Dredgers are equipped with various sensors and indicators. Some have very technical purposes like the temperature of the Main Engine.
But today I want to talk about the number one most important sensor for a good production, and the five top reasons why you definitely need it, the vacuum sensor.
1. Minimum requirement for Operators
An operator controls the dredging process by using the controls of the equipment, much like a car driver uses the pedals and steer to control the behavior of the car. The vacuum sensor is for an operator much like a speed indication on a car, the most basic and most important measure.
Without a good indicating vacuum sensor he will not be able to control the dredger in such a way that he can get the highest production.
2. Detect clogging
When a cutterhead or suction mouth gets clogged the vacuum sensor is the first indicator of problems. The vacuum will increase and subsequently stay high. This by itself is not an indication of clogging, but when the swingspeed has been reduced and the vacuum stays high there must be a clogging in the suction line. Without a vacuum sensor the clogging can only be detected once the pump starts cavitating heavily and you hear or feel it.
A clogging in the suction line inevitably leads to lower productions as more vacuum is used to get the slurry to the pump instead of achieving a high density.
3. Prevent Cavitation
When your process is suction limited you want to dredge with the highest vacuum possible, but you don’t want cavitation. Without the vacuum sensor the is no way to know whether you are close to the cavitation limit are still have a way to go.
Cavitation occurs all of a sudden, so the pump is either cavitating or not. Once you feel it you are too late with preventing it. Cavitation leads to high wear of the pump and all kinds of damages. Preventing it from happening should be number one priority, which means the vacuum sensor should be a number one priority.
4. Mixture Velocity Indication
With some preparation a vacuum sensor can be used as a crude, but effective, velocity meter. A dredger provider should be able to inform you of the vacuum reading at various mixture speeds, when pumping water, this is important. This only works when pumping water.
They can tell you if the vacuum is 60 kPa the velocity is 4 m/s, when it hits 70 kPa its 5 m/s, etcetera.
Then when you are on a project you can pump water for a while and compare the vacuum reading with the table. This gives you an upper limit of the mixture velocity. If the velocity is already down to 3 m/s you know you can’t really add sand to the mixture otherwise the pipe will clog.
A crude method, but it gives you some indication of where you are in terms of mixture velocity.
5. Production Indication
When pumping water for a while the vacuum will also stabilize around a certain value. Then when you start adding soil to the mixture the vacuum increases. The higher the vacuum reading the higher the production. Although it doesn’t give an exact figure it does give you an idea whether you are on the right track or not.
These are the top 5 reasons why you need a vacuum sensor. I’m always disappointed when I get onboard and the sensor is either not working or completely missing. It is such a cheap sensor and has such huge benefits.
I dare to say, if you are serious about production, you will make sure the vacuum sensor is always working 100%, which means regular calibrations as well.
To your success,