PREVENTIVE MAINTENANCE OF INDUSTRIAL PUMPS

  PREVENTIVE MAINTENANCE OF INDUSTRIAL PUMPS

Pumps Maintenance

Suggested Actions

Establish a pumping system maintenance program that includes the following:

• Preventive actions

• Predictive actions

• Periodic efficiency testing.

Resources

DOE and Hydraulic Institute, Improving Pumping System Performance: A Sourcebook for Industry.

Hydraulic Institute—HI is a non-profit industry association for pump and pump system manufacturers; it provides product standards and a forum for the exchange of industry information for management decision-making. In addition to the ANSI/HI pump standards, HI has a variety of energy-related resources for pump users and specifiers, including training, guidebooks, and more. For more information, visit www.pumps. org, www.pumplearning.org, and www.pumpsystemsmatter.org.

U.S. Department of Energy—DOE’s Pumping System Assessment Tool (PSAT) can help you assess pumping system efficiency and estimate energy and cost savings. PSAT uses pump performance data from Hydraulic Institute standards and motor performance data from the MotorMaster+ database.

Visit the BestPractices Web site at www.eere.energy.gov/bestpractices for more information on PSAT and for upcoming training in improving pumping system performance and in becoming a qualified pumping system specialist.

Maintain Pumping Systems Effectively

Effective pump maintenance allows industrial plants to keep pumps operating well, to detect problems in time to schedule repairs, and to avoid early pump failures. Regular maintenance also reveals deteriorations in efficiency and capacity, which can occur long before a pump fails. Wear ring and rotor erosions, for example, can be costly problems that reduce wire-to-water efficiency by 10% or more.

The amount of attention given to maintenance depends on how important a system is to a plant’s operations. Downtime can be expensive when it affects critical processes. Most maintenance activities can be classified as either preventive or predictive. Preventive maintenance addresses routine system needs such as lubrication, periodic adjustments, and removal of contaminants. Predictive maintenance focuses on tests and inspections that detect deteriorating conditions.

Preventive Actions

Preventive maintenance activities include coupling alignment, lubrication, and seal maintenance and replacement. Mechanical seals must be inspected periodically to ensure that either there is no leakage or that leakage is within specifications. Mechanical seals that leak excessively usually must be replaced. A certain amount of leakage is required, however, to lubricate and cool the packing seals. But the packing gland needs to be adjusted if the leakage exceeds the manufacturer’s specifications. The packing gland must be replaced if it has to be tightened excessively to control leakage. Over tightening causes unnecessary wear on the shaft or its wear sleeve and increases electric power use. Routine maintenance of pump motors, such as proper lubrication and cleaning, is also vital.

Predictive Actions

Predictive maintenance helps minimize unplanned equipment outages. Sometimes called “condition assessment” or “condition monitoring,” it has become easier with modern testing methods and equipment. The following methods apply to pumping systems:

Vibration analysis. Trending vibration amplitude and frequency can detect an impending bearing failure. It can also reveal voltage and mechanical imbalances that could be caused by impeller erosion or coupling problems. Changes in vibration over time are more meaningful than a single “snapshot” of the vibration spectrum.

Motor current signature analysis. Sometimes called “dynamic analysis,” this reveals deteriorating insulation, rotor bar damage, electrical system unbalance, and harmonics. It can also pick up system problems such as malfunctioning control valves that cause flow rate disturbances. Tracking the signature over time is more valuable than a single snapshot.

Lubrication oil analysis. This applies only to large, oil-lubricated pumps, and is an expensive procedure. Oil analysis can detect bearing problems caused by metal particles or chemical changes that result from overheating, and seal problems caused by pumped fluid in the oil. It also provides guidance on proper oil-change intervals.

Periodic efficiency testing. Testing the wire-to-water efficiency and keeping records to spot trends is useful. Finally, see the checklist of maintenance items below, which can be tailored for many kinds of systems, applications, and facilities.

Basic Maintenance Checklist

• Packing. Check for leakage and adjust according to the instructions of the pump and packing manufacturers. Allowable leakage is usually 2 to 60 drops per minute. Add packing rings or, if necessary, replace all the packing.

 • Mechanical Seals. Check for leakage. If leakage exceeds the manufacturer’s specifications, replace the seal.

 • Bearings. Determine the condition of the bearing by listening for noises that indicate excessive wear, measuring the bearing’s operating temperature, and using a predictive maintenance technique such as vibration analysis or oil analysis. Lubricate bearings according to the pump manufacturer’s instructions; replace them if necessary.

 • Motor/Pump Alignment. Determine if motor/pump alignment is within the service limits of the pump.

 • Motor Condition. Check the integrity of motor winding insulation. These tests usually measure insulation resistance at a certain voltage or the rate at which an applied voltage decays across the insulation. A vibration analysis can also indicate certain conditions within motor windings and lead to early detection of developing problems.

 References Extend Your Motor’s Operating Life, DOE Motor Systems Tip Sheet, 2005. Test for Pumping System Efficiency, DOE Pumping Systems Tip Sheet, 2005.

PREVENTIVE MAINTENANCE OF INDUSTRIAL PUMPS

From the design phase to proper start up and post installation, pump maintenance is critical to pump reliability, performance and longevity.

On the front side of an installation, provisions should be made to allow for ample accessibility to service the pump without effort. Lifting arrangements for ease of removal should be considered as well. Finally, ensuring that isolation valves are in place to avoid draining the system if / when the pump is to be serviced, along with getting gauges installed on the inlet and discharge flanges for pump monitoring, are good preparatory activities for an installation.

If a pump is not matched correctly to the application, much more than simple maintenance will be required to keep the pump up and running without failure. The pump’s construction materials must be compatible with the pumped media, and a properly sized pump for the respective application is the answer to trouble-free operation. A pump sized too small for the application will not maintain proper pressures and flows. Conversely, a pump sized too large can incur substantial energy costs and worse, can damage both the pump and the entire system.

Proper installation will save a lot of headaches down the road. Is the pump installed per the manufacturer’s instructions? This is not a good time to take shortcuts. To avoid future breakdown or pump failure, it is integral to the pump’s stable operation to follow these instructions closely.

PUMP START-UP

Once the best suited pump for the application has been made and the pump has been installed per the manufacturer’s instructions, a proper start up is critical for circumventing future pump problems or unscheduled maintenance events. The Installation and Operation manual for proper pump start up should be followed to the detail and will provide the sound foundation for optimum pump operation. The following is a check list that is standard to pump start up procedures:

                        Follow Installation and Operation manual for proper start up procedure

                        Ensure that all lines supplying the pump have been flushed before the pump is installed

                        Check that all filtering / straining devices are clear of debris

                        Vent all air from the pump lines

                        Ensure that all valves are open to the appropriate amount

                        Check for proper motor protection

                        Check for proper motor rotation

                        Check for leaks and ensure all fittings are properly tightened

                        Bump start the pump and listen for any unusual sounds and watch for leaks

                        Check for proper voltage (under load, as close to the motor as possible)

ROUTINE SCHEDULING OF PREVENTIVE MAINTENANCE

Scheduling maintenance events at regular intervals which best accommodate conditions and time of operation can assure optimum pump performance and avoid unplanned downtime throughout the life of the pump. The event should be well-planned in advance so that when the activity is to take place, all the resources including tools, spare parts and / or service kits are readily available. It’s also a good practice to ensure that tools and spare parts are checked and verified that they operate correctly prior to beginning the event. The goal of a scheduled maintenance event is to perform the task scrupulously, correctly, and efficiently, with minimal downtime.

Following the event, documentation is critical to meaningful record keeping, as the tracking of the maintenance event provides useful performance-related information and can provide diagnostic clues pertinent to troubleshooting and adjusting for the pump’s best performance. This documentation also provides a good starting point for the next routine maintenance event.

Finally, detailed procedures outlining the related tasks specific to the pump should be reviewed prior to the event. The following discussion highlights basic maintenance tasks that should be included in preventive maintenance procedures.

PUMP END MAINTENANCE

Regular pump maintenance is fairly simple and can keep your pump downtime to a minimum. These maintenance events can also be beneficial to other system components. Here are simple procedural tasks associated with the care of the pump end:

                        Ensure pump meets required performance and is operating smoothly and quietly

                        Listen for any abnormal noises / vibrations

                        Check for leaks, particularly at the shaft seal

                        Check flow and pressure

                        Remove and clean all system strainers or filters

                        Lubricate according to manufacturer’s specifications using the proper lubricant

                        Check for loose bolts / nuts and fittings

                        Open the air vent to remove any trapped air

MOTOR MAINTENANCE

Getting the best possible overall efficiency out of your pump makes sound financial sense, and routine motor maintenance is critical to that end. The following check list provides the most basic tasks associated with motor maintenance:

                        Clear dust and dirt from the motor

                        Check winding resistances, voltage, amp draw and phase imbalance

                        Grease bearings according to manufacturer’s instructions; use only the suggested lubricant; do not over                      grease or   mix grease, types of checks:

                        Check for corrosion and condensation

                        Check for excessive heat / noise / vibration

If excessive heat from the motor is observed, check the motor’s amp draw and line voltage. High heat in a motor can also be caused by a lack of cooling. Ensure that ambient conditions around the pump are within the manufacturer’s specifications and that the cooling fan blades are intact and operating properly

ELECTRICAL AND ELECTRONICS INSPECTIONS

Examine the wire connections and look for signs of heat or arcing. Be sure that terminal screws are tight. Inspect terminal boxes and enclosures with particular attention to areas that may be a conduit for moisture intrusion.

Check the pump fault log for alarms or warnings since the last maintenance. Ensure the pump is operating within the manufacturer’s environmental specifications, as electronics can be sensitive to both heat and moisture.

  GETTING THE MOST VALUE OUT OF PREVENTIVE MAINTENANCE

A successful preventive maintenance event is a well orchestrated, well led activity with careful planning and attention to detail. The fact that it is a routine activity poses the risk that the tasks could become mundane and therefore inadvertent neglect could jeopardize the quality of the event. A pre-meeting with related parties to identify the specific details and expectations of the event, along with a checklist and / or report to document results, and finally a follow up review of the event with the parties involved may help to optimize preventive maintenance events.

PREVENTIVE MAINTENANCE OF PUMPS

The best safeguards against unplanned shut-down or system failure are good preventive maintenance practices and proper pump diagnosis. Cat Pumps triplex pump design offers easy on-site maintenance without the use of special tools, making a routine maintenance achievable without difficulty. Each pump has a Data Sheet, Service Manual and Diagnosis Chart to simplify the periodic servicing required. Every installation differs from one another, so a unique maintenance schedule may be required. Below you will find more information about adopting a proper maintenance schedule as well as how to diagnose any pump issues.

Custom Maintenance Schedule

The table above shows the recommended preventive maintenance schedule, however it is only to be used as a guide. The life of your pump and wear parts will vary by application depending on duty-cycle, pumped liquid, temperature, inlet conditions, location of installation and system accessories. It is important to monitor your system carefully and at the first sign of low pressure, examine your pumping system. Low pressure may be caused by system components other than the pump such as:

• Clogged filter
• Leaks from fittings or connections
• Cracked or kinked hoses
• Worn o-rings in safety regulators, check valves or relief valves
• Loose or worn belts
• Worn nozzles

If no problems are found with other system components, shut down system and inspect pump. Check for debris in valves. Change seals and record hours for your preventive maintenance schedule. Typically valves should be replaced at every other seal replacement.

After maintenance is performed continue to monitor all system components. Often it is other elements in the system that will be the cause of poor performance. In order to protect the pump, always inspect the entire system when there is a decrease in system performance. 

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