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1、 n 28 February 2009 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - W W D - w - - - - CEN/TR 13930:2009 (E) 2 Contents Page Foreword 3 Introduction . 4 1Scope 5 2General 5 2.1Factors which influence the operation of the plant . 5 2.2General design principles for a pumping plant 6 3Plan
2、t with vertical suction inlet 7 3.1General arrangements . 7 3.2Diameter (D) at the entrance of the bellmouth or the tapered suction. 9 3.3Distance (C) between the bellmouth or the tapered suction inlet and floor 10 3.4Distances between suction inlet axis and walls . 11 3.4.1Distance (L) between suct
3、ion inlet axis and side walls . 11 3.4.2Distance (E) between suction inlet axis and rear wall . 11 3.5Submergence (S) . 11 3.5.1Conditions to be satisfied for the determination of submergence . 11 3.5.2Determination of submergence (S) 12 3.6Strainer . 12 3.7Feed intake - Pump environment . 13 3.7.1F
4、eed intake . 13 3.7.2Immediate environment of the pump . 20 3.8Case of pumping plant with vertical suction inlet and flow rate less than 50 m3/h 23 4Plant with intake with top suction inlet . 23 5Plant with intake with floor suction inlet . 24 5.1Bellmouth . 25 5.2Submergence of horizontal plate . 2
5、5 5.3Special anti-vortex devices . 25 6Plant with intake with wall suction inlet 25 6.1Shape and position of suction inlet . 25 6.2Submergence . 27 6.3Special anti-vortex devices . 27 Bibliography 29 CEN/TR 13930:2009 (E) 3 Foreword This document (CEN/TR 13930:2009) has been prepared by Technical Co
6、mmittee CEN/TC 197 “Pumps”, the secretariat of which is held by AFNOR. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document s
7、upersedes CR 13930:2000. CEN/TR 13930:2009 (E) 4 Introduction In addition to the risks of cavitation that may exist at the intake of any pump depending on the NPSH available, pumping from a sump poses specific problems. In fact, if the water passes from a flow state with an exposed surface to flow u
8、nder pressure, significant swirling movements may occur and sometimes be amplified, thus creating a sort of funnel or vortex which opens out into the exposed surface of the sump with a risk of air being entrained or creating a swirling chimney, or whirl between the bottom and the intake producing de
9、gassing or vaporisation of the liquid in the entrance of the pump (see Figures 1a) and 1b) below). These phenomena, which are generally unsteady, can have unwanted effects on the plant: undesirable vibration of various pump components; increased risk of cavitation; drop in efficiency; reduction in f
10、low rate and/or head; risk of floating bodies being sucked in; intense and irregular noise. Compliance with the recommendations in this document makes it possible, in most commonly encountered industrial applications, to avoid or at least limit the phenomena mentioned above. 1a) Vortex causing entra
11、inment of air in suction piping 1b) Chimney or whirl between the floor and the suction inlet Figure 1 Types of possible disturbances CEN/TR 13930:2009 (E) 5 1 Scope 1.1 This technical Report contains recommendations for the design of pump intakes and the installation of pumps. As far as possible, th
12、ese recommendations should be adhered to in order to obtain correct operation of the plant. These recommendations are applicable regardless of the flow rate of the plant: plant which works with clear water (or relatively unclouded) and relatively non-aerated water or any other liquid having physical
13、 and chemical properties which are similar to those of water; NOTE This document nevertheless contains several general recommendations for operation with cloudy (or very cloudy) water. pumping plant which has its own floor. 1.2 This document deals with various intake configurations: Clause 3 contain
14、s recommendations which apply to intakes with vertical suction inlet; Clause 4 contains recommendations applicable to intakes with top suction inlet; Clause 5 contains recommendations applicable to intakes with floor suction inlet; Clause 6 contains recommendations applicable to intakes with side-wa
15、ll suction inlet. 2 General 2.1 Factors which influence the operation of the plant The following factors have an effect on the operation of the plant: a) Characteristics and position of the suction inlet: arrangements of the suction inlet (vertical with bellmouth or tapered suction, top, floor or si
16、de-wall intake); presence or absence of a bellmouth or tapered suction; distance between suction inlet and floor; distance between suction inlet and side-walls; submergence (level of liquid relative to suction inlet); strainer. b) Inflow of liquid to the intake: inflow velocity of the liquid; shapes
17、 and dimensions of inflow; CEN/TR 13930:2009 (E) 6 position of inflow. c) Environment of the pump in the plant: velocity of liquid close to the pump; shapes and dimensions of the plant; special devices (gratings), anti-vortex device; relative positions of pumps to each other and in the plant. Clause
18、s 3 to 6 below contain recommendations concerning the determining factors for each arrangement of the suction inlet. NOTE If the liquid is charged with solid particles in suspension, the following recommendations may be amended. Prevent the velocity of the fluid falling below a value which allows th
19、e deposition of solid materials. A minimum value of 0,7 m/s close to the suction inlet is currently admitted. 2.2 General design principles for a pumping plant In order for the pump to be fed under the best possible conditions, effort should be made to obtain a permanent, uniform and even flow in th
20、e suction pipe. To achieve this, it is necessary to: supply the suction pipe for each pump with a balanced flow which is free from swirl; ensure that the water accelerates gradually along the intake; any deceleration generates flow instabilities; avoid any entrainment of air by suction (vortex) or b
21、y churning (weir). Ensure that these conditions are adhered to as closely as possible regardless of the operating conditions of the plant (one or more pump(s) working, one or more intake sluice(s) or filter(s) in service, high water level or low water level, etc.). The stipulations in the following
22、clauses are aimed at achieving this. In those, inevitably numerous, situations that are not dealt with in this document, the plant designer should adopt the following principles: a) in water inflows intakes, stay within moderate velocities which allow gradual acceleration: examples of such velocitie
23、s are those of the order of 0,3 m/s in the approach channel, 0,5 m/s in the strainer, 1,5 m/s in the bellmouth or tapered suction, and 4 m/s in the suction pipe; b) avoid excessively large chambers and dead zones which generate overall swirl in the flow and vortices as well as the deposition of soli
24、ds if the water contains substances in suspension; c) prevent separation by avoiding sudden widening and excessively divergent angles by preferring shaped forms for pillars, low walls, bellmouth or tapered suction, etc; d) avoid sudden changes in direction caused, for instance, by lateral feed and e
25、xcessively sloping falls; e) eliminate any obstacle which might interfere with flow over a sufficient distance (of the order of 10 times the diameter D at the entrance to the bellmouth or tapered suction) before the suction pipe; f) avoid any asymmetry in the mode of operation as well as in the desi
26、gn of structures; g) at the entrance to the suction pipe, ensure an adequate submergence for the minimum working level and increase the submergence recommended below in this standard significantly if flow conditions are mediocre; h) if a chamber is fed with water by an overflow, ensure that the late
27、r does not entrain air and provide a baffle device. CEN/TR 13930:2009 (E) 7 It is far preferable to design a plant which is intrinsically problem-free from the outset rather than to rely on baffles or anti-vortex accessories which are often only a palliative offering efficiency which is difficult to
28、 predict. In difficult cases and if the importance of the plant justifies it, it is recommended to use a reduced model to check whether there is any need to improve the arrangements made. 3 Plant with vertical suction inlet 3.1 General arrangements In these configurations the presence of a bellmouth
29、 is necessary but alternatively, the bellmouth may be replaced by a tapered suction. Installations with a vertical suction are shown diagrammatically in Figures 2 and 3. a) The pump design may be: axial flow without exceeding the outside diameter of the bellmouth or tapered suction greatest diameter
30、; centrifugal or mixed flow with bellmouth possibly wider than diameter of the bellmouth or tapered suction greatest diameter. b) The position of the pump on the piping can be: horizontal or vertical; immersed or not immersed. Figure 2 Vertical suction inlet with bellmouth - Normal configuration CEN
31、/TR 13930:2009 (E) 8 3a) Centrifugal impeller a) a) The number of stages is stated for information only 3b) Mixed-flow impeller a) a) The number of stages is stated for information only 3c) Axial flow impeller a) a) The number of stages is stated for information only 3d) Non-immersed horizontal pump
32、 3e) Non immersed vertical pump 3f) Non immersed vertical pump 3g) Immersed vertical pump Figure 3 Vertical suction inlet with bellmouth (or with tapered suction) - Example of possible configurations CEN/TR 13930:2009 (E) 9 3.2 Diameter (D) at the entrance of the bellmouth or the tapered suction Fig
33、ure 4 shows typical profile of bellmouth. Figure 4 Bellmouth The diameter D at the entrance to the bellmouth is a result of the bellmouth profile, which is generally a quarter ellipse of which the short and long axes have the values 2a and 2b respectively. If Do is the diameter of the piping at the
34、entrance to the impeller of the pump, the value of D is generally between 1,4 Do and 1,8 Do inclusive, the most common values are between 1,5 Do and 1,6 Do inclusive. It is this value which is used as a reference for the recommendations given in sub-clause 3.3 and so on. As an alternative of a sucti
35、on by bellmouth, Figure 5 illustrates typical profile of tapered suction. Figure 5 Alternative with tapered suction CEN/TR 13930:2009 (E) 10 3.3 Distance (C) between the bellmouth or the tapered suction inlet and floor Figure 6 indicates the recommended dimensions between suction inlet and the floor
36、, in the case of a bellmouth. Figure 6 Distance between the bellmouth and the floor The distance (C) between the suction inlet and the floor should be between 0,25 and 0,5 times the diameter (D) at the entrance to the bellmouth; the most common values are between 0,4 and 0,5 D inclusive. NOTE In the
37、 case of an intake on a natural floor (river, pond, sea, etc.) where there is always a risk of filling with sand, silting up or changing water levels, the distance (C) should be increased. Its value should be specified jointly with the pump manufacturer. As an alternative of bellmouth suction, the c
38、ase of tapered suction inlet is illustrated by Figure 7. Figure 7 Distance between the tapered suction inlet and the floor CEN/TR 13930:2009 (E) 11 3.4 Distances between suction inlet axis and walls Figure 8 indicates the dimensions between suction inlet axis and walls. Key 1 Rear wall 2 Water inflo
39、w Figure 8 Distance between suction inlet axis and walls 3.4.1 Distance (L) between suction inlet axis and side walls The recommended dimension (L) is 1 D. 3.4.2 Distance (E) between suction inlet axis and rear wall The recommended dimension (E) is 0,75 D. NOTE If cloudy or very cloudy water is suck
40、ed in, consult the pump manufacturer before specifying dimensions (L) and (E). In fact, it is necessary to take into account the risks of the pump feed being disturbed if deposits form (see note to sub-clause 2.1). 3.5 Submergence (S) 3.5.1 Conditions to be satisfied for the determination of submerg
41、ence Figure 9 shows a typical submergence. Key S = 1 D to 1,5 D Figure 9 Submergence CEN/TR 13930:2009 (E) 12 The submergence value (S) should satisfy two conditions: a) the NPSH available should exceed the NPSH required at the maximum flow rate during use by a sufficient margin. In particular, this
42、 margin should make allowance for the air content of the water; b) the maximum submergence value selected (S) should prevent the formation of a vortex or whirl by taking into account all the layout and installation conditions. Sub-clause 3.5.2 contains recommendations on the selection of S. 3.5.2 De
43、termination of submergence (S) The choice of submergence should result of an exchange of information between the pump manufacturer and the plant designer. As a general rule, the submergence should be between 1 D and 1,5 D inclusive with a minimum of 0,5 m but the parameters stated below influence th
44、e required submergence and may result in a different value being adopted. For instance, if the values of the following parameters are high, the submergence should be increased: air content of the water; linear velocity of the fluid at the entrance to the bellmouth or tapered suction; pumps with high
45、 rate of flow and extremely small head, etc. In addition, other parameters such as intake environmental conditions, number and spacing of pumps, layout of feed intakes, presence of walls or anti-vortex devices, occurrence of ripples or waves, etc. may influence the submergence value to a greater or lesser extent. 3.6 Strainer The shape of the strainer depends on the environment of the intake. Its shape should not inte