Mechanical Seal Failure in Vertical Lineshaft Turbine Pumps

The vertical lineshaft turbine pump is essential in water supply, agriculture, power plants, and industrial applications. While known for its robust construction and long service life, one of its most common points of failure is the mechanical seal. In fact, mechanical seal failure accounts for a significant percentage of pump downtime and maintenance costs.

Understanding the causes of mechanical seal failure—and recognizing that the seal itself is often not the root cause—is key to improving pump performance, reducing repair frequency, and minimizing operational interruptions.

Why Mechanical Seals Fail in Vertical Lineshaft Turbine Pumps

Although the mechanical seal is the first component to show signs of trouble, the actual reason for failure typically lies elsewhere in the system. Below are the primary contributors to mechanical seal failure in vertical turbine pump systems:

No.	Cause of Mechanical Seal Failure	Description
1	Bearing Wear	Worn or damaged bearings can cause shaft deflection, leading to seal misalignment, excessive wear, or leakage.
2	Excessive Vibration	Vibration from imbalance, hydraulic forces, or foundation issues causes seal faces to separate or wear prematurely.
3	Shaft Misalignment	Poor alignment between motor and pump shaft can apply uneven pressure on the seal, resulting in surface damage or failure.
4	Improper Seal Installation	If the mechanical seal is not installed per manufacturer guidelines (e.g., incorrect face loading or O-ring placement), early failure is likely.
5	Incorrect Seal Selection	A seal designed for clean water may not withstand slurry, corrosive fluids, or high pressures. Always match the seal to the fluid and operating environment.
6	Lubricant Contamination	Contaminated lubricants can degrade seal faces and lead to increased friction, overheating, and eventual breakdown.

Key Diagnostic Questions During Seal Failure Analysis

When a mechanical seal fails in a vertical lineshaft turbine pump, it’s important to go beyond just replacing the part. A proper root cause analysis should ask:

Is the pump properly aligned and free from excessive vibration?

Was the seal correctly installed by trained personnel?

Is the selected seal compatible with the pumped media and pressure/temperature conditions?

Are the system’s environmental controls (lubrication, cooling, and filtration) operating within required limits?

Identifying the true cause of failure helps prevent repeat issues and enhances system reliability.

How to Improve System Reliability After Seal Failures

Correcting mechanical seal issues not only solves the immediate problem but also unlocks broader operational benefits:

No.	Benefit of Proper Mechanical Seal Management	Description
1	Optimized Operating Conditions	Proper alignment, balanced flow rates, and correct seal settings extend seal life and improve overall pump efficiency.
2	Reduced Downtime	A reliable sealing system prevents unexpected failures, ensuring longer intervals between repairs.
3	Extended Equipment Life	Minimizing seal-related stress on bearings, shafts, and motor components improves the longevity of the deep well vertical turbine pump.
4	Enhanced Performance	Stable seal operation ensures consistent pressure delivery, less leakage, and better overall pump performance.
5	Lower Maintenance Costs	Avoiding frequent seal replacements saves on labor, parts, and lost productivity.

Conclusion

Mechanical seal failure in vertical lineshaft turbine pumps is a common issue—but often a symptom, not a root cause. By taking a systems-level approach to troubleshooting and incorporating preventive measures such as proper seal selection, installation, and routine alignment checks, facilities can significantly enhance pump reliability and reduce long-term costs.

Investing time in seal failure analysis and proactive maintenance leads to fewer breakdowns, smoother operations, and better return on investment for one of your facility’s most critical assets.

FAQ – for Vertical Turbine Pump

Learn about the key spare parts commonly used in vertical turbine pumps.

Vertical Turbine Pump Spare Parts & Qty (2 Years)
For Packing Seal Pump
Spare Parts/Qty	Pump Qty (Including Spare Pump)
Spare Parts/Qty	1	2	3	4	5	6	8	≥10
Shaft Sleeve（Packing）	1	2	3	3	5	5	7	8
Shaft Sleeve（Middle）	1	2	3	3	5	5	7	8
Shaft Sleeve（Lower）	1	2	3	3	5	5	7	8
Packing	1	2	3	3	5	5	7	8
O Ring	1	2	3	3	5	5	7	8
Wear Ring	1	2	3	3	5	5	7	8
Adapter Coupling	1	2	3	3	5	5	7	8
Guide Bearing	1	2	3	3	5	5	7	8
Bearing	1	2	3	3	5	5	7	8
Impeller Shaft	1	1	1	2	2	3	4	5
Middle Shaft	1	1	1	2	2	3	4	5
Transmission Shaft	1	1	1	2	2	3	4	5
Impeller	1	1	1	2	2	3	4	5
Packing Gland	1	1	1	2	2	3	4	5


For Mechanical Seal Pump
Spare Parts/Qty	Pump Qty (Including Spare Pump)
Spare Parts/Qty	1	2	3	4	5	6	8	≥10
Shaft Sleeve（Mechanical Seal）	1	2	3	3	5	5	7	8
Shaft Sleeve（Middle）	1	2	3	3	5	5	7	8
Shaft Sleeve（Lower）	1	2	3	3	5	5	7	8
Mechanical Seal	1	2	3	3	5	5	7	8
O Ring	1	2	3	3	5	5	7	8
Wear Ring	1	2	3	3	5	5	7	8
Adapter Coupling	1	2	3	3	5	5	7	8
Guide Bearing	1	2	3	3	5	5	7	8
Bearing	1	2	3	3	5	5	7	8
Impeller Shaft	1	1	1	2	2	3	4	5
Middle Shaft	1	1	1	2	2	3	4	5
Transmission Shaft	1	1	1	2	2	3	4	5
Impeller	1	1	1	2	2	3	4	5
Mechanical Seal Gland	1	1	1	2	2	3	4	5

Under harsh operating conditions, the quantity of spare parts should be doubled.

Discover how to select the right vertical turbine pump materials based on fluid properties and operating conditions.

Pump Parts	For Clear Water	For Sewage	For Seawater
Discharge Elbow / Casing	Carbon Steel	Carbon Steel	S.S / Super Dulex
Diffuser / Suction Bell	Cast Iron	Cast Iron / Ductile Iron / Cast Steel / S.S	S.S / Super Dulex
Impeller / Impeller Chamber / Wear Ring	Cast Iron / Cast Steel	Ductile Iron / S.S	S.S / Super Dulex
Shaft / Shaft Sleeve / Coupling	Steel / S.S	Steel / S.S	S.S / Super Dulex
Guide Bearing	PTFE / Thordon
Remark	Final material depends on the liquid condition or the client’s request.

Follow the essential installation steps to ensure safe and reliable operation of the vertical turbine pump.

Standardized Installation Procedure for Vertical Turbine Pump
Work Stage	No.	Main Steps	Key Operations & Notes
I. Pre-Installation Preparation	1	Site & Foundation Inspection	• Clean the wellhead or pit, ensure no debris. Check foundation (well or concrete pedestal) verticality, levelness, and dimensions meet drawings. • Verify positions and specifications of anchor bolts or embedded parts.
	2	Equipment Unpacking & Inspection	• Count all items according to packing list: motor, pump base, drive shaft, delivery pipe, guide bearing housing, impeller, coupling, etc. • Check all parts for transport damage, especially drive shaft threads, keyways, and flanges of delivery pipe.
	3	Tools & Material Preparation	• Prepare lifting equipment (hoist, crane), special wrenches, level, dial indicator, plumb line, lubricant (oil/grease), raw tape, lifting beams, etc. • Prepare cleaning agents and cloths.
II. Pump Casing & Shaft Installation	4	Install Pump Base & Outlet Elbow	• Lift pump base onto foundation, preliminarily position, insert anchor bolts but do not tighten. • Install outlet elbow and connect outlet piping.
	5	Install First Section of Delivery Pipe & Drive Shaft	• Lift the first delivery pipe section, install guide bearing housing at lower end, slowly lower to pass through pump base and preliminarily connect. • Insert drive shaft from top of delivery pipe, connect lower end via coupling to pump shaft (or next shaft section). Ensure firm keyway connection and install drive shaft protective tube. • Core: maintain verticality and concentricity. Each section must be checked with level or plumb line (typical tolerance ≤2 mm/m).
	6	Install Delivery Pipe Sections & Drive Shaft	• Install guide bearings in each pipe section (water or grease lubricated) ensuring drive shaft passes through center. • Connect each drive shaft section, ensure keyway/coupling connection is firm and concentric. Check rotation manually for smoothness.
	7	Install Final Impeller & Suction Bell	• Install final stage impeller, adjust axial clearance via upper drive shaft adjustment nut (refer to manufacturer’s manual). • Install suction bell.
III. Alignment, Grouting & Motor Installation	8	Overall Alignment & Primary Grouting	• Use pump base as reference, check overall verticality with level. • Perform primary grouting, fix anchor bolts. Wait until grout fully cures (usually 3–7 days).
	9	Install Motor & Alignment	• Lift motor onto base. • Key alignment: use dial indicator to adjust motor and drive shaft coaxiality (radial deviation ≤0.05 mm) to reduce vibration and wear. Tighten motor anchor bolts after alignment.
	10	Install Coupling & Guard	• Install coupling and connections, install protective guard.
IV. Piping & Accessories Installation	11	Lubrication & Sealing System	• For grease-lubricated guide bearings, inject specified grease via lubrication line. • For water-lubricated guide bearings, connect water pipes and ensure clean water supply. • Connect pump base stuffing box or mechanical seal cooling/flushing water lines.
	12	Electrical & Instrumentation Installation	• Connect motor power cables, install ammeter, temperature sensors, etc. • Install outlet pressure gauge, flow meter.
V. Post-Installation Inspection & Test Run	13	Final Checks	• Manual rotation: rotate motor-coupling system, check smoothness, flexibility, and absence of binding. • Check all connection bolts are tightened. • Jog motor: confirm rotation direction (typically clockwise from top view).
	14	Priming & Test Run	• Fill pump with delivery medium (for deep well pump, pre-lubricate via auxiliary pipe and stuffing box). • Start: close outlet valve, start motor. • Commissioning: slowly open outlet valve, monitor current, pressure, flow, vibration, bearing temperature, and check stuffing box leakage (droplet form preferred). Test run ≥2 hours.

Explore proper disassembly and maintenance procedures to maximize the vertical turbine pump service life.

Standardized Disassembly & Maintenance Procedure for Vertical Turbine Pump
Work Stage	No.	Main Steps	Key Operations & Notes
I. Pre-Disassembly Preparation	1	Shutdown & Isolation	• Safety first: slowly close the outlet valve, cut off power, and apply lockout/tagout (LOTO). • Close the inlet valve, open pump vent, drain pump and piping. For deep well pumps, lower water level below pump suction.
	2	Disconnect External Connections	• Disconnect motor power cables. • Remove coupling bolts and guard. • Disconnect all connected pipelines (lubrication, cooling, pre-lubrication water pipes) and seal pipe ends.
	3	Tools & Preparation	• Prepare lifting equipment (tripod, hoist), shaft clamps, special wrenches, marking pens, parts boxes. • Prepare shaft support frame for placing removed long shaft.
II. Pump Casing Disassembly (Top to Bottom)	4	Remove Motor & Pump Base Accessories	• Lift motor and place safely. • Remove stuffing box covers or mechanical seal, lubrication pipe fittings, and other accessories.
	5	Remove Drive Shaft Adjustment Mechanism	• Loosen and remove adjustment nuts and shaft end fixing devices.
	6	Lift Drive Shaft & Delivery Pipe Sections	• Core: lift in sections to prevent bending and dropping. • Use shaft clamp to support top section of drive shaft, lift a short distance to disconnect from next shaft coupling. • Place removed shaft sections horizontally on support; do not lean. • Disconnect top delivery pipe flange from pump base and lift out the section. • Repeat for all shaft and pipe sections. Number each section sequentially.
	7	Lift Impeller & Suction Components	• Lift final-stage impeller, guide vane assembly, and suction bell.
III. Parts Cleaning, Inspection & Measurement	8	Cleaning, Inspection & Measurement	• Thoroughly clean all parts. Key checks: – Drive shaft: straightness, keyway wear, surface corrosion. – Coupling: check keyway, end faces. – Impeller: cavitation, wear, corrosion, dynamic balance if necessary. – Guide bearings (rubber or metal): check inner diameter, replace if worn. – Delivery pipe: flange surfaces, internal corrosion, scaling. – Seals: check stuffing box or mechanical seal wear.
IV. Reassembly (Reverse Order)	9	Reassembly	• Core principle: clean, align, vertical, tighten section by section. • Replace all damaged O-rings, gaskets, guide bearings. • Start from lowest suction component, reinstall delivery pipes and drive shaft sequentially. Check drive shaft flexibility and delivery pipe verticality. • Install impeller, adjust axial clearance via upper adjustment nut to manufacturer specification. • Reinstall motor and perform precise alignment (same as installation standard). • Install stuffing box or mechanical seal, adjust gland tightness.
V. Final Verification	10	Final Inspection & Test Run	• Manual rotation: rotate coupling system, check entire long shaft assembly moves freely. • Connect all pipelines, inject grease or start lubrication water. • Follow “Priming & Test Run” procedure from installation, paying attention to vibration and current after start-up.

Find practical solutions to the most common vertical turbine pump operating issues.

Common Faults and Solutions for Vertical Turbine Pump
No.	Problems	Causes	Solutions
1	Pump cannot start	1. Power failure (power off, phase missing, voltage too low). 2. Motor failure (stator short circuit, wiring error). 3. Pump shaft jammed, bearing seized, or foreign object inside. 4. Start conditions not met (e.g., deep well pump not pre-lubricated). 5. Packing gland too tight.	1. Check power, switch, fuses; restore three-phase voltage. 2. Inspect and repair motor, correct wiring. 3. Manually rotate, clean debris, replace seized bearings. 4. Add sufficient pre-lubrication water as per procedure. 5. Loosen packing gland appropriately.
2	Insufficient flow or no water	1. Suction filter, impeller, guide vane body, or piping blocked. 2. Insufficient submergence, air suction causing cavitation. 3. Wrong motor rotation. 4. Seal ring (wear ring) worn or impeller damaged. 5. Low speed (voltage/frequency mismatch). 6. Water level drops, suction bell exposed. 7. Discharge pipe broken or leaking. 8. System resistance mismatch.	1. Clean filter, impeller, guide vane, and piping. 2. Lower installation height, increase water level (>1 m recommended). 3. Swap any two motor phase wires to correct rotation. 4. Replace worn seal ring or impeller. 5. Check voltage/frequency; ensure rated speed. 6. Increase submergence or extend delivery pipe. 7. Inspect and repair discharge pipe and connections. 8. Recalculate system conditions to ensure efficient operation.
3	Low head / low pressure	1. Wrong impeller stages or severe wear. 2. Low speed. 3. Cavitation. 4. Seal ring worn, high internal leakage. 5. Excessive pipeline resistance (valves partially closed, too many elbows, small diameter).	1. Check impeller stages, replace worn impeller. 2. Check voltage/frequency, increase to rated speed. 3. Increase inlet pressure, improve suction conditions, prevent cavitation. 4. Replace worn seal ring. 5. Fully open outlet valves, optimize piping layout and diameter.
4	Severe vibration, abnormal noise	1. Insufficient submergence, cavitation (high-frequency popping sound). 2. Impeller unbalanced (scaling, wear, deformation). 3. Drive shaft misalignment, bent or excessive intermediate bearing spacing. 4. Pump-motor shaft misalignment. 5. Bearing (including guide bearing) damaged or excessive clearance. 6. Uneven foundation, loose anchor bolts. 7. Improper support of discharge pipe. 8. Operation near critical speed.	1. Increase suction water level, ensure proper submergence. 2. Clean impeller, perform dynamic balancing. 3. Correct shaft concentricity; straighten or replace bent shaft; install and tighten intermediate bearing brackets. 4. Use dial indicator to correct coaxiality (≤0.05 mm). 5. Replace damaged bearings and worn guide bearings. 6. Re-level foundation, tighten all anchor bolts. 7. Check and reinforce pipe supports; avoid resonance frequency. 8. Adjust operating speed to avoid critical region.
5	Motor overload (high current)	1. Low supply voltage. 2. Bearing damage, impeller rubbing seal ring or casing. 3. Pump suction blocked with sand or debris. 4. Flow too high. 5. Packing gland too tight. 6. Single-phase operation due to supply line fault.	1. Start when supply voltage normal. 2. Replace bearings; check and adjust impeller axial clearance. 3. Stop pump, clean sand/debris. 4. Adjust outlet valve to limit flow to rated range. 5. Loosen packing gland appropriately. 6. Professional electrician inspect and repair supply.
6	Bearing overheating (including motor bearings)	1. Insufficient lubrication or grease aging/deterioration, wrong type. 2. Bearing contaminated by water, lubrication failure. 3. Incorrect bearing clearance (too small or too large). 4. Long shaft misalignment, radial load on bearing. 5. Bearing damage. 6. Speed exceeds bearing limit.	1. Refill or replace qualified waterproof grease (high speed ~400 h, low speed ~600 h). 2. Replace grease, repair water ingress seal. 3. Adjust bearing clearance per manufacturer. 4. Re-align long shaft system. 5. Replace bearing. 6. Control speed within allowed limit.
7	Severe shaft seal leakage (mechanical seal)	1. Seal face wear, scaling. 2. Seal water pressure insufficient or interrupted (0.1–0.3 MPa). 3. Excessive shaft axial movement. 4. Installation deviation. 5. Particles in medium causing seal wear.	1. Grind seal face or replace mechanical seal. 2. Ensure stable seal water supply. 3. Repair thrust bearing, control shaft axial movement. 4. Realign and standardize installation. 5. Install inlet filter, purify medium.
8	Severe shaft seal leakage (packing)	1. Packing worn, aged. 2. Gland too loose or uneven, too tight. 3. Shaft or sleeve damaged, bent. 4. Insufficient lubrication/cooling water. 5. Medium contains high sand content.	1. Replace packing (check every 2000 h). 2. Evenly tighten gland, adjust to slow drip. 3. Repair, polish, or replace shaft/sleeve. 4. Ensure clean cooling/lubrication water. 5. Purify water; replace sleeve if necessary.
9	Long shaft axial movement / large axial vibration	1. Thrust bearing wear. 2. Incorrect shaft end clearance. 3. Loose or poorly lubricated coupling. 4. Vertical deviation of delivery pipe.	1. Inspect and replace thrust bearing. 2. Adjust shaft end clearance per manufacturer. 3. Tighten and lubricate coupling. 4. Correct verticality of delivery pipe (≤2 mm/m).
10	Sudden increase in operating power	1. Impeller axial clearance too small, rubs guide vanes. 2. Sand in water causing blockage. 3. Motor bearing damaged.	1. Stop pump, adjust impeller axial clearance. 2. Dismantle and clean pump, improve water quality. 3. Replace motor bearing.
11	Pump body or connection leakage	1. Pump seals (O-ring, gasket) aged or damaged. 2. Loose or uneven bolts. 3. Casting defects (porosity, cracks).	1. Replace damaged seals. 2. Tighten all bolts evenly. 3. Repair defects; replace pump body if severe.
12	Delivery pipe or drive shaft breakage	1. Material defect, fatigue, or corrosion. 2. Misalignment causing additional bending. 3. Operation in resonance zone. 4. Water hammer.	1. Replace with qualified material, apply anti-corrosion treatment. 2. Ensure coaxial alignment during installation. 3. Eliminate vibration source, avoid resonance. 4. Install water hammer eliminator or slow-closing check valve.
13	Deep well pump-specific faults	1. Cable or joint water ingress. 2. Motor chamber not filled with clean pre-lubrication water. 3. Phase missing or long-term overload.	1. Repair or replace waterproof cable/joints. 2. Ensure motor chamber always filled with clean water. 3. Check protection devices, avoid phase loss and overload.

Learn the maintenance practices that help improve vertical turbine pump reliability and reduce downtime.

Daily Maintenance and Care for Vertical Turbine Pump
Maintenance Category	Maintenance Item	Detailed Content & Standards
I. Pre-Operation Inspection	1. Appearance & Connection Inspection	• Check pump, motor, pipelines, and pipe joints for looseness, leakage, damage, or deformation. • Check whether anchor bolts, coupling guards, and other fasteners are secure.
	2. Lubrication System Inspection	• Oil lubrication: Check whether the oil level in the bearing housing is at the centerline of the oil sight glass and whether the oil is clean and transparent. Replace immediately if emulsified, discolored, or contaminated. • Grease lubrication: Check whether grease quantity is sufficient. It is recommended to use special waterproof or water-resistant grease.
	3. Manual Rotation & Rotation Direction Confirmation	• Manual turning: Rotate the coupling manually to check whether the rotor rotates flexibly and evenly without abnormal friction noise. • Jogging rotation check: Jog the motor to confirm that the rotation direction matches the arrow indicated on the pump.
	4. Sealing & Priming Water	• Check whether the cooling/flushing water system of the mechanical seal is unobstructed and whether the pressure is normal (recommended 0.1–0.3 MPa). • For packing seals, check the gland tightness. • Open the pump vent plug, fill the pump with liquid, and completely vent the air inside the pump.
II. Monitoring During Operation	1. Operating Parameter Monitoring	• Pressure & flow: Monitor outlet pressure and flow to ensure operation within the rated range on the pump nameplate for optimal efficiency. • Motor current & temperature: Motor current should remain within the rated range; motor surface temperature should not be excessively high.
	2. Bearing Condition Monitoring	• Temperature: Bearing temperature should not exceed ambient temperature by 35°C, and the maximum temperature should not exceed 80°C. • Vibration: Measure vibration regularly. At 1800 r/min, vibration velocity RMS should generally not exceed 4.5 mm/s.
	3. Seal Leakage Monitoring	• Mechanical seal: Normal leakage should not exceed 5 drops/minute. • Packing seal: Adjust the gland to maintain leakage at approximately 30–60 drops/minute. Adjust if leakage is too much or too little.
	4. Abnormal Noise & Vibration Monitoring	• Monitor operating sound. Normal sound should be stable and uniform. If severe friction, knocking, or periodic vibration occurs, stop the pump immediately for inspection.
III. Periodic Maintenance (Preventive)	1. Lubrication Management	• Oil change cycle: Change oil after the first 100 hours of operation, then every 500 hours thereafter. Depending on speed: high-speed pumps (2900 rpm) every 400 hours; low-speed pumps (1450 rpm) every 600 hours. • Grease replenishment: Replenish regularly; inspect grease condition every 200 hours of operation.
	2. Shaft Seal System Maintenance	• Packing seal: Regularly adjust gland tightness. “Three-finger method”: slight resistance during manual rotation is appropriate. Replace packing approximately every 2000 operating hours. • Mechanical seal: Check flushing water pressure and flow to ensure clean water continuously passes through the seal faces.
	3. Bearing & Shaft Sleeve Inspection	• Regularly inspect wear of guide bearings and thrust bearings. • Inspect shaft sleeve wear and replace promptly if severe.
	4. Impeller & Clearance Inspection	• Inspect impeller for cavitation, corrosion, wear, or scaling, and clean flow passages. • Check the clearance between impeller and seal ring (wear ring). Allowable deviation is generally ≤0.5 mm; replace if worn beyond the limit.
	5. Alignment & Tightening	• Regularly inspect and correct alignment between pump shaft and motor shaft (deviation requirement generally ≤0.05 mm). • Retighten all anchor bolts and pipeline connections.
	6. Electrical & Pipeline Inspection	• Regularly inspect motor insulation performance. • Check whether valves operate flexibly, whether pipe supports are secure, and clean inlet filters.
IV. Long-Term Shutdown & Seasonal Maintenance	1. Winter Freeze Protection	• When ambient temperature is below 0°C, drain all liquid from the pump and cooling water system to prevent freezing and cracking.
	2. Long-Term Shutdown Maintenance	• Drain the medium inside the pump and thoroughly clean the pump body and flow passages. • Disassemble the pump, wipe all parts clean, apply anti-rust oil to rotating and mating surfaces, and reinstall the piping. • For standby pumps, implement the “3-3-3 activation system”: rotate manually every 3 days by 120°, run with load for 30 minutes every 3 weeks, and replace sealing water every 3 months.
V. Special Structural Maintenance Requirements	1. Long Shaft Alignment & Verticality	• During installation and maintenance, ensure concentricity of each transmission shaft section and verticality of the delivery pipe to prevent abnormal vibration and wear caused by misalignment.
	2. Guide Bearing Lubrication	• For water-lubricated guide bearings, ensure clean lubrication water is continuously supplied. For grease-lubricated guide bearings, add grease strictly according to schedule.
	3. Submergence Depth Monitoring	• Ensure the pump suction bell has sufficient submergence depth (generally >1 m) to prevent air entrainment, cavitation, and vibration.