There is a myriad of flow sheet design options for liquid desanders. These depend on location, type of operation, materials, pressure rating, safety requirements, level of operations, etc. I will keep this very simple and you as an engineer need to adapt as appropriate to your facility. If you have any questions email me. While we standardize the liners and vessel packing, the many options available prevent standardizing the skid or system.
Simple PID
The graphic blow shows an example or standard PID to start with. This drawing lists a liner desander vessel with basic input and output lines. Process inlet enters the side of the vessel through N1. Liquid overflow is out the top-side (N2), while underflow solids are directly out the bottom (N3). A level switch may be installed (N5) in the underflow chamber and a drain point (N4) may be installed on the inlet chamber. Pressure differential measurement is made from inlet-overflow to monitor operation. Many operations require a fire-save PSV for the vessel which most commonly is installed on the overflow line. Pretty simple system design.