planning civil design

If most of the plant operation time the underground drainage system (UDS) does not work, why is it critical? It is heavily used in three distinct cases.

  1. the plant's abnormal operation when the control system fails
  2. the plant start-up and shutdown
  3. the plant commissioning

The underground drainage system is a means of dividing the desalination plant into operating modules (OM). As shown in "Design Principles", they are a critical element of fail-safe plant design. Its task is to stop the propagation of the emergency shutdown (ESD) upstream. ESD is a cornerstone of the alarm philosophy.

Thanks to UDS, any chain of OMs beginning from the first (intake station) may operate continuously without interaction with downstream OMs. It drastically simplifies the plant commissioning, start-up, and shutdown.

The UDS design includes four steps.

  1. Identifying the P&ID items to be linked to UDS
  2. Building the network connecting the drainage points and the outflow point
  3. Listing all the possible scenarios of the UDS operation
  4. Sizing the pipes, channels, and pits

The crenger.com framework for UDS design is bundled with the PlantDesigner software. It automatically selects the P&ID items requiring the drainage outflow. To create the drainage network the user maps the P&ID items to the plant layout using only two clicks. If a P&ID item is not mapped, the software raises an alert. After having been mapped, the points may be connected manually or automatically using available algorithms.

Step 3 shall list all the UDS operation scenarios likely to be observed during commissioning, start-up, planned or unplanned shutdown, and loss of control. It requires consulting such documents as the plant control philosophy, the commissioning plan, and the HAZOP report. All the mentioned documents are part of the FEED package.

underground drainage system design automation

The image above shows some details of the framework in question. Every scenario is a collection of the drain flowrates entering the network. As seen, the flowrate may be easily changed. Once all the scenarios are in place, the software sizes the network by running through all the cases. The output data is summarized in a report shown below.

underground drainage system sizing

The network sizing algorithms are far from trivial as they first try to assess the transient performance of the system during the first seconds of the water inrush. It means that the controlled UDS flooding is an indication of the optimal design.

© 2025 crenger.com