How to Replace the Mechanical Seal of a Vertical Turbine Pump
The vertical turbine pump, as a critical fluid transfer device, relies heavily on the integrity of its mechanical seal, which directly impacts the system’s reliable operation and on-site safety. After prolonged service, the mechanical seal may fail due to wear of the dynamic/static rings, aging of auxiliary seals, spring failure, or debris intrusion, leading to leakage, overheating, or complete failure. Replacement must follow standardized procedures. This guide outlines the detailed process and key technical considerations for replacing the mechanical seal in a vertical turbine pump.
1. Key Preparation Points
Given the structural characteristics of vertical turbine pumps, confirm the seal type (single-face cartridge seals are recommended to simplify deep-well installation) and accurately document the pump’s head, well depth, and medium solid content (which determines material selection, such as silicon carbide or cemented carbide). Prior to operation, fully drain the well liquid via the drain valve or siphon to eliminate fall risks, lock out and tag out the lifting motor power supply, and secure the lifting mechanism with chains or slings to prevent accidental descent of the long shaft. Essential tools for deep-well operations include an extended torque wrench, shaft protection tooling (critical to prevent shaft bending), deep-well lighting, and guide chains (to ensure safe component lifting/lowering).
2. Core Disassembly Process
Principle: Disassemble from top to bottom in sections, ensuring the shaft alignment is protected throughout.
a. Disassemble Upper Drive Components
Remove the motor coupling (mark alignment positions), then detach the bearing housing and seal gland.
b. Extract the Drive Shaft in Sections
Number each shaft section and coupling sequentially.
Disassemble and lift out each section, storing them vertically on a dedicated stand (never lay flat to avoid bending).
c. Access the Seal Chamber (Deep-Well Section)
·fter lifting out the final impeller, expose the seal chamber (typically located at the pump head or above the guide vane).
d. Remove the Old Seal (Deep-Well Operation Notes)
Cartridge Seal: Remove the fixing bolts and lift out the entire assembly.
Component Seal: Remove the static ring gland first, protect the shaft sleeve, then extract the dynamic ring assembly (use guide chains for stability).
3. Cleaning and Inspection
a. Seal Chamber Cleaning
Clean the chamber and shaft sleeve, focusing on removing sediment such as well sand.
b. Critical Dimension Checks
Shaft Runout: Place the shaft on V-blocks and use a dial indicator to ensure radial runout ≤0.1 mm/meter (correct if exceeded).
Seal Installation Section Wear: Shaft sleeve wear ≤0.05 mm (replace sleeve if exceeded).
4. Seal Installation
a. Deep-Well Operation Preparation
Pre-assemble the new seal (cartridge type preferred) and apply compatible lubricant.
b. Shaft Protection and Lowering
Install a guide cap on the shaft end and use guide chains to lower the seal into the chamber slowly, ensuring vertical alignment without deviation.
c. Precise Positioning (Critical!)
· Pre-tighten static ring gland bolts to 50% torque → verify compression amount with a gauge (per manual, ±0.2 mm) → tighten diagonally to 100% torque.
5. Shaft Reassembly and Alignment
Reinstall shaft sections per numbering, checking shaft alignment after each connection (smooth rotation without vibration).
Restore motor alignment marks and use a laser alignment tool to ensure deviation ≤0.05 mm (a critical quality point for deep-well pumps).
6. Commissioning
a. No-Load Test
Perform a brief motor start (<1 second) and listen for abnormal noises at the seal position (to prevent dry friction).
b. Initial Run-In (30 Minutes)
· Leakage Rate: Single-face seals allow ≤3 drops/min (stricter control for deep-well pump leaks).
· Vibration Monitoring: Bearing housing vibration ≤2.8 mm/s (check shaft alignment if exceeded).
· Temperature: Seal chamber temperature rise ≤25°C (monitor closely due to slow heat dissipation in deep wells).
7. Safety and Professional Warnings
Deep-Well Fall Prevention: Cover the wellhead during operations and ensure personnel wear safety harnesses.
Shaft Protection: Use shaft supports throughout disassembly/installation; never use levers to pry the long shaft.
Medium Compatibility: For well fluids containing chlorine or H₂S, use special alloy or ceramic seal materials.
Mandatory Standards: Operations must comply with API 610 (11th Edition) or the manufacturer’s maintenance manual for vertical turbine pumps.
Conclusion
Efficient replacement of the mechanical seal in a vertical turbine pump hinges on precise operations, shaft protection, and thorough coordination:
Professional Precision: Strictly adhere to manufacturer specifications and API standards, ensuring critical parameters like seal compression and shaft alignment are met.
Safety First: Implement energy isolation, shaft protection, and wellhead fall prevention measures to eliminate mechanical and medium-related risks.
Long-Term Reliability: Through standardized run-in and continuous monitoring (leakage, temperature, vibration), prevent unplanned downtime and extend pump service life.
By integrating technical rigor with operational safety, the mechanical seal system of a vertical turbine pump can achieve”zero leakage, long service life, and high reliability.”
