Also for a given flow rate the power absorbed increases with increased viscosity, and reduces with reduced viscosity. It is important that checks are made with your nearest Flowserve office if changes in viscosity are planned.
5.7.3 Pump speed
Changing pump speed effects flow, total head, power absorbed, NPSHR, noise and vibration. Flow varies in direct proportion to pump speed, head varies as speed ratio squared and power varies as speed ratio cubed. The new duty, however, will also be dependent on the system curve.
If increasing the speed, it is important therefore to ensure the maximum pump working pressure is not exceeded, the driver is not overloaded, NPSHA
>NPSHR, and that noise and vibration are within local requirements and regulations.
5.7.4Net positive suction head (NPSHA) NPSH available (NPSHA) is the head available at the impeller inlet, above the vapor pressure of the pumped liquid.
NPSH required (NPSHR) is the minimum head required at the impeller inlet, above the vapor pressure of the pumped liquid, to avoid excessive cavitation and extreme performance degradation.
It is important that NPSHA > NPSHR. The margin between NPSHA > NPSHR should be as large as possible.
If any change in NPSHA is proposed, ensure these margins are not significantly eroded. Refer to the pump performance curve to determine exact requirements particularly if flow has changed.
If in doubt please consult your nearest Flowserve office for advice and details of the minimum allowable margin for your application.
5.7.5 Pumped flow
Flow must not fall outside the minimum and maximum continuous safe flow shown on the pump performance curve and or data sheet.
5.8.1 Cleaning prior to operation
Pumps that are to be used for a food or drinking water application should be cleaned before being put into initial operation and after the installation of spare parts that are in contact with the liquid.
Cleaning once the pump has been commissioned will depend on the application and operating conditions. The user must ensure that the cleaning procedures are suitable for the application and operating conditions, and local regulations.
6MAINTENANCE 6.1 General
If a belt drive is used, the assembly and tension of the belts must be verified during regular maintenance procedure.
In dirty or dusty environments, regular checks must be made and dirt removed from areas around close clearances, bearing housings and motors.
It is the plant operator's responsibility to ensure that all maintenance, inspection and assembly work is carried out by authorized and qualified personnel who have adequately familiarized themselves with the subject matter by studying this manual in detail (see also section 1.6.2).
Any work on the machine must be performed when it is at a standstill. It is imperative that the procedure for shutting down the machine is followed, as described in section 5.6.
On completion of work all guards and safety devices must be
Oil and grease leaks may make the ground slippery. Machine maintenance must always begin and finish by cleaning the ground and the exterior of the machine.
5.8Pumps for Food Use or Potable Water
If the pump has not been specifically ordered for a food or drinking water application it must not be used for these types of applications. If it has been ordered for this type of application the following recommendations are to be followed.
If platforms, stairs and guardrails are required for maintenance, they must be placed for easy access to areas where maintenance and inspection are to be carried out. The positioning of these accessories must not limit access or hinder the lifting of the part to be serviced.
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