Pressure guage innaccuracies!

[rmoore8118]

Ok, so I had an old SIB which was worn out. It had a hand pump with a guage and life was good.

I got a new SIB this fall which also came with a nice high pressure hand pump with a guage. Life was still good. I decided to get a manometer to use on the water as it is more convenient than pulling out the pump just to check pressure. Upon comparing the new pump guage with the new manometer, I found a 1 full PSI difference between the two. THAT's HUGE when you factor in possible pressure increases in the sun.

The Manometer reads 1 pound higher than the new pump (meaning I had been overinflating my SIB with the pump?????)....or was the manometer wrong?

Then I remembered I had retained the guage off of my old worn out pump from the old boat. It matched the manometer. So, I guess the odds are that the new pump guage reads 1 PSI low???!!!!!

It seems when I inflate the boat per the manometer, it is soft....or is it just that I got used to the "feel" of the boat overinflated?

Can anyone think of a good accurate way to "calibrate" my guages, short of buying several more and working the odds?

Before you say take it out and see if it handles right at the manometer pressure.....the water is a little cold and extra hard here in the northlands!

Thanks

 

[Sea Rider]

Re: Pressure guage innacuracies!

Re: Pressure guage innacuracies!

Had same bad experience with 3 different well known brands gauges, we sell inflatables and engines, the gauges are given to clients for their boats to perform as expected. The only way to solve the issue was taking several ones to match a 3.0 psi lab calibrated gauge. Picked one that matched 3 psi as a standard measurement called the master, the sib is inflated to 3.0 psi with it, the one that will de given to client is compared to the master reading to see pressure differences, according to the final reading, we tell client to inflate their sibs to that given obtained pressure, but in reality they are inflating to 3.0 psi with a false number reading.

Other issue would be to buy 2 of the same brand and compare readings between them, or compare between different brands. Thought that buying expensive, state of the art gauges would have precise readings, but no, assume a bad quality control at the factory Don't intend to open them up, are very delicate and mission impossible to fix.

Other issue about innacuracies readings are related to gauge valve adaptors, too much air is being released when pushed and twisted on valve specially Halkey Roberts type, finally have solved the problem by making at a machine shop a proper state of the art gauge adaptor, the pin valve is only pushed 1 mm downwards giving precise readings that using as factory delivered which released too much air (as much as 0.5 psi) when finally seated on valve pin.

Happy Boating

 

[Dry Diver]

Re: Pressure guage innaccuracies!

ok here is a stupid question. If my SIB has overinflation valves on it then is there any reason that I can not just inflate the chamber till the pressure relief valve "vents" some air out. My understanding is that the valves are there to prevent over pressurization. So in effect the chamber should be in no danger of being hurt while being inflated as long as you are not using a really high volume pump that can put air in faster than you could react to the valve venting.

This is not how I currently inflate my SIB, I have heard a few different dealers say that was an acceptable way to inflate. If that is the case, why the reason for the gauge. Are they for older SIBS and RIBS that don't have the OP valve?

 

[rmoore8118]

Re: Pressure guage innaccuracies!

That may be true for those SIBs that have n overpressure valve. Not all do and mine does not. However I did red that the overpressure valves do not close back up at the prescribed inflation pressure. I'm going from memory here but as an example if your recommended inflation pressure is 3.6 psi, the valve may pop off at 4.5 psi and re-close at 4.0 psi. Is that enough to hurt the tubes? Probably not, but what if it is always is at 4.0 psi? Over time does that tend to stretch and deform the tubes? I don't know. The pop off valves certainly will keep from dangerous catastrophic failure, like a rupture, I am sure. I wish I had relief valves, but if I did I would still want a guage to keep in mfr. specs. You can check with your mfr. for your specific valve and ask them about just inflating till pop-off.

 

[Bama7474]

Re: Pressure guage innaccuracies!

Is it bad to leave your SIB inflated while not in use? I know that our RHIB's on our ships are always inflated, usually for 6-9 month periods but those are built for at sea purposes. Just curious.

 

[Dry Diver]

Re: Pressure guage innaccuracies!

I usually store mine with some air in it. I will take the valve out and let the air inside bleed off till I stop hearing it come out. I keep mine on a trailer so there isn't any issues about moving it about.

When it is time to inflate I will fire up the compressor and fill'er up till the tubes start to get hard and then set the pressure. I know that I might get a hard time for using a compressor, keep in mind that my SIB is 16' long. It does not fill quickly. I understand the whole pressure vs. volume relationship. I have never had a problem doing it this way. I do not have over pressure relief valves. so I am very careful when I do this. Even with a compressor it can take 10 min or so to get it inflated correctly.

 

[Sea Rider]

Re: Pressure guage innacuracies!

Re: Pressure guage innacuracies!

Is it bad to leave your SIB inflated while not in use? I know that our RHIB's on our ships are always inflated, usually for 6-9 month periods but those are built for at sea purposes. Just curious.

No, you can leave a sib/rib inflated to 2.5 -3.0 psi for as long as you want, that is indoor and shaded, lying horizontal on floor without engine or vertical against a wall. Normally never deflate mine once inflated, as they live on trailers with engine on. You can store them on ship decks, relief pressure accordingly if in hot environments places, excesive sun like in the tropics, place a proper thick cover on sib.

Happy Boating