Ultrasonic Slurry Density Meter · PS7000

Coal flotation feed: online solids concentration

Q: Is the PS7000 ultrasonic density meter a radiometric device? Does it need a radiation license?

The PS7000 is an acoustic-impedance ultrasonic density meter with no radioactive source whatsoever. No radiation license is required. It uses only piezoelectric transducers to send and receive ultrasonic signals — the same physical principle as medical and NDT ultrasound. If you're currently using a Cs-137 / Co-60 source-based meter and want to remove the regulatory burden, PS7000 is a practical alternative; it installs differently, so check straight run and spool fit before a retrofit. A gamma gauge with an exempt-activity Na-22 source (< 1000 KBq) also needs no radiation license, but we no longer supply that class of instrument.

Q: Can an ultrasonic concentration meter measure mine backfill slurry?

It can, depending on the slurry. The PS7000 acoustic-impedance meter covers 0–80 % by mass and its window sits flush with the pipe wall, so it suits fine-grained backfill slurry on a full pumped line (the datasheet recommends at least 65 % by mass finer than 75 μm). Paste close to the 80 % limit, slurry carrying coarse aggregate or coarse waste rock, and scaling cemented mixes need window wear, scaling and representativeness assessed first; the standard pressure rating is 1.6 MPa, and higher-pressure sections such as backfill pump discharges are rated case by case. It is a non-nuclear alternative to Cs-137 gauges — see /industries/mining.

Q: Can PS7000 really measure stably in bubbly mining slurries?

Yes, with one distinction. The PS7000 employs a linear frequency-modulated (Chirp) acoustic impedance algorithm: after transmitting a broadband ultrasonic pulse, the host unit analyzes the echo in the frequency domain, and multiple-reflection interference from fine, dispersed bubbles is identified and suppressed. That is the main difference from conventional single-frequency reflective meters. The meter also outputs a 0–100 gas index and a bubble flag, so the DCS can tell a real change in concentration from a bubble-driven high reading. Heavy free gas (pump suction drawing air, a falling stream entraining it, a point directly above an aeration header) or a continuous gas film over the sensor face pushes the reading high or stops it altogether. That is a limit of acoustic measurement: it is avoided by where the sensor goes, not corrected in calibration. At the gypsum discharge line of an absorption tower in a thermal power plant in Inner Mongolia (under conditions of continuous air oxidation that generate dense bubbles), the PS7000 has been operating stably for several years after replacing the original tuning fork concentration meter.

Coal preparation

Online solids concentration on coal flotation feed (50–120 g/L), where concentration × flow gives the dry solids for reagent feed-forward: where a non-nuclear ultrasonic meter goes, how to keep bubbles and reagent off the reading, and how to accept it.

Applicable industries

Coal Preparation

Discuss this application View product PS7000

PISONICS

PS7000 Series

Ultrasonic Slurry Density Meter

Acoustic impedance · non-nuclear · sensor flush with the pipe wall

Coal Flotation Feed — Online Solids Concentration

—— Dry solids to flotation = concentration × flow, the feed-forward input to reagent dosing ——

【Key measurements: feed solids concentration g/L / slurry density】

Reagent Follows the Dry Solids

Collector and frother in coal flotation are dosed per tonne of dry solids. Plants that automate dosing usually fit a concentration meter and a flow meter on the flotation feed line, multiply the two into dry solids to flotation (t/h) as the feed-forward term, and trim the dose on clean-coal or tailings ash. A wrong concentration reading takes the feed-forward with it: read high and the circuit is overdosed; read low and it is underdosed and clean-coal ash drifts.

Item	Typical value	Note
Feed concentration	50–120 g/L	Common set points sit between 60 and 100 g/L
Density above water	About 19–53 kg/m³	Slime solids density 1.6–1.8 g/cm³; about 0.4 kg/m³ per g/L
±1 % w/w in g/L	About ±10–11 g/L	9–21 % of reading, so not an acceptance figure as it stands
Water from 10 °C to 30 °C	Equivalent to 9–11 g/L	Temperature compensation and the calibrated temperature span must cover the whole year

Like the thickener feed, flotation feed is a small-signal point: the meter earns its place by being continuous, stable and open about bad readings, and the acceptance figure comes from site comparison data. The slurry concentration calculator converts between w/w, g/L and density.

How PS7000 Measures

PS7000 measures acoustic impedance with a single chirped ultrasonic transducer. The sapphire window sits flush with the pipe wall and does not project into the flow, so there is nothing for flocs or fibre to hang on. There is no radioactive source, so no licensing, leak testing or disposal.

Alongside the concentration it reports a 0–100 gas index, a bubble flag, echo energy, signal quality and a fault word over Modbus; the two 4–20 mA loops follow NAMUR NE43 and go to 3.5 mA on a fault by default. Bubbles are the commonest upset on flotation feed, and the gas index is what flags those readings.

What to watch: free gas biases acoustic readings high, which pushes the feed-forward to overdose and can only be avoided by siting; an oil or mud film on the window makes the reading creep up and flatten out; and a change of coal or of feed size distribution calls for a calibration check.

Where the Sensor Goes

On the full line after the feed pump, preferably a vertical upward run; on a horizontal line, at mid-height on the side of the pipe, clear of settled solids and of air at the crown.
Upstream of the conditioner and the reagent addition point, so the window sees undosed slurry, away from reagent emulsification, air worked in by mixing, and oily collector filming the window.
Away from pump suction, free-falling gravity sections, sieve-bend underflow launders and sump outlets, where air is drawn in or the line runs part-full; where the feed gravitates into a sump, use the line after the pump.
Straight run ≥ 10D upstream and ≥ 5D downstream (5D / 3D minimum); velocity above the deposition velocity.
The flow meter on the same stream and close by, so the two signals line up when multiplied; the sample point beside the sensor at the same height.
Check the feed size distribution: the datasheet recommends at least 65 % by mass finer than 75 μm (200 mesh); a coarser feed needs representativeness and window wear assessed first.

The concentration meter sits on the vertical run after the feed pump, with the flow meter on the same line; the conditioner and reagent addition are downstream (schematic, not to scale)

Working with the Dosing Loop

Dry solids (t/h) = concentration (g/L) × flow (m³/h) ÷ 1000, computed in the DCS or dosing PLC. PS7000 supplies concentration over 4–20 mA or Modbus; the flow meter is sourced to suit the site, usually electromagnetic.
When the gas index is above its set point, the feed pump is stopped or flow is below a minimum, hold the last good concentration so bad readings never reach the feed-forward.
Concentration × flow sets the base dose only; clean-coal and tailings ash still trim it. No single concentration meter should decide the dose on its own.
Reagent savings come from the whole dosing system — model, ash feedback, actuators and operating practice — and should not be credited to one instrument.

Calibration and Acceptance

Use oven-dried gravimetric samples as the reference, not quick density-cup checks; sample beside the sensor at a recorded time and take meter values from the DCS or cloud log.
Spread calibration points across the working range (at least three near each end, for example around 60 and 100 g/L). The meter fits Y = aX + b with up to 20 points and, from three points on, refuses a fit with r² below 0.8; calibration is done online, without a shutdown.
Plants that alternate coals can keep a calibration per coal and switch between them.
Accept on at least 20 paired samples, judged on mean bias, trend agreement and the standard deviation of the differences; agree the figure from trial-period data.

In Coal Preparation

PS7000 is in service on flotation feed and thickener feed points in coal preparation plants; customers are not named. See coal slurry thickener feed and underflow and density control of dense-medium suspensions.

Buying from China

CE marked; Ex d IIC T6 Gb available on order. Quotations in USD or EUR, EXW / FOB / CIF, with HS code and declaration of conformity. Send the feed line size and material, the feed concentration and flow range, where the conditioner and reagent addition sit relative to the pump, the water temperature range and the slime size distribution, and the selection takes one exchange.

Selection support

Guides

Comparisons

Voices from users of this product

"Our original tuning fork and differential pressure meters on the absorber gypsum discharge main had recurring problems with bubbles and scaling — we had to shut down weekly to clean them. After switching to PS7000, both problems disappeared. Basically maintenance-free now, accuracy is stable, and it fully meets our FGD process control needs."

"After switching to the PS7000, our overflow density readings finally stabilized — we stopped tuning reagent dosing by feel. The unexpected win was not having to clean the sensor weekly; our previous radiometric meter needed window-wiping almost daily in the scaling slurry."

"Our potash blending tank is a harsh environment — KCl near saturation, 30~40% crystal content, temperature swinging 5~20°C. Traditional density meters can't hold up here. After two weeks of PS7000 service, the deviation from manual lab samples stayed in the 0.5~0.8% range, even during concentration peaks. No anomalies."

FAQ

Will bubbles in the flotation feed make the concentration read high?

Yes — high, not low. Fine dispersed bubbles matter little; free gas from pump suction, a falling stream or a mixing point makes the reading high, and a dose-per-dry-tonne feed-forward then overdoses.

That is why the sensor goes on the full line after the feed pump, upstream of the conditioner and the reagent point, and why the gas index is used as a quality flag: above its set point the DCS holds the last good concentration.

Why should the concentration meter sit upstream of the reagent addition point?

Two reasons. Dosed slurry goes through a conditioner or agitated tank that works air into it, and oily collectors such as diesel or kerosene can film the window and hold fine slime on it, so the reading creeps up. Upstream of the reagent point the window sees undosed slurry.

Wherever it sits, put the point on the inspection round and fit a flush connection.

How much flotation reagent will a concentration meter save?

Savings belong to the dosing system as a whole — the feed-forward model, ash feedback, the dosing actuators and how the circuit is run. The concentration meter is one input, so we do not promise a saving for the instrument on its own.

What we do commit to is the measurement: gravimetric comparisons during the trial, with the acceptance figure agreed from their mean bias and standard deviation.

Can the concentration meter go in without a flow meter?

You get the concentration trend but not dry solids to flotation. Dosing per dry tonne needs a flow signal on the same stream, usually from an electromagnetic meter, multiplied with concentration in the DCS or dosing PLC; PS7000 supplies concentration over 4–20 mA or Modbus.

How is dredge production (dry solids per hour) measured?

You cannot get it from density alone. Dry-solids production P_dry (t/h) = Q x Cv x rho_s, where Q is the volumetric flow (from a flow meter), Cv = (rho_m - rho_w)/(rho_s - rho_w) is the volumetric concentration from the mixture density rho_m (from an inline density meter such as the PS7000), and rho_s is the dry-solids density. The Pisonics Dredge Production Monitor reads the density and flow meters over Modbus and computes this every second, with dashboard and shift totals. See /guides/dredge-production-calculation-density-flow.

Can I measure dredge slurry density without a radioactive source?

Yes. An ultrasonic acoustic-impedance meter (PS7000) reads discharge-line slurry density inline (accuracy ±1 % by mass concentration, calibrated on the dredged material) with no radioactive source, so there is no shipboard radiation licence, no port-inspection delay and no radiation-safety officer. A clamp-on option (PS7010) allows no-hot-work retrofit, but it needs low gas content and is ruled out on lines that draw in air. See /guides/non-nuclear-density-meter-for-dredgers.

What density meter should go on a cutter-suction dredger discharge line?

A PS7000 ultrasonic acoustic-impedance meter suits CSD discharge lines (DN50-DN1000): flush sapphire window for abrasion, Chirp wideband to reject entrained air, non-nuclear. For no-cut retrofit use the clamp-on PS7010. Pair with a flow meter and the Dredge Production Monitor to also get dry-solids t/h. See /industries/dredging.

Is the PS7000 ultrasonic density meter a radiometric device? Does it need a radiation license?

The PS7000 is an acoustic-impedance ultrasonic density meter with no radioactive source whatsoever. No radiation license is required. It uses only piezoelectric transducers to send and receive ultrasonic signals — the same physical principle as medical and NDT ultrasound.

If you're currently using a Cs-137 / Co-60 source-based meter and want to remove the regulatory burden, PS7000 is a practical alternative; it installs differently, so check straight run and spool fit before a retrofit. A gamma gauge with an exempt-activity Na-22 source (< 1000 KBq) also needs no radiation license, but we no longer supply that class of instrument.

Can an ultrasonic concentration meter measure mine backfill slurry?

It can, depending on the slurry. The PS7000 acoustic-impedance meter covers 0–80 % by mass and its window sits flush with the pipe wall, so it suits fine-grained backfill slurry on a full pumped line (the datasheet recommends at least 65 % by mass finer than 75 μm). Paste close to the 80 % limit, slurry carrying coarse aggregate or coarse waste rock, and scaling cemented mixes need window wear, scaling and representativeness assessed first; the standard pressure rating is 1.6 MPa, and higher-pressure sections such as backfill pump discharges are rated case by case. It is a non-nuclear alternative to Cs-137 gauges — see /industries/mining.

Can PS7000 really measure stably in bubbly mining slurries?

Yes, with one distinction.

The PS7000 employs a linear frequency-modulated (Chirp) acoustic impedance algorithm: after transmitting a broadband ultrasonic pulse, the host unit analyzes the echo in the frequency domain, and multiple-reflection interference from fine, dispersed bubbles is identified and suppressed. That is the main difference from conventional single-frequency reflective meters. The meter also outputs a 0–100 gas index and a bubble flag, so the DCS can tell a real change in concentration from a bubble-driven high reading.

Heavy free gas (pump suction drawing air, a falling stream entraining it, a point directly above an aeration header) or a continuous gas film over the sensor face pushes the reading high or stops it altogether. That is a limit of acoustic measurement: it is avoided by where the sensor goes, not corrected in calibration.

At the gypsum discharge line of an absorption tower in a thermal power plant in Inner Mongolia (under conditions of continuous air oxidation that generate dense bubbles), the PS7000 has been operating stably for several years after replacing the original tuning fork concentration meter.

What installation requirements does the PS7000 have?

PS7000 installs in one of two ways, and both have the same process requirements:

Spool type: a flanged measuring spool (ANSI / DIN / JIS) goes into the line, with the sensor face made flush with the bore at the factory. Weld-in type: a Ø60 mm hole and a welded boss on the existing pipe, with no cut-out, which suits large existing mains;
Straight run ≥ 10D upstream and ≥ 5D downstream (5D / 3D minimum where space is tight), away from pump discharges, valves and bends;
Prefer a vertical run with upward flow. On a full horizontal line, mount at mid-height on the side of the pipe, clear of settled solids at the invert and air at the crown;
The pipe need not run full, but the sensor face must stay submerged under every operating condition — on a part-full line, mount on the lower half of the side wall, below the lowest operating level and above any deposit at the invert;
Keep velocity above the deposition velocity and preferably no more than 5 m/s. Readings taken while the line stands after a pump stop do not represent the process; gate them with the pump-running signal in the DCS;
Line sizes DN50 to DN1000 (larger on request). The window is sapphire; for heavy abrasion choose 316L with special ceramics or a 2205 duplex probe, and for strong corrosion a PTFE lining.

For how to choose the angle and level on a part-full line, see coal slurry thickener feed and underflow. If the line cannot be drilled, hot-worked or shut down, select the PS7010 clamp-on meter instead.

PS7000 vs nuclear density gauges: which costs less over the life cycle?

On purchase price alone, ultrasonic and nuclear gauges sit in a similar bracket. The gap opens over 5 to 10 years of ownership.

Hidden cost list of a Cs-137 / Co-60 nuclear gauge:

Radiation safety licensing and annual reviews, plus operator training and certification;
Licensed transport and installation filing for the source;
Dose monitoring and record keeping during service;
Source replacement as activity decays (purchase, transport, commissioning, return of the old source);
End-of-life disposal of the spent source — often the single largest bill.

PS7000 acoustic-impedance ultrasonic gauge: no radioactive source and no permits of any kind; non-intrusive sensor that does not project into the flow, so no insertion-type erosion or build-up points, sensor life of 5 years or more, virtually maintenance free with no consumables. Power plant, potash and iron ore sites have run 2+ years at near zero maintenance.

Bottom line: on a 5-year basis the total cost of ownership of the PS7000 is typically far below a nuclear gauge. Where a nuclear principle is genuinely required, a gamma gauge with an exempt-activity Na-22 source is genuinely a lighter route than Cs-137 and needs no license, though the roughly 2.6-year half-life still implies periodic source renewal. We no longer supply that class of instrument; it is noted here for completeness.