Design of pipeline pure water system

Design of China Water Supply and Drainage Pipe Pure Water System An Xianfeng\Li Zhimei 2 (Zhejiang Dean Group Technology Development Department, Ningbo 315040, Zhejiang; 2. Ministry of Machinery Second Design and Research Institute Ningbo Branch, Zhejiang Ningbo 315000), etc. Discussion and related experience.

At present, the supply of pure water on the market is mainly bottled and canned. Although it has the advantages of convenience and convenient transportation, it is a more economical and convenient water supply method considering the cost of construction. At present, there is no standard or norm for the design of pure water pipe network in China. Now I have comprehensively designed the experience and experience of many pure water projects, and summarized some views on the design of pure water pipeline. I would like to ask for valuable comments and suggestions. Communicate together.

1 Pipe network layout To avoid the formation of pipeline secondary pollution and "dead water" phenomenon, the entire water supply pipe network should be arranged in the same program circulation pipeline, which is often used by the author.

50m, buildings with fewer risers.

Several arrangements of pure water circulation lines (b) are suitable for high-rise buildings with a height of >50m and a large number of risers.

(d) Applicable to multiple multi-storey or residential buildings.

(e) Applicable to high-rise, multi-story group buildings.

Regardless of the type of pipe network used, the network network adjustment must be carried out. Otherwise, there may still be problems of poor return water and "dead water".

2 Hydraulic calculations According to the quality of water, people are currently only used for direct drinking and basically not used for other purposes, so the water consumption is basically irrelevant to the nature of the building.

The second-flow formula of the building life water supply pipeline design: the a and k values ​​in qg=0.2a are mainly determined by the use of the building, so it is neither reasonable nor accurate to apply this formula to calculate the design second flow of high-quality water.

2.1 Flow The author believes that according to the formula in the “Indoor Water Supply and Drainage Engineering” textbook published in 1981: Qp average daily water consumption, m3/d for high-quality water for drinking only, the main factor affecting the water consumption is the water consumption standard and The number of users, namely: formula (3) is the design second flow formula of high quality water, and the water consumption standard is affected by the season and the region. For example, the water consumption standard in the northern region is about 5L/(person.d), the southern region At around 8L/(person.d).

In the "Construction Regulations", the rated flow rate of a drinking fountain nozzle can be found for the southern region: 0.05 n moxibustion 2.6 people for the northern region: 0.05 It can be seen that for the southern region, whether it is a residential or office building, more than 3 people At the same time, there should be a nozzle for the drinker, generally adding one nozzle per person for adding 3 people; in the north, a nozzle should be added when there are more than 5 people.

2.2 Flow rate According to the author's experience, the flow rate of the riser in the design of pure water pipeline is generally controlled at 0.3~0.6m/s, and the control of the transverse pipeline is between 0.6~1.0m/s.

2.3 Pipe diameter To ensure water quality, the diameter of the largest water supply pipe is > DV50, and the remaining pipe diameters are determined by calculation.

Determination of 24i value The calculation formula of the head length loss of several common pipes per unit length is as follows: stainless steel pipe: same as aluminum-plastic pipe, according to DarcyWeisb-bah formula, Y movement viscosity can be introduced, m2/s (“10C 10-6m2/s, its value changes with temperature) dj* pipe calculates the inner diameter, m local head loss of various pipes is 20% of the loss along the way. 3 Water supply mode In general, the main water supply equipment of pipeline pure water has circulation Pumps, variable frequency pumps, solenoid valves, etc., the water supply method is also no more than several combinations of the above equipment.

The circulation pump can be set according to the scale and specific conditions of the building. This method requires the circulating pump to circulate regularly and should avoid the peak of water to prolong the service life of the pump. The number of pump start-stops should not be too complicated. It is best not to exceed 6 times/h. The circulating flow rate is based on 80% of the feed water flow. The advantage of this water supply method is that it can guarantee the water quantity and water pressure requirements as well as save energy. The disadvantage is that the water-making equipment can only be placed on the roof, which is very demanding on the building and inconvenient for installation and maintenance.

The frequency conversion pump + circulation pump + solenoid valve combined water supply is closed, and the frequency conversion pump automatically converts the water supply according to the user's water condition. The nighttime variable frequency pump stops working, the solenoid valve opens, and the circulation pump works. The circulating water volume can be calculated as 100% of the water supply, and the cycle time is generally 2h, which can ensure the supply of water during the day and save energy. The disadvantage is that the frequency of the inverter equipment is higher.

To remove such a water supply system, there are two variable frequency pumps (one for each use), which are reserved for each other. The minimum flow rate of the control variable frequency pump is 40% of the total water consumption is the circulating flow rate (A). When there is no user water, the circulating flow rate of the variable frequency pump is A; when the user uses the water quantity A, the variable frequency pump changes with the motor speed. The variable frequency water supply is carried out according to the change of the user's water volume, and the circulating return water flow rate in the return water pipe is zero. If the minimum flow rate of the variable frequency pump is set to be small, the circulating flow rate in the pipeline is small, the efficiency is low, and the energy saving is not significant; and if the minimum flow rate of the variable frequency pump is set to > 40% of the total water consumption, the flow rate It will be very large, the water quality can not be guaranteed, so it is advisable to control the minimum flow of the variable frequency pump to 40% of the total water consumption. Compared with the method a, the water consumption is removed, and the water production amount is set to 1.5 times of the water consumption. Regardless of whether the user uses the 7 water circulation return flow rate, the circulation is 1/3 times of the water production amount, and the variable frequency pump is based on the user water consumption. Change the frequency of water supply. Compared with method b, the circulation pipeline maintains a normal circulation state, but the water-making equipment is added, the investment is large, the land occupation is large, and the power consumption is large.

4 water supply pipe several commonly used pure water pipes are as follows: stainless steel pipe. Advantages: strong resistance to high pressure, strong resistance to corrosion and rust; disadvantages: high cost.

Smooth, good hydraulic conditions, easy to bond, and low cost; Disadvantages: the bonding interface is easy to age and the high pressure bearing capacity is poor.

Pressure, stability and durability are good; disadvantages: only metal connectors can be used, and the price is high.

Free of their own shortcomings, easy to bend, high pressure, linear expansion coefficient; Disadvantages: uneven overall wall thickness, affecting the quality of pipe joints, the use of special copper joints, the price is more expensive.

Polypropylene tube. Advantages: temperature resistance, cold resistance, high pressure resistance, low cost; Disadvantages: easy to crack, the same pressure and temperature, the thickest wall.

In summary, various pipes have their own advantages and disadvantages. Users should choose from the actual situation, but it must be ensured that the selected pipe will not bring secondary pollution to the pure water.

From the pipeline design of the multiple pipelines of pure water that the author has done, most of the operations are good, and there is no obvious giving or returning water.

Finishing Nails

Finishing Nails