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Cutaway demonstration pump showing shaft, bearing housing, mechanical seal and closed impeller
Solution

Back Pull-Out Maintenance

Four of the five Flowsteer series use back pull-out construction. Here is what that changes about a maintenance window.

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The Situation

Why This Matters

A seal change on a conventional end-suction pump starts with breaking two flanges. Gaskets come out, pipework is supported, the pump comes off the baseplate, and after the rebuild everything has to be re-aligned and re-gasketed. Most of the hours go on the pipework, not the pump.

Back pull-out construction removes that entirely. The casing stays bolted between the suction and discharge flanges. The bearing frame, shaft, seal and impeller withdraw rearwards as one assembly.

The Flowsteer ISO CI, KCP, FA and VNP series are all built this way. The ANSI CN series follows ANSI/ASME B73.1, which is itself a back pull-out standard.

Cutaway demonstration pump showing shaft, bearing housing, mechanical seal and closed impeller

Cutaway demonstration pump showing shaft, bearing housing, mechanical seal and closed impeller

Step by Step

How It Works in Practice

  1. Isolate and drainClose the suction and discharge valves and drain the casing. The pipework is not disturbed, so no pipe supports are needed.
  2. Uncouple the driverRemove the coupling guard and the spacer or coupling element. On a spacer coupling the motor does not have to move at all.
  3. Withdraw the rotating assemblyUnbolt the bearing frame from the casing and draw the whole assembly rearwards, clear of the casing.
  4. Service off the pumpImpeller, mechanical seal, shaft sleeve and bearings are all accessible on the bench rather than in the pipe rack.
  5. Refit and re-checkReturn the assembly to the casing, reset the impeller clearance where the design allows it, and re-make the coupling.
  6. Record the clearanceNote the impeller clearance set at refit. On open impeller pumps that figure is what tells you when head loss is wear rather than a process change.
What You Gain

What Changes When You Do This Properly

  • Pipework never brokenNo flange gaskets, no pipe supports, no re-alignment of the pipe run.
  • Shorter maintenance windowsThe job reduces to uncoupling, withdrawing and refitting.
  • Work done on a benchSeal and bearing work happens where it can be done properly rather than over a pit.
  • Fewer alignment errorsWith the casing undisturbed, the pump-to-pipe relationship cannot drift.
Applies To

Pumps This Solution Covers

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Questions

Back Pull-Out Maintenance FAQ

How much clearance do I need behind the pump?

Roughly the length of the shaft and bearing housing, so the rotating assembly can come fully clear of the casing. Allow for it when the plant room is laid out.

Does a spacer coupling matter?

It helps considerably. With a spacer coupling the motor stays bolted down and only the spacer comes out, which removes a re-alignment step from the job.

Which Flowsteer series are back pull-out?

The ISO CI, KCP, FA and VNP series all state back pull-out construction. The ANSI CN series is built to ANSI/ASME B73.1, which is a back pull-out standard.

Do I still need to re-align after a back pull-out service?

The pump-to-pipe alignment is untouched, but the pump-to-motor coupling alignment should still be checked before the guard goes back on.

Put Back Pull-Out Maintenance to Work on Your Plant

Tell us the pumps you have and the duties they run, and we will say where this applies and what it would change.

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