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BOMBAS CENTRIFUGAS - SISTEMA DE CAÑERIAS
- 2. PIPING BOMBAS •SOPORTAR LAS CAÑERIAS EN LAS BRIDAS DE SUCCION Y DESCARGA • VERIFICAR LA ALINEACION ANTES Y DESPUES DE CONECTAR LAS CAÑERIAS • INSTALAR LA CAÑERIA PARTIENDO DE LAS BRIDAS DE LA BOMBA HACIA AFUERA • INSTALAR SOPORTES TEMPORARIOS DURANTE LA INSTALACION • MONTAR ADECUADAMENTE LOS REDUCTORES EXCENTRICOS • PROVEER UN TRAMO RECTO EN LA SUCCION Y DESCARGA DE POR LO MENOS 5 VECES EL DISMETRO DE LA CAÑERIA • COLOCAR FILTROS EN LA SUCCION • MONTAR LA VALVULA DE RETENCION ENTRE LA BRIDA DE DESCARGA Y LA VALVULA DE CIERRE • ALINEAR LAS BRIDAS ADECUADAMENTE ANTES DE ABULONAR • ANALIZAR LA POSIBILIDAD DE VIBRACIONES
- 3. LAYOUT
- 4. LAYOUT
- 5. CAÑERIA DE ASPIRACION Figure 1 – Cañería típica bomba simpe etapa Codo a 90 nominal de la cañeríapuede ser corto o largo, en el caso del corto A=D diámetro Figure 2 – Regla 10D
- 9. REDUCTORES
- 10. PIPING SUCCION
- 11. PIPING SUCCION
- 12. CAÑERIA DE ASPIRACION- MANIFOLD DE CAÑERIAS INCORRECTO CORRECTO Figura 5 Figura 6
- 13. CAÑERIA DE ASPIRACION Entrada suave y simple Figura 3 – Válvula de pie y filtro de aspiración en lo posible deben ser evitados INCORRECTO CORRECTO Figura 4
- 14. PIPING – BOLSONES DE AIRE
- 15. CAÑERIA DE ASPIRACION- MANIFOLD DE CAÑERIAS RECOMENDACIONES PARA BOMBAS CENTRIFUGAS “DRY PIT”
- 16. CAÑERIA DE ASPIRACION Figura 7 Figura 8 VISTA EN PLANTA DE LA ASPIRACION DE UNA BOMBA DE CARCASA PARTIDA HORIZONTALMENTE VISTA LATERAL DE LA ASPIRACION DE UNA BOMBA DE CARCASA PARTIDA HORIZONTALMENTE POBRE INSTALACION INSTALACION MEJORADA
- 17. ASPIRACION – REDUCTORES EXCENTRICOS PARTE PLANA ABAJO PARTE PLANA ARRIBA Figura 9
- 18. ESTABILIZADOR FLUJO Figure 10 –Aspiración con estabilizadores de flujo (Difusor)
- 19. ENDEREZADOR ELEMENTAL DE FLUJO SOLDADO A LA LINEA DE SUCCION ENDEREZADOR DE FLUJOFigure 10 Figure 11 Figure 12
- 20. LINEAS DE RETORNO - VORTICES Figure 13
- 23. SUMERGENCIA -SUMIDEROS Figure 16 Figure 17 Figure 18
- 24. ASPIRACION - CAMARAS Figure 19
- 25. VELOCIDAD DE FLUJO vs SUMERGENCIA Velocity (feet/sec) Figura 20
- 26. MULTIPLES BOMBAS - SUMERGENCIA
- 27. BRIDAS - JUNTAS
- 28. PIPING BOMBAS - EJEMPLOS PIPING TIPICO BOMBA HORIZONTAL FILTRO Y REDUCTOR EXCENTRICO EN ASPIRACION
- 31. CAÑERIA DESCARGA
- 33. ESFUERZOS SOBRE LAS BRIDAS TENSION EN CAÑERIAS EFECTO SOBRE LAS BOMBAS CARGA SOBRE BRIDAS FUERZAS – MOMENTOS PERMISIBLES CARGAS SOBRE BRIDAS POR TIPO DE BOMBA INFORMACION NECESARIA PARA ANALISIS DE STRESS CASOS ESPECIALES
- 34. ESFUERZOS SOBRE LAS BRIDAS
- 35. SOPORTES - GUIAS
- 36. SOPORTES
- 37. SOPORTE RESTRICCION MOV. TERMICO
- 38. PARA REDUCIR CARGAS SOBRE BRIDAS CASOS ESPECIALES
- 39. API vs ANSI
- 40. API vs ANSI
- 41. API vs ANSI
- 43. PARA REDUCIR CARGAS SOBRE BRIDAS CASOS ESPECIALES
Notas del editor
- Beyond what would logically be surmised to be unbalanced flow attribut- able to the elbow, studies have determined that a secondary, rotating flow, is imparted in the fluid by elbows. This secondary rotating flow is superimposed and conveyed with the main momentum flow in the axial direction. In addition to an axial force in the x direction, ancillary forces are imparted to the surroundings in the y and z directions. This secondary flow, sometimes referred to as pre-rotational flow, is ultimately carried into the impeller imparting additional damaging turbulence and inefficient internal recirculation. Bottom line: Directly connected or closely placed elbows are detrimental to pump operation because of multiple and compounding reasons.
- Confusion on Diffusion Controversial opinions can be found on the subject which has become known as suction diffusion. Actually, diffusion means to disperse or spread out. A suction diffuser is a special pipe fitting, sometimes in the configuration of a tee or sharp elbow, which is installed directly on the pump’s suction connection which contains, depending on the make, various configurations of flow straightening elements. Often these special fittings may also incorporate some type of straining feature. Figure 9 shows a cut-away view of a typical diffuser attached directly to a pump suction. Manufacturers of suction diffusers state that they can be utilized to smooth, balance, and otherwise streamline liquid flow to the impeller eye when physical space is not available to accommodate the recommended 5D to 10D full-size straight pipe provision. The attribute of spatial compensation is somewhat debatable. A comparative examination of a number of commercially available diffuser models indicated that the average physical take-out, or length, plus the required space for the removal of the screen, was equivalent to 5D.
- Return pipe lines to sumps or tanks that allow the liquid to free-fall and impact on the suction reservoir’s liquid surface can aerate the vessel’s contents. Unless the process prevents such an arrangement, returned liquids should not be allowed to cascade, but rather should terminate below the liquid level in order to minimize turbulence, agitation, and the creation of entrained gas. In a similar fashion, return lines should not terminate in close proximity to the suction outlet. Feed lines for that matter, that could possibly introduce gas-entrained liquid to the sump or suction tank should be positioned to be physically distant from the suction point to alleviate the possibility of hydraulic short-circuiting. Doing so allows the freshly entering liquid important residence time in the suction vessel to dissipate gas. If this arrangement is not feasible, baffles can be installed in the sump to cause the liquid to have hold-up time before making its way to the pump suction port. A vortex is a smooth, roughly conical, rotating liquid void that forms in a fluid body as a result of a low pressure area. Vortices exist as both free-surface and subsurface manifestations. Regardless of form, this liquid void spells trouble for pumps; it allows, and brings with it, air into the pump’s suction. Fluidic studies have dem- onstrated that vortices collapse, otherwise break-up, or fail to form before entering a suction conduit, as the low pressure source’s (inlet’s) distance is increased vertically from the free liquid surface level. It is therefore important that proven and established minimum submergence depths be maintained based upon the amount of liquid being handled and the inlet fluid velocity.
- The graph following, Figure 20, shows the relationship between inlet fluid velocity (V) and the recommended minimum submergence depth (H ) to avoid vortices. The approximate mathematical relationship of these two variables is:
- Associated piping and fittings The following are some of the recommended practices in regard to piping associated withthe centrifugal pumps . Piping associated with the pump must be anchored and supported independently of the pump. In absence of adequate anchorage, the expansion and contraction of line can causethe transfer of forces to the pump casing. When the pipes are not supported, their weight is borne by the pump casing and nozzles causing them to deflect and crack. The seal life of the pump also gets affected due to this strain. It is important that the connections be carefully aligned axially, angularly, and in length. The flange boltholes too have to be in phase with the pump nozzle holes. One good check to perform is to disconnect all the suction and discharge flanges on the pumps. If levers are required to force the pipe flange on to the pump nozzles (to facilitate bolting of the flanges), one can be certain that the pumps will sooner or later start giving bearing and other problems.
- Inlet piping The piping run and the connection fittings should be properly aligned and supported separately to reduce strain on the pump casing. The straight run of the piping leading to pump suction nozzle should be at least 3 to 6 times the diameter of the pipe from the upstream elbow. The elbow should be of a standard type or of the long radius type. If the pump has a negative suction, all suction piping must be airtight. Suction pipe size should be at least one commercial size larger than the opening of the pump inlet. The reducer joining the straight length of the pipe in the pump line should be an eccentric reducer with the flat side of the reducer as the topside. The straight length of the pipe after the eccentric reducer should be 2 times the pipe diameter. The suction pipe should be sized to insure a liquid velocity of not more than 2 to 3 m/s. All suction pipes in negative suction should have a continuous rise to the pump suction inlet. A 6 mm per 100 mm minimum slope is recommended. This may not be required in a flooded suction. In a negative suction, no isolation valves are recommended but can be provided in the flooded suction. Isolation valves even in open condition contribute to pressure losses due to friction and result in lowering of the available NPSH. In pumps with higher negative suction lift, NPSH-a is on the lower side and addition of a valve does not help the cause in any way.
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- Discharge piping The piping run and the connection fittings should be properly aligned and supported separately to reduce strain on the pump casing. Discharge pipe size should be at least one commercial size larger than the opening of the pump outlet. The number of fittings and size changes should be minimum to prevent fluid friction losses. The check valve used in the discharge should be of the non-slam type to prevent hydraulic shocks. The isolation valve is provided downstream of the check valve so that these can be taken up for servicing whenever required. Concentric reducers are installed in the discharge pipe to minimize friction losses. There should be a pressure tapping as close as possible to the pump outlet and before the isolation valve to measure the pump shut-off head . Another pressure tapping downstream of the reducer is a good indicator of the pump operating pressure. Expansion joints maybe used only after a careful piping analysis, especially when the discharge pressures are on the higher side.