Xylem P2001406B Series e-1510 Centrifugal Pumps - Manual (Page 26)

of time before you continue to tighten the gland. Tighten the gland nuts slowly and one
flat at a time.
Leakage rate
An adequate leakage rate is not one single value for all pumps and installations, but is the
amount required to provide adequate cooling and lubrication. The required leakage is
influenced by operating pressure, fluid temperature, shaft speed, and so forth. For fluid
temperatures in the range of 32°F to 190°F (0°C to 88°C), average leakage rates of 60 to
80 drops per minute are recommended. However, each individual pump and installation
has unique operating conditions that result in widely-variable leakage rate requirements.
Maximum fluid temperature
At fluid operating temperatures near the upper limit of 190°F (88°C), the maximum
temperature rise of the leakage is important. Never operate a packed pump with steam
forming at the gland. This limits the temperature rise to a maximum of about 20°F (-7°C). If
the formation of steam persists at higher leakage rates, you must provide cooling water by
means of an external supply, or a heat exchanger used to cool the bypass flush.
Commissioning, Startup, Operation, and Shutdown
24 Series e-1510 Installation, Operation, and Maintenance Manual