I need help in designing a logo program for a pressure wash system. I am using a 4-20ma pressure transducer. I want to maintain 2500 psi pressure on the line. I have 4 pumps. When I pull the trigger on the first gun, pump one starts and gives me 2500psi. Suppose second gun trigger is pulled, I want the second pump to kick on and so on with third and fourth pump. Same thing other way as well. If some one can help me please. I am new to analog program. Thanks in advance.

Hello AutoGen,

I think you're making a small mistake in your thinking. The task is not that simple, especially with non-compressible liquids. The limiting factor is the diameter of the pipe and thus the flow rate.

What's the use of four pumps if there's a pressure build-up at the beginning of the pipe and the pressure drops at the guns ?

Starting, but especially switching off, causes a massive shock wave in the system and also affects all other pumps (if the pump is connected incorrectly, the water pipe of the supply line can even fly apart).

What's left for you is an oversized pressure pipe with a pressure limiter on each of the gun pipe connections.You can't switch the pumps based on the guns being operated, however, you have to align it with the value of the total pressure. As the fluctuations are smaller due to the larger pipes in the entire system, it may also be more difficult to adjust the switching point.

As I said, liquids cannot be compressed, unlike gases.

Regards Ella_68

(translated by google)

The blocks B003 and B019 are the switch-on and switch-off points. The block B002 is used for the safety shutdown, which switches off all pumps immediately. With the block B005 you can specify a certain delay for the additional pumps if necessary. The counter B004 is intended for suppressing the second pump when the first starts and only passes on the next pulses. The rest is the logic of the pump sequencing.

As there are no more precise details about the pressure sensor, I have entered some to test the circuit. You will of course have to adapt this to your circumstances .