Ball valves can be an incredibly useful addition to many different types of systems. However, that doesn't mean that they're without their disadvantages. Some of these include the following:
If you use a valve with a ball for slurries, it's liable to get stuck in the open position.
Thick liquids may solidify within the valve body, increasing the operating torque required.
Most ball valves have limited flow control (meaning it doesn't make an optimal control valve).