Sherman Wu Viking Pump Stephen Blyth Viking Pump · Sherman Wu Senior Applications Engineer for Viking Pump Canada with 19 years experience in positive displacement ... failure allowed

10 WAYS TO KILL YOUR PUMP

• Sherman Wu – Viking Pump

• Stephen Blyth – Viking Pump

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Sherman Wu Senior Applications Engineer for Viking Pump Canada with 19 years experience in positive displacement pumps

Stephen Blyth Calgary Engineering/BC District Manager for Viking Pump Canada; 20 years in the positive displacement pump market.

Presenters

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The twin gear pump unit below delivered over 8 million gallons of fuel oil during its lifespan.

What determines the life of a pump?

• Design

• Materials of construction

• Application

• Misuse and abuse

This presentation will highlight the 10 most common ways to kill your pump. Conversely, it will also outline countermeasures you could implement should you want long pump life and reduced downtime.

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10 Ways to Kill Your Pump

1. Death by Debris

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Death by Debris

While many gear pumps can be properly fitted to handle fine abrasives, they’re not well suited to handling large foreign objects like:

Large foreign particulate may lock the pump (at best) or may lead to catastrophic failure. Either way this may be the fastest way to kill a gear pump.

Hand Tools Rags Zip Ties Safety Glasses Wires

Bolts Dead Animals Weld Rods Rocks Flashlights

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Death by Debris Example

Cause of Death:

• A wire brush fell into a tank and was sucked into the pump.

Result:

• The pump locked up. • Downtime to open the

pump and remove the foreign object.

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Death by Debris Example

Cause of Death:

• A nail was in the process line at startup and was sucked into the pump.

Result:

• The nail pierced the composite idler gear, shattering the part.

• Catastrophic failure and downtime

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Preventing Death by Debris

In each of the previous examples the customer refused to install a strainer because they were “sure” their process contained no foreign solids.

Foreign solids like these are common and are found in new and old systems alike.

Strainers are the best and most reliable option to ensure that large foreign solids do not enter the pump. The size of solids allowed is known and controlled.

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Preventing Death by Debris

In addition to installing the strainer, it should be checked and cleaned regularly as part of the preventative maintenance process.

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1. Death by Debris

2. Death by Improper Installation

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Death by Improper Installation

Gear pumps are robust. They will tolerate some misalignment, pipe strain, and vibration without significant impact to the service life.

However, severe improper installation can lead to shortened pump life and in rare cases, immediate part failure.

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Death by Improper Installation Example

Cause of Death:

• Severe shaft misalignment.

Result:

• Coupling failure

• Shaft failure

• Bearing failure

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Cause of Death:

• Severe misalignment of the pillow block bearing

Result:

• The pump seized frequently.

• Excessive internal wear

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Cause of Death:

• Severe pipe strain Result:

• The pump casing cracked under the load.

• Asphalt leakage occurred due to the crack.

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Preventing Death by Improper Installation

• First, make sure the unit has a firm and level foundation.

• Align the pipes to the pump. Do not force pipes to line up with the ports.

• Once the pump and pipes are aligned, align the drive to the pump. Precision alignment is always recommended. The faster the pump is run, the more critical the alignment.

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1. Death by Debris


3. Death by Starvation (NPSH)

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Death by Starvation

Gear pumps will operate successfully at a moderate vacuum. Too little pressure at the inlet port however and they can start to cavitate (insufficient NPSH).

Cavitation symptoms include:

• Noise

• Loss of capacity

• Erratic gauges

• Vibration

• Localized pitting of the pump internals

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Death by Starvation Example

Cause of Death:

• Inadequate NPSHA (net positive suction head available) leading to cavitation

Result:

• Pitting of the pump internals including the faces of the gears, roots of the gear teeth, and discharge side of the head.

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Preventing Death by Starvation

• Monitor the inlet conditions with a suction gauge or transducer to ensure adequate inlet pressure.

• Slow the pump if cavitation starts.

• Improve the NPSHA (net positive suction head) in your system.

– Larger inlet pipes

– Reduce the inlet pipe length

– Control the liquid temperature

– Control the liquid level in the supply tank

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1. Death by Debris



4. Death by Dry Run

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Death by Dry Run

Gear pumps can run dry short term with little to no damage. Reasons to do this would include:

• Checking rotation as part of startup procedure

• Priming

• Clearing the line from loading or unloading

Long term dry run can result in shortened seal life or wear to shafts, pins, and bushings.

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Death by Dry Run Example

Cause of Death:

• Lack of lubricity / dry run

Result:

• Rapid wear of bushings, pins, and shafts.

• Frequent seal failures

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Preventing Death by Dry Run

Devices and Controls Commonly Employed to Prevent Dry Run:

• Flow Meters / Flow Sensors

• Pressure Transducers

• Motor Power Monitors

• Liquid Tank Level Sensors or Scales

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1. Death by Debris



4. Death by Dry Run

5. Death by Over-speed & Over-pressure

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Death by Over-speed & Over-pressure

In many applications pumps may be run over catalog rated speeds OR over catalog rated pressures, but doing both can result in rapid failure.

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F

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Death by Over-speed & Over-pressure Example

Cause of Death:

• Significant over-pressure overloading the thrust bearings of the pump.

Result:

• Premature bearing failure allowed the rotor to thrust into the head of the pump, failing the pump.

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Death by Over-speed & Over-pressure Example

Cause of Death:

• Significant over-pressure bending shaft

Result:

• Rotor to head contact wear (on suction side) and eventual shaft fatigue failure.

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Preventing Death by Over-speed & Over-pressure

For controlling speed:

• VFD Controls properly set and protected.

For controlling pressure:

• Properly set relief valves

• Proper monitoring of gauges or pressure transducers

• Power monitoring

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1. Death by Debris



4. Death by Dry Run


6. Death by Deadheading

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Deadheading a PD Pump

Centrifugal pumps are pressure creating machines, resulting in varying flow over a narrow range of pressures.

0 Flow, Shut Off Head

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Deadheading a PD Pump

Positive Displacement pumps are flow creating machines, maintaining consistent flow over a wide range of pressures.

0 Flow, Shut Off Head

Consistent Flow Regardless of Pressure

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Death by Deadhead Example

Cause of Death:

• Deadhead

Result:

• Burst hose or pipe

• Coupling failure

• Shaft failure or other pump failure

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Preventing Death by Dead Head

Relief valves must be installed anywhere where the system can be isolated and over pressure may occur. This may include system valves and/or a pump-mounted internal relief valve.

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1. Death by Debris



4. Death by Dry Run



7. Death by Full Bypass

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Relief Valve Operation

An internal relief valve or other pressure limiting device should be used to help protect the system from over pressure.

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Running the Relief Valve in Full Bypass

Running a relief valve in full bypass long term can be detrimental to the pump or system. This can cause heating of the pump and product and may also cause accelerated wear to the pump due to the higher pressures.

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Relief Valve Full Bypass Example

Cause of Death:

• Frequent full bypass of relief valve

Result:

• Heat

• Reduction of liquid lubricity

• Wear

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Preventing Death by Relief Valve Full Bypass

• Relief valves should not be opening as part of normal pump operation.

– Make sure the setting is adequately high to keep the valve from opening under normal pump operation.

• Minimize full bypass frequency and duration.

– Gauges

– Monitor the Power, Pressure, Temperature and/or Flow

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1. Death by Debris



4. Death by Dry Run




8. Death by Changing Conditions

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Changing the Service Conditions

• Gear pumps are very versatile and cover a wide range of operating conditions: – Viscosities from <1 cSt to >1,000,000 cSt

– Temperatures from -120°F to >750°F

– Corrosive or Abrasive liquids

• This does NOT mean that a single pump construction will support all applications.

• Sometimes service condition changes are necessary due to process changes or applying pumps to new services.

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Changing the Service Conditions

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Death by Changing Conditions Example

Cause of Death:

• Adding corrosive to liquid

Result:

• Corrosion to pump internals

• Severe loss of capacity and eventual failure

Before

AFTER

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Death by Changing Conditions Example

Cause of Death:

• Changing the liquid viscosity from thick to water-thin

Result:

• Stainless steel idler galled, resulting in wear and lost flow.

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Preventing Death by Changing Service Conditions

• Always consult with your distributor or the pump manufacturer before changing the operating conditions.

– Reference the serial number

– Have all minimum and maximum limits defined

• If the pump is to be used for multiple liquids, provide all liquids and operating conditions.

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1. Death by Debris



4. Death by Dry Run


6. Death by Deadheading.


8. Death by Changing Conditions

9. Death by Failure to Maintain

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Death by Skipping Maintenance Example

Cause of Death:

• Failure to grease bearings.

Result:

• Break down of the grease’s lubricating property

• Bearing failure

Before

AFTER

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Preventative Maintenance

Pump Type Preventative Maintenance Required

Gear Pumps Sometimes none, but some require periodic greasing of bearings or seal chambers

Lobe Pumps Periodic greasing and/or oil condition monitoring and replacement

Vane Pumps Periodic monitoring of the condition of the vanes

Pumps with Double Seals

Barrier fluid condition monitoring and periodic replacement

Following recommended preventative maintenance procedures and intervals can help to prevent costly down time and failures down the road.

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1. Death by Debris 2. Death by Improper Installation 3. Death by Starvation (NPSH) 4. Death by Dry Run 5. Death by Over-speed & Over-pressure 6. Death Deadheading 7. Death by Full Bypass 8. Death by Changing Conditions 9. Death by Failure to Maintain 10. Death by Run to Failure

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Run to Failure

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Run to Failure

• Monitoring conditions of the system and pump can help to prevent catastrophic failures and costly downtime. These can include: – Flow rate

– Pressure (in and out)

– Temperature

– Noise

– Vibration

– Power consumption

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Death by Run to Failure Example

Cause of Death:

• Run to failure without valve or controls

Result:

• Pump ran overpressure

• Pin and bushing wear went undetected, resulting in idler and head wear

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Preventing Death by Run to Failure

• Continuous monitoring

• Periodic Inspections (pump inspection reports)

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1. Death by Debris 2. Death by Improper Installation 3. Death by Starvation (NPSH) 4. Death by Dry Run 5. Death by Over-speed & Over-pressure 6. Death by Deadheading 7. Death by Full Bypass 8. Death by Changing Conditions 9. Death by Failure to Maintain 10. Death by Run to Failure

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Documents

Sherman Wu Viking Pump Stephen Blyth Viking Pump · Sherman Wu Senior Applications Engineer for Viking Pump Canada with 19 years experience in positive displacement ... failure allowed