Stability fire hydrant application in high-rise building
"high-rise civil buildings design Fire Protection specifications" (GB50045-95) requires: fire hydrant port input water pressure should not larger than 0.80Mpa, and should adopt regional water supply system. The fire hydrant port output water pressure is more than 0.50Mpa, the fire hydrant should set up pressure relief devices.
Zoning by district, customary practice is achieved through establishing middle tank. Since the late eighties, the reduction of dynamic and static pressure new reducing valve and proportional reducing valve come out, gradually using reducing valve to implement the partition decompression. Promotion and application of reducing valve, saving covered area and space, saving project investment and getting good economic results.
Fire hydrant decompression, it has been using the traditional decompression orifice plate way. This approach, on the one hand to result in the complicated engineering calculating workload for designers; on the other hand, in the installation and construction process, we must weld flange or install live joints in fire hydrant water supply branch pipe, to fix the reducing orifice. The early eighties, the relevant departments improve the design of structure of indoor fire hydrant, change fire hydrant inlet end and input water connection outer thread into internal thread, with the aim of enlarging the inlet end internal thread back knives groove, in order to install pore plate. Some manufacturers cast out the pore plate in fire hydrant interface, in order to solve the decompression problem of fire hydrant. The aboved approaches have been implemented for many years with little success, installating and constructorrs feel much inconvenience. Some buildings even occur leaking installation of orifice, wrong equipped and so on. Even if the design staff calculates accurately, constructors install correctly, but due to the change with the system flow and pressure fluctuations in actual using process, the pressure after the bolt can not be stable.
Indoor pressure reducing and stability fire hydrant is aimed at ordinary fire hydrant deficiencies and defects reflected in high-rise building fire protection design and construction process, in particular, according to the users’ requests for pressure stability after fire hydrant to develop the new products. The product appearance and structural size is absolutely same with the general indoor fire hydrant, not only has the switching function, but also has automatic decompression and pressure stability function. It can change the changed water pressure before bolt into stab enriched water column after bolt, and this process is achieved automatically by its internal pressure reducing and stability devices.
Indoor pressure reducing and stability fire hydrant decompression working principles are different from ordinary pressure reducing valve. Ordinary reducing valve generally adopts sampling after valve technique, that is, through detecting pressure changes after valve to control the valve working. While indoor pressure reducing and stability fire hydrant adopts sampling before bolt technique, makes it having an automatic identifing ability of pressure change before bolt, and quickly control its internal pressure reducing and stability device works according to the pressure changes before bolt freely, and maintain the outlet pressure stability after the bolt.
Indoor pressure reducing and stability fire hydrant technical parameters is set strictly according to "high regulation" (GB50045-95) requirements. It includes: test pressure is 2.4Mpa, nominal pressure is 1.6Mpa, water inlet pressure is 0.4-0.8Mpa, the outlet pressure is 0.3Mpa, regulation accuracy is ± 0.05Mpa, the water flow rate is ≥5L/S.
At present, the domestic related manufacturers develop three kinds of structural forms of indoor pressure reducing and stability fire hydrant, and all passed the public security fire protection department testing, obtained the permitted production and sales and patented products related certificate. The internal structures of these three products are shown in Figure 1.
In the high-rise building fire protection system design, using indoor pressure reducing and stability fire hydrant, you can remove the cumbersome setting orifice hydraulic calculation. The designer, only need to start to set pressure reducing and stability fire hydrant in the position of static pressure is larger than 0.3-0.4Mpa, while in the place that hydrostatic pressure is smaller than the value, we also set common indoor fire hydrant.
It is noteworthy that, in high-rise building fire protection system design, we can not cancel vertical partition due to adopting pressure reducing fire hydrant. Designers still in accordance with the "high regulation" requirement, when the system hydrostatic pressure is greater than 0.8Mpa, take regional water supply system.
Recently, " Indoor Fire Hydrant Installation" (87S163) national common water supply and drainage standard atlas is by our institute responsible revision, according to relevant national standards and peer institutions views, after extensive investigation and research, including in this aspects. In new figure, in single indoor fire hydrant to equip SNJ65 pressure reducing and stability fire hydrant, DN65 rubber lining hoses and QZ19/ø19 and water gun. Since currently there is no developed double-valve double-outlet pressure reducing and stability fire hydrant and "high regulation" strict restrictions for ordinary double-valve double-outlet indoor fire hydrant (commonly known as claw-type two-head fire hydrant) using place, so, to the place that needs to set up double bolt indoor fire hydrant boxes, you can install two SNJ65 pressure reducing and stability fire hydrant and the same size hose and water gun in the bolt box.
In addition, because indoor pressure reducing and stability fire hydrant works rely on the inlet pressure before bolt to automatic regulating scupper effective section, in order to avoid draining hole blocked by the pollutants and failed, it is recommended to use hot dip galvanized steel pipe in the system design, and set Y type filter on the fire protection pump suction pipe. At the same time, the installing personnel should be civilized to construct, and completely remove water tanks and pipes that may exist in a variety of dirts, to ensure the system safe use.
