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Help with a Piston (rod) Seal?

Help with a Piston (rod) Seal?

Help with a Piston (rod) Seal?

Hi All,

I'm a bit of a hacker and I am trying to design a simple small piston pump. Most of it is coming along nicely, but I want to check the seal design. I have been recommended a U-cup seal with an oring to energize the seal and improve the low-pressure seal. It is made out of food-grade TPU + food-grade silicone O-ring.

Here are the parameters. I added extra detail just in case I am using the wrong words and just wanted to be clear.

Fluid: Water for drinking; seal must be food-safe.
Pressure: 30bar Max. Being a piston pump, the pressure will go from a small negative pressure during suction to 30 bar positive during each stroke.
Speed: 50mm/s, reciprocating (ie accelerate to 50mm/s, stop, and accelerate to -50mm/s, stop etc.
Rod Diameter: 25.0mm
Stroke length: 40mm
Temperature: 10°C to 60°C
Service life: I hope it is a set-and-forget for 5 years, but the pump is not in high demand, around 20 minutes a day.

The other side of the seal is the atmosphere, but I really need no leaks as there are some bearings, etc., below, so I really want a tight seal here.

Is the recommended seal okay? Is it lacking? Do I need a secondary seal or something else to ensure a reliable quality seal?

Thank you for your comments.

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