Cooling Water Systems
Data Requirements
The following data is required in order to undertake a detailed surge analysis of a cooling system. The data which is relatively easy to assume has been marked with an asterisk (*).
Drawings
- Process and Instrumentation Diagrams.
- Isometric drawings detailing pipe lengths and elevations for all pipework.
- Flow Utility diagrams for all platforms (if available).
Pipework
- Internal diameters.
- Wall thicknesses.
- Pipe wall material type and its pressure rating, particularly any ability to accept negative pressures.
Pumps and Pump Pipework
- Pump Head / Flow / Efficiency and Power / characteristics.
- Run up times, impeller diameters(*) and inertia's(*).
- Pump pipework data (diameters and wall thickness).
- Automatic air vents on the risers (type, size and manufacturer).
Recirculation Valve / Test Lines
If recirculation lines are installed on the pump pipework, the following is required:
- Recirculation dump valve size for each pump.
- End to end stroke times.
- Proportional band and Integral Reset time (*).
- Flow / Pressure drop characteristics of any back pressure devices to valve.
Heat Exchangers
- Type of heat exchanger (plate / tube)
- Number of tubes, layout and dimensions
- Heat exchanger end box dimensions
- Pressure loss at duty flow rate
- Type and control mechanism for trim valves
Back Pressure Control Valves and Discharge Conditions
Details of any control valves in the system, particularly any used to main positive pressures within the system. Details of the systems discharge are also required (cooling tower, river discharge, closed circuit with pressure vessel etc).
Isolation Valves
Isolation valves may be installed throughout the system to allow isolation of any section. It is generally assumed that these valves will not be closed against pumped flow and typical valve characteristics can be assumed. If it is requested that the precise characteristics of these valves are modelled, the valve manufacturer and type details will be required.
Air Valves / Vacuum Breakers
If any automatic air valves or vacuum breakers are incorporated on the system (usually on high points), the following is required:
- Valve type and manufacturer (*)
- Valve size.
- Valve location and elevation.
Duty Flowrates and Pressures
The design duty flowrates and the pressures that are expected to be used throughout the system (this may be available from the UFD's).
Proposed Operation of the System
In order to obtain a clear understanding of the system operation and to be able to determine the worst case scenario's, a description / clarification of the mode of operation of the system, including any automatic pump re-start or standby pump start logic, is required. For example:
- What are the maximum number of pumps that can start into the system simultaneously, and what are the delay times between pumps. If a pump fails to start, what is the delay time for the next pump to be started?
- What is the maximum and minimum number of heat exchangers that can be on line simultaneously and how is their selection controlled?