An often overlooked aspect of a distillation ejector system is the condensate drain legs and hotwell. If the condenser drain leg or the system’s hotwell become fouled with process build up or debris, it can lead to a back-up of condensate. This can flood the system’s condensers and upset the tower’s operating pressure. These condensate drain legs are also under vacuum the entire way down to the liquid level in the hotwell. If one were to develop a leak, air would be pulled into the drain leg and upwards towards the system’s ejectors. This too can cause condenser flooding. This is why cleaning out these down legs and verifying their mechanically integrity is important for the long term reliability of the system. A turnaround also provides an excellent opportunity to clean process build up and debris out of the hotwell.
In order to understand how an ejector system is operating, multiple test points are needed to take various pressure readings. In order for these readings to be taken while a system is in operation, an isolation valve is needed at each test point. A turnaround provides an opportunity to install isolation valves at existing plugged connections or to weld in new connections where none exist. Doing so allows for a more comprehensive assessment of the vacuum system operation.
It’s understood that turnarounds by their very nature are filled with many needed maintenance activities, limited resources, and the discovery of unplanned issues, all of which can distract from the needs of the vacuum distillation ejector system. Care needs to be taken when looking at turnaround scope to make sure that the vacuum system’s needs are addressed during each turnaround so that the ejector system is able to operate to its design and maintain its reliability.