This article explains the operation of peristaltic (hose) pumps and gives twelve points to be aware of when using them. [Read more…]

Shaft alignment on pumps. Shaft misalignment is one of the most common reasons for bearing and mechanical seal failures. Rotating misaligned shafts produce vibration and complex fluctuating radial and axial loads that lead to breakdowns. Shaft alignment is a precision maintenance requirement that requires exacting care and detail and if not performed will cause much production down time.

Keywords: axial alignment, laser alignment, dial indicator, soft foot, shaft coupling. [Read more…]

Experiences with magnetic (magdrive) pumps. Magnetic drive pumps come in three varieties – canned motor pumps, all metal pumps and plastic lined metal pumps. They are sealless and cannot leak into the environment. Long, repair- free service life depends on recognising the limitations of these pumps. This article covers issues with using direct mounted, lined magdrive pumps experienced ‘in the field’.

Keyword: separation liners, chemical compatibility, sediment, particulate.  [Read more…]

Net positive suction head losses (or why you can suck through a straw).

Pumps cavitate and run dry when the pressure leading into them falls below the vapor pressure of what they are pumping. At vapor pressure, the liquid boils into a vapor and fills the pipe.

In order to know that the pressure to a pump is always above the vapor pressure, it is necessary to calculate that the pressure losses from pipe friction and suction lift will not cause the pressure to drop under the vapor pressure.

The presence of dissolved gas in the liquid complicates the problem.  [Read more…]