- How does SCIAM ensure accuracy?
- How was the DM3 developed?
- How does the SCIAM DM3 System compare with microwave density meters?
- How does the DM3 compare with auto sampling?
- How does the SCIAM DM3 compare with ultrasonic density meters?
- What are SCIAM DM3’s long term cost benefits in reduced downtime and ‘green’ operation?
- How does SCIAM’s DM3 compare with a nuclear density gauge?
- Why gum rubber?
- What ensures the DM3′s durability?
- How often does the DM3 require maintenance?
- How often does the flow tube and/or load cell need to be replaced?
- Reducers & Expanders – When To Use
- Rules for Selection
- Is the DM3 the only product SCIAM will manufacture?
- What are SCIAM’s plans for the future?
1. How does SCIAM ensure accuracy?
2. How was the DM3 developed?
The DM3 was developed to meet the needs of a direct mass per unit volume system as an preferred alternative to nuclear, ultrasonic and microwave phase shift techniques. Before the product came to market it was thoroughly tested for insensitivity to plant vibration, vibration of the media itself and temperature change. These were always the parameters that have prevented such favorable technology being used typically in mining, dredging, oil, paper and waste water applications. SCIAM technology has overcome these major difficulties and has a world wide patent pending. At the same time high pressure or full vacuum conditions are added to the list of viable applications.
3. How does the SCIAM DM3 System compare with microwave density meters?
Microwave techniques are used to measure density of slurries by sensing the phase shift of microwaves passing through a slurry and comparing the phase shift with water. Slurries having a reasonably constant electrical relative permittivity (also called dielectric constant) are suitable, such as slurries used in sewage treatment, paper pulp and the food industry. However, mining, dredging and inorganic slurries are not suitable because of their large variation in relative permittivity, which causes a noisy signal and unacceptable errors.
Pipe sizes are also normally limited to 12″ diameter (300mm) using microwave techniques. Even then, the sensing path is narrow across the diameter of the microwave flow tube. Media either side of this narrow path simply does not get measured, which leads to large errors or ambiguity over the long term. Response time is typically limited to 1 – 100 seconds, dependent on the homogeneity of the slurry and its variation in relative permittivity. This again results in large errors or ambiguity over the long term.
By comparison, the DM3 has a response time of 45 milleseconds from zero to full scale and a truly representative and continuous sample is measured directly as mass per unit volume. Nothing is lost in the measurement, nothing is lost in compromised speed of response, resulting in higher accuracy over short and long terms.
4. How does the DM3 compare with auto sampling?
The DM3 Density Meter provides an accurate, continuous and direct mass per unit volume measurement. The reference volume is relatively large to provide a true representation of the media being measured. The media is actually interrogated 110 times per second, ensuring a fast response time, adjustable down to 45 milleseconds, to ensure no variations in the slurry is missed. By contrast, auto sampling takes a ‘grab’ at regular time periods, such that the sample can be taken away to the laboratory for weighing in a known volume to determine the density. During the time interval between grabs, the slurry density can vary significantly and is not monitored. The volume of the sample is relatively small and may not be representative of the media density. Auto sampling also requires the time of expensive laboratory technicians.
5. How does the SCIAM DM3 compare with ultrasonic density meters?
Ultrasonic techniques may be used to measure the density of slurries by emitting ultrasonic waves to a receiver at the opposite side of a pipe diameter. A strong echo is received with low % solids or density, but as the density or % solids increase the sonic energy is absorbed by the particles and the signal weakens. However, the system suffers from it’s own modus operandi, since as the % solids increase typically > 10%, the signal to noise ratio increases to the extent that dynamic damping is required. Such damping is not the true average of the randomly dispersed noise, which can significantly affect accuracy.
Damping affects the response time to typically 30 seconds to minutes, which in turn can cause long term errors. Changes in the % solids or density are simply not measured.
The signal is also affected by high media velocity, which does not appear in manufacturer’s specifications.
Pipe sizes are normally less than 16″ (400mm). Larger pipes use insertion sensor techniques, but these are subject to rapid wear in mining and dredging slurries, with significant errors due to misrepresentation of variation in % solids and density of the media over the complete pipe cross section.
Under normal conditions accuracy is typically + – 1000 mg/liter to +- 5% of full scale, dependent on the sonic attenuation of the media and variation in % solids, and provided the media velocity is not too high. Additional errors and are due to the line of sonic waves across the pipe diameter being thin and not taking account of the variation in % solids either side of them. Prices vary considerably with manufacturers from about $5000 to $15,000.
By contrast, the DM3 measures a truly representative mass per unit volume of media, in length and diameter, interrogates it at 110 times a second, and has a response time of 45 milleseconds. The measurement is direct, not inferred, traceable to international primary standards and, in terms of variation in media density or % solids, nothing is missed.
6. What are SCIAM DM3’s long term cost benefits in reduced downtime and ‘green’ operation?
During the long term life of the its flow tube, DM3 requires no periodic downtime for maintenance, except an occasional on-site calibration check. This may be quickly achieved by running water through the DM3 in situ, without taking it out of the pipe line. No test weights are necessary, just a 3-second push of a DM3 transmitter button to automatically diagnose the complete system. If acceptable this revalidates DM3’s original calibration, uniquely and directly to international weight standards, such as NIST.
Compare this with a nuclear density gauge: Wipe tests are required typically twice per year and must be reported to authorities. This requires typically one hour per gauge. An annual site survey must be reported, typically one day, dependent on number of gauges, by a specially trained safety officer. The cost in a typical dredging or mining operation, including safety operators wage or fee, runs into $50,000 to $120,000 per year. At the end of the nuclear gauge life a nuclear source disposal fee normally runs into $10,000. Calibration is inferred, not traceable; the nuclear gauge should taken off-line, cleaned, and down time is additive cost.
7. How does SCIAM’s DM3 compare with a nuclear density gauge?
DM3 brings a refreshing change to measuring the density of mining and dredging slurries, retrospectively only done by nuclear gauges. Unlike nuclear devices, with DM3 there are no wipe tests, no governmental surveys, no costly safety officers, no possible health hazards, and no costly transport or disposal of nuclear sources.
DM3 interrogates mass per unit volume at 110 times per second, bringing a response time of 45 milleseconds to any changes in the media density. In a mass flow system, this brings a new dimension of savings due to long term accuracy. A nuclear device has a response time often in minutes, meaning significant lost data, which in turn could result in tens or thousands of dollars per year in lost revenue.
A nuclear gauge measures just a thin ‘slice’ of the media, both across the pipe diameter and longitudinally. This is hardly representative of the media, meaning much of the true density is not measured. By contrast, DM3 interrogates a truly representative and continuous sample, accounting for density variation across. the complete diameter and several feet in length of the media. DM3 also measures uniquely every 9 millseconds, and nothing is lost.
DM3 has a direct measurement of mass per unit volume, traceable to international standards, such as NIST and Canadian Weights and Measures. No special test weights for on-site calibration are necessary. Just a 3-second push of a button diagnoses the system and revalidates the original calibration in-situ. Nuclear gauges infer density by measurement of nuclear radiation, are not traceable and should be removed from the pipe line, thoroughly cleaned, and calibrated, with costly down-time.
8. Why gum rubber?
SCIAM’s obstruction- less rubber flow tubes are designed for long service life when used with highly abrasive dredging and mining slurries. The flow tubes are a customized composite structure, typically 1” (25mm) thick. They have a ½” (13mm) thick liner of gum rubber, while the outer structure is of a harder rubber, reinforced with multiple weaves of polyester. This allows the flow tube to be flexible so that the weight of the slurry passing through it is readily transferred to the density transducer measuring its mass. We say measuring mass because the SCIAM system accounts for variation of gravitational force at different parts of the world. Yes, the SCIAM system is that sensitive.
Inside the DM3 the rubber flow tube is supported by the density transducer. In operation the flow tube and density transducer movement is just a few tenths of a thousandth of an inch (a few microns) for a full scale change in density. As such, it is virtually solid state performance.
The gum rubber is natural and offers superior wear resistance, even with the highest velocities at which today’s mining and dredging slurries are pumped. The gum rubber has been successfully used for years when handling dredging slurries, abrasive rocks, sands, coal, tailings, fly ash, lime, clay, cement, as well as slag and many other materials. The high demands of the mining industry are successfully met when measuring highly abrasive iron, copper, platinum, bauxite, gold and other metallic or non-metallic ores.
Gum rubber is an elastomer. While steel or ceramics present a rigid surface to the particles and larger solids of a slurry, gum rubber has the huge advantage of having the highest possible resilience. The kinetic energy of pumped slurries eventually generates cracks and deformations on a rigid surface, compromising its service life. By contrast, the internal surface of SCIAM’s gum rubber locally deflects on the impact of slurry particles, ores, stones or rocks, and absorbs their kinetic energy. The localized deflection of the gum rubber then returns to its original form. The outer polyester reinforced harder rubber construction ensures integrity, even at high static pressures. Vibrations due to ‘pink’ media noise, as well as pumps, rock crushers and other machinery in the vicinity are simply absorbed by the SCIAM flow tube and by the low natural frequency of the DM3 itself.
The angle at which particles, ores, stones or rocks strike the inner diametrical surface of a flow tube is decisive in determining its wear. Laboratory tests and practical experience show that gum rubber is more resistant than other materials when the impact angle is less than 5º or greater than 50º. With mining and dredging slurries, the angle of impact is normally significantly less than 5º, and often close to 0º. The carrier liquid is almost always process water, which has no corrosive effects on the gum rubber, but rather acts as a lubricant, further extending service life to many years.
9. What ensures the DM3′s durability?
The DM3 contains a flow tube of proven durability when mining, dredging and similar abrasive slurries pass through it, even at high velocity. The flow tube is a composite structure and comprises a inner liner of natural gum rubber, typically 1/2″ (10mm) thick, which is soft and allows sharp particles or rocks to simply bounce off it. Gum rubber has been shown to be the most effective in terms of longevity and cost effectiveness. The outer structure is of a harder rubber reinforced with several layers of polyester ply. A metal spiral molded in over its full length allows for high pressure or full vacuum applications.
10. How often does the DM3 require maintenance?
SCIAM DM3 has no moving parts and is virtually solid state. A service life of decades could therefore be reasonably expected. However, the flow tube, which is replaceable on-site, may have to be replaced typically after 5 – 20 years, dependent on the media passing through it. On-site calibration may be performed, typically between 3 months and 1 year, dependent on how critical the application is. However, this is performed by simply running water, or whatever the carrier liquid is, through the flow tube for a short time. At the press of a button on the SCIAM transmitter, not only is the calibration verified and traceable to NIST and other international standards, but the complete system is diagnosed. No test weights are necessary.
11. How often does the flow tube and/or load cell need to be replaced?
The flow tube is typically replaced every 5 to 8 years on dredging, mining and similar slurries, dependent on its abrasiveness. However, with a clay slurry application the flow tube may well last 20 years. There flow tube can easily be rotated which also extends the life of the tube.
12. Reducers & Expanders – When To Use
Reducers and expanders are sometimes connected to a SCIAM density meter for use with a downstream magnetic flow meter or the customer’s downstream pipe. They are flanged spool pieces, normally having the same flange sizes each end of a tapered flow tube, and normally lined with polyurethane for good service life. They are offered by SCIAM for 2 basic reasons:
13. Rules for Selection
- DM3 Inlet:
- Knowing the customer’s pipe internal diameter (ID), select the same or next size up DM3 ID.
- Example : Customer’s pipe ID is 425 mm. Select an 18” DM3 (ID 18” = 457mm).
- This avoids using an expander or reducer at the inlet of the DM3 and will not cause measurement errors.
- DM3 Outlet Into Customer’s Pipe (No Magnetic Flowmeter):
- If the customer’s pipe ID is arithmetically less than 0.3” (8 mm) of the DM3 ID then a reducer is advised. It will have the same ID as the DM3 one end and the same diameter as the customer’s pipe ID at the other end to provide smooth transition.
- DM3 Outlet Into A Downstream Endress & Hauser 55S Magnetic Flow Meter:
- For DM3 ID sizes 2” (50.8mm) to 12” (305mm) the E+H 55S mag meter has virtually the same size as a DM3, No expander or reducer is necessary.
- For DM3 ID sizes 14” (356mm) and larger use the next size larger 55S mag meter with polyurethane liners and next size larger for all sizes of 55S mag meters with natural rubber liners. The errors will be negligible up to 24” 55S mag meters without an expander.
- If the ID of the E+H 55S mag meter is arithmetically greater than 0.5” (13mm) of the customer’s downstream pipe ID, then a reducer is advised. This will have the same ID as the E+H 55S one end and the same ID as the customer’s downstream pipe ID at the other end to provide smooth transition.
Apply the same rules based on ID when dealing with magnetic flow meters other than E+H.
14. Is the DM3 the only product SCIAM will manufacture?
Future density meters will be developed for high pressure shale oil applications, with pressures up to 15,000 psig (1000 bar g). Also density meters specifically for the food, oil and aree currently being developed. New to the market is a SCIAM Density Meter used in series with the CiDRA SONARtrac flow meter. This provides for the first time a mass flow system for slurries containing entrained gas.
15. What are SCIAM’s plans for the future?
SCIAM’s plans for the future is to extend its manufacturing base world-wide to provide ‘green’ density and mass flow systems to a wide range of industries.