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Groupe de SANTENEUTRE

Public·24 Les heylers
Sebastian Ross
Sebastian Ross

Water Pump Station V 1.0


Pumping stations can be grouped as follows:- pumping water from a water source such as a river;- for lifting water (high quantity, low pressure) from a well;- for pumping water into a supply system, elevated water tank or water tower;- to increase pressure.Pumping stations for the first two functions are generally of 2-20 m lifting capacity. Pumping stations for obtaining water from a water source have two types depending on the source:- pumping from surface water (river, canal, lake, reservoir, etc.);- pumping from subsurface water (soil water, deep seated spring, cavern water, spring water, marginal water, etc.) as shown on Figure 2.For the water supply to fish ponds the first two types are the most commonly used. The construction of these two types are largely the same. The general arrangement of these two types are shown in Figures 1 and 3.For the water supply to hatcheries, recirculation systems and central pumping stations of fish farms, pumps to catch subsurface water are used as shown in Figure 4.A pressure intensifier device inserted into the water supply system compensates for lack of pressure, which can be done by:- discharge air chamber (Figure 7 b)- revolution control of the pumps (Figure 7 a).2. PUMP WELLObstacles to the operation of the pump should be removed, such as branches, sand, pebbles, etc. The pump well for the inlet pipe should be furnished with a grid of 20 mm mesh in case of smaller pumps, and with a grid of 20-50 mm mesh in case of pumps with capacity higher than 1 000 l/sec. The inlet pipe of smaller pumps can be furnished with an inlet rose head for protection.The size of the pump well should be ten times the water discharge/min. A pump well of bigger size may promote swirling of water.The difference between the lowest possible water level in the pump well and the inlet part of the suction pipe, can be calculated as follows: (m)wherev = is velocity of water in the suction pipe (m/s)g = 9.81 m/sec2 gravitational acceleration.Generallyh = 0.5 dt (m)wheredt is the maximum diameter of the bell mouth entry but at least h = 0.3 m.Figure 1. Pump housesFigure 2. Pump wellsFigure 3. Pump housesFigure 4. Deep tubewellPumps or suction pipes with a vertical shaft should not be arranged in series, since swirling of water at the first bell mouth entry may disturb the function of the others, An arrangement, where the water flows perpendicular to the centre line of the bell mouth entry is more favourable. The centre line of the bell mouth entry should be fairly close to the opposite wall of the inlet chamber (the optimal distance is 0.75 dt). Examples for optimal arrangement of pump wells are shown in Figures 5 and 6.In cases of pumps with large delivery a guide cone should be inserted under the bell mouth entry on the bottom of the pump well so as to control the water stream. Thus the distance between the bell mouth entry and the bottom of the pump well is 0.8 to 1.0 dt (which is 0.35 to 0.5 dt without the guide cone).3. SETTING OF PUMPSThere are three ways of setting, considering the type of pump and the inlet chamber.(a) Pumps of vertical shaft sunk in the water of the pump well; (b) pumps with vertical or horizontal shafts set in a dry chamber located beside the pump well; (c) pump of generally horizontal shaft located above the water level.Within the arrangement mentioned in (a) three further cases are possible:- Pump is under water and the driving motor is above the water levelIn this case the electric motor is directly joined to the vertical shaft of the pump and is located in a water-free, dry place. The advantage of this solution is the relatively small space-requirement (there is no suction pipe and foot valve) and the easy start and operation (priming is not needed because air can not penetrate into the suction pipe). Its shortcomings are, especially in case of a large level difference between the motor and the pump, the difficulties in fitting the bearings in the vertical shaft, loss in efficiency (due to the several guide bearings), increased corrosion, and difficulty of checking, maintenance and repair (the pump should be drained first). This setting is illustrated in Figure 1. In cases of small delivery sometimes flexible shaft-driven pumps can be used.- Driving motor and main pump are above the water and the first stage under the water levelBy applying a first stage submerged part, the pump gets inflow water. No priming is necessary before starting. The level of water delivery is controlled by the upper part, thus the pump in fact, has a double stage made up of a low-pressure (.submerged stage) and a higher-pressure stage. This solution partly eliminates the above-mentioned shortcomings, by having several advantages (power take-off shaft with lower capacity, main part of the pump is easy to maintain).This solution is applied mostly to pumps of high pressure.- Pump and driving motor under the water levelTo these belong the submerged and deep-well pumps. Characteristic settings of these types of pumps are shown in Figure 4, where a submerged pump is set in a driven well, and in Figure 3, where a lifting submerged pump of high delivery is illustrated.Installing and setting expenses of a pump placed separately in a dry chamber (cf. (b)) are high. Its mechanical construction, operation and maintenance, however, are more economical. The advantage of this arrangement is that no priming or foot valve is necessary. For automatic operation this is the most suitable solution.Figure 5. Arrangements of pump wellsFigure 6. Arrangements of pump wellsFigure 7 a. Revolution control of pumpsFigure 7 b. Discharge air chamberPumps working above the inlet level (cf. also (c) above) are of mostly horizontal arrangement, with lower building and installation cost. Its disadvantage, beside suction difficulties (e.g. leakage, air - or gas development - caused water break, vacuum, cavitation), is that foot-valve and priming is necessary before starting - and all the extra costs coming from these difficulties, and in automatic starting. There are many pumps of this type working well with a suction head of 5-7 m, nevertheless, suction head higher than 3-4 m should be avoided.4. CHARACTERS OF PUMP SETTINGThe pump stations can be:- permanently set or- mobile (Figure 8).A permanently set pump station should be used if:(a) the pumping delivery is extremely high; (b) the annual utilization of the pump station is high (close to 600 hrs); (c) high operational safety is needed.A mobile pump station should be used if:(a) the use of the pump is occasional only, and the utilization is less than 200 hrs annually; (b) the location of pumping is not permanent.There is an in-between solution, a temporary set pump station, where the structural parts (tubes, mountings) are built, and the driving motor and pump are mobile.5. CAPACITY OF THE PUMP STATIONThe water delivering capacity, and thus the number of pumps, is defined by the amount of water to be pumped and its actual fluctuation in time and quantity (daily average, minimum or maximum).The total capacity of a pump station should be established in such a way that the minimum water discharge is ensured even if several pumps are broken down.The following Table gives data on the number of pump units and spares making up the total installation.Table 1Pump unitsTotal numberDelivery of spare pumps as a % of the total numbernecessary for maximum deliveryfor reserve11250213333142542633527296282572922.5821020Figure 8. Mobile pumpThe reserve pump is the so-called operational reserve ready to work. In small pump stations, where there is a proper staff, half of the spares are ready to work and the other half in store.If no significant fluctuation can be expected in consumption, there are generally three pump units of the same delivery, two of them are operating and the third one is the reserve.6. CALCULATION OF HEAD 6.1 Entrance Loss: 6.2 Resistance of Suction Screen 6.3 Resistance of Foot Valve 6.4 Pressure Loss Coming from Pipe Friction (h3) 6.5 Valves Built in the Pipeline (Gate Valve, Check Valve, etc.) 6.6 Pressure Loss from Inversion (h7)




Water Pump Station v 1.0


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To determine the total head of a pump, the geodetic level difference between the inlet-side and delivery-side water levels and the pressure affecting them (e.g. in a discharge air chamber) should be known as well as the various hydraulic losses during lifting. (m)whereH = total head (m)hg = geodetic lifting level (m)h0 = entrance loss (m)h1 = resistance of the filter (m)h2 = resistance of the foot valve (m)h3 = loss by pipe friction (m)h4 = loss from increase in cross section (m)h5 = loss from reduction in cross section (m)h6 = loss from valves (m)h7 = loss from inversion (m)Ps = external pressure on the inlet-side water (Pa)Pd = external pressure on the delivery-side water (Pa)r = density of water 1 000 kg/m3g = 9.81 m/sec2 gravitational accelerationIf atmospheric pressure affects the water levels of both inlet and delivery sides the last item is:6.1 Entrance Loss: (m)wherev = velocity of water on entering the inlet of the pump (m/sec)x 0 = value in case of not rounded inlet part: 0.8 - 1.0; in case of properly rounded inlet 0.04, i.e. the entrance loss is practically equal to the value which is necessary to accelerate the water.6.2 Resistance of Suction Screen (m)wherex 1 = value depends on the suction screen; according to preliminary calculation can be 2-3.In case of a suction screen of proper size and shape with free surface this loss can be markedly reduced.6.3 Resistance of Foot Valve (m)which is equal to the specific valve-loading, and the loss-factor is gradually decreasing along with the increasing velocity if the valve is automaticif v = 1234thenx 2 = 6.91.70.770.436.4 Pressure Loss Coming from Pipe Friction (h3)If is higher than 2320, in case of turbulent water stream,wherel = pipe friction constantl = length of the pipe-line (m)v = water velocity in the pipe (m/s)d = inner diameter (m)l = kinematic viscosity (m3/sec) as a function of water temperature.It is 1.3 . 106 at 10C and 1 . 106 at 20CPipe friction constant according to the latest research data should be calculated with consideration of Re and wall roughness of pipe. The International Congress on Water Supply held in Paris in 1952 accepted the formula of Colebrook for calculating the pipe-friction constant.Which iswherek= the absolute roughness of the pipe which can be selected from Table 2.Values of pressure loss by pipe friction are determined with approximate equations, nomograms or tables. Figure 9 shows the resistance values in cases of steel and polyethylene pipes, while in Table 3 different approximate equations are collected.Figure 9. Pipe flow diagramsTable 2 Absolute values of pipe frictionType of pipeCondition of the pipek absolute roughness (mm)drawn glass-, brass-, lead-, copper-, aluminium-, polyethylene pipesnew, with smooth wall0 (glazed)- 0.0015drawn steel pipenew, with different smoothness0.01-0.05welded steel pipenew0.05-0.1corroded0.1 -0.2heavily corrodedup to 3.0galvanized steel pipenew0.02-0.12asbestos cement pipenew0 - 0.1concrete pipe, tube from concretenew concrete, with smoothing, prestressed0 - 0.15new, without smoothing0.2-0.3 orreinforced concrete mains with smoothing after few years operating0.2-0.3 or aboveIn case of gradual (increasing) of cross-section (diffusor), the pressure loss is; (m)where the length of diffusor piece is at least six times the difference in diametersx 4 = 0.15 - 0.24v = the velocity value of the smaller cross-sectionIf the increase in cross-section is very sudden, i.e. Bordas's loss: (m)wherex 4 = 1.2 - 1.3v1 and v2 are the velocity values belonging to the larger and smaller cross-sections, respectively.In case of a reduction in cross-section (confusor) the pressure loss is: (m)wherex 5 = 0.02 - 0.05v = the velocity measured at the narrowest section.6.5 Valves Built in the Pipeline (Gate Valve, Check Valve, etc.) (m)the value of x 6, for a gate valve depends on A/A0 where A is the whole, and A0 is the gate-valve reduced cross section of the pipe.If A/A0 =1.051.11.41.82.53.05.07.010.0thenx 6 =0.10.211.154.09.715.042.072.0121.0If a flap valve or regulating flap is used,x 6, values depending on the construction o installation of the flap valve or regulating flap are 1.0-10.0, where the higher values correspond to pipe diameter of 80-300 mm and the lower ones to the diameter of 400 mm or more. As an average, a value of 2-3 can be approximated, but the exact number can be give experimentally only.For the x 6 value of a butterfly valve, denoting the angle between the plate of the valve and the axis of the pipeIf CT =0102030404550606570thenx 6 =0.10.521.543.9110.818.732.61182567506.6 Pressure Loss from Inversion (h7)In case of a bend in the pipe (m)wherex 7 depends on the relation of pipe diameter and radius r of the pipe bend midline, and on the central angle of the bent pipe, that is the degree of inversion.Using a standard bend of 90 (r = d mm + 100 mm) x 7 = 0.2 if the angle of bending iss = 22456090thenx 7 = 0.0450.0750.090.10If there is a direction-break (r = 0), the pressure loss in the pipe-line 2 (m)wherex 7 = 0.7 - 1s = the vectoral difference between the velocity values before (v1) and after (v2) the breaking point.Practically speaking v1 = v2 = v, that is the cross-section of the pipe is constant, thus there is no change in the velocity.If a = 2230456090thens = 0.37 v0.5 v0.75 v1.41 vWith T-profile - the pressure loss corresponds to a 90 direction-breakwith Y-profile - the pressure loss is of the 90 direction-break.Values given for pressure loss are related to clean water. With sandy or muddy water these values have to be increased according to the extent of pollution.Table 3 Approximate calculation of pipe friction factor for different types of pipesl A . da . Rebwhered = inner diameter of the pipe (m)Type of pipeFaultAabLimit of applicationSteel10%0.094- 0.055- 0.14New cast-iron10...13 %0.053- 0.2- 0.08Re 0.0156 ha k = 0.4- 0.200.0180 ha k = 0.70.218 ha k = 1.50.29 ha k = 4.0Asbestos-cement0.220- 0.21104 041b061a72


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