Bubbler system vs ultrasonic level sensor

Dear,

Consultant wants to use a bubbler system for storm water pumping stations, pumping stations is 800 liter/Sec.

What is the benefit of using a bubbler system over a ultrasonic sensor for this type of system? 800 liter/s pumping stations and storm water.

My idea was that bubbler system will have a lot of maintenance and more expensive but the consultant was telling that similar systems were used in this area and approved by the client.

level switches will also be provided and connected to PLC for controlling the storm water pumping station and the level sensor will be used as a backup.

For this critical system, do we require redundancies in term of PLC? or use a control cabinet (using relays) connected to the MCC for controlling the pumps based on level?

i appreciate any feedback on this issue.

A bubbler system works well because it is always blowing a small amount of air to clear out any obstructions. So it is less impacted by things like foaming.

Since it is just an air tube going to the sensing point, it doesn't matter if it gets submersed.

The electronics can be mounted remotely, so a bubbler can be used in hazardous applications.

It can also be useful if you are trying to measure a very low height of liquid. For example, sensing if there is 1/8" of oil in the bottom of a vessel. Most sensors would stuggle to be calibrated/located to be able to differentiate between seeing the bottom of the vessel vs sensing the oil.

A poor application of a bubbler would be detecting glue or paint that would be prone to drying/clumping/blocking the air.

I only ever used "home made" bubblers. We always used a good precision air pressure regulator and differential pressure switch. We had good success using bubblers.

Bubblers were the standard of the wastewater industry for decades, and are still used with success. For the reasons kekrahulik pointed out they are quite low maintenance, and generally you only need to blow out or at least check the bubbler tube once a month or so.

In my experience the bubbler will be at least as accurate and more reliable than ultrasonic, and probably lower cost to boot. If I were looking for an alternate I'd use a submersible pressure transmitter. I have had excellent results with them, even in digesters - a more severe environment than a lift station wet well.

I would advise against the expense of a redundant PLC or redundant I/O racks. Most of your failures are going to be in field devices. Assuming your stations will be connected by telemetry you should monitor communications and a comm fail alarm will alert you if the PLC is dead.

I would definitely recommend using a high-high level float switch hardwired to bring on a pump and trip an alarm - one that annoys the neighbors is very effective.

bubblers are good, you can put the sensor anywhere you like even in the cabinet, the only thing is frost.
in every washing machine this contact is used.put a cheap aqaurium airpump in front and you have a system working in mm.

I've used bubblers in the past with good success. Ultrasonics have worked good in a stilling will with little water movement and no foam. Submersible PT (as mentioned by Tom) worked very well also as long as they didn't get too mucked up (we used in a tank that had a lot of mud in it).

I would say bubbler/submersible almost a tie with ultrasonic coming in last.

Foaming is the biggest problem with ultrasonics, and with storm / sewer stations, you literally never know what is coming down the pipe. Wave guided radar can overcome this with effort and tuning, but is likely more expensive than a bubbler system with no real advantages. Plus of it goes down, replacements are expensive.

On a bubbler, field repairs are relatively easy and Murphy's Law says that if it is going to go down, it will do so at 3AM Saturday in the midst of a raging storm, on your wife's birthday, as she is delivering your first child and all of your coworkers are at a mountain retreat with no communications. Simplicity and the ability to fix it with duck tape and a can of WD-40 can be a Godsend in those moments.

jraef said:

On a bubbler, field repairs are relatively easy and Murphy's Law says that if it is going to go down, it will do so at 3AM Saturday in the midst of a raging storm, on your wife's birthday, as she is delivering your first child and all of your coworkers are at a mountain retreat with no communications. Simplicity and the ability to fix it with duck tape and a can of WD-40 can be a Godsend in those moments.

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LMAO. I always encouraged my engineers to remember O'Brien's Law: Murphy was an optimist.

Thank you guys for your valuable replies, indeed Murphy was optimist

http://davetgc.com/Murphys_Law.html

... indeed Murphy was optimist

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The real-life Captain Edward A Murphy, Jr was an optimist and thought of his famous 1949 saying as a defensive method to help prevent worst-case accidents caused by thoughtless acts.

http://en.wikipedia.org/wiki/Edward_A._Murphy,_Jr.

"If there are two or more ways of doing something, and one of those can lead to a catastropne, then someone will do it."