Problem with my 1995 xantia suspention?

The accumulater on my 1995 Citroen Xantia vsx with active suspention started to leak. Whet to my local Citroen dealer. they said the accumulater needed replaceing.
The price was very high. I went to a car brakers and bought a used one, I saw it working before I took it off. I changed the accumulater and bought a brand new sphere from main dealer. fitted it all ok. Started the car car went up and down ok. took for a test drive and there was a loud bang. looked under the car and the sphere had split releasing all the fluid. Any ideas as to why this happened. I depressurised the system before working on it. Followed Haynes manual instructions.