Tuesday, January 12, 2016

Wastewater Pump Repair Time, Choosing Parts, and Excess Vibration Factors

In correlation to the last Colonial Seal blog post, “Water Reuse Systems Provide Solutions For The Future,” this week we will be considering wastewater pump repair. Ultimate performance of pumping equipment can be advanced only when equipment is efficiently designed for the specific needs of the unique pump at hand. Varying services and pump equipment will have differentiating lifespans and outcomes depending on how well they are maintained.

Vertical sump pumps or submersible pumps are the most common pump types for wastewater processes. An average timespan between each pump repair usually lasts between two to eight years. This of course is highly dependent on the severity of maintenance for the individual pump. Pumps that need 285 pounds per square inch gauge of pressure usually take two to four years to repair. This timeframe also applies to pumps that are exposed to temperatures up to 450 degrees Fahrenheit or are exposed to rough environments. If any pump falls short of these averages, an in-depth evaluation should be carried out.

There are many factors that should be considered when selecting wetted parts for pumps (casings, impellers, etc.) This includes the temperature of the liquid being pumped and factors that result in excessive pump vibration. Careful selection of materials and equitable awareness of construction details are extremely important influences when handling liquids at temperatures below 32 degrees Fahrenheit or above 250 degrees Celsius. High or low temperatures greatly affect the corrosion-resistance and physical properties of many of these parts. Due to this importance, consumers must be aware of the liquid’s temperature that is being pumped.

Referencing applicable codes and methods of the industry in which each distinct pump operates is essential in order to make material selections appropriate for the temperature ranges involved. Consumers may consider a heat treated, fine grain, low-carbon fusion steel with reasonable hardness and low phosphorus, nickel and molybdenum as a foundation when selecting sufficient ferric steel for low-temperature liquids.

Considering austenitic stainless steels and bronzes for service in low-temperature pumping operations is ideal. Presenting improved toughness with decreasing temperature, austenitic stainless steels are fully annealed and display no transition point. If applicable for the application, most bronzes and aluminum blends are not weakened at low temperatures. Therefore they may also be of use to this form of practice. Before composing a final decision, circumstances such as cost, corrosion-resistance, availability, erosion-resistance, hardness, and toughness and fatigue strength should be examined.

Excessive pump vibration is a common indicator of damage within a pump or the immediate pump system. With there being many potential vibration excitation sources, experts have narrowed down the most common root causes. These include mechanical unbalance of rotating parts or from abrasive fluids wear, pump and driver natural frequency & resonance, hydraulic resonance in piping, and poor structure rigidity. Worn or weakened rolling element bearings can also be a problem due to their vibration frequency signatures. These signatures are based on the number of bearing balls or rollers. Bearing manufacturers determine and can therefor provide the exciting frequencies of their distinct products.



The table below identifies possible sources of high pump vibration.


For more information on this topic or mechanical seals 

About Colonial Seal Company
Founded in 1994, Colonial Seal Company is a registered Vietnam-Era, Veteran-Owned, ISO 9001:2008 certified company providing cost effective sealing solutions for over 20 years. Our products include customized applications and have been proven to reduce production downtime and keep maintenance costs low on machinery. Our seals have been used in windmills, mining machinery, food & beverage equipment, pharmaceutical applications, and many others!
Ph: 1-800-564-2201 Fax: 800-564-2204

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