ROUTE-1. Connection with Pump
Before we discuss about piping connect with pump, we should also know ‘how to be good position for pump location’. The location of the pump in the system has a major effect on the NPSH calculation. When designing new system, it is much easier to lower a pump or increase the elevation of a tank before the system is built. After the system is built, it is much more difficult to change the elevation of the tank or pump suction, but the same result can be realized by increasing the operating liquid level in the supply tank.
1. Pump Suction Piping
NPSH > The head loss component of the NPSH calculation is based on the losses associated with the pump suction pipeline. Often, these losses can become significant, especially when the flow rate through a process increased. Increasing the flow rate through a pipeline ( caused by increasing the system capacity ) will sometimes cause a pump to start cavitating. This occurs for the following two reasons. First, the NPSHa at the pump suction decreases because of the increased head loss resulting from the increased flow rate. Secondly, when the flow rate through the pump increases, the NPSH required by the pump also increases. ( base on : piping system fundamentals )
One way to increase the NPSH at the pump suction is to reduce the head loss. This can be accomplished by increasing the diameter of the suction pipeline or selecting valve with lower losses ( for example replacing a globe valve with a gate valve ). Both of these changes will reduce the head loss in the suction pipeline but required major changes on an existing system. ( base on : piping system fundamentals )
Line size > Suction piping usually is one or two line sizes larger than the pump suction nozzle size. Suction piping more than two sizes larger should be queried with the process department. For example, a 10” suction nozzle on a pump where the suction size of the pipe is 6” or 8” is probable, but the same suction nozzle where the suction size of the pipe is 3” or 4” is questionable. ( base on : process piping design handbook )
Eccentric Reducer > Generally used at pump suction to avoid cavitation and to maintain elevation (BOP) in rack. Why cavitation in pump have to avoid ? because a pump is designed to transfer liquid not vapour. Vapour form if the pressure in the pump falls below the liquid’s vapour pressure. The vapour pressure occurs right at the impeller inlet where a sharp pressure drop occurs. The impeller rapidly builds up the pressure which collapses vapour bubles causing cavitation and damage. This is avoided by maintaining sufficient NPSH.
flexible joint > If necessary we need it to minimize vibration from pump that could be impact to the piping connection. But still have to clarified with schematic or P & ID.
Strainer > this component generally used for filter that not recommended for transferring, for example: stones, or unnecessary material.
2. Pump Discarge Piping
Line size > Generally, discharge piping is one or two size larger than the pump discharge nozzle size. For example, a 10” discharge nozzle on a pump where the discarge size of the pipe is 12” or 14 “ is probable.
Conc. Reducer > Due to discharge lines being larger than the discharge nozzle, concentric reducer are required in this line. Reducer should be as close as possible to the nozzle; with top suction – top discharge pumps.
Check valve > if necessary we need it to avoid direct impact liquid to the impeller pump when the process shut down. But we have to clarified with schematic or P & ID.
ROUTE-2. Recommended & Unrecommended Pipe Route
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