Is it worth the expense of putting a pressure gauge onto the Racor

GHA said:
Says "absolute" pressure, doesn't that mean anything under 1 bar is negative? A vacuum is just a pressure less than air pressure?
Not sure. Anyone?
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Could be. I wasn't sure either.

If that's correct, it encodes a gauge pressure of -0.8 bar to +2.5bar into a voltage range of 4.6v, or 1.39 volts per bar. We're only interested in 0 to -0.8 bar, or a range of just over a volt. How accurately does the ADC on an Arduino or similar measure that kind of range? (Genuine question, I've never tried it)

If you already have lots of monitoring electronics then this might be worthwhile - it's true that a trace over time could be mildly useful to someone who's into gathering data. But for the vast majority of sailors, the £7 gauge still makes more sense :)

Pete
 
prv said:
Could be. I wasn't sure either.

If that's correct, it encodes a gauge pressure of -0.8 bar to +2.5bar into a voltage range of 4.6v, or 1.39 volts per bar. We're only interested in 0 to -0.8 bar, or a range of just over a volt. How accurately does the ADC on an Arduino or similar measure that kind of range? (Genuine question, I've never tried it)

If you already have lots of monitoring electronics then this might be worthwhile - it's true that a trace over time could be mildly useful to someone who's into gathering data. But for the vast majority of sailors, the £7 gauge still makes more sense :)

Pete
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The arduino adc is 10 bit so theoretical resolution of max 5v of about 5mV so plenty accurate enough for this. Would make sense in my case, readable from the cockpit on a tablet and easier then finding somewhere to mount another gauge :)
 
It always happens Nigel. Soon the insults will start. I think a simple gauge is the best solution, mounted somewhere you can easily see it. I'm not a fan of too many electronic things on a boat because I don't understand them.
 
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I think that differential pressure across the filter(s) would be more useful. That way you can tell if its the primary, secondary or in tank jobbie thats the problem. Sure final absolute just before lift pump is a good overall health indicator, but not as handy as individual readings. This is where the digital solution wins hands down since you dont need a display for each sensor, dont need plumbing for each sensor and can wire them all with one twin screened cable.
 
prv said:
I would definitely recommend a vacuum gauge. Not having one is a bit like not having a fuel gauge, and filling the tank every 20 engine hours (or whatever) just in case.
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Yeag, but there are two approaches to consider, depending on how you use the engine. Just as an example (following on your analogy) Fuel guages being famous for misreading - the fleet of buses I work on simpy have the guages disconnected the first time they misbehave - being in use daily, the tank is brimmed daily - just as you said. The whole ethos of maintenance is based on responding immediately to any symptom and regular, frequent servicing.

My boat being the opposite - very infrequent use - I have a sight tube (always correct) but rarely look at it. I'm much more likely to check the filter bowl!

Rob.
 
prv said:
I would definitely recommend a vacuum gauge. Not having one is a bit like not having a fuel gauge, and filling the tank every 20 engine hours (or whatever) just in case.
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Yeah, but there are two approaches to consider, depending on how you use the engine. Just as an example (following on your analogy) Fuel guages being famous for misreading - the fleet of buses I work on simpy have the guages disconnected the first time they misbehave - being in use daily, the tank is brimmed daily - just as you said. The whole ethos of maintenance is based on responding immediately to any symptom and regular, frequent servicing.

My boat being the opposite - very infrequent use - I have a sight tube (always correct) but rarely look at it. I'm much more likely to check the filter bowl!

Rob.
 
KellysEye said:
The best thing to do is clean the fuel get a professional company to do it.
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So the longer version of the saga is:
Initial problem came to light when I had 750L in the tank. In corfu had the fuel polished by cycling through three filter system. Fuel was not truly clean and still had a bit of water coming into the racor, so drained every week. Now have run fuel down to 150L so man in Zea marina could empty the tank and clean it. Then will refill with new fuel.
Have had a Fuelguard fitted upstream of the Racor. Now have 10micron filter in the Racor instead of the standard 30 micron. I have not fitted the polisher that Fuelguard also sell.
Basically now a bit obsessed with water and dirt in diesel!
Thanks for all the suggestions.
Tudorsailor
 
Dougal Tolan said:
I think that differential pressure across the filter(s) would be more useful. That way you can tell if its the primary, secondary or in tank jobbie thats the problem. Sure final absolute just before lift pump is a good overall health indicator, but not as handy as individual readings. This is where the digital solution wins hands down since you dont need a display for each sensor, dont need plumbing for each sensor and can wire them all with one twin screened cable.
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What sort of pressure would it be across a filter in reasonable health?
 
GHA said:
What sort of pressure would it be across a filter in reasonable health?
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Not answering your question exactly, but hopefully useful information.

I've just got the vacuum gauge between the primary filter and the lift pump. The problem on my boat is not necessarily the filter as there is a long convoluted pipe run from the tank and gunk seems to congregate at certain points along the pipes.

Fresh filter, clean pipes <5ins/Hg. At this vacuum the needle is affected more by engine vibration than the vacuum. It can be a bit of a blur.

Get ready to change filter & clean pipes at 8ins/Hg.

Noticeable impact on engine performance at 10 ins/Hg

Engine stops at about 12 ins/Hg
 
lpdsn said:
Not answering your question exactly, but hopefully useful information.

I've just got the vacuum gauge between the primary filter and the lift pump. The problem on my boat is not necessarily the filter as there is a long convoluted pipe run from the tank and gunk seems to congregate at certain points along the pipes.

Fresh filter, clean pipes <5ins/Hg. At this vacuum the needle is affected more by engine vibration than the vacuum. It can be a bit of a blur.

Get ready to change filter & clean pipes at 8ins/Hg.

Noticeable impact on engine performance at 10 ins/Hg

Engine stops at about 12 ins/Hg
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Ta, just the info I was after. Too much for a sensor I was looking at unfortunately, never mind :)
 
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