Raw water flow sensor

[richardsnowstar]

I have a raw water cooled Bukh 36 engine and I have fitted a temperature alarm sensor to the outside of the exhaust hose. However it didn't work the other day when I noticed that the engine temp guage was showing very high. It turned out the strainer on the inlet was blocked with weed and little or no water was getting through.

I have fitted the sensor to the outside of the rubber exhaust hose, should I fit it to the metal exhaust elbow? Also does anyone know of a way of testing these type of sensors?

Alternatively I seem to remember seeing mention of a flow sensor in these forums but cannot find it. Does anyone know of a flow sensor system I can fit?

Thanks.

 

[nimbusgb]

I fitted a flow sensor and alarm to my raw water system. The sensor needs a sense swap relay but it's fairly simple to do. http://uk.rs-online.com/web/p/flow-controllers/0257076/

I have a spare sensor if you want.

 

[David2452]

Most overheat sensors I've seen need the strip tucked in between the elbow and hose in direct contact with the metal. The hose will act as an insulator, not much but probably enough. A flow sensor will give the alarm before an overheat situation so has to be a better option surely.

http://www.aqualarm.net/comerus/store/comersus_viewItem.asp?idProduct=8

 

[Graham_Wright]

http://www.aqualarm.net/comerus/store/comersus_viewItem.asp?idProduct=8

I like that. I wonder if it imposes any restriction on the flow? It could be installed anywhere in the sea valve and the exhaust injection. Any dealers in the UK?

 

[pampas]

PBO no 474 June 2006. describes the complete system. sorry scanner us.

No it does not interfere with water flow except on the micro level.

 

[srp]

Details of a flow sensor here - towards the bottom of the page.
There have been a few other threads here in the past, eg http://www.ybw.com/forums/showthread.php?t=199955
From memory the sensor that I used was from CPC, is the same as the one Nimbus linked to, and needs 0.5litres/min flow to operate (which is just about ok on a Yanmar 1gm10). And I think there is a bigger one available as well, or there was when I made mine up.
The trouble with a temp sensor on the exhaust is that the alarm only goes off once the engine has got too hot, and a flow alarm will hopefully prevent that happening.

 

[pampas]

Here is the article and bits required.

 

[Ruffles]

Most overheat sensors I've seen need the strip tucked in between the elbow and hose in direct contact with the metal. The hose will act as an insulator, not much but probably enough. A flow sensor will give the alarm before an overheat situation so has to be a better option surely.

http://www.aqualarm.net/comerus/store/comersus_viewItem.asp?idProduct=8

I was going to buy one of those but couldn't work out what pipe fittings I would need. I couldn't get any sense from the suppliers.

 

[concentrik]

This might be a start:

http://goo.gl/px71L

I asked already, and since the water contact parts are plastic and stainless they are ok in seawater.

You'll need a bit of electronics to convert the pulse output to a useable form - this is a good start, using an IC type LM2907 very simple:

http://www.ti.com/lit/an/snaa088/snaa088.pdf

 

[Graham_Wright]

Here is the article and bits required.

Now £14.63 from Farnell.

 

[petersto]

Google Yachtmates, less hassle.

 

[Martin_J]

To be brutally honest I find the idea of hoping the sensor will work well on either the outside or the exhaust hose or the outside of the metal mixing elbow both rather wishful thinking..

Just think... That exhaust elbow normally runs cold (because the sea water is in between the double skins).. If the cooling water stops.. the hot exhaust gases will be in the centre of the elbow.. and now there will be an air gap to the outside of the elbow.. just like in a vacuum flask.

Since this is an important area to monitor (and all the US boats I have come across must have them) - why not go the whole way and mount the sensor within the hot exhaust gases...
Vetus exhaust hose temperature sensor

Now as a money saving tip (since I'm not into spending money for the sake of it) - Wire it in parallel with your engine temp sensor and your standard external panel alarm will beep if either sensor reaches threshold.

 

[David2452]

I was going to buy one of those but couldn't work out what pipe fittings I would need. I couldn't get any sense from the suppliers.

They do actually sell the threaded hosetails on their site, only a few hose sizes available though which is a bit restrictive. I suspect they are NPT.