the flange / coupler is screwed on in the direction so as it tightens as the pump is loaded ( right tight , left loose), it usually needs a special tool to get them loose as they can be very tight , the ears snap easily if you force them too much. i have had to cut a few off over the years and bought replacements because they were just so darn locked on. they are not that expensive so the head ache wrestling with a stuck one is not worth it.
the cases should be split to replace the seals ,even although seals can be done without case splitting ,its not recommended. iv got lucky more than once pulling them out and drifting a new one in
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