LPS 1283 Issue 1.1 Requirements and test methods for the approval of watermist systems for use in commercial low hazard occupancies
This document specifies the requirements and test methods for LPCB approval of fixed watermist systems for use in commercial low hazard occupancies within buildings. It is underpinned by the requirements of DD 8489 Part 1, Fixed fire protection systems. industrial and commercial watermist system systems. Code of practice for design and installation.’, DD 8489 Part 7 : 2011. ‘Fixed fire protection systems. Industrial and commercial watermist system systems. Tests and requirements for watermist systems for the protection of low hazard occupancies.’ and includes additional requirements.
A fixed watermist system is a fire suppression system designed to protect an enclosed volumetric space from fire. For the purposes of approval, the watermist system comprises a set of components, a set of design parameters, a system manual, a design software/calculation method and a scope of application.
Watermist systems covered by this document are for the protection of specific areas within buildings and are not intended for whole building protection. Some areas found in buildings can not be protected by the watermist systems covered by this standard (see excluded areas and spaces below) and will require other solutions.
- Seating areas
- Classrooms and office areas
- Entrances foyers and display areas
- Bedrooms and sleeping areas
- Common rooms in apartments, nursing or convalescent homes and residential facilities not covered by DD 8458-1:2010 ‘Fixed fire protection systems. Residential and domestic watermist systems. Code of practice for design and installation’.
- Corridors
- Data processing areas
Examples of types of areas or spaces which are unsuitable for protection by an LPCB approved watermist system in accordance with LPS 1283 typically include;
- Storage areas
- Bin stores, recycling areas and facilities
- Void areas, e.g. floor and ceiling
- Libraries
- Maintenance areas, service areas
- Workshop areas
- Machinery areas
- Laboratories
- Areas containing flammable or combustible liquids
- Kitchen areas, e.g. commercial restaurants
- Theatres and auditoria
- Atria
- Garages, parking areas, car parks, vehicle sheds and appliance bays The listed examples are illustrative.
Particular configurations of these excluded areas or spaces can be considered, subject to suitable fire performance testing as defined and agreed with LPCB. This information will appear on the LPCB Approval certificate, see clause 4.
Categories of watermist system protection
DD 8489 Part 7 defines three categories of commercial low hazard occupany watermist system protection:
- Category 1 – systems that cover rooms up to 37m2 containing low hazard fire loads
- Category 2 – systems that cover rooms above 37m2 containing low hazard fire load
- Category 3 – systems that cover rooms containing obstructed low hazard fire loads
This document employs the same categories, but specifies additional requirements.
Commercial low hazard occupancy
non-storage, non-manufacturing occupancy where the quantity and/or combustibility of the contents is low and fires with relatively low rates of heat release are expected. This descriptor is different from ‘light’ and ‘ordinary hazard’ as described in International sprinkler standards.
Equivalent fire load density
fire load density expressed as an equivalent mass of wood rather than in terms of its calorific value
Fire load
sum of the calorific energies, which could be released by the complete combustion of all the combustible materials in a space including the facing of the walls, partitions, floors and ceilings
Fire load density
fire load divided by the floor area
Fire suppression
reduction in the heat release rate and prevention of re-growth of a fire over the discharge duration
Minimum/maximum nozzle pressure
Limiting parameter for a watermist nozzle, the minimum/maximum allowed water pressure measured at the nozzle controlled document containing design, installation and maintenance rules for all details of a watermist system designed to protect an enclosed volumetric space
Volume protection system
watermist system designed to protect an enclosed volumetric space
Watermist system
distribution system connected to a water supply, fitted with one or more watermist nozzles and intended to suppress a fire.
Prior to system examination and testing an applicant shall provide LPCB with comprehensive information about the components and system. All documents shall be dated and given a reference number, issue and title. These documents shall include:
- Document Register (containing date, issue and status of all documents)
- Production Drawings (including materials and finish)
- Full material specification of components, manufacturer and designation
- Details of jointing compounds/materials/tools and procedures (including manufacturers of tools, materials and compounds)
- System manual
- Full user documentation
- Details of any training which may be available or required
Documents shall be sufficient so that LPCB can carry out a full review of the system design. If the applicant is not the manufacturer i.e. is a supplier, then an application must be accompanied by written permission for testing from the manufacturer(s).
Fire performance tests
The watermist system design criteria for the protection of low hazard occupancies shall be verified by fire testing. The parameters verified by testing are: nozzle spacing, nozzle location, nozzle flow and pressure, nozzle height, additive quantity, discharge time and effective discharge duration.
Category 3 (see 3.4.1) simulated work station fire test protocol shall be undertaken to verify the fire performance of the watermist system design. This watermist system design shall also be deemed acceptable for Category 1 and Category
Where a different watermist system design is employed for Category 2, the watermist system design shall be verified by testing to the associated fire test protocol, i.e. large compartment and open space sofas. This watermist system design shall also be deemed acceptable for Category 1.
Where a different watermist system design is employed for Category 1, the watermist system design shall be verified by testing to the associated fire test protocol, i.e. small compartment and large compartment.
All tests shall be undertaken with the watermist system components (e.g. nozzles, pipe, valves, strainers, pumps, tanks) configured exactly as defined in the system manual (which shall use design criteria specified in DD 8489-1 and DD 8489-7). Testing shall be undertaken with any additive that forms part of the system, using the test arrangement considered by LPCB to be the most appropriate.
Category 3 fire performance tests
The watermist system shall be tested against the simulated work station fire test protocol defined in DD 8489 Part 7:2011 Category 3. The test procedures, test room, fuel package, pass/fail criteria are defined in clause 5, 6.1, 6.8, Annex A.4, Annex B.4, clause 7 f.
One test shall be repeated with the maximum nozzle pressure, using the test arrangement considered by LPCB to be the most challenging test for a maximum nozzle pressure system.
An additional optional test programme can be undertaken to determine baseline low hazard requirements at a second lower ceiling height.
Category 2 fire performance tests
Category 2 requires fire testing to two fire test programmes; large compartment and open space sofas.
Large compartment fire test programme
The watermist system shall be tested against the corner crib and simulated furniture fire test protocol, DD 8489 Part 7:2011 Category 2. The test procedures, test room, fuel package, pass/fail criteria are defined in clauses 5, 6.1, 6.3, Annex A.2, Annex B.2, clause 7 b.
Four additional tests shall be undertaken:
- One test with a modified fuel package (specified in DD 8458 Part 1:2010 Figure A.5) placed between two nozzles
- One test with a modified fuel package (specified in DD 8458 Part 1:2010 Figure A.5) placed under one nozzle
- One test with a 1 m/s ventilation rate (arrangement specified in DD 8458 Part 1:2010 A.4 d)), using the test arrangements that resulted in the least suppression
- One test with the maximum nozzle pressure, using the test arrangement considered by LPCB to be the most challenging test for a maximum nozzle pressure system.
Open space sofas fire test programme
The watermist system shall be tested against the sofas fire test protocol DD 8489 Part 7 : 2011 Category 2. The test procedures, test room, fuel package, pass/fail criteria are defined in clauses 5, 6.1, 6.4, 6.5, 6.6, Annex A.3, Annex B.3,
One test shall be repeated with the maximum nozzle pressure, using the test arrangement considered by LPCB to be the most challenging test for a maximum nozzle pressure system.
Large compartment fire test programme
The watermist system shall be tested against the corner crib and simulated furniture fire test protocol, DD 8489 Part 7 : 2011 Category 2. The test procedures, test room, fuel package, pass/fail criteria are defined in clauses 5, 6.1, 6.3, Annex A.2, Annex B.2, clause 7b.
Four additional tests shall be undertaken:
- One test with a modified fuel package (specified in DD 8458 Part 1:2010 Figure A.5) placed between two nozzles,
- One test with a modified fuel package (specified in DD 8458 Part 1:2010 Figure A.5) placed under one nozzle
- One test with a 1 m/s ventilation rate (arrangement specified in DD 8458 Part 1:2010 A.4 d)), using the test arrangements that resulted in the least suppression
- One test with the maximum nozzle pressure, using the test arrangement considered by LPCB to be the most challenging test for a maximum nozzle pressure system.
Small compartment fire test programme
The watermist system shall be tested against the bunk beds fire test protocol, DD 8489 Part 7 : 2011 Category 1. The test procedures, test room, fuel package, pass/fail criteria are defined in clauses 5, 6.1, 6.2, Annex A.1, Annex B.1, clause
System verification method
For confirmation of real application design methodologies and practices, a complete watermist system shall be designed and installed with the following attributes:
- Designed in accordance with the system manual
- Hydraulically calculated by systems software
- Installed with components in accordance with the system manual
- Installed with pumped water supply
Measurements shall be made of water pressure, water flow rate and temperature.
Environmental conditions
System design
The watermist system shall employ a set of components specified by the client in agreement with LPCB.
Three designs of the watermist system shall be tested. The arrangements shall be agreed with LPCB and typically include:
- The four nozzle arrangement employed in the system fire performance tests (Section 3.4)
- An eight nozzle watermist system arrangement at 9 m height
- A one nozzle watermist system arrangement at 1 m height
Additional tests may be required for other system design arrangements (depending on the test schedule).
Full details of the hydraulic calculation for each test shall be provided to LPCB before testing.
Discharge time
Measurements shall be made of the following times: pump start, first water delivery, water delivery at design flow rate.
Maximum flow
Measurements shall be made of pressure and flow at the pump and pressure at selected location(s) in relation to particular components, e.g. nozzle(s).
Pass/fail criteria
All watermist system components shall operate to their specified design criteria.
The predicted hydraulic calculation shall be representative of the measured pressure and flow for all tests.
The pump and systems delay time before attainment of design flow rate shall be less than 30s.
3.6 Component examination and test methods
Set out below are the outline requirements, assessments and test methods which LPCB will consider when assessing the performance of the major components in a watermist system. The assessment will be defined by LPCB, in consultation with the applicant, based on both LPCB experience and changes in standards currently under development from bodies such as BS, CEN and ISO.
Examples of components required to be assessed by LPCB for approval include:
- Water distribution nozzles
- Water control valves
- Water check valves
- Water pumps
- Water pipe, fittings and couplings
- Water strainers and filters
- Water flow switches
- Water tank
- Water ball valves and drain valves
- Water level switch
- Water sight glass
- Water flexible connectors
- Water pressure switches
- Water manifold
- Water pressure reducing valves
- Water pipe hangers
- Manual release
- Water additive
The assessment and test of all components shall, as a minimum, include the following, as appropriate:
- Examination
- Marking
- Strength test
- Internal pressure test
- Leakage test
- Corrosion tests
- Function/operation tests
- Long term ageing tests
- Thermal shock test
- Nozzle clogging test
- Pump running test
The test programme required for a particular system will depend on its design and method of operation as described in the system manual. The test programme shall be developed in a test schedule (provided by the LPCB).
Scope of application
LPCB approved watermist systems shall have a scope of application for each type of area and space. Examples of the scope of application and limits are detailed in Table 2.
LPCB approved watermist systems shall have limiting parameters for each designated category. Examples of the limiting parameters for each of the categories are detailed in Table 3.