An IMS FAH 8x6 slurry pump with gland packing is losing shaft sleeves (the failing "horns" in the maintenance report are the sleeves) and packing at a high rate. The maintenance window only allows a wet-end change. The crew has no way to balance the impeller or measure shaft runout inside that window. Field-balancing this impeller is not possible, and it is not the first problem to fix. Sleeve and packing life is governed mainly by gland flush and shaft runout, and both can be checked in minutes. The impeller balance can be moved out of the window entirely by purchasing balanced spares.
Confirm what is failing before changing anything
Record these facts on the work order first, because every later branch depends on them: pump maker marking (IMS), model FAH, size 8x6, shaft sealing by packing (not a mechanical seal), and replaceable shaft sleeve under the packing. The FAH designation follows the Warman AH heavy-duty slurry pump layout, and the unit may be a licensed or rebranded copy. Use the original AH-style parts list and the supplier's manual for the pump you actually have, and confirm dimensions against the nameplate rather than assuming interchangeability.
Also record the duty: is this pump alone, or in series with another pump, and is it the last stage (highest suction pressure)? Is the impeller metal (high-chrome) or rubber lined? These answers select the branches below.
Check 1: Locate the wear band on the removed sleeve
Read the wear pattern on the sleeve outer diameter when it comes off. Where the scoring sits tells you which mechanism dominates.
| Wear pattern on sleeve | Mechanism | Next check |
|---|---|---|
| Grooves under every packing ring, evenly distributed, packing burnt or hard | Insufficient cooling and lubrication; flush not reaching the packing | Check 2 |
| Heavy erosion on the volute side of the box, light wear at the gland end | Slurry entering the box; flush water passing straight through the lantern ring to the volute instead of cooling the packing | Check 2 |
| Wear on one side of the sleeve circumference only, or a polished band at one angular position | Shaft bend or sleeve eccentricity; the shaft is running off-center against the packing | Check 3 |
| Even wear, but the pump also shows housing vibration at running speed after each rebuild | Impeller unbalance loading the shaft | Check 4 |
Check 2: Gland flush flow and pressure at the stuffing box
Gland flush (also called gland seal water) is clean water injected through the lantern ring into the stuffing box. It does two jobs: it cools and lubricates the packing, and it holds slurry out of the box. Stuffing box designs range from ultra-low-flow to normal-flow arrangements. In service, the packing loosens with wear and the box tends toward normal-flow behavior. Most of the water then takes the path of least resistance into the volute, and little reaches the packing and sleeve.
- Measure flush flow with a flow meter or rotameter on the gland supply line. Compare to the flow value in the pump manual for your box arrangement.
- Measure flush pressure at the gland connection. It must exceed the stuffing box pressure or slurry enters the box. Read stuffing box pressure limits from the manual.
- During repacking, verify the lantern ring sits under the flush port after the packing is compressed. A misaligned ring blocks the flush path.
Outcome: flow or pressure below the manual value, or lantern ring misaligned, means you have found the primary cause of short sleeve and packing life. Correct it and go to the procedure below. If flush is correct and the wear is one-sided, go to Check 3.
Check 3: Shaft runout with a dial indicator
Runout is the radial deviation of the shaft surface from its rotational axis, read as total indicator reading (TIR) on a dial indicator. A bent shaft or an eccentric sleeve makes the packing rings work harder on one side each revolution, which accelerates sleeve wear regardless of flush quality. This check takes minutes with the wet end removed.
- Mount the indicator on a rigid stationary base with the probe perpendicular to the shaft or sleeve surface.
- Rotate the shaft by hand through one full turn and read TIR at the sleeve seating area and, if reachable, at the impeller end of the shaft.
- Compare against the runout limit in the pump manual for the FAH 8x6 shaft. Read that limit from the manual; do not use a value from another pump.
- Measure the new sleeve after fitting. An eccentric sleeve adds runout on top of the shaft.
Outcome: TIR within the manual limit removes shaft bend from the list and points to flush (Check 2) or balance (Check 4). TIR above the limit means the shaft or bearing assembly is the fault, and replacing wet parts will not cure the wear.
Check 4: Impeller balance and why the field cannot supply it
With the AH-style casing and cover plate removed, only part of the impeller is accessible. That prevents a field balance of the impeller on the shaft and makes trim-balancing with a portable analyzer impractical in a short window. Balancing is a shop operation on a balancing machine, with the impeller on a proper arbor.
The grade G equals the product of permissible eccentricity and angular velocity in mm/s. For a required grade, the permissible residual unbalance per plane is:
U_per [g*mm] = 9549 * G * m [kg] / n [rpm]Here m is the impeller mass and n is the operating speed. Read both from the pump data or measure them; do not estimate. A lower G number is tighter: G6.3 is tighter than G14. Specify G14 as the minimum and G6.3 as the preferred grade on the purchase order. A reasonable supplier delivers the impeller balanced and provides a balance report.
Balance also degrades with wear. Before an impeller returns to stock or service, inspect vane leading edges, vane tips and side liner clearances. Uneven vane wear creates unbalance that no original balance grade can hold. If a wear-induced unbalance is suspected, the fix is rebuild or replacement plus a fresh balance, not a shim or weight added in the field.
| Impeller condition | Action |
|---|---|
| New, supplier balance report at G14 or better | Fit as delivered; log the report against the serial |
| New, no balance report | Reject or send for balancing before fitting |
| Used, uneven vane or tip wear | Replace, or rebuild and rebalance in a shop |
| Used, even wear, previously balanced | Re-balance in a shop before reuse if vibration was elevated on the last run |
Procedure for the resolving branch: window-time work and off-window work
The shortest reliable path shifts balance out of the window and puts flush and runout checks inside it.
- Before the shutdown: order the spare impeller balanced to G6.3 (G14 minimum) with a written balance report. Stock spares so the window only involves removal and fitting.
- At shutdown: pull the wet end. Before fitting new parts, measure shaft runout at the sleeve seat with a dial indicator (Check 3) and record TIR.
- Fit a new sleeve, then measure its runout.
- Repack the stuffing box per the manual, with the lantern ring aligned under the flush port after compression.
- Fit the balanced impeller and set the clearances per the manual.
- Before start: set gland flush flow and pressure to the manual values, using the highest suction pressure in the train if this pump is the last stage in a series (Check 2).
- After the window: send the removed impeller for inspection and shop balance so it returns to stock as a ready spare.
Verification checks after restart
- Shaft runout recorded at rebuild is within the manual limit. Expected: both the shaft and the fitted sleeve TIR are inside the limit, with values written on the work order.
- Gland flush flow and pressure at running conditions. Expected: flow at or above the manual value and pressure above the stuffing box pressure, with the packing showing a light drip or the flow the manual specifies.
- Packing temperature at the gland after warm-up. Expected: stable and not rising; a gland that keeps heating means flush is not reaching the packing.
- Vibration at the bearing housing on the first run compared with the previous rebuild. Expected: level equal to or lower than baseline, with no strong running-speed component that points to unbalance. Use the site vibration acceptance criteria or the applicable pump vibration standard for the limit.
- Sleeve inspection at the next stop. Expected: an even wear band under the packing, with no one-sided scoring and no erosion on the volute side of the box.
FAQ
How do I balance a slurry pump impeller in the field?
You cannot on an AH-style FAH casing: with the cover plate removed only part of the impeller is accessible. Buy impellers balanced on a balancing machine to G6.3 (G14 minimum) with a balance report, and send used impellers to a shop.
How do I check shaft runout on a slurry pump during a short maintenance window?
Remove the wet end, mount a dial indicator on a rigid base against the shaft or sleeve, rotate one full turn by hand and read TIR at the sleeve seat. Compare it to the runout limit in the FAH manual; it takes a few minutes.
How do I stop the shaft sleeve and packing from wearing out early on an FAH pump?
Measure gland flush flow and pressure and compare to the manual values, using the highest suction pressure if the pump is last in a series train. Align the lantern ring under the flush port after packing compression, and confirm shaft runout is within the limit.