Sometimes the elegance of a design is in using a single component for multiple tasks, saving space, component count and costs in the overall solution. One such case came when Sensor-Technik UK was asked to design a system for monitoring the water consumed by spray trucks typically used to damp down dust in quarries, construction sites and the like.
Dust is not only an annoyance, it can be a serious health hazard. So these water spray vehicles play an invaluable role in improving the health and safety of both the site workforce and the general public. But water is becoming an increasingly precious commodity the world over, and so accurate control over its use in this application is essential – not only to avoid waste, but also so that the truck driver knows how much is left in the onboard reservoir and can plan refills accordingly.
The design proposed by Sensor Technik used a single pressure sensor fitted at the base of the onboard tank to measure both the level in the tank and the rate of delivery through the truck’s spray heads. This sensor would be connected to a digital readout in the cab with programmable setpoints and an audible alarm to warn the driver of critical water levels.
The design was accepted, and initial installations were promising but highlighted two limitations in the design, both of which were easily resolved.
First, the sensor was being overpressurised while the tank was being filled. And while STW pressure sensors all have ample overpressure capabilities, the decision was made to resite the sensor away from the water inlet to avoid the false readings that had been occurring.
Secondly, the inherent sensitivity of the STW pressure sensor was greater than that required for the application, leading to fluctuating readings on the onboard digital readout. The simple addition of a digital filter between the sensor and readout provided the averaging effect required, stabilising the readings and providing the operators with a clear unambiguous readout of the pressure, level and flow.
The revised design of the single-sensor system has now been in service for several years. Its simple design and multiple capabilities have enabled payback many times over, maximising the efficiency of vehicle use, reducing wear and delivering savings on time, fuel and money.
