Excessive vibration, noisy noise, higher-than-normal temperature heat, off-curve pressure readings, and process fluid leakage are all signs of impending pump failure. In order to avoid more damage to the pump and downstream equipment, as well as costly downtime for maintenance, the root cause of the pump problem must be found and quickly restored to optimal performance. 

Bearings, couplings and seals are the most prone to failure of the pump components. Experience has shown that ignoring these items will not only lead to maintenance costs, but also increase resources and downtime, thereby increasing operating costs. Here is how to identify these parts failures, find the root causes, and prevent them from happening again. 

Many red flags can be signs of bearing failure: increased vibration readings, louder than usual operating noise, and increased temperature around the bearing housing are common warnings. Pay attention to these small signs. Don't ignore even a slight rattle; when a loud scream is heard, the bearing is usually hit and the pump is about to lock. 

Although bearings are usually lubricated at the factory, they require a personalized lubrication plan based on the pump's application and operation plan. (Sealed bearings are an exception.) Failure to keep the bearings properly lubricated can lead to overheating and early failure.

Another threat to normal bearing operation is lubricant contamination. Gravel and other contaminants can damage the bearing surface, cause inconsistent operation and shorten bearing life. A less common threat to bearings is misalignment and vibration, which can cause peeling and damage to the bearing surface over time. 

Develop a regular lubrication plan and record the lubrication in the maintenance log. Avoid the common lubrication errors outlined below. 

When the pump shaft and motor shaft are not aligned, the coupling will fail. They may not be aligned from the beginning due to improper installation, or they may become so over time due to system vibration. One way to visually identify a faulty coupling is to look for black debris under the coupling area of ​​the pump. This comes from the coupling insert placed between the coupling flanges. On misaligned couplings, the flange faces rubbing together will grind off the blade over time, creating a pile of shavings. 

Another key indicator of coupling misalignment is vibration. Any vibration beyond what is normally observed during normal operation of the pump should be investigated.

Whenever a problem (due to the shavings or vibration mentioned above) is suspected as part of the daily maintenance plan, the alignment of the coupling should be checked. Whenever the pump is being serviced, the correct alignment should be verified before starting and after the pump is at operating temperature (called "hot alignment").

First, check the alignment of the parallel coupling by placing a ruler on the two coupling flanges and measuring the maximum offset of each point around the coupling. If the maximum deviation exceeds the value specified by the coupling manufacturer, the coupling should be readjusted. 

Once you are satisfied with the parallel alignment, you should check the angular alignment of the coupling with a micrometer or caliper. Measure from the outside of one flange to the outside of the other flange around the outer circumference of the coupling. If the difference between the maximum and minimum values ​​exceeds the tolerance specified by the coupling manufacturer, the coupling should be readjusted. If correction is required, parallel alignment should be rechecked. Refer to Figure 2 for the correct coupling alignment technique.

Mechanical seal failures are usually easy to spot-the slow dripping or sometimes steady flow of process fluid from the seal gland is a fatal gift. Seals are the cause of most rotating equipment failures during the life of the equipment, but they are rarely the root cause of failures. 

The wrong choice of sealing material in the process is a common mistake. Improper selection will cause the O-ring of the seal to swell or rupture or the seal surface to corrode. Although most people know to choose seals based on the process fluid (for example, corrosive fluids require stronger seals), many people do not take into account the operating conditions. Fluids like water are generally considered inert. However, at extreme temperatures, the sealing surface may flash and become damaged. 

Another temperature consideration that may affect the sealing, even if the sealing material is selected correctly, is also related to the operating conditions. Raising a stopped pump from ambient temperature to immediate operation. Extremely high temperature or subcooled fluids may thermally shock the seal and cause rupture. 

Pumps that deliver more viscous fluids (such as paint) can see accumulations along the sealing surfaces and edges. Over time, this can make the seal sticky and cause failure. See Figure 3 for an example of seal failure due to paint buildup.

 In addition to these specific seal selection and application issues, the main reason for seal failure is the dry running of the seal, which can cause thermal shock or burn the elastomer of the seal. Any number of systemic problems can cause idling. Low-level fluid from the source, blockage on the suction side of the pump, or closed discharge (dead heading) can cause temperature spikes and cause seal failure.

The first step to avoid mechanical seal failure is to select the appropriate seal for the process fluid and operating conditions. Review the application in detail with the application sales engineer instead of selecting by fluid type by default.

If extreme temperatures are involved, consider changing the startup procedure to avoid thermal shock to the seal. Gradually introduce process fluid into the pump to bring all components to full temperature more slowly. Adding external heating or cooling elements is another possible solution.

For applications that are prone to process buildup on the seal, an external seal flushing system can be added to prevent these particles from sticking to the seal. If there is an external flushing system on the pump, keep it in good working condition and check for seal accumulation and malfunction. 

Once a suitable sealing material is selected for the application, the focus should be shifted to the suction side of the equipment to prevent dry running. If the source fluid is often low, a level control switch should be installed to prevent the supply level from being too low. If a drop in discharge flow or pressure is observed, it indicates that the air inlet should be checked for blockage. Except for the short duration of the pump performance test, the pump should not be operated with a closed discharge-marking and monitoring procedures can prevent this from happening.  

One solution to the sealing problem is to use a sealless pump to transform the process. These vertically enclosed column designs reduce the leakage of the throttle bushing, collect any accidental leakage in the pump column and discharge it back to the suction or supply tank. Vertical sealless pumps are suitable for a variety of challenging applications-even those with high solids content or high temperature fluids. The use of closed-column vertical pumps to transform a horizontal pump installation usually requires minimal piping changes and additional support for the external installation configuration.

Conventional wisdom asserts that those who do not learn from history are destined to repeat the same mistakes-this is also true in the maintenance and repair of pumps. Logging repairs can help identify future problem pumps and help diagnose future pump failures. Once the pump is up and running again, this important last step is often overlooked. 

There are several key elements to be aware of. The more details recorded, the easier it is to identify these abnormal factors. First, the maintenance instructions should include any abnormal operating conditions around the time the maintenance problem occurred (for example, holiday shutdowns, abnormal high temperatures, etc.). Write down the location of the pump in the process and determine the reason why the pump needs repairs (shutdown, performance, leakage, noise, current, etc.).

The repair instructions should also include the steps taken to diagnose and repair the pump. When a problematic pump is identified, it can be marked for more careful inspection of installation, piping, operation, and maintenance procedures. This closer inspection should be able to determine the root cause of the failure.  

Using historical data to eliminate recurring problems will extend the life of the pump and prevent process downtime.  

Jim Clayton is the general manager of Ruthman Pumps & Service, the field service division of Ruthman Companies. You can contact him at 513-559-3546 or jclayton@ruthmanservice.com. For more information, please visit ruthmancompanies.com.