Tech Seminar Pump Troubleshooting & Maintenance Tech Seminar Pump Troubleshooting & Maintenance Session will begin in 5 Minutes Session will begin in 4 Minutes Tech Seminar Pump Troubleshooting & Maintenance Session will begin in 3 Minutes Session will begin in 2 Minutes Session will begin in 60 Seconds Welcome A Few Housekeeping Items Course Workbook Additional materials: • Supplemental Material Packet • At Your Service Bulletins Pump Troubleshooting and Maintenance Seminar P H O TO O P P O R T U N I T Y – G R O U P P H OTO Table of Contents Introduction 4 Pump Basics 8 Pump Safety 28 Tool of the Trade 40 Pump Forensics (Troubleshooting) 44 Troubleshooting Checklist & Guide 52 Noisy Operation 67 Reference 86 Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pg. 3 Introduction More pumps are manufactured than any other piece of machinery with possibly the exception of electric motors Several applications and uses including: • • • Transportation - Automobiles, ships, airplanes, or trains • Service Stations, Treatment plants, Oil Fields, Farming… Appliances - Washing Machines, dishwashers, or air conditioners Commercial Buildings – Boiler feed service, hot water service, water service, & sanitation service Text Ref: Pg. 4 Introduction (cont.) If not moved by gravity, pumps are needed to move any liquid Dating back to the time of the early Egyptians & Pharaohs – Pumps were used to raise water from the Nile River for irrigation purposes Archimedes Screw Shaduf Text Ref: Pg. 4 Introduction (cont.) What is a pump? • A device that adds energy to a liquid in order to move it from one point to another There are several types and styles of pump designs • Our focus will be on a variety of G-R’s more popular products • Self-priming, priming-assisted, submersibles, & positive displacement Text Ref: Pg. 5 Introduction (cont.) Basic hydraulic terms: • Gallons per Minute (GPM) • Static • Dynamic • Friction Head • Atmospheric Pressure • Performance Curve (Chart) Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pg. 5 Pump Basics Text Ref: Pg. 6 Pump Basics (cont.) Text Ref: Pg. 7 Pump Basics (cont.) Centrifugal Force ?? • Outward force placed on rapidly spinning (rotating) objects • Fc=mv²/r Examples of Centrifugal Force • Sports car on a circular race course • Spinning a bucket of water tied to a rope • Tire on a wet roadway Text Ref: Pg. 8 Pump Basics (cont.) Centrifugal pumps operate on a similar principle • Impeller with vanes guide and increase the velocity of the liquid • Casing (volute) controls the path of the liquid as it leaves the impeller Text Ref: Pg. 8 Pump Basics (cont.) Types of Pumps Discussed • Standard (Straight) Centrifugal • Self-Priming Centrifugal (Wet Primer) • Priming-Assisted (Dry Prime) • Submersible • Positive Displacement • • Diaphragm Internal Rotary Gear Text Ref: Pgs. 8-12 Pump Basics (cont.) Standard Centrifugal Pumps • Most common of centrifugal pumps • Typically driven by electric motors or engines • Used for a variety of water like liquids: • • • • Water Sewage Petroleum Petrochemical Text Ref: Pg. 8 Pump Basics (cont.) Self-Priming Centrifugal Pumps • • • • • Hyperlink to Priming Video Capable of “self-priming” with dry (empty) suction line Pump needs to have liquid in casing to prime Some models capable of a 25 ft. (7.6 m) lift Some designs capable of “re-priming” (half casing) Many applications • • • • Water like liquids Excellent trash (solids) handling Industrial, Municipal, Construction Agriculture and Petrochemical Text Ref: Pg. 9 Pump Basics (cont.) Priming-Assisted Pumps • • • • • • Hyperlink to Priming Video Designed to handle large volumes of air Dry-prime capable (empty pump casing) Requires an external priming device (venturi, diaphragm, or vacuum pump) Large seal oil chamber for extended dry run capability Suitable for long suction lines, snoring or slurping applications Many applications: • • • • Water like liquids Excellent trash (solids) handling Industrial, Municipal, Construction Mining & Agriculture Text Ref: Pg. 10 Pump Basics (cont.) Submersible Pumps • • • • • Operates on same principle as all centrifugal pumps Designed with integral watertight motor assembly Entire assembly typically submerged in liquid Depending on environment may require explosionproof design (UL, FM, CSA, or MSHA) Many applications: • • • • Water like liquids Excellent trash (solids) handling Industrial, Municipal, Construction And Agriculture Text Ref: Pgs. 10-11 Pump Basics (cont.) Diaphragm Pumps • Positive displacement style of pump • Operates in combination of a reciprocating • • • diaphragm and two valves on either side of diaphragm pot chamber Work well on viscous or liquids containing large solid content Flow is typically not linear (subject to surging) Many applications: • • • Excellent trash (solids) handling Industrial, Municipal Construction & Agriculture Text Ref: Pgs. 11-12 Pump Basics (cont.) Internal Rotary Gear Pumps Hyperlink to Operation Video • • Positive displacement style of pump • • • • Work well on thick viscous liquids to 2,000,000 SSU Operates in combination of a rotor with internal cut teeth and a nested idler with external cut teeth Flow remains constant with change in pressure Relatively high pressure capability - 300 psi Many applications • Industrial, Municipal, & Petrochemical Text Ref: Pg. 12 Pump Basics (cont.) • Typical Pump installations? Text Ref: Pg. 13 Pump Basics (cont.) How does liquid get in the pump? • Atmospheric Pressure @ sea level Atmospheric Pressure – • • Pushes liquid into the pump Keeps liquid in a liquid state 14.7 psi 33.96 Ft of Water 29.9 In. Hg. 10.3 Meters or 1 Bar Text Ref: Pg. 13 Pump Basics (cont.) How much will a pump produce? • Centrifugal Pump Elements • Pump Design – Size of pump, impeller design & quantity • • • Speed (RPM) of impeller Impeller size (diameter) System pressure (Total dynamic head – TDH) Text Ref: Pg. 14 Pump Basics (cont.) How much will a pump produce? • Positive Displacement (Gear) Elements • • • Rotor & idler design Speed (RPM) of rotor Size of rotor and tooth profile depth along with idler height Text Ref: Pg. 14 Pump Basics (cont.) Reading Pump Performance Curves and Charts • Manufacturer’s chart plotting the performance characteristics • Use to select and troubleshoot pump performance • Use in conjunction with speed, pressure and electrical data • Often contain additional useful information • Every pump model has its own exclusive curve Text Ref: Pg. 15 Pump Basics (cont.) Text Ref: Pgs. 16-17 Pump Basics (cont.) Text Ref: Pgs. 18-19 Pump Basics (cont.) Text Ref: Pgs. 19-20 Pump Basics (cont.) Text Ref: Pg. 21 Pump Basics (cont.) Text Ref: Pgs. 22-23 Pump Basics (cont.) Text Ref: Pgs. 23-24 Pump Basics (cont.) Text Ref: Pgs. 24-25 Pump Basics (cont.) Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pgs. 26-27 Pump Safety Text Ref: Pg. 28 Pump Safety (cont.) This material is meant to be a “Quick-Reference” guide only! Use it with an Installation, Operation and Maintenance Manual • Typically developed to alert personnel of situations that could damage equipment and/or could be dangerous to personnel Follow all established safety guidelines and protocols It is the responsibility of the owner, operator and maintenance personnel to assure that only safe procedures are followed! Text Ref: Pg. 29 Pump Safety (cont.) Hyperlink to Pump Safety Video Potential Pump Hazards • High Voltage • Automatic Equipment • High Pressure • Physical Heights • Rotating Equipment • • Confined Space Entry Open Sumps • • • Hazardous Gases Cool, Damp Environment • Pump Basics Pump Safety Tools of the Trade Drowning and Diseases Insects, spiders, bees, snakes, rats, alligators… Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pg. 29 Pump Safety (cont.) Potential Pump Hazards • High Voltage • Automatic Equipment • High Pressure • Physical Heights • Rotating Equipment • • Confined Space Entry Open Sumps • • • Drowning and Diseases Hazardous Gases Cool, Damp Environment • Insects, spiders, bees, snakes, rats, alligators… Text Ref: Pg. 29 Pump Safety (cont.) General Pump Safety • • • • • • • Do NOT operate pumps without all guards and shields in place Pump ONLY liquids for which pump was designed Do NOT pump flammable or corrosive liquids unless pump and driver is design for such NEVER operate pumps in explosive or volatile atmospheres unless designed for environment CAUTIOUSLY approach any pump that has been in operation Do NOT operate a pump against a closed suction or discharge Unless designed, NEVER operate centrifugal pumps with no liquid in the pump casing Text Ref: Pg. 30 Pump Safety (cont.) General Pump Safety (cont.) • • • • • • DISCONNECT driver and/or lock-out and tag control panel before maintenance Overheated pumps can cause severe burns and injury • Approach a hot pump cautiously ALWAYS allow pump to cool to room temperature Isolate suction and discharge lines • Lock-out and tag all isolation valves SLOWLY and CAUTIOUSLY vent pump at drain Do NOT work underground or in limited egressed areas without following confined space guidelines Text Ref: Pg. 31 Pump Safety (cont.) Electric Motor Driven Pumps • • • • • ONLY have qualified personnel install, wire and operate electric driven pumps Make sure all electrical connections are in accordance with all local and National Electrical Code requirements ALWAYS properly ground electric-driven units Check an assure proper rotation on threephase electrical power installations DISCONNECT driver and lock-out and tag control panel before maintenance Text Ref: Pg. 32 Pump Safety (cont.) Engine-Driven Pumps • Assure ONLY qualified personnel operate • • • • engine-driven pumps Do NOT operate combustible engines without proper ventilation DISCONNECT spark plugs and/or battery from starter before working on pump NEVER refuel a hot or running engine Follow the engine manufacturer’s OM manual instructions Text Ref: Pg. 33 Pump Safety (cont.) Electric-Driven Submersible Pumps • • • • • • ONLY have qualified personnel install, wire and operate submersible pumps Make sure all electrical connections are in accordance with local and National Electrical Code requirements Always operate with properly sized and protected control panel NEVER attempt to lift pump by its power cord or discharge hose (portable pumps) Check an assure proper rotation on three-phase electrical power installations DISCONNECT or lock-out and tag control panel before any maintenance Text Ref: Pg. 34 Pump Safety (cont.) General Electrical Safety • Severity of electrical shock depends on: • • • • • Amount of current Person’s resistance How well-grounded the service tech is Path the current takes through a body Length of time a body is exposed to current Text Ref: Pg. 35 Pump Safety (cont.) General Electrical Safety (Cont.) • Possible effects of low-voltage contact (110V): • • • 1 mA – No sensation 2-8 mA – Slight sensation, not harmful except possibly to pacemaker wearers 15-20 mA – In the “can’t let go” range; likely to cause painful shock, muscle control loss & ventricular fibrillation should current flow across the heart Text Ref: Pg. 35 Pump Safety (cont.) General Electrical Safety (Cont.) • Possible effects of high current exposure: • • • Severe burns Loss of limb Muscular contractions to the point where the heart is stopped (Requires CPR and/or defibrillation shock to revive victim) Text Ref: Pg. 35 Pump Safety (cont.) General Electrical Safety (Cont.) • Before maintenance of any electrical device: • • • • Read all warning tags Shut-off main power Follow proper lockout and tag protocol Adhere to all caution and warning labels • If you do NOT have a good basic knowledge of electricity LEAVE IT ALONE! • Good rule in Electrical Safety: Text Ref: Pg. 36 Pump Safety (cont.) General Confined Space Guidelines • Before entering make sure protocol is • followed Confined spaces include - tanks, vessels, silos, vaults, pipelines, sewers, tunnels, or pits Text Ref: Pg. 37 Pump Safety (cont.) General Confined Space Guidelines (cont.) • In addition, any open top space 4 ft. or deeper with at least one of the following: • • • • • • • Limited means of egress Not designed for continuous occupancy Less than 19.5% O2 Flammable, combustible, or explosive atmosphere Toxic atmosphere Substances that could potentially trap, suffocate, or harm – (Water, gas, sand, gravel, ore, grain, coal, biologicals, radiation or corrosives) Poor ventilation Text Ref: Pg. 37 Pump Safety (cont.) Commonly Found Hazardous Gases • Methane – CH4 • Ammonia – NH3 • Hydrogen Sulfide – H2S • Carbon Dioxide – CO2 • Carbon Monoxide – CO • Chlorine Gas – Cl2 Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pg. 38 Tools of The Trade Text Ref: Pg. 39 Tools of the Trade (cont.) Essential Tools for the Job • Equipment data • Record-keeping program • Education on product(s) • Physical tools • • • • • Gauges Amp Probe Tachometer Voltmeter Temperature probe • Unique or special tools Text Ref: Pg. 40 Tools of the Trade (cont.) What Gauges Can Tell You? • • • • • Where system is allowing the pump to perform If pressure is too high or low If there is an obstruction in suction Evidence of vortexing or entrained air When pump is not running: • • • Static pressure Suction leak Discharge check valve problem Text Ref: Pg. 40 Tools of the Trade (cont.) • Connect gauges close to • • pump inlets and outlets Account for gauge correction Adding the values of the two gauges will provide system performance Text Ref: Pg. 42 Tools of the Trade (cont.) • Use quality gauges • Consider using hose connections to raise or lower gauge height Text Ref: Pg. 42 Tools of the Trade (cont.) • To assure accurate gauge • • readings consider a bleed valve Vacuum gauges should be absent of any liquid Pressure gauges should be absent of air Text Ref: Pg. 43 Tools of the Trade (cont.) • • • Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Gauge corrections may require addition or subtraction of value Zero gauges (vent) to assure accuracy If permanently mounted, use isolation valves Noisy Operation Reference Section Text Ref: Pg. 43 Pump Forensics (Troubleshooting) Text Ref: Pg. 44 Pump Forensics (cont.) My Pump Isn’t pumping… Why? • First reaction – It’s the pump fault! • Reality is – 85-90% of the time it’s • a system problem Pump is simply responding to changes in the system Text Ref: Pg. 45 Pump Forensics (cont.) Troubleshooting Topics Discussed • Low Performance • Reduction in flow, pressure or no flow • Loss of prime, slow to prime, failure to prime • Mechanical Causes • Priming challenges • Air Bound • Noisy Operation • Shaft Failures • Corrosion and Abrasion Damage Text Ref: Pg. 45 Pump Forensics (cont.) Low Performance – Cause #1 • Excessive Clearances • • • • • • Over equipment lifespan performance lowers as internal components wear Critical components include; wear rings, wear plates, impellers, & pump casing cutwater area Real cause is excessive clearances Solution - Replace worn components Some models have adjustable clearances Field analysis and shut-off test will assist in performance validation Text Ref: Pg. 46 Pump Forensics (cont.) Low Performance – Cause #2 • Reverse rotation • • • Typical result is lower flows and pressures In addition, increased amperage due to increased horsepower Cause in new installations, typically due to improper wiring • Cause in existing installation ,occur from a variety of reasons: • • Modification of wiring will correct the problem • Modification of electrical panel, motor, or incoming power grid transformer change out Note – Running PD pumps in reverse will reverse the flow • Suction becomes discharge and discharge becomes suction Text Ref: Pg. 46 Pump Forensics (cont.) Low Performance – Cause #3 • Change in Speed (RPM) • • • • Typical cause - Incorrect speed selection Slower speed – Lower flow and less pressure Incorrect replacement motor – 3450, 1750, or 850 RPM Noted – Increase of RPM typically results in higher flow rate and pressure Text Ref: Pg. 46 Pump Forensics (cont.) Low Performance • Additional Common Causes • • • Incorrect replacement impeller Debris lodged in impeller Partially blocked or clogged piping Text Ref: Pg. 47 Pump Forensics (cont.) Priming Challenges – Cause #1 • Excessive Clearances • • Worn components reduce ability to create a vacuum • Replace or adjust clearances Note – Priming-Assisted pump priming issues can stem from worn auxiliary priming system components Text Ref: Pg. 47 Pump Forensics (cont.) Priming Challenges – Cause #2 • Air Relief System Issues • • • Air Bleed Line Air relief line missing Incorrect air release valve Poor ARV plumbing design Text Ref: Pg. 47 Pump Forensics (cont.) Priming Challenges – Cause #3 • Leak on vacuum side • • • • Often difficult to locate Thoroughly review all suction piping, hose, joints, & pipe plugs Could be mechanical seal Use gauge and monitor vacuum reading when pump is not running Text Ref: Pg. 48 Pump Forensics (cont.) Priming Challenges – Cause #4 • Obstruction in Plumbing or Pump • • • Slow to prime or failure to prime as a result of an obstruction Typical cause- Debris in impeller or a partially block suction line or suction strainer Solution remove, clean and restart Text Ref: Pg. 48 Pump Forensics (cont.) Air Bound (Failure to go Dynamic) – Cause #1 • Too much air in impeller/casing area • • • Problem can occur with standard centrifugal, submersible and certain self-priming pumps At start up on new installations typically this is a result of air left in suction lines Manually fill pump and bleed off air Text Ref: Pg. 48 Pump Forensics (cont.) Air Bound (Failure to go Dynamic) – Cause #2 • Failure to overcome static discharge pressure (head) • • Air Bleed Line • Missing air bleed (vent) line Often Self-Priming pumps require an air release line when there is more static head on a system check valve to push the air out discharge Automatic air release valves (ARV) are recommended to operate more efficiently and/or to reduce potential nuisance clogging Text Ref: Pg. 48 Pump Forensics (cont.) Air Bound – Cause #3 • Failure on existing installation • • Result of air entering pump inlet Typical causes include: • • Solutions include raising liquid level and/or redirecting inflows Noted – Applications where slurping and snoring cannot be designed out, a priming-assisted (dry prime) pump may be a better solution • Insufficient submergence – (vortexing, slurping, snoring) • Force entrapped air – inverts cascading over pump inlets Text Ref: Pg. 48 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) • Noise can be hydraulic or mechanical • Will cover Hydraulic Noise in a separate section • • • • Submersible - Remove pump from liquid and run briefly dry Centrifugal, self-primer or PD pump - drain pump and run briefly dry If noise goes away it’s hydraulic challenges If noise remains… • How can you tell the difference? Text Ref: Pg. 49 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) – Cause #1 • Debris in the pump causing hydraulic imbalance Text Ref: Pg. 49 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) – Cause #2 • Badly worn or damaged bearings Text Ref: Pg. 49 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) – Cause #3 • Impeller rubbing due to improper clearances • • • • • • Debris lodged between Wear ring(s) Wear plate(s) Seal plate Suction head Diffuser Text Ref: Pg. 49 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) – Cause #4 • Impeller out of balance • • Damaged (Vane broken) Severe wear Text Ref: Pg. 49 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) – Cause #5 • Drive Alignment • • • Misalignment or worn Coupling Belt(s) & Sheaves Text Ref: Pg. 49 Pump Forensics (cont.) Noisy Operation (Mechanical Noise) – Cause #6 • Driver Issues • Motor bearing problems • If possible uncouple motor from pump and run briefly • Follow motor manufacture’s procedures Text Ref: Pg. 49 Pump Forensics (cont.) Shaft Failures • Shaft breakage occurs typically in one of two modes • • Radial (fatigue) breaks Torsional (twisting) breaks Text Ref: Pg. 50 Pump Forensics (cont.) Shaft Failures (cont.) • Radial (fatigue) breaks • • Impeller end failure due to hydraulic imbalance (air) or TDH too high Drive end failure due to improper drive arrangement including extreme side load such as belts over tightened Text Ref: Pg. 50 Pump Forensics (cont.) Shaft Failures (cont.) • Torsional (twisting) breaks • • • Failure cause is typically due to something being injected into the pump causing it to lock-up Extreme start torque due to reverse rotation with sudden call to start Typically a result of discharge check valve failure or absent of valve causing flow to pass back through pump when not running Text Ref: Pg. 50 Pump Forensics (cont.) Chemical and Abrasion Damage • Abrasive Damage • • Pumps are often exposed to fluids that have small suspended solids such as sand or grit traveling a high velocities Typical failure mode will be a smoothing, rounding or grooving of areas of the pump in direct contact to the flow Solution is an alternate material more suitable • Wear will also transmit to casings, shafts, wear rings, etc. • • Austempered Ductile Iron • High-Chrome • Polymer based (urethanes) • Specialized coating (ceramics or epoxy) Text Ref: Pgs. 50-51 Pump Forensics (cont.) Chemical and Abrasion Damage (cont.) • Corrosion or Chemical Attack • • • • Pump Basics Pump Safety Tools of the Trade Stems from material compatibility Under dynamic operation, chemical attack can soften surface of material - gives appearance of divots/ melon balling In extreme cases, chemical attack erodes or dissolves the material (all surfaces get thinner and any holes grow in size) Solution - Select a more suitable material more compatible with liquid Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pg. 51 Troubleshooting Checklists & Guides Text Ref: Pg. 52 Checklists & Guides (cont.) Suggested checklists and troubleshooting guides • Assist in keeping pump at peak performance • Decreases operation cost and/or boosting profits • Reduce fuel consumption • Reduce unnecessary replacement parts use • Minimize down time Text Ref: Pg. 53 Checklists & Guides (cont.) Refer to text for further details • Use of Checklist • Preventative Maintenance • Schedules Maintaining these records will assist when problems arise Text Ref: Pgs. 53-58 Checklists & Guides (cont.) Troubleshooting guides are useful tools when you are unfamiliar with equipment Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pgs. 60-66 Noisy Operation (Hydraulic Noise) Text Ref: Pg. 67 Noisy Operation (cont.) My pump is noisy… Why? • Mechanical noise challenges were • • discussed earlier Nonetheless, hydraulic noise is another challenge that causes a variety of pump issues Addressing these will not only improve the site operating conditions, but will improve the life of the equipment Text Ref: Pg. 68 Noisy Operation (cont.) Items to discuss in this section include: • Vortexing • Air entrainment • Cavitation • Improper inlet spacing • Surging or water hammer • Excessive velocity Text Ref: Pg. 68 Noisy Operation (cont.) #1 Cause - Vortexing • One of the more common problems of • • • • hydraulic noise challenges Makes a growling noise within pump Can produce a visible whirlpool at surface Created due to insufficient surface tension Caused due to insufficient submergence Text Ref: Pg. 68 Noisy Operation (cont.) Vortexing (cont.) • In extreme cases, a vortex tail will extend • to pump inlet, allowing a direct path for air to enter pump inlet Will cause noise, vibration and potentially can cause several failure modes: • Bearings, shaft fatigue, seals, weldments… • Solution is to increase level in sump and/or add an increaser to pump inlet • Larger cross-sectional area - reduces the inlet velocity, eliminating vortex formation Text Ref: Pg. 69 Noisy Operation (cont.) Vortexing (cont.) • Minimum submergence recommendations to resist formation of vortexes Text Ref: Pg. 69 Noisy Operation (cont.) #2 Cause - Air Entrainment • Standard centrifugal, self-priming or • submersibles are not designed to operate continuously on mixtures of liquid and gases (air) Continued operations in these conditions lead to: • • • Shortened life Unsatisfactory performance Serious mechanical trouble Text Ref: Pg. 70 Noisy Operation (cont.) Air Entrainment (cont.) • 2% free air can result in a 10% • reduction in capacity Additional challenges may include: • • • Destructive vibration Loss in prime Accelerated corrosion • Solution is to install a baffle or extend the invert below the surface of liquid Text Ref: Pg. 70 Noisy Operation (cont.) #3 Cause - Cavitation • All types of pumps can suffer from effects of cavitation • • • • • Standard Centrifugal Self-Primer Priming-Assisted Submersible Rotary Gear Text Ref: Pg. 71 Noisy Operation (cont.) #3 Cause – Cavitation (cont.) • What causes cavitation? • • The rapid formation and collapse of vapor pockets in a flowing liquid in regions of very low pressure When these collapse, pitting or other damage is caused on metal surfaces in contact Text Ref: Pg. 71 Noisy Operation (cont.) #3 Cause – Cavitation (cont.) • When does cavitation occur? • • • • When negative pressure exceeds the vapor pressure of a liquid These vapor bubbles collapse when sufficient localized pressure is found The concentrated force of implosion can exceed 100,000 psi Metal in close proximity will flake or chip away by this exerted force Text Ref: Pg. 71 Noisy Operation (cont.) #3 Cause – Cavitation (cont.) • What causes cavitation? • Suction (Eye) Cavitation • Discharge (Tip) Cavitation • Occur in eye of an impeller • Caused by too high of a vacuum • Occurs at external tips of an impeller as it crossed the cutwater • Caused by too high of discharge pressure Text Ref: Pg. 72 Noisy Operation (cont.) #3 Cause – Cavitation (cont.) • Damage caused by discharge cavitation • • • • Breaks shafts Shortens bearing life Destroys impellers and volute casings Ruins mechanical seals Text Ref: Pg. 73 Noisy Operation (cont.) #3 Cause – Cavitation (cont.) • Damage caused by suction cavitation • • • • Shortens bearing life Destroys impellers Destroys wear plates Ruins mechanical seals Text Ref: Pg. 74 Noisy Operation (cont.) Text Ref: Pg. 76 Noisy Operation (cont.) #4 Cause – Pump and Suction Spacing • In multiple pump installations spacing and invert locations should be reviewed to prevent starvation Text Ref: Pg. 77 Noisy Operation (cont.) #5 Cause – Net Positive Suction Head (NPSH) • Measure of liquid pressure at the pump end of a suction system • • NPSHa – Difference between atmospheric pressure and (atmospheric pressure at site, TDSL, vapor pressure, and a safety factor) NPSHr – Atmospheric pressure required to move liquid through suction side of a pump • When finished for any pump to operate satisfactory the value must be a positive number. Text Ref: Pg. 77 Noisy Operation (cont.) #5 Cause – NPSH (cont.) • NPSH Calculation (five deductions) • • • • • • Starting with standard atmospheric pressure Altitude elevation at job site Vapor pressure of liquid pumped Total Dynamic Suction Lift (TDSL) Safety Factor (2 ft. water/3 ft. fuel) NPSHr @ flow rate Text Ref: Pg. 80 Noisy Operation (cont.) #5 Cause – NPSH (cont.) • NPSH value must be a positive number • If negative, NPSH needs to be • increased To increase NPSH - Reduce the TDSL • • • Lower pump elevation Raise liquid level Increase suction line diameter Text Ref: Pg. 82 Noisy Operation (cont.) Review example in text Pump Basics Pump Safety Tools of the Trade Pump Forensics Checklist & Guide Noisy Operation Reference Section Text Ref: Pgs. 83-85 Reference Text Ref: Pg. 86 Reference (cont.) Variety of useful materials • • • • Terminology Charts and Tables Formulas Affinity Laws Text Ref: Pgs. 87-108 Reference (cont.) Variety of useful materials • Motor Maintenance • Electrical Insulation Resistance • V-Belt Maintenance • Coupling Alignment Text Ref: Pgs. 87-108 Questions and Comments Thank you for completing your survey!
