Pressure outside Specification Design Limit (Nodes and Demands): This warning occurs when the user has specified pressure limits in the Design Limits section of the Specification dialog box.

If the pressure is greater than the design limit, the node will turn red. If the pressure is less than the design limit, the node will turn green.

Fluid Changes States (Nodes, Demands, Tanks, Components, Control Valves, and Pumps): When the user selects a fluid, based on the temperature and pressure entered, PIPE-FLO will determine if the fluid is a liquid or a vapor, and fill in the density, viscosity, specific heat ratio (for gases) and vapor and critical pressure (for liquids).



If a fluid changes states warning occurs when the fluid is liquid, it means that the vapor pressure calculated by PIPE-FLO is below the vapor pressure. If a fluid changes states warning occurs when the fluid is gas, it means the pressure at that point in the system went above the vapor pressure for that fluid.

Pressure < Absolute Zero – Calculated Result is not Valid (Nodes, Demands, Components, Control Valves, and Pumps): This warning occurs when PIPE-FLO calculates the pressure to be less than absolute zero. If the pressure is gauge pressure, it is possible to have a negative pressure as long as it is still above absolute zero.

Flow Exceeds Range of Supplied Curve (Components and Control Valves): This warning will occur when the flow rate calculated through a component is greater than the last data point entered for the component. When the flow rate exceeds the supplied data, the program extrapolates the component curve, which may or may not be accurate. If the entered data is all that you have for this particular piece of equipment, you may want to consult the manufacturer to make sure that you are not going beyond a recommended operating range.

Flow Reversed (Components and Pumps): When the user draws a pipe, PIPE-FLO assumes the direction of flow to be the direction the pipe is drawn. This warning will occur when PIPE-FLO calculates the flow in the pipelines connected to a device going in the opposite direction of the direction the pipes were drawn, which, in turn, has the flow through the device going in the opposite direction.