When you start using a pump, are you sure whether the pump that you have installed in your facility needs priming? Do you know which pumps are self-priming? In case you are not aware about it then starting your pump will be little risky for you, as you may be taking a big chance. Don’t start any unfamiliar pump just based on your guesses, that may go wrong too. Read this small write-up to know why priming is so important and which kind of pump will need priming before you start it.
What is priming?
Priming is needed for all sanitary Valves in order to make them ready for use. The casing of the pump must be filled by the fluid before you start. Otherwise, your pump may not be able to function. If there is any gas or vapor present inside the casing, then the pump may become gas bound, as a result it will not pump. Therefore, priming is the process of filling your casing with necessary fluid before startup.
Priming is necessary for the proper function of any centrifugal pump. Either water or any fluid that is pumped will act as a coolant to prevent the pump getting overheated. Not doing it will cause your pump running dry and mechanical seal may fail and seriously damage any of the pump components.
Based on the piping configuration, any pump may also not need any manual priming. Under flooded suction condition, when the pump’s suction port is lower than level of liquid to be pumped then the pump is filled already with fluid and hence is considered primed.
If liquid level is much below pump’s suction port, priming will be more difficult. In such situation, it is imperative to have a pump having suction lift capability.
Positive displacement pumps
Any positive displacement pump, will generally be a self-priming pump, though it will depend on the pump and its application. This allows for certain flexibility in the layout of the system and eliminates any need for suction priming.
As an example, self-prime of any air-operated diaphragm pump can create pressure differential in diaphragm chamber. This will draw air in and will pull the fluid in the suction port. These positive displacement pumps do have very good suction lift capabilities.
To conclude, for avoiding any failures, all centrifugal pumps should always be primed prior to their operation. Positive displacement pumps usually are self-priming having suction lift capability, however, always check your manual or consult with any engineer to ensure that the pump will not need any priming first.