DIY failsafe idea w/ schematic

[HmanEVO]

Here is an idea for a DIY failsafe utilizing two inline pressure sensors to detect a fault. One sensor is used to detect low pressure (pump failure, line leak, etc) and the other for detecting high pressure (clogged nozzle).

Failsafe w/ two pressure sensors



Let me start by saying that I run a SMC kit which most people already know uses a progressive controller. Right now I have the spray start point at 12psi with full spray at 16-17psi(almost an on/off system but not quite).

-The idea is that once the Hobb's pressure switch see's aprox 18psi, it's contacts close. If the low pressure sensor does not see line pressure above lets say 75psi by this time(which it should under normal conditions), it's contacts remain closed and the circuit breaker is popped. Thus removing power from the relay and shutting off the greddy ebc. When the ebc loses power its solenoid defaults to normally open dropping boost down to wga pressure. For mbc users, another solenoid could be used in the same fashion and triggered by the circuit breaker/relay.

-As for the high pressure line sensor, it works very similar. If boost is above ~18psi(hobbs switch closed) and line pressure exceeds the sensors set point due to a clogged nozzle, it's contacts close causing the circuit breaker to be popped, etc etc.

-I've also incorporated two lamps or led's. One indicates when the system is at operating pressure and the other is used to indicate a fault has occurred.

I'd appreciate hearing any suggestions or concerns any of you might have. I'd like to get some feedback before I go further with this.

EDIT: Thanks to a point brought up by SlowCar, it looks as if the high pressure sensor(clogged nozzle detector) is a no-go for use with an on-demand pump like that which SMC uses. At this point I'll probably just go with the single low pressure sensor and call it a day. This is not something I recommend doing so please do at your own risk. I perform periodic maintenance of my alky system and am confident not running a sensor for clog detection.

Failsafe w/ single low pressure sensor

[Richard L]

You may need to incorporate a delay timer with the low pressure sensing side as the system take a few tens of second to build pressure up to 75psi. Ignore my comment if the failsafe is not used to cut boost or switch MAP etc.

[Richard L]

If you copy post your failsafe idea to the sticky, it will remain useful for the rest of the discussion. Just a suggestion.

[bnice01]

Originally Posted by Richard L

You may need to incorporate a delay timer with the low pressure sensing side as the system take a few tens of second to build pressure up to 75psi. Ignore my comment if the failsafe is not used to cut boost or switch MAP etc.

but if he has a water solenoid or check valve then it should be alright but richard is right pending on how long your w/i lines are it may take a bit to reach 75psi of pressure (or you can set it lower) . If you have the water solenoid/check valve once the pump turns off pressure will reamin in the lines, since its an instant stuff from the pump and water solenoid/check valve.

but yeah Ignore my comment if the failsafe is not used to cut boost or switch MAP

not bad man great work

[HmanEVO]

Originally Posted by Richard L

You may need to incorporate a delay timer with the low pressure sensing side as the system take a few tens of second to build pressure up to 75psi. Ignore my comment if the failsafe is not used to cut boost or switch MAP etc.

That's a good point. Also, the failsafe is used to cut boost. Once the failsafe is triggered, power is removed from the ebc, solenoid opens, and boost drops down to wastegate pressure.

I figured the operating line pressure under full boost to be aprox 90-95psi. Since I have the SMC controller setup to go full spray by 16-17psi, I was hoping line pressure would be above 75psi by the time the hobb's switch see's boost at 18psi. Like you said though, it may take a few 1/10th's of a second to build pressure above 75psi and that would cause a problem. Incorporating a delay timer seems like the proper solution if I find that to be the case. I'll have to look into that as a possibility and whether it's cost effective.

Originally Posted by Richard L

If you copy post your failsafe idea to the sticky, it will remain useful for the rest of the discussion. Just a suggestion.

Sure I can add it to that thread. You're referring to the "There are failsafes, failsafes, and failsafes..." thread correct?

Originally Posted by bnice01

If you have the water solenoid/check valve once the pump turns off pressure will reamin in the lines, since its an instant stuff from the pump and water solenoid/check valve.

The SMC kit uses a check valve right before the nozzle which I believe has a cracking pressure somewhere around 20psi. So I'd agree that some pressure should still be remaining in the line after the pump shuts off.

[SlowCar]

Originally Posted by HmanEVO

-As for the high pressure line sensor, it works very similar. If boost is above ~18psi(hobbs switch closed) and line pressure exceeds the sensors set point due to a clogged nozzle, it's contacts close causing the circuit breaker to be popped, etc etc.

what pressure does the on-demand pressure switch on the pump kick in?

[HmanEVO]

Originally Posted by SlowCar

what pressure does the on-demand pressure switch on the pump kick in?

I believe it's somewhere around 35-40psi if I remember correctly.

Edit: Nevermind, I was thinking of something else. Excuse my ignorance but the on-demand pressure switch is what regulates the pumps peak pressure correct? If thats the case, I see 115-120psi at the nozzle under no boost and the pump at full speed.

[SlowCar]

yep, the little square box on the pump head



i am thinking how you can make your upper limit pressure switch failsafe work in the very unlikely event a clog or crushed line occurs with the demand switch inplace

[HmanEVO]

I had to think about it for a minute but I think I get what you're saying. Because the demand switch is in place, it's not going to allow line pressure to increase beyond it's set point.

So if there is a clog or some type of restriction, pressure is not going to increase any further because the pump is being regulated by the demand switch correct? There will just be a drop in flow. This means the high pressure switch in the failsafe as it stands now won't be able to actually detect a restriction.

[SlowCar]

yeah...

[bnice01]

Originally Posted by HmanEVO

I had to think about it for a minute but I think I get what you're saying. Because the demand switch is in place, it's not going to allow line pressure to increase beyond it's set point.

So if there is a clog or some type of restriction, pressure is not going to increase any further because the pump is being regulated by the demand switch correct? There will just be a drop in flow. This means the high pressure switch in the failsafe as it stands now won't be able to actually detect a restriction.

OOOOOOO THATS right freaking pressure switch damn back to the drawing board

you can always bypass it but you want be able to use your progressive controller, your pump will not pulse and will spray like a water hose in time that will lead to failure. usually what happen the motor bushing wear out problem overheating been there before. lost a few pumps

also pending on the maxium burst of the lines (most are rated up to 350-500psi) I can only see the pump failing another way because of the stress on the motor with the restriction being so great. man this sucks I really was excited about your diagram bro but still a great idea

[HmanEVO]

Updated original post.

[darqnez]

keep up the good work