pub...    ...& your comments on the subject are totally valid ...keep up the good work  ....Derek

[kiwimodeller]

Hi, would Greg, or anyone else for that matter like to expand on the part of this discussion about condensate coils/loops etc? I have never been able to understand how putting a simple "U" siphon in a gauge line stops water that may condense in the line from making its way to the gauge the next time the boiler comes up to pressure. I know that in theory any air/steam on the gauge side of the condemsate should transmit the pressure to the gauge without compressing but I still suspect that the condensate would make its way to the gauge. Also if it does get water to the gauge does it matter? I have one of my boilers (a Cheddar Puffin) with the gauge siphon connected to the steam dome and laying horizontal. It was like that when I got it at least five years ago and it is still working fine. Maybe attenuators/regulators are more sensitive but I still struggle to see how a coil in the pipe leading to them will stop condensate getting to the diaphram. Please enlighten me! Thanks, Ian.

[Bernhard]

hi........haaaaa What great  memory you have Derek.. ..... yes thats true...i did have 3 from that UK place ...and only one iwhas working..2 whas send back..and i get my payment back,,,.and yes i have to from Germany...they work to,,ok to,,,,,,,

Bernhard

[gondolier88]

Hi ian,

You have a common misconsception held by many;

I have never been able to understand how putting a simple "U" siphon in a gauge line stops water that may condense in the line from making its way to the gauge the next time the boiler comes up to pressure....Also if it does get water to the gauge does it matter?...Maybe attenuators/regulators are more sensitive but I still struggle to see how a coil in the pipe leading to them will stop condensate getting to the diaphram.

The 'U' bend or a small coil in the pipe provides a solid plug between the steam and the fragile internals of the gauge- you WANT water to be acting on the bourdon coil in the gauge- if it has condensed it is likely not to rise above 40-50degC and stops thermal shocks and repeatability (see post above by an EXPERT ) something that will eventually stop the coil working to it's calibration and may show the wrong pressure.

The only reason that you may have got away with it being straight off the dome is that our plants work at such low temperatures that, yes, yours might just be okay, but I wouldn't gaurentee it.

Hope that helps.

Greg

[derekwarner]

OK....we are all learning  ...so I pose a question to benjaml1 & gondolier88 ...

Please consider the simple U tube gauge syphon ....why does the condensed steam which is now water displace the trapped pocket of air which was in the tube ...so that the water now acts upon the gauge internal Bordon tube?

It has nothing to do with the Boyle's & Charles combined gas equation 
It has nothing to do with permeability of gases....... 

So if this event within science does not take place we would need to bleed all trapped air prior to any gauge or gas regulator diaphragm...... ....Derek

[gondolier88]

Hi Derek,

Quite simply, air compresses and the compressed air fills the gauge to a corresponding pressure of the pressure vessel, be whatever that is.

Liquids or gasses acting on the bourdon coil, as long as they are of a constant pressure and of a low temperature in the limits of the gauge will display the correct pressure and protect the gauge from becoming damaged.

This can be seen on a valve chest pressure gauge on a full size engine- if a guage is subject to the full fluctuations of the chest it bounces dangerously and could easily become damged, but put an isolation valve on the supply and shut it to within a gnat's right family vegetable and a smooth and slow average pressure is shown that is safe and easy to read.

Greg

[benjaml1]

To add to the most excellent prior postings. The correct installation for a primary measuring device (on saturated steam) is below the pressure tap...This ensures the wet leg is always.....wet. Some of it flashes off on reduction of pressure but is quickly satisfied on resumption. Differential devices ( two or more pressure taps) incorporate "flash pots" to minimise the effect of drifting wet legs...

[derekwarner]

Thanks benjaml1 & gondolier88..........I had previously asked Anton if I should bleed the condensate line to just under my V71 regulator [to displace the entrapped air].......his partner Christine Betrange ....came back & said "unnecessary"

Even though my communicatiopns to Anton were in French/English ....dedicated responses were just single words ...without explanation 

I fully understand that if we pressurize the condensate, we pressurize the trapped gas equally.......however any trapped air will behave like a gas accumulator when pressure fluctations occur within the boiler - the result being a lack of the word "stability" that we have spoken about previously

Greg also mentions "if a guage is subject to the full fluctuations of the chest it bounces dangerously and could easily become damged'  ...I also understand this.....but  it is also the high frequency pressure oscillations or reversals that the gauge mechanics cannot resolve or display [time frequency to pressure varience] that will also cause gauge damage

Hence the importance of the WET leg as noted by benjaml1

Still a good learning curve..........seems to me that we should not just accept that condensate will occur....but in an optimal situation we should attempt to bleed all entrapped air just prior to the gauge or regulator......Derek 

[benjaml1]

Still a good learning curve..........seems to me that we should not just accept that condensate will occur....but in an optimal situation we should attempt to bleed all entrapped air just prior to the gauge or regulator......Derek 

Unnecessary.... The volume of the wet leg should exceed the mechanical & volumetric displacement of the diapragm/bourdon tube mechanism. In the model world that is minute.

It is almost impossible to saturate a bourdon tube. Although I have done it on full sized gauges by drilling the block connector & installing a vent screw. This was for a remote gauge application where it was necessary to fill the entire sealed system with silicone. However I digress.... Most gauges have built in restrictors (also called snubbers) at the connection to dampen wild action, often they are not enough, hence the use of remote isolation dampers. The prime duty of a wet leg on saturated steam is that of temperature isolation to reduce the operating temperature of the device & reduce thermal shock..

Have I mentioned freezing ? Don't leave said same device in your garden shed (over the winter) without draining. I have seen DP cells rated at 10,000 psi separate...

[Bunkerbarge]

In my drive to try to get more and more modellers interested in model steam I am often met with a level of uncertainty based on fear of the unknown. I spend a lot of time trying to explain the processes involved and remove some of the mysticysms involved with model steam but when I read through this lot I can see why things are as they are. 

While it may make members feel good to be talking almost a foreign language I hope we are always able to relate our levels of expertise to newcomers and provide a welcoming environment where questions are encouraged.  Let's not also forget that a very high percentage of model steam boat plants are below the 'Blue Book's' required 3 bar-litre limit and operate at temperatures not very far above around 120-130 degrees C so is temperature shock really an issue on a model boat plant in the middle of a boating lake?  If we then consider the significant number of plants of the Mamod and Wilesco type that are not even fitted with pressure gauges and work at about 15 to 30 psi then the whole explanation below seems to be, whilst very interesting, somewhat acedemic.

I think there would be some real value in trying to explain to the other 95% of the membership who haven't got a clue what is being talked about here just what does "saturate a bourdon tube" mean and enlighten every one on some of the other phrases being bandied around.

I'm sure there will be a tirade of indignant posts now extoling the virtues of being able to freely express thier opinions etc..etc.. but I'd really like to see posts such as these offerred as something to learn for everyone rather than just the benefit of a very few.  To me there is no point in being an expert if you can't pass your expertise on to others so now that we have defined the experts maybe they could help to remove some of the shrouds of mysticysm surrounding steam systems rather than adding to them.

[gondolier88]

Hi,

Perhaps as a moderator BB you would be willing to make one of those permanent threads at the beginning of steam R&D that could be entitled 'Beginner's need to know info on Steam' or some other suitable title that members could add SIMPLE hints and tips- perhaps sending them to a moderator first to help keep it simple, free of repetition and interesting. Along with this could be included a glossary of terms from everything from 'boiler' to 'bourdon tube' and 'safety valve' to 'thermal efficiency' etc?

I agree that steam at it's simplest is a kettle harnessed to a piston- but the guys on here with full size experience know that it is much more than that- and for most, once a certain level of knowlege is reached it becomes enjoyable to research the developement of steam over the ages upto the stupidly high temperatures and pressures and efficiency we see in Nuclear sub's or a powerstation.

Just a suggestion...

Greg

[Circlip]

Wait until they start on about "Superheating" BB 

  Regards  Ian.

[Bunkerbarge]

Hi,

Perhaps as a moderator BB you would be willing to make one of those permanent threads at the beginning of steam R&D that could be entitled 'Beginner's need to know info on Steam' or some other suitable title that members could add SIMPLE hints and tips- perhaps sending them to a moderator first to help keep it simple, free of repetition and interesting. Along with this could be included a glossary of terms from everything from 'boiler' to 'bourdon tube' and 'safety valve' to 'thermal efficiency' etc?

I agree that steam at it's simplest is a kettle harnessed to a piston- but the guys on here with full size experience know that it is much more than that- and for most, once a certain level of knowlege is reached it becomes enjoyable to research the developement of steam over the ages upto the stupidly high temperatures and pressures and efficiency we see in Nuclear sub's or a powerstation.

Just a suggestion...

Greg

I think that's a great idea Greg and something I'll have a play around with.  I don't think they need to go via a moderator but we would obviously reserve the right to remove anything that wanders off topic.

Thanks for the suggestion.

As for superheating Circlip, we could start a whole thread on it's own for that but perhaps it would be best behind locked doors of a small padded room?!!  I'm with you on that one though, let's just call them driers

[red_noir]

OK did some piping rework ! and I'm submitting it for approval !

ReD

[gondolier88]

I wouldn't worry about approval- I think we'll all be coming to you for approval!

Greg

[benjaml1]

I couldn't agree more with the prior post.... May I also respectfully add..... Lovely work...  

[red_noir]

hey thanks ! that put a smile on my face  

well to sum it all up i put a dip in the sense piping to the valve. after all the soldering was done it didn't work !   no gas ! what the h3LL !!!!


i began doing a pipe by pipe check, all pipes were clear then I realized it was the regulator that was stopping flow and acting like a check valve, after much cursing I realized i had installed the valve the wrong way around the first time and it worked???? Now suddenly it wouldn't.

I also found that the no.5 jet was now clogged ! So i disassembled the valve ( its actually quite simple all the parts are brass and stainless and the seals are butyl rubber o'rings) after all was assembled and the piping sorted out, and the n0.5 jet un-clogged every thing work as advertised ! set to 30psi and the valve regulates gas pressure !!

[red_noir]

before image of the valve !

[benjaml1]

A simple mistake, one that I almost made myself....