Motor Control and Run Dry Protection for a Pump

If I am reading this right:

You need to refill this overhead tank during it's usage = maintaining a certain level in the tank? Also that the pump can not be run dry, which also indicates that there needs to be product in the pump before it operates? Where does the original product come from? Is there a separate tank that is filled to a certain level, then 2nd pump you are asking about refill the overhead tank?

If you are just wanting to maintain a certain level in the overhead tank, and there is no way of running this dry.(meaning there is always product available) you can use several different sensors to detect the level in the tank which will operate the contactor to run the pump to that level and then wait for the level to drop to a pre determined level, then refill overhead tank to the determined level.

You can use ultrasonic sensor, liquid level sensor, a simple float switch.

Is this tied into a PLC/SLC?

What is your control voltage?

On the other hand, if you don't always have product available for the pump to refill the over head tank, then there is more to plan on for that stage.

you need to install High and low level sensers interfaced with motor starter and set the low level senser at least 6inches above the suction filter Numbers of senser manufacturers are out in the market you can select from and you need to clean the sense surface once in a month depending upon the quality of water you are pumping if you see thin coating of salts present in the water.second you need to choose a sense for cold water application.I had this problem of senser not functioning and latter found out that i was using cold water application senser for hot water

good luck

crm

Without the required details, here is a simple solution.

Suggested products:

Pressure Sensor

https://www.kele.com/olcat/P4/M230-V.PDF

https://www.kele.com/olcat/P4/M230.PDF

Float Switch

https://www.kele.com/olcat/SS6/F7.pdf

Assuming the product originates from a bulk container and is pumped to your overhead tank:

1. Install simple PLC or adjustable timer and program for appropriate start/stop timing.

2. Install submersible monoblock pump with integral float to prevent pump running when the bulk product container is empty. Wire to PLC or timer.

3. Install pressure sensor or float switch in overhead tank to shut off pump to prevent over filling. Wire to PLC or timer.

***********************************************************

Pictorial Logic-For Reference ONLY!

24vdc|------------------| |----------------------------------| |---------------------------------( R )

Power---------------Float Switch--------------------Timer/PLC Start/Stop---------------------Pump Relay

240vac|-----------------------| |--------------------------------| |-----------------------------(M)

Power---------------Integral Float on pump--------------------Pump Relay---------------------Pump Motor

*******************************************************************

I hope this helps?

The simplest thing may be a float switch.

There are many 7 day programmable timers available on the market (OMRON is one) this would easily and inexpensivly solve the periodic on time for the motor.

There are also several current sensing relays with trip points available for monitoring the load current of motors. These can be set to shut down the motor when there is a dry reduced load.

Using a PLC, with a flow switch (a switch that turns on with flow, and off without, or a pulse feedback of flow)

if there are pulses & pump run, pump ok

if there are no pulses & pump run, stop pump, sound warning (audio & visual)

Or if you can monitor the current of the motor with a clamp meter, while pumping it will have a specific current, when it runs dry, the current should drop (cavitation possible)

There are dozens of ways.

Among the most popular are:

• a hard-wired low level switch in the tank on the suction side of the pump
• an electromechanical liquid presence detector in the line on the suction side of the pump
• an electronic low-load detector in the motor wiring
• etc.
• etc.

re: "an electromechanical liquid presence detector in the line on the suction side of the pump." can you recommend a brand sir that is possibly available in our local market(Philippines) my customer just recommended the OMRON brand but unfortunately, i cant find one in their catalog(or maybe i need more to widen my search to find it in their brochures) thank you sir.

See #9⇓.

Everyone has mentioned float switches but no one has brought up a flow switch (paddle switch). The flow switch normally open contact (NO) is in series with the motor contactor and is in parallel with a normally closed contact (NC) on a timing relay. The clock in the timer is set to open the NC contact before pump damage occurs. I once designed a system with this circuitry and based on the pump manufacturers data, set the clock for 60 seconds. If the paddle in the flow switch did not detect a flow in the pump pressure piping and close the NO contact after 60 seconds, the timer would open the NC contact and the motor contactor would drop out, stopping the pump. My designs used a momentary switch to start the pump and would not recycle, but your system timer that starts the pump several times a day could probably be programmed so that the pump doesn't start, run for 60 seconds, stop, then run again for 60 seconds, and on and on.

No one has mentioned "Flow Switch" ?

Try post 7?

Uh......being able to read is not a requirement for my job.

if you want to protect your pump from dry run. you need to have a recirculation valve on the discharge line connected with the reverse circulation line. for more such type of valves ,you can visit http://www.hbe-engineering.com/ or google HBE recirculation valves.

regards

NS

hello everyone! can anyone suggest an protection relay? i need a "LOSS OF PRIME PROTECTION" that will turn off the pump if in case the suction pipe went empty to prevent the pump from dry running. im going to use it in installing a 5.5HP 230V, 3ph, CR Grundfos pump.

re: "an electromechanical liquid presence detector in the line on the suction side of the pump." can anyone recommend a brand that is possibly available in our local market(Philippines) my customer just recommended the OMRON brand but unfortunately, i can't find one in their catalog(or maybe i need more to widen my search to find it in their brochures) thank you all. a.gatan@yahoo.com.ph