Good afternoon, I'm after some advice about how to select the appropriate type of oil seal (lip seal) for my application.

I can find plenty on what's available, but nothing on why to choose one type over another.

My application is to replace the shaft seal on a hydraulic gear motor, nothing special, it's an 18 mm shaft in a 30 mm seat, seal length 7 mm. Load's of 'em on the net. Working pressure probably 100 – 200 psi, as the oil its contains is at return (tank port) pressure. Shaft rotation is reversible and typically 2000 rpm.

What are the rights and wrongs of a single lip seal against a double lip seal, and why. The original wasn't spring energised, I guess the oil pressure against the seal energises it, but what little I can find on the 'net says that seals for use with oil would normally have a spring. I have no idea if the one I took out (double lip, no spring) is the appropriate choice, but it has lasted years so it must have had something in its favour.

Thanks, as always, in anticipation of some help.

Best rgds Simon