The Rebuild vs. Replace Decision: A Strategic Framework
When a rotary gear pump begins to show signs of wear—declining flow rate, increased noise, or seal leakage—facility managers face a critical decision: invest in a repair kit rebuild or purchase a new pump? This choice has profound financial implications, spanning not only the direct cost of parts but also production downtime, labor, and operational risk.
The rebuild-versus-replace decision depends on three primary factors: the extent of pump damage, the cost differential between repair and replacement, and the availability of a replacement unit. Understanding these factors enables informed capital planning and optimizes pump lifecycle value.
This guide provides a practical framework for evaluating this decision, including cost analysis, downtime comparison, and guidance on what's included in NAPCO repair kits to restore pumps to like-new performance.
When to Rebuild: Identifying Candidates for Repair Kit Service
Rebuild with a repair kit when the pump housing and shaft are structurally sound but internal wear components have degraded. Typical candidates for repair kit rebuilds include:
Seal Leakage and Dripping
The most common failure mode is seal degradation after 3–8 years of continuous operation. Primary and secondary seals wear, leading to visible fluid dripping around the pump shaft area. Seal failure does not damage the pump housing or gears; replacement of seal sets alone often restores performance. A NAPCO repair kit addresses this by including both primary and secondary seal sets matched to your pump model.
Decision Rule: If leakage is the primary symptom and the pump otherwise operates normally, rebuild with a repair kit. Cost is typically $800–1,200; a new pump would cost $6,000–8,000.
Reduced Flow Within Normal Wear Parameters
Gear pumps naturally experience some flow decline over time as gear tooth surfaces wear, reducing compression and allowing internal slippage. A pump that delivered 150 GPM new might deliver 140 GPM after 5 years—a 7% decline. If flow remains within specification limits or functional for your process, the pump is still serviceable.
However, if flow has declined beyond your process requirements (e.g., a 20% drop reduces filling line throughput unacceptably), a repair kit rebuild with new gears and wear plates restores flow to original capacity. The pump housing remains unchanged; new internal components restore performance.
Decision Rule: If flow decline is the issue and the housing is intact, a repair kit restoration makes economic sense. Replace if flow decline is accompanied by housing damage or corrosion.
Increased Noise and Vibration
Bearing wear in the pump shaft and gear shafts can cause increased noise and vibration after extended service. Worn bearings allow excess play between rotating components, creating gear mesh noise. Replacement of bearings (included in NAPCO repair kits) eliminates this issue and extends pump life another 4–5 years.
Decision Rule: If noise and vibration began gradually and the pump is otherwise functional, a repair kit rebuild restores quiet operation. If noise began suddenly (indicating a crack or internal damage), replace the pump.
Mid-Service-Life Status
A well-maintained rotary gear pump typically operates 10–15 years before major structural failure occurs. If your pump is 5–8 years old (mid-service life) and experiencing wear symptoms, a repair kit rebuild is the economically sound choice. The pump has another 5–7 years of life remaining, making the $1,200–1,600 repair investment highly favorable against the $6,000–8,000 cost of replacement.
Decision Rule: For pumps 4–10 years old with normal wear symptoms, rebuild. For pumps >10 years old approaching end-of-life, consider replacement investment for reliability and future-proofing.
When to Replace: Failures Beyond Repair Kit Scope
Replace the pump (rather than rebuild) when damage extends to the pump housing or shaft. These failures cannot be corrected with internal component replacement alone and warrant full unit replacement.
Cracked or Fractured Housing
A cracked housing is catastrophic and cannot be field-repaired. Cracks typically occur due to freezing (fluid left in pump over winter expands and splits the housing), cavitation damage (low inlet pressure causes vapor bubbles that implode and erode the housing), or impact damage. Once a housing cracks, fluid leaks externally at the crack location and the pump cannot maintain pressure.
Decision Rule: If the housing is cracked, replace the pump immediately. Repair kit components cannot address structural failure.
Shaft Damage Beyond Tolerance
The pump shaft supports the drive gear and must maintain precise dimensional tolerance for proper gear mesh. Shaft damage (bending, spalling, corrosion pitting) cannot be field-corrected and requires shaft replacement as an assembly. While a repair kit does not include shaft replacement, shaft removal involves substantial disassembly—approaching the cost and complexity of full pump replacement. In such cases, replacement is more economical.
Decision Rule: If shaft damage is confirmed (requires measurement or inspection by NAPCO engineering), replace the pump.
Corrosion Pitting in Housing
Extensive pitting corrosion (common in stainless steel pumps exposed to chloride environments) weakens the housing structure. Localized pitting may be manageable, but widespread pitting across the housing reduces structural integrity and increases risk of catastrophic failure. Once pitting is advanced, a new pump investment is preferable for reliability.
Decision Rule: Light surface pitting can be tolerated; deep pitting across large areas warrants replacement. Consult NAPCO engineering for severity assessment.
Obsolete Model or Discontinued Parts
NAPCO has produced rotary gear pumps since the mid-1990s. Some models are no longer in production, and repair kits for discontinued models may become unavailable. If a repair kit for your pump model is out of stock or discontinued, replacement with a modern pump is the practical solution. Modern pumps offer improved seals (Viton vs. older nitrile), better materials, and superior reliability.
Decision Rule: If repair kit availability is uncertain, contact NAPCO engineering before committing to a replacement decision. We may still have kits in inventory or be able to source components.
End-of-Life Status (10+ Years)
A pump that has operated successfully for 10+ years is reaching end-of-life. While a repair kit rebuild is technically possible, the economic case weakens. An older pump that experiences failure may fail again soon in other components; a new pump provides a fresh 10+ year service window. Additionally, modern pumps may offer efficiency improvements, reduced noise, or material upgrades (stainless steel options, advanced seal materials).
Decision Rule: For pumps >10 years old with repeat failures or significant issues, replacement investment is justified for long-term reliability and peace of mind.
What is Included in a NAPCO Repair Kit?
A complete NAPCO repair kit contains all wear components necessary to restore a pump to like-new condition. Factory-matched kits eliminate the guesswork of sourcing individual components and guarantee compatibility and performance.
Primary Components
Seal Sets (Primary and Secondary): The kit includes both high-pressure primary seals and low-pressure secondary seals, typically Viton elastomers for superior fluid compatibility and durability. Seal sets are the most frequently replaced components and the main reason for pump rebuilds.
Drive and Idler Gears: Both gears are included, featuring hardened tooth surfaces with nitrile or Viton liners (depending on pump model and fluid compatibility). Factory-matched gears ensure proper tooth profile and mesh alignment.
Shaft Bearings: Pump shaft bearings support the drive gear and maintain runout tolerance. The kit includes replacement bearings to eliminate noise and restore smooth operation.
Wear Plates: Wear plates (also called end plates) locate against the gear sides and wear over time as gears rotate. Replacement wear plates restore close tolerances and reduce internal leakage.
Gaskets and O-Rings
The kit includes all gaskets and O-rings required for reassembly: housing cover gasket, port gaskets, and shaft sealing rings. Using fresh gaskets during rebuild is critical to prevent fluid leakage at assembly joints.
Lubrication and Assembly Aids
Many NAPCO repair kits include assembly lubricant and instruction documentation. Assembly lubricant ensures proper bearing and seal seating during installation, reducing the risk of seal damage during startup.
Why Factory-Matched Kits Matter
NAPCO repair kits are engineered for exact fit in NAPCO pumps. Gear tooth profiles, seal cavity dimensions, and bearing tolerances are precision-matched to your specific pump model (PA200 vs. PA300, ductile vs. stainless). Generic aftermarket kits, while cheaper, often contain oversized or undersized components that fit poorly, causing:
- Excessive gear mesh noise and vibration
- Seal leakage due to improper cavity fit
- Reduced flow capacity from improper gear dimensions
- Premature bearing wear from loose tolerances
NAPCO kits are backed by a warranty covering parts and workmanship, providing assurance that your rebuilding investment will be successful.
Cost Comparison: Repair Kit Rebuild vs. New Pump
The financial case for repair kit rebuilds is compelling. A complete rebuild typically costs 15–25% of a new pump, with additional downstream benefits in reduced downtime and facility disruption.
Direct Cost Comparison
NAPCO Repair Kit (PA300 Model): $1,200–1,600 including all components, gaskets, seals, gears, and bearings.
New PA300 Pump: $6,000–8,000 depending on material specification (ductile vs. stainless, nitrile vs. Viton seals).
Cost Savings per Rebuild: $4,400–6,400 (55–75% savings).
Labor and Installation Costs
Field rebuild labor is 2–4 hours for a trained technician ($200–800 depending on labor rates). Installation of a new pump requires not only technician labor but also site preparation, piping modification, pressure testing, and commissioning—often 6–10 hours ($400–1,600). Rebuild labor is substantially less.
Labor Advantage: Rebuild ($200–400 cheaper than new pump installation).
Lifecycle Value Over 12 Years
Consider a facility operating 10 identical pumps over a 12-year period. Under normal wear conditions, each pump experiences one major rebuild around year 6–8. Using a rebuild strategy:
Rebuild Scenario (10 pumps, 1 rebuild per pump over 12 years):
- 10 pumps × $7,000 per pump = $70,000 (initial capital)
- 10 rebuilds × $1,400 per rebuild = $14,000 (maintenance)
- Total 12-year cost: $84,000
Replace-at-Failure Scenario (10 pumps, replacement after failure):
- 10 pumps × $7,000 per pump = $70,000 (initial capital)
- 6–8 replacement pumps (end-of-life failures) × $7,000 = $42,000–56,000
- Total 12-year cost: $112,000–126,000
- Additional emergency downtime costs (lost production): $20,000–50,000+
Net Savings from Rebuild Strategy: $28,000–92,000 over 12 years, depending on production value and downtime costs.
Downtime Comparison: Field Rebuild vs. Full Replacement
Beyond cost, downtime is often the decisive factor. A field rebuild takes hours; a full replacement can take weeks.
Field Rebuild Timeline
A typical field rebuild using a NAPCO repair kit follows this timeline:
- Hour 0–0.5: Isolate pump, drain fluid, disconnect inlet/discharge lines
- Hour 0.5–1.5: Remove housing bolts, separate pump halves, remove internal components
- Hour 1.5–2.5: Clean internal cavities, inspect housing and shaft for damage
- Hour 2.5–3: Install new seal sets, gears, bearings, wear plates, gaskets
- Hour 3–3.5: Reassemble pump, reconnect piping, fill with fresh fluid
- Hour 3.5–4: Pressure test, run-in at low RPM, monitor for leaks
Total Downtime: 4–6 hours (typically a single shift or overnight rebuild).
Full Replacement Timeline
Replacing a pump with a new unit involves additional delays:
- Day 1: Identify compatible new pump model, place order
- Day 2–7: Manufacturing lead time and shipping (varies; 2–6 weeks typical for NAPCO pumps, longer for expedited)
- Day 8: Receive pump, inspect for shipping damage
- Day 8–9: Remove failed pump, install new pump, piping work, pressure testing
- Day 9: Commissioning and verification
Total Downtime: 8–50 days (1–7 weeks depending on shipping and procurement).
Downtime Cost Impact
For a facility running a process that generates $5,000–10,000 per hour in revenue, the difference between a 4-hour rebuild and a 2-week replacement represents:
- 4-hour rebuild: $20,000–40,000 lost production
- 2-week replacement: $400,000–800,000 lost production
- Downtime Cost Differential: $360,000–760,000
This analysis shows that even for moderate-revenue operations, field rebuilds have a massive downtime advantage.
Preventive Maintenance: Extending Pump Life and Minimizing Repairs
While repair kit rebuilds are cost-effective, the best strategy is preventive maintenance to extend pump life and reduce failures altogether.
Regular Inspection and Monitoring
Establish a routine inspection schedule: monthly visual checks for fluid leaks, noise changes, or vibration increases. Track flow rate monthly and pressure drops over time. Early detection of seal wear (visible drips) allows planned rebuilds during scheduled maintenance windows, avoiding emergency downtime.
Fluid Quality Management
Pump fluid quality dramatically affects seal life and internal wear. Maintain proper fluid filtration (150–250 micron inlet strainer), monitor viscosity (stays within specification), and change fluid annually or per manufacturer recommendations. Contaminated or viscosity-drifted fluid accelerates seal degradation and gear wear.
Thermal Management
Excessive pump operating temperature (above 180°F for most fluids) accelerates seal degradation. Install temperature gauges on pump discharge and monitor for heat issues. If temperature trends upward, investigate for inadequate cooling or system restriction.
Scheduled Field Maintenance Guide
Consult NAPCO's field maintenance guide for detailed procedures on seal inspection, bearing auditing, and preventive component replacement. This guide helps facility technicians identify wear patterns and plan repairs proactively.
Proper preventive maintenance and regular equipment inspection extend pump service life and help avoid costly replacements.
Related Technical Resources
Explore these additional resources to support pump maintenance and repair planning:
Ready to Evaluate Your Pump Repair or Replacement Options?
Send NAPCO photos or a description of your pump condition, including flow rate, pressure, noise symptoms, and leak locations. Our engineering team will assess whether a repair kit rebuild is suitable or recommend replacement, and provide a cost estimate for either path forward.
Contact NAPCO Engineering