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brass overflow tube 8a

author:MF manufacturerstime:2022-03-10 20:22:21

from《Design code for water supply and drainage in buildings》GBJ15-88Start,my country has set requirements for overflow openings for roof rainwater drainage systems。《Design code for water supply and drainage in buildings》GB50015-2003Edition starts,Further clarified the design parameter requirements of overflow drainage system,That is, the total drainage capacity of gravity flow roof drainage works and overflow facilities of general buildings should not be less than10Annual return period rainfall;important public buildings、The total drainage capacity of roof rainwater drainage works and overflow facilities of high-rise buildings should not be less than their50Annual return period rainfall。Birds on the Tree Education Online Teaching of Water Supply and Drainage Design Teacher Yang。

Code-specified overflow facilities include overflow ports、Overflow weirs and overflow piping,Among them, the overflow port design is the simplest,Also the most widely used。In recent years,With the large-scale commercial complex、The proliferation of super high-rises,Especially the style of the curtain wall is changing with each passing day,The simple way of opening the overflow directly on the curtain wall is less and less accepted by the owners and architects,Therefore, the use of overflow piping has become the rainwater overflow solution for this type of building.。But about how to reasonably design the overflow piping system,Specifications and manuals are rarely covered,Many designers are also unable to start。The author combines several recent project design practices,Talk about the roof rainwater overflow pipe system(hereinafter collectively referred to as the overflow piping system)how to design。

brass overflow tube 8a

one、Several types of overflow piping

Distinguish from the way of setting,The overflow piping system can be divided into three types:Decentralized、centralized、Outboard。

Decentralized The usual type is that rainwater risers and rainwater buckets are arranged in pairs,The normal rainwater bucket is installed on the bottom of the ditch,High installation of overflow rainwater bucket,The schematic diagram of the design is shown in Fig.1。Such as general building roof,5Annual return period rainwater is drained by normal rainwater buckets,Exceed5Annual return period rainwater is drained by overflow rainwater buckets。Such as important building roof,10Annual return period rainwater is drained by normal rainwater buckets,Exceed10Annual return period rainwater is drained by overflow rainwater buckets。

Decentralized The usual type is a catchment area with an overflow rainwater bucket,Rainwater is drained from normal rainwater buckets during the recurrence period,Rainwater that exceeds the return period is drained by the overflow rainwater bucket,The schematic diagram of the design is shown in Fig.2。

The usual type of the external discharge type is the deformation of the original overflow type.,That is, the original overflow is replaced with a customized side-entry rain bucket of the same size,Rainwater risers run down the façade or in voids in the curtain wall to the ground,The schematic diagram of the design is shown in Fig.3。


brass overflow tube 8a

picture1 Schematic diagram of the design of decentralized rainwater overflow piping system


brass overflow tube 8a(brass overflow tube 8a)picture2 Schematic diagram of the design of centralized rainwater overflow piping system


brass overflow tube 8a

picture3 Schematic diagram of design of external drainage rainwater overflow piping system


two、Design points of overflow piping system

for decentralized,The design point of the overflow piping system is to determine the size of the overflow pipe diameter and the installation height of the overflow rainwater bucket.。for centralized ,The design point of the overflow piping system is to determine the number of overflow rainwater buckets,Then the overflow amount is determined according to the catchment area burdened by the overflow rainwater bucket,Select rain bucket model and riser size based on overflow volume,Finally determine the installation height of the overflow rainwater bucket。For outboard,The design points of the overflow piping system are firstly based on the layout of the gutter.,Combine the facade at the same time、The design of the curtain wall determines the number and location of overflows,Calculate overflow based on the catchment area served by each overflow,Determine the size of the overflow port according to the calculation formula of rectangular weir flow,Select or customize side entry rainwater buckets according to the size of the overflow,Finally, choose the diameter of the rainwater riser according to the overflow。

brass overflow tube 8a

roof rainwater overflow pipe

The amount of overflow rainwater per bucket,Can be based on known design return period,Return period required after adding overflow system,using normative4.9.2strip Calculate。For example, a design return period10Years of Building Roofing,After the overflow system is added, the design return period is not less than50year,Then its overflow rainwater volume is calculated as follows:

(brass overflow tube 8a)brass overflow tube 8a

in the formulaq y — Overflow Design Stormwater Flow(L/s);q 50— return period50Annual Design Rainfall Intensity(L/s·ha);q 10— return period10Annual Design Rainfall Intensity(L/s·ha);Ψ— Runoff coefficient;Fw— The catchment area served by this overflow stormwater bucket(m2)。

According to the amount of overflow rainwater,as a decentralized or centralized system,according to the table1pick rain bucket,At the same time, you can choose the rainwater riser with the same diameter。external type,Simplified hydraulic calculation based on gutter overflow[3]The size of the overflow port can be found,Select or customize the corresponding side drain bucket in this size。

brass overflow tube 8a(brass overflow tube 8a)

The key to the design of the entire overflow piping system is to determine the overhead installation height of the rainwater bucket。For siphon systems,Relatively simple to determine the installation height,It can be directly used according to the water depth data in front of the bucket under the design rainwater volume given by the manufacturer,The installation level of the bottom surface of the overflow rainwater bucket can be higher than this height.,It can be understood as the siphon system as long as the height of the water depth in front of the bucket exceeds the design value,It can be judged that the occurrence of rainwater conditions exceeding the return period,At this point, the overflow piping should intervene。

For gravity flow drainage systems,especially the current87Bucket system,Hydraulic flow regime is a very fluid system,That is, with the increase of the water depth in front of the bucket,Stormwater drainage systems experience full gravity flow、Two-phase flow and fully saturated pressure flow,It means that the height of the water depth in front of the bucket under the design flow cannot be calculated.。At this time, the installation height of the overflow rainwater bucket can only be calculated from another aspect。The reason why the rainwater system is equipped with an overflow system,Mainly to ensure the safety of the roof structure,That is, the control rain load cannot exceed the design live load of the structure.。Therefore, the allowable water depth of the roof can be calculated from the value of the uniformly distributed live load of the roof structure.。

brass overflow tube 8a

Generally, the live load of the roof is not taken by people.0.5kN/m2,The maximum allowable water depth is calculated as50mm;The live load of the roof of the occupant is taken1.0kN/m2,The maximum allowable water depth is calculated as100mm。Test consider a certain safety margin ,The allowable depth of water accumulation on the unmanned roof can be set as40mm,The allowable depth of water accumulation on the roof can be set to80mm。Therefore, we can conclude that the installation elevation of the bottom surface of the overflow rainwater bucket that cannot reach the roof is the minimum elevation of the roof plus40mm,The installation elevation of the bottom surface of the overflow rainwater bucket on the roof is the minimum elevation of the roof plus80mm。

e.g. effluent system,The setting height of the overflow can be obtained by looking up the table according to the simplified hydraulic calculation of the overflow of the gutter,but two conditions must be met:(1)The top of the overflow port on the roof is higher than the lowest line of the roof100mm,not on the roof50mm。(2)Bottom of overflow is lower than top of gutter wall50mm(Master Roof)or100mm(not on the roof)。

three、Epilogue

with the bulk,There are more and more high-rise commercial complexes,The use of siphoning rainwater in this type of building is becoming more and more popular,However, the technical characteristics of siphon rainwater itself determine that its drainage margin is very small.,This pushes the design of the overflow system to a very important position。At the same time, the curtain wall design of buildings is becoming more and more complex,Owners and architects are increasingly unable to accept the practice of opening overflows directly on the curtain wall,This requires our water supply and drainage designers to give corresponding solutions in a timely manner。Overflow piping as an overflow solution,To ensure the safe and reliable operation of the rainwater system,Without destroying the design of building facade or curtain wall,After all, it is a solution to the similar problems encountered by colleagues。

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