There are some alternatives to nuclear density meters for mining slurries.
An ultrasonic density meter passes sound waves across the pipe diameter. A strong echo is is received with low % solids, but as the solids increase the sonic energy is absorbed by the particles and the echo weakens. The problem is above 10% solids the signal has to be correspondingly damped. This causes errors, since the damped signal is not the true average of the random noise. Such devices only measure across a thin diameter, which is not representative of the complete cross section.
Microwave phase shift techniques should not be used with mining slurries, since reliance is placed on a reasonably constant dielectric strength of the media. Mining slurries do not exhibit this characteristic.
The best non-nuclear device appears to be a simple direct mass per unit volume system. It actually continuously measures mass of a relatively large, and hence representative, volume. It is vibration and temperature insensitive, while accurate to < 0.5%. It may be used in series with a magnetic volumetric flow meter for wet or dry mass flow, wet density or % dry solids in pipes 2" - 40" diameter. A good explanation is given on www.sciamworldwide.com
 

• http://www.sciamworldwide.com

londnbob is on the right track regarding NON-Nuclear density metering systems. Sciam Worldwide DM3 non-nuclear units are your best choice for removing all hazardous nuclear devices from your mining operations. These units can be fitted to be operated with a significantly reduced maintenance burden and greater benefit from increased accuracy over nuclear units. If there would be any questions you might still need answered after visiting the Sciam Worldwide website, access the Sciam Inquiry Form located at http://www.sciamworldwide.com/enquiry-form/ and type in B. Moore in the "Comments" section and I will make sure personally that you are contacted to answer any questions you may have and to provide any additional information needed.

• http://www.sciamworldwide.com/enquiry-form/

Thank you for the info bmoorewithsciam. After researching microwave and ultrasonic techniques, your Sciam stuff looks good. However, there is another problem I've encountered that I put out for discussion herewith. What about entrained gas in the slurry ? I know it causes a noisy signal with all inferential techniques (microwaves, nuclear and ultrasonic). Does anybody know how slurries with entrained gas can be accurately measured as a mass flow system, or do we just live with noisy signals and a positive error ?
londnbob