This webinar discusses issues experienced during commissioning and operation. It is commonplace for a membrane plant to encounter early stage problems arising from stresses experienced during delivery or installation. These issues can be exacerbated by intermittent or low flow operation. Procedures are described to improve early stage experience. In longer term steady state operation, membranes initially operate stably, but fouling problems, low feed temperature, or feed quality perturbations can cause stress. The webinar describes techniques to establish whether the membranes continue to maintain integrity and to calculate whether the system continues to meet the required performance standard. Expected and acceptable failure rates are discussed together with the issues covered by a typical membrane warranty. Finally, fibre repair techniques are discussed. The content can be summarized as follows: • Delivery, storage, commissioning, shutdown, mothballing, and maintenance • Membrane integrity testing, calculating Log Removal Values (LRV) from pressure decay data • Membrane System Warranty • Fibre repair, operating plant experience of fibre breakage frequency