So, if i have understood your demands correctly, you want set of icons that will fill key points in schematic of some sort of valve/sensor controlled pipe system, like touch screen controlled production line, for example, but in your case it will be some fluid passing and/or mixing controls/reading values panel. Sorry if i am not using quite correct english words, it is not my native language, but i get the idea of what you want, what your icons should represent. At least i think i am, cause i dont know are they going to be used for reading, controlling or both. I am not only sure what should happen when you press one of the icons or some part of it, should it somehow stop or increase or decrease flow of the liquid, or your icons should only represent the sensor reading, or do the both jobs? That is what can make icons easy to create, or make it complicated, but i assume you want them to be as simple and intuitive as possible. Now, only think i would like to know is how many different type of sensors you have and need completely different design for? If some icons are almost the same, but with some small modifications, i dont count them as big deal to modify. Its all kinda Scada design sort of schematic, right?