Disassembling an ISG vertical pipeline centrifugal pump without disturbing the connected piping system is a field-proven procedure that cuts downtime, eliminates the need for full system draining, and prevents unnecessary stress on flanged joints that can lead to persistent leaks after reassembly. This workflow relies on the pump’s compact, inline structural design, but it still requires strict adherence to step-by-step field safety practices to avoid component damage or accidental fluid release during service.

Begin the full pre-work preparation sequence before loosening any pump fasteners, to lock in safety and avoid mid-procedure delays. Lock out and tag out all electrical power to the driving motor, and confirm no remote startup signal can reach the circuit, to eliminate any risk of unintended shaft rotation while technicians are working on the unit. Close and securely lock both suction and discharge isolation valves, then open the local vent and drain valve on the pump casing to release all residual internal pressure and drain trapped fluid into a suitable collection container, ensuring zero pressure remains inside the pump chamber before any disassembly starts. Place a stable work platform around the pump to provide clear access to all casing and motor connection points, and arrange all required hand tools, clean storage trays, and non-marring drift punches within easy reach, so small removed parts can be organized and tracked in the exact order they are taken off.

Move next to separate the rotor assembly from the fixed pump casing, without applying any side load to the adjacent piping flanges. Loosen and remove the bolts that connect the motor bracket to the pump casing, taking care to turn each bolt a small amount in alternating, even increments to avoid uneven binding that can tilt the assembly and place unwanted stress on the pipeline. Once all connecting bolts are removed, use a rubber mallet with a soft brass drift to gently tap the mounting flange joint around its full circumference, breaking the seal between the bracket and casing without prying against the piping itself. Lift the motor and rotor assembly straight upward along the shared shaft centerline, keeping the unit perfectly aligned as it clears the casing, and set it down on a clean, flat work surface nearby, so the impeller, mechanical seal, and shaft components are fully exposed for inspection and service.

With the rotor assembly fully separated from the piping-mounted casing, perform all required component service, inspection, or replacement work without touching any pipeline connections. Secure the impeller from rotating using a soft jaw clamp that will not scratch the machined impeller face, then loosen and remove the impeller locking nut, and slide the impeller carefully off the extended motor shaft. Extract the old mechanical seal components from the shaft and seal seat, then wipe down the entire exposed shaft surface with a clean lint-free cloth to remove all scale, corrosion, and residual seal debris, checking for any deep grooves or pitting that could compromise sealing performance after reassembly. Inspect the inside of the piping-mounted pump casing through the open joint, clearing any trapped debris, checking volute vane conditions, and verifying the wear ring seating surface is clean and free of damage, all while the casing remains firmly bolted to the undisturbed suction and discharge piping.

When reassembling, follow the reverse order of disassembly, taking extra care to keep all moving parts perfectly aligned to avoid seal damage during reinstallation. Lower the fully reassembled rotor assembly straight back into the fixed pump casing, aligning the flange bolt holes by hand without forcing or prying the unit into position, then tighten all connecting bolts in a cross-torque pattern to the manufacturer’s specified value. Close the casing drain valve, open the suction isolation valve slowly to flood the pump chamber, and perform a static pressure check to confirm no leaks exist at the casing joint before restoring full system pressure. Remove all lockout and tagout devices, manually rotate the shaft several full turns to confirm no binding, and jog the motor briefly to verify smooth operation before returning the pump to normal service.