Inside a water pressure gauge

[RickCamilleri]

I had a water pressure gauge that wasn't working. I decided to take it apart and was a little surprised at what I found. Attached is a picture of a Teleflex Amega series water pressure gauge, 0 to 30 PSI
It appears that pressure enters the tube and acts like a little pendulum. Attached to that thicker tube through a few hinges is a serrated Hammer type mechanism. As the pressure increases in the tube it lifts moving the hammer which is attached to a cog which moves your gauge needle. Pretty interesting

[fishin couillon]

THat's it and they arent cheap.....

[billnorman1]

The actuator of a water pressure gauge is the thing in the picture called a Bourdon tube. Yours has a kink in it so I doubt it will ever be accurate. It may indicate but not necessarily the exact pressure. The water pressure causes the curved tube to try to straighten out which moves the semi-round gear and in turn that gear acts on the small gear on the same shaft as the indicator needle.

https://www.google.com/search?q=bour...hrome&ie=UTF-8

[twitch]

did that guage ever freeze that might account for the kink....

[RickCamilleri]

did that guage ever freeze that might account for the kink....

It's a new to me boat, so I can only assume it froze. I've installed a new one and am in the process of finding a tee fitting to drain it for next falls winterizing

[RickCamilleri]

The actuator of a water pressure gauge is the thing in the picture called a Bourdon tube. Yours has a kink in it so I doubt it will ever be accurate. It may indicate but not necessarily the exact pressure. The water pressure causes the curved tube to try to straighten out which moves the semi-round gear and in turn that gear acts on the small gear on the same shaft as the indicator needle.

https://www.google.com/search?q=bour...hrome&ie=UTF-8

That's an awesome explanation. Thank you. By tinkering around with it I was able to figure out the mechanics, but now we can see what freezing does to a guage like this.

Are all marine water pressure guages built this way?

[CJ1]

Mechanical gauges are. Cj

[Rip Bass]

I have taken several of them apart and reset the gears back to zero after they froze. None of mine ever had a kink in them though.

[billnorman1]

Freezing would tend to make that tube straighten out, and run the semi-round gear off the pointer gear. The usual result is a gauge that reads water pressure when there is none. Anyhow, they are expensive, usually the most expensive of the small gauges.
My Suzuki doesn't have a tap for a WP gauge and I think the master gauge has an overheat warning light.

[Marinadan]

That round tube should be almost flat. The pics you show are of a gauge that has been frozen.

[billnorman1]

That round tube should be almost flat. The pics you show are of a gauge that has been frozen.

[Jonestrollingmotor]

The actuator of a water pressure gauge is the thing in the picture called a Bourdon tube. Yours has a kink in it so I doubt it will ever be accurate. It may indicate but not necessarily the exact pressure. The water pressure causes the curved tube to try to straighten out which moves the semi-round gear and in turn that gear acts on the small gear on the same shaft as the indicator needle.

Air pressure should be inserted where you have water pressure. You cannot compress water, however, the water being pumped from the outboard on the other end of the line, pressurizes the air in the line. As I said in another post, if there is water in the gauge, the air is gone and the gauge is said to be waterlogged and any reading will not be trusted. Should not be water in that line, it is/should be a sealed system.
John

[TrackerPro16]

Air pressure should be inserted where you have water pressure. You cannot compress water, however, the water being pumped from the outboard on the other end of the line, pressurizes the air in the line. As I said in another post, if there is water in the gauge, the air is gone and the gauge is said to be waterlogged and any reading will not be trusted. Should not be water in that line, it is/should be a sealed system.
John

This. It probably got a crack in the bladder (happens occasionally) or leak at the solder joint and bled out the air until it filled with water, then it froze, ballooning it out.

[Casslaw]

Thanks for that. I wondered how they worked but I Assumed it was an electronic gauge.

If I can understand your explanation than you did very well! Hope your new gauge works out Op, can’t imagine that poor bladder blowing up that much.

[CastingCall]

There's a thread on "fixing" damaged PSI gauges, but safe to say that one is beyond repair! lol

http://www.bbcboards.net/showthread.php?t=874817

[billnorman1]

Air pressure should be inserted where you have water pressure. You cannot compress water, however, the water being pumped from the outboard on the other end of the line, pressurizes the air in the line. As I said in another post, if there is water in the gauge, the air is gone and the gauge is said to be waterlogged and any reading will not be trusted. Should not be water in that line, it is/should be a sealed system.
John

John, the air inside can be compressed by the water coming in and water squeezed into the cavity of the tube also. The air doesn't freeze. The water does and straightens the tube. I've lost a few myself due to frozen water.
On old recip aircraft we used to have direct reading oil pressure gauges in the cockpit, but of course if an oil line broke any where between the gauge and the motor it would be catastrophic so there was an inert liquid in the lines that transmitted the pressure to the gauge via a sender diaphragm on the motor. If it got aerated which it did on occasion we'd have to add fluid and bleed the system. Like today's cars but a liquid instead of electricity carrying the logic.

[Jonestrollingmotor]

John, the air inside can be compressed by the water coming in and water squeezed into the cavity of the tube also. The air doesn't freeze. The water does and straightens the tube. I've lost a few myself due to frozen water.
On old recip aircraft we used to have direct reading oil pressure gauges in the cockpit, but of course if an oil line broke any where between the gauge and the motor it would be catastrophic so there was an inert liquid in the lines that transmitted the pressure to the gauge via a sender diaphragm on the motor. If it got aerated which it did on occasion we'd have to add fluid and bleed the system. Like today's cars but a liquid instead of electricity carrying the logic.

I agree with what you're saying, but what I'm trying to state, is "if" there is water in the gauge it is because the air that is suppose to be there has been pushed out by the force of the water coming from the water pump. The air is what compresses to give the reading -- not the water so in theory, when installed there is uncompressed air in the gauge and the hose, the water being sent from the water jacket of the outboard into the hose, compressing the air that was in the hose and gauge to get the reading. When the water makes it's way to the gauge, then it has pushed the air out of a closed system and there is problems somewhere. When there is water in the gauge, you're not getting a reliable reading. Now, when freezing weather comes and water expands, it will compress the same air and give a reading on the gauge -- if the gauge has air in it as it should. If it is waterlogged (water has replaced the air) then it will freeze, malform, and possibly bust.

[dkibat]

The gauge may be expensive but how about a rebuild or new motor.

[CastingCall]

The gauge may be expensive but how about a rebuild or new motor.

Aside from the cost, availability is an issue. Some of the old gauges aren't available anymore. Sucks if you want to retain OE looks between all gauges.