Why a hydrated lime slurry can block a pump despite a passing assay

Is “lime” specific enough for a purchase order?

Retain separate samples of incoming sieve residue, settled slurry solids and pipe deposits. Mixing these samples obscures where the obstruction formed.

Sample the three residue locations separately

Prepare slurries at the same solids content. Under equal agitation and settling conditions, collect samples from the top, middle and bottom. Compare residue on the same sieve with the pump inlet’s particle-size allowance. State the sieve opening in the acceptance specification.

What if the assay passes but the pump still blocks?

Compare as-received sieve residue and site slurry dispersion. Check pump suction limits and residence time. Lime softening: Track raw-water alkalinity, treated-water hardness and sludge settling. Wastewater pH control: At a fixed endpoint, compare reaction response, slurry handling and residue.

Checking Available calcium hydroxide and Sieve residue

Available calcium hydroxide (% by mass): State whether the result is expressed as Ca(OH)₂ or as CaO equivalent. Sieve residue (%): Specify sieve aperture to match the particle-size limits of pumps and lines. Slurry solids (% by mass): For slurry deliveries only. Record homogenisation before sampling.

What to record

• Sieve aperture
• Incoming sieve residue
• Slurry solids
• Sampling location
• Settled residue

Technical references

• NHMRC: hydrated lime in water treatment ↗

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