Model SN Pump Shafts
Model SN pumps (Self-Priming Non Clogging) come with either a solid or a sleeved shaft. Most people know to use a solid shaft when the pump is being driven by an engine (internal combustion engines have intermittent versus continuous torque. Consequently, engine driven requires a “beefier” shaft).
Did you know, if you use a solid shaft, there is a spacer that fits on the shaft before you put the impeller on? However, if you use a sleeve option the spacer is not utilized as the sleeve consumes this space.
The above image shows a solid shaft with and without a spacer. Without a spacer, the impeller is unable to be locked in place. The impeller washer will bottom out on the shaft, allowing a gap between the impeller and impeller washer.
Air, it has to go somewhere!
The air vented during startup on a self-primer pump has to go somewhere. When it has nowhere to go, it will create issues with pump operations, as the pump cannot compress the air. Recently, we had an end user experience pump issues with an SN pump. After looking at the installation, we noted there was no air vent or auto release mechanism between the discharge and check and isolation valves. Once the air vent was added the trapped air issue disappeared.
– The Summit Pump Team
Jim Elsey's Pumps and Systems Articles
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