BS 8663-1:2019 pdf free.Fixed fire protection systems -Components for watermist systems.
4.7.1 For automatic nozzles, when tested in accordance with Annex D (D.1), the watermist nozzle shall open and within 5 s of release of the thermally sensitive element shall operate as intended. Any lodgement of released parts shall be cleared within 60 s of the release of the thermally sensitive element. 4.7.2 For nozzles with deflectors or separate/ moving parts for the development of a spray, when tested in accordance with Annex D (D.2), the deflector and its supporting parts shall operate as intended. 4.7.3 . For open nozzles with blow-off caps, when tested in accordance with Annex D (D.3), the cap shall fully release and not impede the discharge. 4.8 Strength of automatic watermist nozzle body and deflector 4.8.1 Strength of nozzle body 4.8.1.1 Mechanical strength test For nozzles with the thermal element on the same axis as the water supply, when tested in accordance with Annex E (E.1.1), the watermist nozzle body shall not show permanent elongation of more than 0.2% between the load-bearing parts when subjected to twice the measured service load. 4.8.1.2 Hydrostatic strength test For nozzles with the thermal element on a different axis to the water supply, when tested in accordance with Annex E (E.1.2), no leakage or permanent visible deformation shall occur.4.8.2 Strength of nozzle deflector For nozzles with deflectors (or other protruding parts which impinge upon the water discharge and alter the spray pattern), when tested in accordance with Annex E (E.2), the watermist nozzle deflector and its supporting parts shall withstand an applied force of 70 N without permanent deformation. 4.9 Strength of release element for automatic nozzles 4.9.1 Glass bulb watermist nozzles For glass bulb watermist nozzles, when tested in accordance with Annex F (E1), the watermist nozzles shall have: a} a mean design bulb strength of at least six times the mean design service load; b) a mean bulb strength not less than the mean design bulb strength; c) a mean service load not more than the mean design service load; d) a design lower tolerance limit (DLTL) on the distribution curve of at least two times the design upper tolerance limit (DUTL) of the service load distribution curve; e) an upper tolerance limit (UTL) less than or equal to the design upper tolerance limit (DUTL);BS 8663-1 pdf download.