Float alarm system for mixing tanks 1

[patriotpickle]

Hello all, I am the maintenance man for a pickle manufacturing company. We have 6 large brine mixing tanks and everything is manual. They have manual ball valves and flow meters with nothing to prevent the tanks from overflowing if the brine maker is not paying attention. We had an estimate done for automatic valves with a controller and it was too much right now. My much more inexpensive idea is as follows:

Each of the six tanks will have its own float and I would like just one 120volt power supply for all six floats. The 120volt supply will go to an e-stop and then to a selector switch (tanks 1, 2, 3, 4, 5, 6) then depending on the position of the selector switch it will send the voltage to one of the float switches. Once the level in the tank raises the float, it will send the 120volts through the float to an alarm which will be turned off by the e-stop. What I cant seem to figure out is how to use only one alarm for all six tanks. I cant run all six wires to the alarm because obviously the power will backfeed back through the system. I have done very little work with relays which I am assuming I will need to incorporate. If anybody can point me in the right direction, I would appreciate.

 

[mcgyvr]

Is only one tank being filled at one time? seems like it since you mentioned a selector switch (which I would not recommend because that requires someone to actually ensure its in the right position...just another place for errors).

Assuming only one filling at a time..
Personally I would just use 6 floats (12VDC or similar low voltage DC for increased safety). When the float is at the max level the float energizes a single 12VDC relay "coil" (all floats are attached to this relay). One pair of the relay "contacts" can be used to stop your filling machine. The other set turns on an audible alarm. The contacts of the relay must be rated for your filling machine voltage/current level.

 

[mcgyvr]

I made a lot of assumptions obviously.. Like I assumed that only one tank is "filling" at one time and the other tanks are not "filled" at that time. If other tanks are left "filled" while others are filling then the selector switch would easily solve that problem by removing the voltage from the "filled" tanks and only applying it to the "filling" tanks.

 

[patriotpickle]

Yes, only one tank will be filling at one time. We never have and never will fill more than one tank at a time. As far as the other tanks, some will be filled and some will be below the float level, it is always random and we will never have control over that. Also, the tanks are filled simply with a manual ball valve so the only thing the float does is send a signal to the audible alarm alerting the brine maker that the tank is almost full and that he will be needing to manually close the ball valve before the tank overflows. So now that you know that the floats are not closing a filling mechanism, would I still need to incorporate a relay? Thanks again.

 

[Compositepro]

If you don't mind the alarm sounding when the level falls below your set point, as well as when it rises above set point, you can wire the alarm like a light operated from multiple switches. One extra switch would be used to silence the alarm when after it sounds. The alarm will sound again when any level switch changes position. Otherwise you will have to use relays.

http://en.wikipedia.org/wiki/Multiway_switching

 

[waross]

Keep filling manually. Put the float positions ABOVE the normal full level. Wire the switches so that any tank will cause an alarm if it is filled ABOVE the normal level. You may also use the same signal to stop the fill pump. You may need a relay to stop the pump. Maybe not.

Bill
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