lift station

has anyone done a lift station? I have lots of ideas but no experience with the application. if anyone can provide sample plc code, that would be great.

jeffyech,

Welcome to the forum.

What is your application? There is so many to discuss

james

water or sewer lift station? I've done both...

I have a waste water application for 1 to 3 pumps

what brand PLC, HMI. What about your application. what have you tried to do and can show us??

i'm wondering about the best practices concerning monitoring and level error detection such as switch failure or transducer failure. i'm using an ABB plc utilizing their water library.

Our typical approach here is PLC or RTU for primary controls using a hydrostatic level transducer.

Backup controls we use either a little smart relay or just individual relays running off an independent 24V DC supply. The idea being that should the PLC or its power supply fail, we have a fully independent control system capable of running the pumps. The floats also are wired to the PLC. When using a smart relay as backup I program an output to act as a heartbeat to the main PLC. If no change seen by the main PLC, an alarm is raised.

I normally have a watchdog relay controlled by the PLC that when released, enables the backup controls.

Pump protection in backup mode is limited to thermal overload only .

In PLC control I generally monitor motor amps, pump run time and flow rate if available.

We typically do not stop a pump if we detect a fault condition. If it's jammed, the thermal overload takes care of things. If it's partially blocked then an alarm alerts the operator but we keep it going.

Standby pump starts at a higher level SP than the duty pump.

Generally most of our clients would rather rather have a tripped pump than an overflow. Environmental discharge here is a big no-no with much paperwork ensuing.

Other than that. .don't make it too complicated!

The complexity of control and monitoring justified depends on the size of the pumps and the criticality of the location. For a simple 5 hp duplex pump station in a typical neighborhood on/off control and alarming on pump fail or high/high wet well level is enough. For 200 hp variable speed pumps in a location with million dollar homes or right next to a critical watershed you need more complex control strategies.

Here is a text that may help you get started: https://www.e-wef.org/Store/ProductDetails.aspx?productId=3684

great site. thanks!

Tom,

in your experience, what would be the most three most common configurations, i.e. float switches vs transduce; one, two or three pump etc.

JY

The most common ones I have dealt with are with transducer for level but with float backups. And 2 pumps. but I have dealt with 3 as well. Again it depends on how critical the application is. most lift stations usually have generator backup. and they'd usually have a spare pump in storage. also I agree most things were alarms out to the operators but not shutdowns.

happy thanksgiving all

Our pumpstations have two or three pumps that alternate each cycle the stations that have vfd control have the ability to increase speed based upon fill rate of the wells. We have13 stations all are different some are float control some are ultrasonic some are pressure transmitter. That being said what type of setup are you interested in.

are both methods used together? if so, in what configuration?

The lift stations with the 4-20 mA pressure transmitters uses two floats to act as a backup high and low alarms, during normal operation where pump on/off and lag pump control is controlled by the 4-20 mA signal. If the 4-20 mA signal goes out of range the program is set-up to switch to float control, now the low and high float are used to turn the pumps on and off. When this condition occurs an output turns on to activate a dialer to alert us about this failure. I did not write this program and do not like the idea of all pump control relying on the PLC. It does work but if the PLC dies in the middle of the night and can't be repaired someone will have to operate the pumps manually. I have modified two of our ultrasonic sites to have a backup float system that is completely independent of the PLC to address this problem.