Raw Water Flow Sensor Question??

[goeasy123]

The exhaust exits underwater on our boat. You can't visually check that there's raw water flow.

Is there an easy to fit water flow detector with a buzzer on some other solution to keep a constant watch on water flow?

 

[pvb]

Lots of them, although they tend to work on exhaust temperature rather than water flow. The cheapest is probably the Nasa EX1 at about a hundred quid. Vetus have a system at around £150, and Halyard have the Exhaust Alert which is around £200.

EX-1 exhaust temperature monitor/alarm - Nasa Marine Instruments
Exhaust Temperature Alarms For Water Injected Boat Exhausts
Halyard Marine Exhaust Alarm Kit

 

[rogerthebodger]

This is the type of raw water flow switch I used on both my main engine and my generator. Fitted in the raw water inlet to the engine.

I connected it to a relay, LED and buzzer all from RS components.

FS22A | N/O liquid flow switch,22mm dia 3.5 l/m | RS Components

 

[pvb]

This is the type of raw water flow switch I used on both my main engine and my generator. Fitted in the raw water inlet to the engine.

I connected it to a relay, LED and buzzer all from RS components.

FS22A | N/O liquid flow switch,22mm dia 3.5 l/m | RS Components

I see from the data sheet that the alarm won't operate until the flow drops below 1.4 litres/min, which doesn't sound much at all. I'd have thought that a partial restriction in the cooling water could lead to overheating before the flow reduced to 1.4 litres/min.

 

[rogerthebodger]

I see from the data sheet that the alarm won't operate until the flow drops below 1.4 litres/min, which doesn't sound much at all. I'd have thought that a partial restriction in the cooling water could lead to overheating before the flow reduced to 1.4 litres/min.

I have never had a issue . What I did have was my alarm light flash and alarm sound on and off while motoring on a winglass day and the engine temperature gauge right on target.

Exhaust water was a little steamy but I could hold my had in the exhaust water. Also checking the exhaust manifold with and IR thermometer I had no concern.

There is a smaller one if the engine has a lower flow rate that could be used .

Shurely we are looking for a very low flow or a blockage so if the flow falls below 1.4 lit/min to sound an alarm is better the nothing.

What is the normal/minimum raw water flow rate for most marine engines.

 

[pvb]

What is the normal/minimum raw water flow rate for most marine engines.

For small marine diesels, around 10 litres/min at say 2000rpm. I believe Jabsco work on the basis of needing a flow of 45 litres/min per 100hp. I'd have thought that dropping to 1.4 litres/min before the alarm sounds could certainly cause overheating, so you've been lucky. The temperature-based exhaust alarms seem infinitely preferable.

As a comparison, the 1" version of the Aqualarm flow sensor triggers the alarm when the flow falls between 12-15 litres/min.

AQUALARM Coolant Flow Detector buy now | SVB

 

[Rich T]

This is the type of raw water flow switch I used on both my main engine and my generator. Fitted in the raw water inlet to the engine.

I connected it to a relay, LED and buzzer all from RS components.

FS22A | N/O liquid flow switch,22mm dia 3.5 l/m | RS Components

Have used one of these for years now, the smaller version to fit 13mm pipe, Beta 20 engine. I have it fitted just before the anti siphon T piece so it will detect any problem from the inlet skin fitting and right through the raw water side circulation of the engine.
Not expensive and simply needs a relay to reverse the switching operation of the flow switch. I then use this to actuate a general engine alarm that looks out for low oil pressure, over temp of coolant and raw water flow. It is sensitive, closing the sea cock even slightly sets off the alarm.
Cheap and effective !
Richard

 

[rogerthebodger]

The temperature-based exhaust alarms seem infinitely preferable.

Well that you choice and may be the real reason for the constant questioning of my suggestions.

Personally I prefer to have a alarm of the cause of the problem rather the effect.

I did fit a bi metal switch on both my engine heat exchanger and exhaust water injection elbow but due to the temperatures at normal running being so low even with low raw water flow rates I did not bother to wire then up.

You do it your way I will do it my way and it up to the OP to decide what he wishes to do.

As a comparison, the 1" version of the Aqualarm flow sensor triggers the alarm when the flow falls between 12-15 litres/min.

AQUALARM Coolant Flow Detector buy now | SVB

In process control Engineering there are numerous flow switches for various side of pipes. The paddle type can even be adjusted for whatever flow rate you wish.

I have this type in the water cooling system of my boat aircon

 

[pvb]

Well that you choice and may be the real reason for the constant questioning of my suggestions.

I always thought that forums were for the free exchange of views; apparently you don't.

An alarm which triggers when the cooling water flow rate drops to 1.4 litres/min seems much too low for safety. But what do I know, I'm just a simple engineer.

 

[Cariadco]

I always thought that forums were for the free exchange of views; apparently you don't.

An alarm which triggers when the cooling water flow rate drops to 1.4 litres/min seems much too low for safety. But what do I know, I'm just a simple engineer.

Aha, A simple Engineer.......I like those...!!

 

[greeny]

Lots of them, although they tend to work on exhaust temperature rather than water flow. The cheapest is probably the Nasa EX1 at about a hundred quid. Vetus have a system at around £150, and Halyard have the Exhaust Alert which is around £200.

EX-1 exhaust temperature monitor/alarm - Nasa Marine Instruments
Exhaust Temperature Alarms For Water Injected Boat Exhausts
Halyard Marine Exhaust Alarm Kit

Or if you're a cheapskate like me, buy a small thermostat off ebay for a fiver and wire it to a buzzer.

 

[rogerthebodger]

I always thought that forums were for the free exchange of views; apparently you don't.

For from it that the point that you and I have different solutions to the potential problem and I do make a point thai this i the way I have solved the problem You raised some issues that you considered to be not to you requirement.

I don't have issue with your solution, in fact I considered it and started to implement a similar solution.

I posted my way 2 minutes after you and I made no reference or comment to your suggestion,.

Yet you responded to mine with criticism not the first time. The perception is you criticize any solution that is different to yours and my be viewed better.

To me its just a different solution to a potential problem and in fact both could be implicated for belt and braces.

But what do I know, I'm just a simple engineer.

In my experience different Engineers will have different solution to a particular problem/issue . This is due to there experience and depth of knowledge throughout their working life

The key is to respect the others person's view. This does not you must agree, it respect.

My posting are generally on what solution I have used on my boating work/building.

Making personal comments about a person is unbecoming the Engineering Profession and specially a Chartered Engineer.

As an Engineer you know that the requirements will dictate the solution. What I want is an indication of a blockage or no flow (pump impeller damage) if I get a reduction in flow that will affect the operation of the engine (over heating) the flesh water temperature gauge will show me that.

Yes an exhaust temperature will also give that alarm

 

[rogerthebodger]

Aha, A simple Engineer.......I like those...!!

I would like to know what kind of Engineer as the term Engineer is a very misused term.

 

[pvb]

Or if you're a cheapskate like me, buy a small thermostat off ebay for a fiver and wire it to a buzzer.

Ha! Yes, even the professional products are basically temperature sensors. A good way of detecting overheating.

 

[PetiteFleur]

This is the type of raw water flow switch I used on both my main engine and my generator. Fitted in the raw water inlet to the engine.

I connected it to a relay, LED and buzzer all from RS components.

FS22A | N/O liquid flow switch,22mm dia 3.5 l/m | RS Components

Yes, that's the one I bought years ago sitting somewhere in my workshop - was going to fit it but then fitted a new engine with the exhaust out the transom so I could see it.

 

[rogerthebodger]

Or if you're a cheapskate like me, buy a small thermostat off ebay for a fiver and wire it to a buzzer.

A fiver, is the five UK pounds why so expensive.

2pcs Manual Reset Temperature Switch 105 °C NC Bimetal disc thermostat KSD301 | eBay

Two for 5 USD

2pcs KSD301 50°C / 122°F Degree Celsius N.C. Temperature Switch Thermostat | eBay

Two for 3.48 USD including postage to the UK

 

[pvb]

I posted my way 2 minutes after you and I made no reference or comment to your suggestion,.

Yet you responded to mine with criticism not the first time. The perception is you criticize any solution that is different to yours and my be viewed better.

More backbiting!

In post 4 I posted an honest observation. How on earth you can construe that to be criticism is beyond me.

Please give it a rest.

 

[rogerthebodger]

More backbiting!

In post 4 I posted an honest observation. How on earth you can construe that to be criticism is beyond me.

Please give it a rest.

To you "honest observation " to any one else the perception is criticism

Its just like one man's terrorist is another man's freedom fighter.

You also need to give it a rest.

 

[pvb]

To you "honest observation " to any one else the perception is criticism

Its just like one man's terrorist is another man's freedom fighter.

You also need to give it a rest.

In post 4 I said "I see from the data sheet that the alarm won't operate until the flow drops below 1.4 litres/min, which doesn't sound much at all. I'd have thought that a partial restriction in the cooling water could lead to overheating before the flow reduced to 1.4 litres/min."

How is that "criticism"? It's an honest observation, based on facts which I subsequently supplied when you asked for them.

I can't believe that anyone else would perceive this as criticism. If we follow your rules of never commenting on other people's recommendations, the forums will soon die. Is that what you want?

 

[greeny]

A fiver, is the five UK pounds why so expensive.

2pcs Manual Reset Temperature Switch 105 °C NC Bimetal disc thermostat KSD301 | eBay

Two for 5 USD

2pcs KSD301 50°C / 122°F Degree Celsius N.C. Temperature Switch Thermostat | eBay

Two for 3.48 USD including postage to the UK

K.I.S.
Don't forget we have to pay import duty. So rounded it up to a fiver.