Determine Relative Density

A density scale is used to obtain the weight/volume ratio (Relative Density) of a liquid/pulp.

The RD plays a very important role in minerals processing, as an incorrect RD will result in sub standard recovery of minerals, or incorrect addition of chemicals.

Deviation from the procedure can affect production adversely and cause minerals losses.

Specified equipment

• Scale
• Flasks
• Hoses

Scale

• The purpose of the scale is to weigh the sample taken in order to determine the relative density. It must be remembered to calibrate the scale before the sample is weighed.

Flasks

• The flask is used to measure the required sample in order for it to be weighed. Ensure that all sampling equipment is cleaned in accordance with the procedure. Failure to comply will result in inaccurate values being obtained.
• The flask must not be damaged in any way.

Hoses

• Hoses are used in this instance for flushing and washing purposes. The washing of equipment to remove unwanted material is essential and all spillage must be flushed as per the plant specified requirements after completion of the sampling. Failure to flush the area when spillage has taken place will result in slipping and falling incidents.

Calibration of sampling equipment

• Density scales must be calibrated at the start of each shift.
• Defective equipment must be reported and replaced immediately.
• Inspect the density flask to ensure it has no defects.
• Rinse the density flask with drinking water.
• Fill the flask with drinking water until the water starts overflowing at the overflow hole.
• Place your finger over the overflow hole.
• Hang the flask on the hook of the scale.
• Allow any excess water to overflow at the overflow hole.
• Carefully dry the outside of the flask with clean tissue paper.
• The weight indicator should read 1000g. If it does not, turn the adjusting screw accordingly until the reading is 1000g.

Sampling Procedure

• Collect a bulk sample of the liquid/slurry to be sampled in a bucket.
• Ensure that the density flask is clean and free of liquid.
• Stir the bulk sample thoroughly to ensure that all particles are in suspension.
• Pour the sample from the bucket into the flask until the sample overflows from the overflow hole.
• Place your finger over the overflow hole.
• Hang the flask on the hook of the scale.
• Allow any excess liquid to overflow at the overflow hole.
• Carefully dry the outside of the flask with clean tissue paper.
• Observe and record the scale reading.