Each of us who maintain a hydraulic system is aware of how complex a system it is. However, another item that needs to be maintained, as part of that package is any schematic drawings of it. Although you won’t need to replace the drawings as you would some components, if you don’t maintain your drawings, you will find that they are no longer accurate and could reach the point of becoming meaningless and therefore useless. Even if you don’t perform any major redesigns, it’s usual for there to be minor change made to the circuit of the system during its lifespan. This might involve the addition of filters, a change out of components (makes or models) or perhaps the re-routing of drain lines or an addition of a pressure test point. Ideally, the drawing of the hydraulic system would be amended every time a change is made. But that does not always happen. This is particularly true if the drawing is electronic, and has been created using a certain brand of software that you don’t have everyday access to. However, there isn’t any excuse for not keeping a note of a change, in the form of a basic and easy to maintain change log. This can be written simply with the date, what was changed and who changed it. Then even if the hydraulic system drawing is not entirely accurate, there is enough information to be able to fit together a true picture of the hydraulic system circuit. Not only is this helpful to the engineer or technician, who may be reliant on the drawing to troubleshoot, but the information can be handed to somebody such as a draughtsman or software graphic expert to update the drawing at some point. In summary, a drawing of a hydraulic system that is accurate has a value, but this is decreased every time a change is made without it being updated. Although this maintenance task might be neglected to some degree, doing so can become an expensive misjudgement for any hydraulic engineer.