Firewater Systems Data Requirements
The following data is required in order to undertake a detailed surge analysis of a firewater system. The data which is relatively easy to assume has been marked with an asterisk (*).
- Process and Instrumentation Diagrams for all platforms.
- Isometric drawings detailing pipe lengths and elevations for all pipework.
- Flow Utility diagrams for all platforms (if available).
- Internal diameters.
- Wall thicknesses.
- Material type and its pressure rating.
Pumps and Risers
- Pump Head / Flow / Efficiency and Power / characteristics.
- Run up times, impeller diameters(*) and inertia’s(*).
- Pump riser data (diameters and wall thickness).
- Automatic air vents on the risers (type, size and manufacturer).
Overboard Dump Valve / Test Lines
If overboard dump lines are installed on the pump risers, the following is required:
- 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 dump valve.
- Control valve size, full open Cv, type and manufacturer.
- If downstream pressure controlled, the set pressure for the design flowrate.
- End to end stroke times.
- Deluge system isolation valve size, manufacturer and anticipated stroke time.
- Size, type and manufacturer.
- If pressure controlled, the set pressure for the design flowrate.
- Monitor isolation valve size, type and manufacturer.
- Monitor isolation valve end to end stroke time (*).
Isolation valves will be installed throughout the firewater ringmains to allow isolation of any part of the system. 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.
If any automatic air valves 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).
Low Pressure Sensors
- Set pressures and location.
- Pressure switch actions.
Under standing conditions, it is likely that the firewater ringmains will be pressurised. This may be achieved by several methods such as a header tank, a jockey pump, seawater pumps etc. and details of this method will be required. For example, if the ringmains are pressurised by a pump, the following is required:
- Pump curves if available.
- Details of any pump control (such as overboard dump lines etc.)
If the ringmains are pressurised by a header tank, the following is required:
- Header tank height, width and operating levels.
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 fire and gas 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 number of deluge systems that could be released from the system simultaneously and how could they be initiated?
- What is the maximum number of monitors that could be released simultaneously?