Ultrasonic Slurry Density Meter · PS7000

Sodium–calcium dual-alkali FGD — regeneration-side density monitoring

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.

Q: 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.

Q: 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.

FGD · Environmental

Sodium–calcium dual-alkali absorbs with sodium alkali and regenerates with lime, so the tower circulates a clear solution and all solids settle outside it. This page says plainly that the absorber side does not warrant an online concentration meter — the three-component split is set by pH, not pinned by stoichiometry, and controlling make-up on pH is the right call — and concentrates on the two points that do: lime slurry preparation and regeneration-basin density.

Applicable industries

Power Emission Control

Discuss this application View product PS7000

Sodium–calcium dual-alkali FGD — regeneration-side density monitoring

PISONICS

PS7000 Series

Ultrasonic Slurry Density Meter

Acoustic impedance · non-nuclear · handles aerated slurry

Sodium–Calcium Dual-Alkali FGD — Density Monitoring on the Regeneration Side

—— Keep pH on the absorber; what is worth instrumenting online is density on the regeneration side ——

Key measurements: slurry density g/cm³ / solids content

How Dual-Alkali Works

Dual-alkali splits desulfurization in two: sodium alkali absorbs, lime regenerates it, and the sodium is recycled.

Absorption: 2 NaOH + SO₂ → Na₂SO₃ + H₂O; Na₂SO₃ + SO₂ + H₂O → 2 NaHSO₃

Regeneration: Na₂SO₃ + Ca(OH)₂ → 2 NaOH + CaSO₃↓ (partly oxidised to gypsum)

That is exactly where its advantage over limestone-gypsum lies: what circulates in the tower is a clear solution. Sodium salts are soluble, so nozzles and pipework do not scale and plug the way a limestone slurry does; all the solids move outside the tower into the regeneration basin. It also means the two systems need different things measured — for limestone-gypsum see absorber gypsum slurry density and limestone slurry preparation.

Something Against Our Own Interest, First

On the absorber side we do not recommend an online concentration meter. The circulating liquor holds NaOH, Na₂SO₃ and NaHSO₃ together, and the split between them is set by pH; meanwhile SO₂ load and caustic make-up vary on independent loops. This is not a system pinned to one dimension by stoichiometry, and a single sound-velocity reading cannot resolve it usefully. Plants control make-up on pH, that is the right call, and we have no reason to argue you out of a cheaper and more direct measurement.

What sound velocity can offer on the absorber side is an aggregate total-salt figure — useful for judging whether the system is accumulating salt and whether it is time to bleed, but a supplement to pH, not a replacement. Whether that earns its own instrument depends on what your bleed decision rests on today; if there is a working rule of thumb in place, leave it alone.

The Two Points Worth Instrumenting

Point	Medium	Why it earns an instrument	Model
① Lime slurry preparation	Ca(OH)₂ milk	Strength sets regeneration efficiency and lime consumption. Too rich wastes lime and plugs lines; too lean leaves regeneration incomplete, so alkali recovery falls and fresh caustic has to make up the difference	PS7000
② Regeneration basin / settling	CaSO₃ + CaSO₄ slurry	Solids content sets when to draw sludge and how hard the dewatering plant works. Too early carries away water and usable alkali; too late fills the basin and regeneration capacity drops	PS7000

Both points are solids-bearing slurry, both opaque, both commonly aerated — which is the duty acoustic impedance was designed for. It does not need light through the sample and is indifferent to colour and opacity. Span and bore are confirmed against the site; see the PS7000 product page.

Why Not a Nuclear Gauge

Both points have historically used Cs-137 nuclear density gauges. There is nothing wrong with the measurement; the trouble is everything around it — licensing, annual inspection, source records, decommissioning, and one more thing on site that has to be managed. Acoustic impedance returns the same density figure without any of those obligations. We have written that comparison out in full at ultrasonic acoustic impedance vs Cs-137 nuclear density gauges.

Before We Quote

Lime slurry strength range and how much it swings; continuous or batch preparation.
Solids content range in the regeneration basin, and roughly the particle size.
Bore, velocity, and whether a vertical full-bore run is available.
Slurry temperature and abrasiveness (heavy abrasion needs a wear assessment).
What the sludge-draw and caustic make-up decisions rest on today — that decides how the control logic changes once there is an instrument.
The pH scheme on the absorber side, and what about it is not satisfying you.

What this page is: a method and selection note, not a case study. There are no unit counts, saving percentages or payback periods here — we do not invent those. Where the page says what the industry does, it cites something you can check for yourself (published vendor literature, granted patents) rather than implying we have installed base there. Send us the process conditions and you get a selection opinion you can check.

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

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.