If you've got a submersible pump that is constantly being exposed to dry or low-liquid environments, check it now for damage even if it appears to be working well -- and get a new pump in there as soon as possible if you do see damage. Submersible pumps not only can function in liquid environments, but they have to function in liquid environments; the submersible part isn't just an option. If the pump is constantly running dry, that creates a lot of problems and may damage the pump so badly that it could fail suddenly and require the installation of a new pump before your work can continue.
Liquid May Provide Temperature Control
That liquid, be it water, oil, or another type, may provide temperature control. As the pump functions, the metal can heat up from friction or from the power source (e.g., a pump fueled by electricity can heat up much as an electric appliance can), and the liquid is a cool counterpart that prevents the pump from overheating. Remove that liquid, such as what happens when the pump runs dry, and the pump could overheat and fail. You have to have a procedure in place to either keep a significant amount of liquid around the pump or to stop the pump once you see the liquid is low.
Liquid May Also Be a Form of Lubrication
That liquid can also reduce the effects of friction, depending on the style of pump and where the liquid around the pump can reach. Reducing friction reduces heat, which reduces the temperature and thus the overheating risk. Allowing too much friction can also create wear on the parts, and that too can lead to failure as parts break or jam up. These malfunctions aren't always easy to fix and can lead to the need for immediate replacement of the pump. All that does is slow down your work.
Cavitation Can Form Early
Remember that running dry isn't the only threat. If the liquid runs low and allows bubbles to form, that too is a hazard. It's called cavitation, and when those bubbles pop, they can create a physical shock that damages the pump. The pump is likely working at higher speeds, so a little bubble doesn't just take up space -- it really packs a wallop if it collapses.
If you have had to deal with the pump running dry or running with little liquid, you need to have it checked out. Contact an industrial pump supplier and start looking at new pumps and what it would take to have one installed so that, if you do find you need to replace a damaged pump, you can spring into action.
Take a look around at the industrial equipment in your facility. Hopefully it is all working and in good shape. If you want to keep it that way, you will need to provide it with the proper care. Every machine has somewhat different maintenance requirements, but in most cases, some lubrication and an annual inspection by a qualified repair professional will go a long way. Here's the thing: you can't be in this industry without the right equipment. So rather than spending more on new equipment, it is wise to care for the stuff you've got. Read more on this and related topics right here on this website about industrial equipment.