Competitive advantages of BTG Rotating Consistency transmitter type MEK-2300

Competitive advantages of BTG Rotating Consistencytransmitter type MEK-2300 Ingemar Jansson BTG Pulp & Paper Sensors P2007en © BTG 2003 some typical applications where it shows specific advantages over other instruments. All data that are stated here are generally based upon practical and theoretical studies obtained in a laboratory environment. And why it Provides the firm foundation for optimal process control. It covers the MEK-2300 Rotating Consistency transmitter section of this presentation. It will show that MEK-2300 is an "Unrivalled transmitter for the most demanding and difficult applications.075%" for the active blade transmitter MBT-2300. based upon theoretical evaluations and practical experiences. © BTG 2003 2 . produced by BTG or some other company. A description of it including its competitive advantages compared to other transmitter types and 3.Competitive advantages of BTG Rotating Consistency transmitter type MEK-2300 This paper is based upon BTG Consistency seminar slide presentation available from BTG. Provides the firm foundation for optimal process control. Unrivalled transmitter for the most demanding and difficult applications. Consistency transmitter MEK-2300 Rotating shear force consistency measurement provides: • High accuracy • Safe operation • Universal use Presently still the safest and most accurate method to measure and control consistency Consistency transmitter MEK-2300 Fig 2: Rotating shear force consistency measurement. Background for the transmitter. Then you extract a large number of lab samples in a very controlled way and evaluate the result in the lab also using very controlled conditions etc. The Paper: The paper is divided in 1. The data stated in the data sheets are basically fully sufficient for all applications. It can measure between 1-16% consistency.. conductivity. the flow velocity. When studying the data sheets for different kinds of consistency transmitters. pressure etc. independent on what transmitter you study. you must understand what a data sheet really says. I. At such a laboratory test you try to keep all variables as controlled as possible to focus on the specific data you are looking for. the temperature. if you are trying to find the data for "Sensitivity" you use one specific kind of fiber at a specific consistency and freeness level. comparing them against each other. Fig 1: MEK-2300 Rotating shear force measurement. air content. The data are probably fully correct and can be trusted. Looking on these data you see that there is no major difference. how can you trust these data and use them in a real specific application? In the specific application/position you probably have a lot of variations in the pulp suspension. The fiber type. The result • Background P2007en • Product description • Applications Fig 3: Background. Applications. This paper will discuss these differences.005% consistency" for the MEK-2300 rotating transmitter or "+/-0. Introduction: The MEK-2300 Rotating consistency transmitter uses the shear force principle. It's a complete family with different variants specified for most applications in the P&P industry. Product description. Applications. Most probably you never have laboratory conditions in this application and you will see distinct differences between the different models. Rotating shear force measurement 1-16 % Consistency Before discussing all competitive advantages and details for the transmitter it is very important to understand some basic facts.e. controlling the temperature and the flow velocity etc. but are normally only valid during the specific test conditions. Consistency transmitter is then statistically evaluated and finally you obtain a figure like: "better then +/." The paper will also describe why MEK-2300 still provides the most accurate. 2. safe and reliable consistency measurement on a general basis although new measuring principles have emerged over the years. all may change from time to time. for all transmitters! MEK-2300 Rotating shear force measurement The question is.0. The mechanical design of the drive part was simplified using a belt driven system instead of an oil-filled gearbox. It was an in-line transmitter using a rotating sensing element to achieve high sensitivity and accuracy and a propeller to avoid the impact of flow changes. the electrical model gave a more accurate measurement. In the mid 50´s the K22 model came. 3 © BTG 2003 P2007en . In the mid 70´s the MEK and MPK-41 model came. resulting in a lower sales price. The model was produced between 1974 and 1984 and also here several thousands of transmitters were sold. the transmitter was cheaper and the MEK-41. Källe. was the dominant player there with their rotating transmitter. At that time DeZurik. Källe understood that you have to avoid the impact of different flows and he implemented a pump in the system to create a stable flow. although the details have been refined by time. Models over the years. The first model was developed in the late 20´s by the former of the original Swedish company AB Källe-Regulatorer.2000 Fig 4: Rotating shear force Consistency transmitters. In the early 60´s the K30/K31 model was developed. The first model was quite simple and it was a kind of predecessor of the later static blade shear force transmitter. was the base of the project to develop an improved model. the MEK-2000 (electrical output signal) and the MPK-2000 (pneumatic output signal) models including their many variants for specific applications. Pneumatic controllers were very popular at that time so the most common transmitter type was the pneumatic one. Background for the transmitter: See fig. no open vessels anymore. Thousands of units were sold all over the world. a record hard to beat. Rotating shear force Consistency transmitters. The model however suffered from maintenance problems mainly relating to the stuffing box for the rotating shaft. A need to increase the reliability of the transmitter and decrease the maintenance cost at the same time as the measuring accuracy was maintained. or preferably improved. Many targets with the project were reached. Models over the years and e 20 I n th 30´s he In t s 50´ In th ´s e 60 K31 K3 The K31 model was economic and easy to find a place for in the piping system since it could be fitted close to the pump. although the transmitter is completely different in its design. Many models have seen the light over the years.Let´s start with 1. It was originally made in a version to fit the Källe hydraulic controller but later on modified to provide 3-15 psi pneumatic output signal and 420 mA electric signal. The weight was reduced from 60 to 40 kg and the target was to make the transmitter less costly to produce. It was used together with the hydraulic controller tied to the dilution valve to form a simple easily maintained control loop. introducing a simple and reliable way to control consistency. Dr. Eur-Control which was the name then. It opened up the world market to the company. It introduced the company. also developed by Dr. It was recognized by its reliability and many units have been working in the field for 20-30 years. to the large American market and became an immediate success there. This is the principle still used in the BTG rotating transmitters of today. an American company.Torsten Källe. The measuring principle developed for the K30 model is the one still used for the BTG rotating transmitter. K22 In the 80´s In the 70´s MEK . The K22 model became a large success and was produced in large numbers for 30 years. Already at that time. At that time the transmitter was used together with the hydraulic controller. Dr. 4 Rotating shear force. By time the mills closed their process. BTG is one of the pioneers making consistency transmitters. The measuring principle from K31 was the same but the design of the transducer for the electrical model was considerably modified to give a more reliable signal. and a new in-line measuring principle was required. A complete consistency control loop was introduced. connected to a control valve for the dilution water. Patents were granted. Close to 10 000 units have been produced between 1984 to 2001. from 1992-2002.e.e. i. With different measuring ranges you can calibrate the transmitter to read very accurate even if you change fiber grade or type etc. They are known for their very high reliability and good measuring properties. Then you first have to understand how the transmitter operates and why it's designed the way it is. and not only at the control point. The output signal can be linearized. the "intelligent" MEK-2200. This is one of the fundamental reasons what makes BTG the leading consistency company. All transmitters are then fed with 24 VDC from a junction box with a common design to fit all models and using a handheld terminal for their setting. This resulted in a new model. They are all inferior in all respects. If you include the older rotating types over 30 000 units have been sold over a period of more than 80 years. P2007en © BTG 2003 4 . The difference to the -2000 is a different electronics unit. You should not equate this method with other shear force measurement principles used. MEK-2000 had an analogue electronics.e.The pneumatic controllers had become more and more outdated and replaced by electrical controllers or even DCS. The need to decrease the sales price and to simplify for the user resulted in the BTG Smart family where all consistency transmitters and also other kind of transmitters were coordinated. why you are able to use it almost everywhere in the process with a good result and in what specific applications it brings an added value. you can sleep well at night! 3. The rotating shear force principle is a unique principle. No worries. i. We will not describe the function of it in this context. Let´s now continue with the Product description. The MEK-2300 model came in 1995 and in the beginning it used a simple junction box (type JCT-1000). why it is able to work well over a very long time of operation and still keeping its high accuracy. in the service manual etc. The user interface is very similar for all the instruments resulting in an easy training procedure and great user friendliness. which result in an accurate measurement over the entire measuring span. The product: The MEK-2300 model is distinguished by 1. High measuring accuracy. Totally from 1984 to 2002 close to 15 000 units in the series starting with MEK-2000 and ending with MEK-2300 has been sold. Consistency transmitter MEK-2300 • Almost 15 000 units installed – MEK-2000 series • Over 25 BTG transmitter MEKMEK-2300 Consistency range: 1-16% • Very high measuring accuracy and repeatability • Universal transmitter suitable for most applications • Very high reliability minimizes need of maintenance Fig 6: Very high measuring accuracy and repeatability. 2. See fig. so the MEK-2000 became the most popular model. is mechanically very similar to the early produced units although numerous modifications have been implemented over the years. Universal use I. Several thousand units have been sold. Safe operation. 7 Measuring principle 000 units installed – all models • Installed in Most Mills – All over the World Proven product – Proven benefits – Proven process savings . the control box mounted on the wall. which will be proven in this paper. but to increase the measuring accuracy a digital electronics can bring considerable advantages.Proven profit $$/££… Fig 5: Number of installed units over the years. These models became a very large success for BTG. The Junction box is mainly a box where the connections for all cables and handheld terminal are made and also a convenient place to fit the power supply. in parallel to the MEK-2000 model. We will just touch the benefits of the design. MEK-2300. High measuring accuracy Let´s discuss the High measuring accuracy properties. The present model. This model was produced. its general design properties and ability to handle disturbances of the measurement. All limitations are known and you know that you can trust the measurenent. In year 2000 this junction box was replaced with type JCT-1100 where a display and pushbuttons for simple settings was introduced together with a new surface mounted digital processor card in the transmitter. it is very different from the measurement made by blade transmitters or even by other types of rotating transmitters. it is already described in the data sheet. As you can see from the description of the measuring principle. We compare MEK to blade and optical transmitters. i. The signal-to-noise ratio shows the quality of the measurement signal. and no such components needed that may fail and disturb the consistency measurement. high signal-to-noise ratio and physical measurement: The sensing element is rotating by its own force independent of the flow velocity in the pipe.). This is partly a result of this fact. Consistency transmitter Measured relative volume Rotating: 100 MEK-2300 Blade: 20 Fig 8: Measured relative volume 5 Optical: < 1 Due to the rotating motion of the sensing element. More of this discussion later. the larger is the possibility for measuring on a representative sample! With MEK it is less critical than with other transmitter types that the pump is a good mixer of the dilution water (which it seldom is). It means that the measurement will be more stable and accurate using MEK. You can see that MEK measures on a five times larger volume than a blade transmitter does. It's the forces created when separating the fiber network because the sensing element is cutting through it (together with drag forces acting on the side of the sensing element). particularly for static blade type transmitters. There are no additional sensors (for compensation) needed. © BTG 2003 P2007en . Consistency transmitter MEK-2300 Measuring principle Difference in light opening 450 rpm Provided that the transmitter is fitted into the pipe in a correct way. it will be virtually unaffected by flow changes in the pipe. the sample volume you measure on is five times larger. supported by the propeller. why not just measure this angular deflection using a force-movement type of system. it will be protected from foreign objects like stones or pieces of metal or lumps of thickened pulp. The pulp is mixed by the propeller and pushed to the sensing element. It is commonly known that blade transmitters often show unstable signal resulting in a need to use a high damping (filter time). which results in a slow and inaccurate consistency control. Compared to static blade transmitters it has been found in independent tests that the ratio for MEK is approximately three times higher. fiber length. nuclear and certain optical types. It is very important that you really measure on a representative sample because it will have a direct impact on the measuring result. flowing into the pipe at certain occasions (start-up or shut-down etc. Also type of fiber. freeness. amount of fines etc. You can say it reflects how much of the measurement signal consists of non-desired background noise and how much the actual consistency signal is. the signal quality of MEK relies on direct physical measurement properties. high sensitivity to fiber consistency.e. but only to the fiber consistency! Compared to blade transmitters this fact is very important when measuring at lower consistency levels due to the higher shear force acting on the sensing element. Compared to measurement methods like microwave. double the normal pipe flow velocity.5% depending on these factors. Representative and stable measurement: Looking on the part of the transmitter located into the pulp stream you find a rotating sensing element and a rotating propeller. Generally spoken you should not use a blade transmitter on a consistency lower than 2-2. will have an impact. The figures are relative to each other and no absolute values. also in this respect MEK provides a more representative measurement. the transmitter will also be very sensitive to consistency changes. No other transmitter type has this advantage and flow velocity problems are very common.e. but also for rotating transmitters using different measuring principles and sometimes even for certain types of optical transmitters. we measure the angular difference between the two shafts when a force created by the fibers in the pulp suspension acts on the rotating sensing element. Its outer speed is typically around 5 m/s. while the MEK can be used down to 1-1. inside the pipe wall. The larger the sample is.5%. Accurate and long-time stable signal transducer: MEK uses the force-balance principle with a built-in electro-magnetic feedback function. 8 you see a comparison of how large portion of the pulp volume in the pipe you are measuring on. It is also fed by its own flow. The higher this level is the higher the quality. Force balance transducer with feed-back function 4-20 mA /HART Fig 7: Measuring principle. accurate and reliable measuring method. Protected sensor: Since the sensing element of MEK is located in the measuring chamber. If you study fig. MEK provides a straight on. which may need their own calibration. Static blade transmitters are often mechanically damaged while MEK very seldom is damaged due to these reasons. They both rotate with the same speed. why use a complicated force-balance system? The reason is that we are looking of achieving very high accuracy and sensitivity and long-time stability of the transducer system. i.Flow independent. So. There are no complicated compensation algorithms needed for MEK. independent of the pipe flow velocity. Then you may ask yourself. shown in % consistency. Consistency transmitter Fiber and grade dependence MEK-2300 Output (%) Consistency transmitter MEK-2300 Specific features MEK-2300 • Representative measurement: Measure on a large sample. Fig 10 is one proof of that. Valmet Automation Fig 10: Flow dependence P2007en Comparing a static blade and MEK.3%. like the lab sample does. Temperature: Normally very small . an error of 0.) and thus a very good long time signal stability of the system.virtually negligible pH.high quality Cons. The test shows the actual consistency deviation. fig 12. Fig 11: Fiber and grade dependence MEK-2300 Multi-point calibration for maximum accuracy Gives best measurement and control result . you find that instead of showing 3. As we concluded earlier. to mechanical groundwood with short fibers and a low network strength. Fillers: None (If total consistency is required compensation can be made) • Signal quality: Signal damping and filtering: Very low . (%) • Calibration: Single sample or preset calibration for quick start. from a CTMP pulp giving a very strong fiber network and thus very high shear force. Since MEK-2300 has four different measuring ranges it can however be individually calibrated for each pulp type and thus avoid this problem. The signal resolution will improve as well as the signal-to-noise ratio.Using a force-balance system you can work with very small movements of the mechanical parts and thus obtain a very high sensitivity. at the same conditions. MEK will have certain sensitivity for different fiber types and different pulp qualities. Fig. i. Flow velocity : Very small . Fiber type.3%. freeness < 200 ml E = Groundwood J = Recycled fiber (OCC) K = Recycled fiber (newsprint) Reference: Valmet Automation Fig 12: Fiber and grade dependence Ref.in most cases negligible (can be compensated if large changes) Pressure. Kappa No.high quality Response time and deadtime: Very short . Air.5% consistency. changing from a kraft pulp to a mechanical groundwood pulp and imaging you try to control consistency to 3% you can see the result in fig 13. the transmitter shows 3. Conductivity. The MEK does not show any error! Comparing to a static blade transmitter you can see that the deviation is much larger than for MEK. at a typical consistency level: 3. but please compare the relative difference between different fiber types.75 %. The fiber types are not identical but it still gives a clue. MEK is virtually unaffected by flow changes.e. You will also simultaneously obtain a compensation for aging of components (rubber parts etc. freeness > 200 ml F = TMP. The next figure shows how different types of fiber qualities influences MEK.good control ability Signal-to-noise ratio: Very high . and imagine that you change the flow velocity from 1 to 3 m/s. Freeness. If you compare the two figures you see that for MEK the difference around 3% consistency is just above 0. a small consistency change will give a large signal difference.at almost all applications Fig 9: Specific features MEK-2300 How disturbances will affect measurement. © BTG 2003 6 . Static blade transmitter Fiber and grade dependence G = TMP. 9 is a summary of all the specific features for MEK-2300 also including how sensitive it is for disturbing factors.45% consistency or approximately 14%. If you compare to a static blade transmitter (type A = common type). The shear force is here shown in force N (Newton) acting on the sensing element.5% consistency while it for the blade transmitter is 2. mixed and separated from main flow: Very good • Sensitivity for disturbance factors: Grade. This will be further discussed and proven in the next section: Universal transmitter for most applications. Here you have very different pulp qualities. "optical reflection" (BTG OCT2300) is overcompensating. Metso claims that their MCA measures the total consistency. First you have to understand what "Total consistency" really means.1% consistency. Fig. Fiber composition: 83% mechanical groundwood. microwave transmitters measure close to total consistency. comes from a test made at BTG R&D. static or active. The idea was to start with a 3% consistency pulp and then just add fillers and observe the consistency reading.10 = 3 = 3. Naturally if you just add fillers. Both MIC-2300 and MCA have a possibility to implement a compensation for different filler types and thus partly avoid the problem. MEK is a fiber consistency transmitter. Ash content (= filler consistency) is 30 %. at least for many applications. 15 Influence of fillers.9% consistency. MEK-2300 Fiber and grade dependence Consistency transmitter Influence of fillers Cons (%) MEK-2300 Groundwood 3. Fig. 17% Hardwood kraft. 15. fig.14 "What does Total consistency mean" The next figure. What does Total Consistency mean? mean? MEK-2300 Consistency transmitter Feedback % Signal % Influence of fillers Total Consistency [%] = Fiber Consistency [%] + Filler Consistency [%] Feedback % B-sensor. calcium carbonate.e. fig. cons. while all shear force transmitters show a very little influence. however.62 = 2.MEK will show 0.3% 3 Microwave MEK-2300 vs. 14 explains this. 10% Hardwood Kraft + 50% Groundwood + 40% Fiber coatingconsistency clay % Fiber Consistency % Example: Total consistency is 3%.9 = 2. Generally you can however say that.13 Fiber and grade dependence MEK Another influence on the signal accuracy is the content of fillers of fines. Fig. 7 B – sensor. the total consistency will increase which is illustrated by "lab. Common type Statical blade transmitter Rotating sensor Active blade Static blade MEK-2300 is much less influenced of changes in furnish Fig.". just the fiber consistency. So. As can be seen.9% instead of the correct 3% while the blade shows 2. Competition claims that their static blades are just as good as an MEK but this is one of the proofs that it is not! Please note that this error does not only apply when changing from one specific pulp type to another. This is where perhaps 90% of all microwave transmitters have been installed and thus replaced or beaten MEK at a project. Coating clay added KR = Sulfate Kraft Optical reflection GW = Mechanical groundwood Lab. only part of it. an actual consistency error of 0. i. does not need compensation and is the only transmitter that really measures total consistency.4% 3-2.62 0.0 m/s Temp 300 C.62%. 2.62 = 16. This is not correct! Different filler types give different result.38 2. This is a fact that is not commonly known. titanium dioxide etc. also changing or having different blends or fiber type (raw material) or changing the freeness level will have the same relative impact.cons/ Optical Peak method Blade Rotating 3-2.0% Flow 2. it's the same in this respect. are these applications proper for and safe for microwave transmitters to be installed at? © BTG 2003 P2007en . BTG TCT-2300. i. a four times larger error for a blade transmitter. Consistency transmitter The microwave transmitter (MIC-2300. This means Filler consistency is 30% of 3% = 0. Metso MCA or Toshiba) does not measure the total consistency. For total consistency measurement a compenstion can be made. Increasing level of fillers (coating clay) Filler content % MEK-2300 does not sense the fillers. Typical filler components are china clay. Typically it measures around 60% on the filler.e. 16 Influence of fillers MEK The most common applications where the question if the transmitter measures total consistency or not. different measuring principles A later made test.38% that is almost four times larger than for MEK. only the fibers. If the filler type varies you cannot compensate for it unless also different measuring ranges are used. correctly adapted. To be able to compare the result between the different measuring principles all results were recalculated to show the absolute consistency deviation expressed in % consistency.1% difference. applies for broke chest. Fiber consistency is 3 – 0. they all mainly measure the fiber consistency only.90 0. 16 conclude that MEK does not sense the fillers. Filler (%) Fig. mixing chest and machine chest. part but this varies. 18 shows an MEK installation in Finland at machine chest where they use TMP pulp and add fillers. Naturally it has been proven that MEK doesn't see the fillers. but it can be much more. Fig 17: Influence of air. pressure and conductivity. For blend. MIC2300 has here an advantage over competition since compensation possibilities are implemented. but so far without success. however. either tied to the fibers or in the form of air bubbles. 17.pipe pressure 1. is that it is sometimes not possible. mixing and machine chest applications. Conductivity is not usually a problem close to the paper machine. Generally. They also become solved in the water with increasing pressure. or even 20% can occur in practice if the process equipment is not arranged in a suitable way so that air can enter. but sometimes acid is used for pH adjustment and sometimes different dyes can make an impact. the signal becomes too much dampened and it's impossible to measure anymore.8 bar pressure. You can make compensation at higher levels but since the compensation also depends upon the media temperature. Microwave transmitters are very sensitive for air in the pulp.5 bar pipe pressure. 10%. Difficult to compensate at lower levels. Other customers have said they even need 2. they would both have been included in one signal.First you must be aware of the general features between the different principles in this context. At the machine chest they have had problems and were forced to install a larger pump. 20. This is valid if the air content is not too high. pressure for a microwave transmitter to avoid influence from the air content to the signal accuracy. Close to the paper machine the air content is typically low. the higher the pressure. MEK-2300: • Not influenced by air content • Not influenced by pipe pressure • Not influenced by conductivity changes Microwave and Nuclear transmitters: • Inapplicable at high air content • Must have a min. pressure and conductivity Fig. MIC has a relatively short distance and is thus less influenced. Knowing the fiber content in the paper is of course also an important issue. Of course. Using a microwave transmitter here they wouldn't know how large the fiber and how large the filler content were. MEK however on the other hand.5 – 2. this all depends upon the air content they have. the measuring principle cannot be used. the compensation is difficult.2 bar line pressure to be able to use microwave transmitters. the signal damping increases with distance between the antennas. but in this case the mill only wanted to measure the fiber consistency. So which transmitter type should be used here? The answer is naturally: you must investigate the actual measuring conditions. This may be the reason why microwave transmitters often operate well here. P2007en MEK-2300 installed at mixing chest at leading paper mill in Finland • Accurate control • Measures fiber consistency • Not dependent upon air content and pipe pressure • No by-pass. but what is an acceptable level? Do you know how much it is for the application in question and are you sure it doesn't increase abowe maximum at certain occasions? Is this a safe and reliable measurement? Will it have an impact on the paper machine runnability? There are many uncertainties. the choice is not obvious without doing that! MEK-2300 Influence of air. to increase the pressure and thus avoiding the problem. fig. We know that attempts have been made to compensate for it. is not dependent of the air content. claim they need 1. The major user of microwave transmitters. but then how much does this add to the energy cost. a Swedish mill. and controlled. they are not interested in measuring the total consistency with the consistency transmitter. see example fig. This is also true. typically around 3%. One problem. installed in-line Fig 18: MEK-2300 installed at mixing chest at leading paper mill in Finland © BTG 2003 8 . Pulp always contain a certain amount of air. Thus you need a certain min. Also here MIC-2300 has an advantage over traditional flow-through models. with reasonable efforts. The larger the pipe size (using flow-through models). microwave transmitters have an advantage over MEK in regard to their ability to closer measure "total consistency" as well as their ability to more closely measure consistency if fiber quality changes. the larger the difference is. the pulp contains too much air. They have a retention analyzer and thus they find out the filler content and can calculate the total consistency. 1. This is true. The size of the air bubbles depends upon the line pressure. If the conductivity exceeds 10 mS/cm. the smaller they become. this is their main disadvantage. microwave transmitters should not be used where there is a conductivity > 3 mS/cm. pressure and conductivity Air is present in the pulp in two forms.2 bar • Can not be used at high conductivity levels. According to information from all companies supplying microwave transmitters the general rquest is min. MEK was not stable enough at the worst operation cases (short fiber recycled combined with high. It is for one typical case.2% consistency. 24 shows major product improvements since the MEK-2000 model was introduced 1984.5 100000 KW Cent/ 3. The data looked very good. an expensive and maintenance-demanding solution. Low pressure and too high air content is the main reason.54 per Kwh. MEK performed very well. 20 shows the economical impact on such a measure. This cost should be added to the increased cost of the microwave (or nuclear) transmitter compared to MEK.55 fps) Operation: 8000 h/year 150000 W /K nt Ce W 08 K/K .5% or more. but because of low shear forces due to bad fiber quality (recycled) and high filler level (30%). © BTG 2003 P2007en . level etc. Competitors claim that the transmitter is unreliable and will cause high maintenance costs. but the result would have been equal to any other brand. Would you really be able to sell a transmitter during so many years and in so many examples if it causes excessive maintenance? The answer is naturally not. Naturally the MEK fixed the problem and worked perfectly. Compared to microwave transmitters it cannot measure total consistency and is more sensitive for fiber property changes but it is not dependent of air.5 2 [bar] MEK is not influenced by air / pulp pressure and conductivity like nuclear and microwave consistency transmitters = Higher accuracy and Reduced costs Fig 20: Cost influence on pump pressure increase Conclusion: Summarizing MEK features regarding its ability to measure accurately and reliably and its usage for most applications you find that MEK provides very small or no sensitivity to most disturbance factors that can occur. it's a false statement! Since the transmitter is the 7th generation since the 60´s. most accurate and reliable choice. 9 The MEK-2300 transmitter is a mechanical transmitter with many components.8 m/s (0. Generally MEK is the safest. when the operating conditions are unsuitable for a microwave transmitter the result is often very large consistency deviations. all weaknesses have been found and the transmitter has been continuously refined ever since . reliability and simplify for the user at the same time as the reliability increases and the maintenance demand decreases. 23. you see that the yearly increased power cost is approximately USD 8. This case also showed another observation. Is this true or just an attempt to attack a competitor? Previously we concluded that the transmitters have been sold in nearly 15. filler level and large flow changes). At another machine chest application in China we tried our microwave transmitter. Also MEK has its limitations.000. in the German case described above it was around 0. Microwave transmitters can only be successfully used for a very limited amount of applications where the conditions are well controlled while MEK works mostly anywhere in the mill. large consistency errors. 0. Due to the stuff box design the pressure could not be increased to reach proper level and the transmitters thus performed badly. Fig. pressure and conductivity changes. high pressure far above min. 13 SE 1 /KW ent 4 C Kw 6. Fig 19: Microwave transmitter installations As mentioned earlier you must sometimes increase the pressure to be able to use a microwave transmitter.5 SEK/ 0. Still the transmitters don't operate fully satisfactorily. The transmitter however failed badly. Later on it was proven that TCT-2300 gave the best result at this particular application. In many other applications of this kind it has been proven that MEK works much better than microwave transmitters and many of them have been replaced by MEK.5 / UScent 6.27 EK/Kw 0. Consistency range: 1-16% • Very high measuring accuracy and repeatability • Universal transmitter suitable for most applications • Very high reliability minimizes need of maintenance Fig 21: Reliability and Maintenance Transmitter design and maintenance questions Microwave transmitter installations at mixing and machine chest. For those interested fig. If you then need to increase the pressure by 1 bar. Recently we replaced two competitive microwave transmitters at the machine chest in Asia. As can be seen they were forced to install separate pump loops just to obtain correct pressure for the transmitters. For MEK the deviation in unsuitable cases is mostly much smaller. rec. 19 shows competitive microwave transmitters installed at a German mill.Fig. MEK was also later on tried here. often 0. All of these improvements are aimed to increase the accuracy.5 1 1.see fig.000 units during a long period of time. The answer to the problem was that the pulp contained a huge amount of air.5% and more.25 S 10000 50000 Pressure increase 0 0 0. It is more expensive than a blade transmitter but superior to them in all other respects. and changing. Imagine the power costs SEK0. Consistency transmitter Cost influence on pump pressure increase MEK-2300 Power cost increase/year m ∆ρ [USD] [SEK] ∆Ρ= η S 30000 200000 20000 Pipe size: 300 mm (12") Flow: 1. is required. corrosive media and atmosphere. Thus a metal bellows seal is used as the rotating shaft seal.All parts and material used in the design are optimized for the very demanding applications in the P&P industry.24: Major product improvements P2007en The shaft bearing arrangement is designed by SKF to obtain a lifetime exceeding 10 year´s operation during highest possible line pressure. It has tropical insulation and is wired to accept very large voltage variations. It is oversized four times in relation to the motor power. to be highly wear resistant. complement to hand-held terminal: 2000 Fig. Standard option is a 3-ph motor that typically gives the highest reliability but as an option a 1-ph motor is available to reduce the installation cost. Typical lifetime exceeds 10 years before a replacement is needed . It withstands vibrations very well. certain dry running operations and high temperatures. © BTG 2003 10 .The most critical parts to prevent failures are seals against the media. More in the paper mill and somewhat shorter in the pulp mill. that this is true. To our knowledge. well proven design Fig 23: Cutaway view Major product improvements MEK (from analogue model MEKMEK-2000) • • • • • • • • • • • • New electronics /MEK-2200: 1991 New transmission: 1991 New fastening of sensing element: 1992 New series of measuring vessel: 1994 New electronics /smart model MEK-2300: 1995 New Hand-Held terminal SPC-1000: 1995 New material Avesta 254 SMO: 1998 Single-phase motor: 1999 New Junction box JCT-1100/ Surface mounted card in tx. prestressed type angular contact bearings supported in a steel sleeve to obtain a very stiff shaft arrangement that is beneficial for the mechanical seal lifetime. The transmitter still worked without problems. The processor card located in the transmitter is of "state-of-the-art" surface-mounted type. if the Oring should leak after a long time in operation. It´s designed to withstand pressure shocks. it's a wide-voltage motor. Reliable.The motor is a special type. We also know that high media or ambient temperatures do not affect the transmitter.The electronics is uncomplicated in its structure to obtain a high reliability. Only for applications where the black-liquor content is very high another quality. High temperatures and vibrations are commonly known problems particularly for certain static blade transmitter types. a material next to diamond in hardness. In all normal cases it is only required to replace the low-cost O-ring on a regular basis as a preventive measure. EPDM. conditions that you hardly see even in the worst possible application. To protect from any possible leakage into the bearings they are protected with labyrinth seals. The wearing faces are made from silicone carbide. water has never penetrated into the bearings. The flexible sealing between the two shafts is in fact a dual seal. we know from all the installations as well as from tests made at certification institutes. corrosive media. It's designed to withstand high temperature. it's a very reliable arrangement. The bearings are permanently greased. Fig 22: Reliability BTG transmitter MEKMEK-2300 Consistency range: 1-16% . a special rubber bushing prevents any further leakage. Then we installed the complete unit into an oven and raised the ambient temperature up to 70ºC. but we have found that the average life time is over five years. When testing the transmitter we first inserted the wet part of it into 95ºC water.. As a back up. but it depends very much upon the application. excessive shaft run-out. high moisture in the surroundings etc. an O-ring made in specially developed highly resistant fluor-rubber to suit virtually all applications in P&P. Typically this is only required after 5-10 years of service. . The transmission is a modern timing type rubber belt. This also applies to the transmitter as a whole.: 2000 Adapted for Fieldbus and OPC: 2000 Preset Calibration curves: 2000 Windowsbased program. A mechanical seal is a wear item. This seal type is an exclusive type designed to be very flexible and sturdy. at the same time it can withstand large temperature shocks. in this case complete with a sampling valve. Fig 26: MEK-2300 installation photo Fig. PC-documentation software. The most important point is however its ability to bring a good consistency control. seals and the drive belt. but in many cases the actual cost for other types of consistency transmitters like blade or microwave types can be just as expensive. 25. This will be discussed later on. 27 illustrates a typical MEK-2300 delivery content. and sometimes even higher. an item highly recommended. which needs very little maintenance! Due to its design and the way it operates. Selecting the 1-ph motor and using the mechanical seal without water flushing can decrease the installation cost for MEK. 26 show a typical installation of the transmitter. a simple and not too expensive action. Fig. Competitors accuse the unit to be expensive and complicated to install.Based upon our vast experience we know that average time before the first maintenance requirement is > 5 years in continuous operation. the unit works very well also in practice! The MEK-2300 transmitter has three years warranty. This may me true. certain aspects upon how the transmitter is installed must be explained. depending upon the application and other factors that may influence. SLS-1000 lab sampler device. you must consider that it can be mounted close to the pump that is advantageous in two ways . Considering the way MEK-2300 is installed. For the consistency transmitter this mainly means that the water flushing system for the mechanical seal should be regularly controlled and cleaned if necessary. 27 Typical delivery content © BTG 2003 P2007en .fig. All of these actions are very expensive. Both of these possibilities can be used for most applications and reduce the cost considerably. This is an installation that can cause measurement problem particularly when the pump operates at low speed since the pulp/dilution water mixing then can become less efficient. complete with options. 25 Typical installation 11 Fig. This particular installation also proves this theory. Fig. a result partly depending upon its location close to the pump. Typical action then is to replace all bearings. various special service tools. MEK-2300 however measures on a very large sample volume and is thus less affected than other transmitter types. Test documentation • Options: SPCWin PC program. This is particularly true if you need to make special piping arrangement to decrease the flow velocity by installing a larger pipe to be within acceptable level (blade transmitters) or increase the pressure by installing a separate pump loop or replace the pump (microwave transmitters). We also know that the transmitter typically requires a major maintenance after 10-15 years in operation. Preventative maintenance is the key factor to minimize actual maintenance. From a user and maintenance demand point of view the location is important since the transmitter in most cases is easy to reach and handle. a proof that it is a very reliable unit. As we concluded earlier. Sometimes also the static blade transmitter needs a separate pump loop to have a stable velocity. Back-up card. These times given are average. Printer. etc. Still such a repair does not cost much more than to have a static blade repaired (not valid for BTG transmitters. In this photo you can also find that the pump is equipped with a variable speed motor. MEKMEK-2300 typical installation Typical delivery content • Consistency transmitter MEK-23XX • Junction box JCT-1100 • Optimal Control • Hand-held terminal SPC-1000 • User friedly • Measuring vessel or Weld-in stud • Easy to access – located close to floor level • Sampling valve type MPS-1000 or MCS-1000 or FVS-1000 • All settings made from hand-held terminal or Junction box • User manual and Service manual. individual units can operate for either longer or shorter periods. they can be more easily repaired). This typically means a replacement of the mechanical seal. The low-pressure vessel is specially designed to avoid any air being trapped at horizontal installations and also to avoid the risk of plugging at higher consistencies. 300 mm and larger. and materials. P2007en • Sampling valve included (option) Weld-in stud • Pipe size ≥300 mm (12”) • Inspection cover (option) B Fig 30: Mounting parts Low pressure © BTG 2003 12 . the rotating shafts and sensing element are quipped with a special protection.0 Basic type G H I % % J 120mm 4.1in Long Short 11 12 % % 18 18 % % Specially adapted sensing elements for all applications Fig 29: Sensing elements When connecting the transmitter to the pipe. 1/3 higher torque levels can be balanced to handle the high shear forces and these high consistency levels. Low pressure PN10 (150 psi) 10 bar/Unscreened 25 bar 25 bar Consistency: 1-16% 10 bar/Anti-spinning 25 bar/Unscreened Open flow box Materials: 316SS (std).5 Short 2.5 % % 1.3 0m in m Transmitter variants and its installation MEK-2300 Consistency transmitter 10 bar/Unscreened Mounting parts. Transmitters in pressure class PN25 have a thicker flange to handle the pressure requirements. The higher the consistency. PN10 or PN25.0 % Short 1. Special: 1-10% MEK-2310 MEK-2308 MEK-2311 MEK-2314 MEK-2312 MEK-2320 MEK-2315 MEK-2340 10 bar The sensing elements for MC are shaped like an S and developed to obtain good sensitivity and to minimize the flow sensitivity.8 % % 2.Designed for specific applications. Variants available in MEK-2300 series The size is selected to maintain a suitable working range for the feedback balancing system and to secure a stable signal combined with high sensitivity for consistency changes. left. 28 is an overview of available models. Basically an expansion of the pipe to 300 mm is needed when the pipe is between 100-250 mm. . Avesta 254SMO or Hastelloy C materials are then available. With "unscreened" pulp we mean pulp that contains large knots or foreign material like stones or pieces of metal that may mechanically damage the unit due to an impact. different materials.The medium consistency models for consistency 8-16% are available in combinations for screened and "unscreened" pulp and in pressure classes PN10 or PN25.8 0. Consistency transmitter MEK family. MEK-2308 is equipped to handle the tough conditions after a blow tank.3 C Medium consistency Upper limit 0.0 % 5. 254SMO.7in 150mm 6in 125mm 5in Fiber type Lower limit Upper limit Long 5 % 10 % Short 6 % 11 % Long Short 7 8 % % 12 % 13 % Long 100mm 4in Short 9 10 % % 14 15 % % 80mm 3. a weld-in stud can be welded directly to the main pipe. Compared to the standard transmitter.5 2. the design is different. It can even be installed at the wall of a chest. named MEK-2300. The transmitter can be used in a large range of applications.fig. MEK-2320 is designed to handle extremely troublesome applications after a recycled fiber pulper where large amounts or spinning materials like strings and plastic strips are present. For larger pipe dimensions. a special mounting arrangement is required . MEK-2300 STD: 1-10% MC: 8-16% MEK-2300 10 bar Consistency transmitter MEK-2300 Sensing elements Normal consistency Basic type A B Fiber type Lower limit Long Short Sludge (2220-2320) 18 m 5m in 7.The basic model.5-2 % 10-15 % Long 1. It is available in a range of variants. Fig. MEK-2340 is adapted for open vessels like for a "stuff box" and has very long shafts. This pipe expansion is called "measuring vessel".0 % % 8.5 % 6. 21 8. Hastelloy C Pressure class: 10 bar (std -150 psi) or 25 bar (360 psi) Measuring vessel Fig 28: Variants in the MEK-2300 series • Pipe size 100-250 mm (4”-10”) weld fitted (std) flange fitted (option) The sensing elements are specifically adapted for different applications. a streamlined model for PN 10 and a globe form for PN25. pressure class PN10. 30. an application where few other transmitters can work.The MEK-2300 transmitter is available in a large number of variants. The idea is to create a representative measurement and avoid any problems from hang-up. up to 1100 mm.or right-hand versions etc. and no shaft seal. To protect the transmitter. welded or flanged to the pipe.5 10. The MEK-2310 and -2312 models are often used in the bleach plant and then the wetted material must often be selected to handle the corrosive bleaching chemicals. the smaller the size is of the sensing element. Depending upon pressure. . . a "banana"-shaped steel bar. Basically the sensing elements are streamlined and shaped like a star for consistency levels up to 10%.5 % Long 1. is used in consistencies from 1-10% and at max. When making a step change. PN25/ANSI 300 (option) • Pipe size ≥ 250 mm (10”). i.Why is accurate Control important ? Consistency transmitter Mounting parts MEK-2300 High pressure version.. mentioned above. designing the Control loop". widening a production bottleneck to increase production rate etc.. Max. 25 bar at 226 °C (363 psi/439 °F) Available in 316SS (std). i. you should reach the new level as soon as possible avoiding oscillations. you tighten the distribution.In an automation dictionary dead time is explained as follows: © BTG 2003 P2007en . Setpoint Response and Regulation Fig 33: Why is accurate control important? A good process control can provide many advantages. By a tighter distribution (better and more accurate control) you can often be able to shift the set target..Recovery from Upsets 9Operating Flexibility Fig 34: Variability reduction Comparing Control ability for different consistency transmitter types: Even if you are only somewhat familiar with control issues you are probably aware of the "dead time issue" which is of central importance if you are aiming at designing a control loop. 34 shows what a good process control can mean at a bleaching stage in a pulp mill.. It is discussed in the general part of "BTG Consistency Control Seminar" and a specific paper is available. why does the selection of transmitter type compared to another one make an impact on the control result? This discussion may seem theoretical to persons used to the day-to-day problems but still it is of greatest importance to the result.e. the well working consistency control loop. can be the result. The consistency control loop itself is not discussed here. Thus consistency control is the basic parameter to control and a tighter distribution here is of greatest importance for the result! Consistency transmitter Typical installation Process Control Provides…. Fig. There are numerous examples why a better control is important. Also reduction of the energy consumption. in this case the consistency varies. 254SMO and Hastelloy C Tightened Distribution Measuring vessel Weld-in stud • Pipe size 150-250 mm (6”-10”) weld fitted (std) Flange fitted. You can perhaps use less amount of expensive fibers and replace with less costly or reducing the amount of expensive chemicals. By introducing a control (control loop) you may reduce the magnitude of the variations.. MEK-2300 Variability Reduction • Optimal Control Example: Bleachplant Control 9Increased Production • Reliable 9Chemical Cost Reduction 9reduction in variability • User friedly 9AOX Reduction 9Environmental Compliance Shift Target = $$$ 9Improved Pulp Quality Fig 32: Typical installation First you may ask yourself: Why is it important to have an accurate control and what are then the implications? Un uncontrolled process shows large variations. changing the controller set point to achieve a lower consistency. reduced costs or better product quality! 13 9Easier Bleach Plant Operation 9. Still the matter is explained in a very simple way compared to what you find in general textbooks available. Reaching the new level faster also means a tighter distribution! A tighter distribution means "money". 200 mm (8”) at suitable conditions Fig 31: Mounting parts High pressure Consistency control The next topic to discuss is "Optimal Control".e. This paper has been presented at Tappi 99 and is called: "Consistency Control. Provides…. The most important control in a pulp or paper mill is consistency! If you know consistency (and flow) you know how much fibers are present in the different process stages. It is also discussed in the book "Accurate Consistency". Sensor Location is Important! The largest dead time however mostly is the dead time between where the dilution water is introduced to the pump suction and the consistency transmitter. You often have to install it after a bend (one or several) on the horizontal section. on the vertical section.The open loop time constant (τ) is the time it takes for the signal to reach 63% of full value. are common and in such a case the recommended calming length is increased even further. For consistency control tuning it is recommended to use Td as the denominating factor (reference: EnTech / Emerson Process Management 2002 . At a certain distance after these disturbance sources the turbulence evens out and the flow seen across the pipe diameter is uniform. it's not on control and the controller is set on "Manual").Also multiple bends. . You have built-in dead times in the equipment involved (in the consistency transmitter.e. Factors that will influence dead time are: Consistency sensors are susceptible to … DEADTIME ________ Place them as close as possible to the dilution Fig 35: Sensor location is important .5 if the transmitter is installed on a horizontal pipe after a bend. © BTG 2003 14 . dead time is the time it takes from making an input change until the change starts to influence the process (or equipment). . chapter 2. whichever is the largest. while MEK requires a relatively straight flow. Thus a short calming length is needed after the pump. This dead time is the time it takes for the pulp to flow between the dilution point and the measurement point. Blade consistency transmitters and other types of rotating transmitters (not MEK) need fully developed plugflow conditions. fiber type and flow velocity.) is that you may decide how rapid the control should be. A turbulence is created in a pump. According to Lambda tuning practice λ should be selected to 3 x τ or 3 x Td. In this method the variable is called λ (Lambda).see "Accurate Consistency". Some optical and microwave transmitter types can be installed on very turbulent flow conditions directly after the pump outlet.). The control loop must be open (i. To achieve the best consistency control it's very important that this dead time becomes as short as possible since it will directly influence the control loop´s ability to reduce disturbances. to install an MEK since it can be installed on a turbulent flow (but also works on a plug flow). but also depending on consistency level. Thus the dead time in most cases can become short and it's also easy to reach the transmitter from the floor. Popularly explained. Effective Consistency Control The location where plug flow is formed is not only depending on the distance in itself. pipe bends directly following each other.Practical possibilities to install a transmitter at a recommended point. You may have a signal filtering damping the signal etc. Some types of consistency transmitters can be installed at more or less turbulent flow conditions. Thus the distance between the dilution water inlet and the consistency transmitter very often becomes very long resulting in a very long dead time. The main advantage of this method compared to traditional methods (Ziegler-Nichols.Consistency Control loop Dynamic Specification)."Time interval between the instant when a variation of an input variable is produced and the instant when the consequent variation of the output variable starts". A blade transmitter always need plug flow conditions and often there is not enough space on the vertical section after the pump to obtain this condition and follow the calming length recommendations. Chien. The dead time (Td) is the time it takes from the change of the set point is made until the consistency transmitter start to pick up the actual consistency change. Generally lower consistency. even if it is turbulent. Normally there is space enough directly after a pump. In a consistency control loop there are several dead times involved. Then you can find out the deadtime (Td) and open loop time constant (τ).The ability for the transmitter itself to be installed on a turbulent flow. bend or at a half-open valve. The fibers in the pipe will have different velocities and the conditions in the pipe are generally unstable. in the dilution water valve positioner/actuator etc. All these factors mean certain dead times. This stage is called plug flow. culated for a vertical installation by a factor 1. in practice all added together to make an influence to the process to be controlled. Hrones and Reswick etc.The recommendation is to multiply the calming length cal- P2007en Fig 36: Effective Consistency control Impact of dead time and controller tuning: The most common method to tune a controller for consistency is the Lambda method (Lambda tuning). . bend or valve. shorter fibers and higher flow velocity all increase the distance to where the plug flow is formed . The piping is in most cases already existing being designed and built without considering the demands for a consistency transmitter. before optimizing it. To decide λ you have to make a step-response test of the process. all the fibers will flow with the same velocity in the same direction. blade 90 s > Slower tuning for blade transmitter > Less response for incoming disturbances > Less accurate control! Larger period disturbances: Cut-off frequency Tc = 2π(λ +Td) is the frequency where the consistency controller can begin to attenuate disturbances of larger period. Fig.5 min and for MEK Tc = 2π (6 + 2) = 50 s < 1 min. . On the other hand. where the course dilution is fed into this mixing compartment and the fine dilution before the pump. and often considered as "difficult". the retention time can become short! Generally spoken. Td is 2 seconds and λ becomes 3 x 2 = 6 seconds. MEK can be successfully installed on a large variety of applications. But what will this mean for the control result using the different types of transmitters? Then you have to study a factor called Cut-off frequency.In the example fig. Blade 30 s Lambda (λ) method most common for consistency control tuning Short period disturbances: λ =Closed loop time constant. what frequency variations can you expect? . Paper mill applications: Two typical examples of applications in the paper mill are shown in figs. i. 38 a typical response for a blade type consistency transmitter is shown when a set point change on the controller is made to increase the consistency. means higher cut-off frequency. 43 is particularly important since it includes two actual proofs that MEK provides an advantage over blade transmitters. © BTG 2003 P2007en . a very common location in practice for a blade transmitter due to the practical implications mentioned above). at different parts. 37 and fig.Small volume tanks or chests. they are really able to treat the incoming variations so that the control loop can make the job: a smooth stable outgoing consistency without variations. in both pulp and paper mills. from 1 to 16%. Blade type consistency transmitters • • • • • Typical Dead time (Td ): Rotating 5 s. λ = τ x 3 for stability > Rotating 30 s. Based upon these values you can then calculate the parameters for the PID controller. screens etc. the cut-off frequency is low. a blade transmitter can work satisfactory in this respect. traditional large volume chests do not require transmitters giving very short cut-off frequency. For modern type of chests using mixing compartment. Since we already know λ and Td we can easily calculate Tc. have long retention time. the value is critical. the Controller gain Kc and the Integrating time Ti (Reset). 37 Excessive dead time and filtering Control ability: ability: Comparison between BTG Rotating (and Microwave/ Microwave/ inin-line optical) optical) VS.e. The cut-off frequency is ~ 4 min for rotating vs.. Excessive Deadtime and Filtering Blade consistency transmitter Dilution valve opening B Td Deadtime ~ 20 sec If you compare to a rotating transmitter type MEK (or microwave /optical). The transmitter is universal in its wide field of applications. In this example Td is approximately 20 s for the blade transmitter. The background for these applications and considerations for control and selection of type of consistency transmitter is not discussed in this paper. The Cut-off frequency Tc is given by the formula Tc = 2π (λ + Td). Then λ becomes 3 x Td = 3 x 20 = 60 seconds. (At a typical flow velocity 1 m/s it means that the distance between the dilution water injection point and the transmitter is 20 m. the control valve is closing. Thus the dead time Td is not a very important issue. in all kinds of processes and in a very large consistency span. type mixing chests or couch pits or process equipment like washers.Large tanks. Blade 20 s (require plug flow conditions) Open loop time constant (τ): Rotating 10 s. For the blade transmitter Tc = 2π (60 + 20) = 503 s ~ 8. 15 4τ Open loop Time Constant (τ) ~ 30 sec Output signal blade type transmitter (not in control) Fig. which can be located much closer to the pump. The Derivate time (Rate) is set to 0. if the chest is equipped with a special compartment using an intense mixing and you have a double dilution. 12 min for blade transmitter > A blade transmitter does not touch disturbances with periods less than 12 min > Less accurate control! Fig 38: Control ability: Comparison between BTG rotating and blade transmitters Applications and Proofs for MEK As we discussed earlier. 39 to 43. storage chests etc. Some applications are particularly interesting. Here consistency transmitters giving a short cut-off frequency can make a significant improvement for the control result. Frequencies faster than Tc will not be attenuated! Looking on the process. please see "Accurate Consistency" chapter 7 for details. they can be better controlled using transmitters like MEK (or optical/microwave). Since the Cut-off frequency Tc is the frequency where the consistency controller can begin to attenuate disturbances of a larger period. This pump loop did cost a lot of additional money for power and maintenance which they wanted to avoid.Final Consistency Control. the paper must be degraded and sold to a lower price or repulped. 50% groundwood pulp.reduces power consumption and product variations. reliable Control for the most critical applications in the Paper mill Refiner Control Standard model MEK-2300 • After Machine chest . The controlled consistency now was improved to 3 +/. the illustration. After replacing the static blade transmitter with an MEK they could see the standard deviation be reduced from 0. When using the static blade transmitter the control accuracy was found to be 3 +/. If it becomes lower the properties do not meet the standard. is controlling the consistency after a mixing chest in the paper mill. FT MEK-2300 • MEK provides Accurate. which is not cost efficient.the foundation for successful Refiner Control • Specific energy refining control – the most advanced control system • Improved and safer runnability of the paper machine . accurate.4343 to 0. They mix mechanical groundwood and kraft stock. 43: The background for the first example.The foundation for successful Paper Machine operation • Stock Proportioning Control.Essential part of the Basis weight Control system (QCS) Wire Pit The result they got was a reduction of expensive kraft stock and they could replace it with the cheaper groundwood stock and thus save 2 MUSD / year! The payback time for the transmitter installation was less than a month! Paper machine Consistency Control Fig 41: Paper machine consistency control P2007en © BTG 2003 16 . The mill produces a paper grade where they use pine or a mixture of pine and/or blend kraft stock.Accurate Control of each fiber flow is essential for optimal product quality and minimized consumption of high cost fiber CRC DRT-5200 I MEK-2300 W • Mixing Chest Control . The consistency control is very important since it decides the amount of kraft stock and also how much it needs to be refined. fiber variations etc Safe. line pressure.less web brakes. Reliable control independent of flow velocity. conductivity. This meant they had to increase the amount of kraft stock to 53% to meet the specification. the mixing chest before the paper machine. higher product quality • Tighter tensile strength settings . Increased amount of low cost fibers can be used and risk for downgraded paper is reduced • MEK provides safe accurate measurement. not depending on flow variations.15% consistency. The good result was distributed in the mill´s internal newsletter.5% Fig 42: MEK for paper machine control Fig 39: Refiner Control MEK for Refiner Control Low consistency 1-10% • Accurate Consistency Control .Local setpoint C ONS IS T EN C Y TR AN SMI TT ER MEK-2300 CS Remote control Specific Refining Energy Control Drainage Rate Control MEK for Paper machine Control Low consistency 1-10% F FT Output Power • Accurate Consistency Control . An MEK was installed directly in-line after the pump. line pressure etc. furnish variations.0477. a reduction of almost 0.4% consistency.0. i.0. located in Louisiana USA. CRC Mixing chest Actual proof and savings fig.05%. USA. is essential for optimal Machine runnability and profitability MPS-1000 Standard model MEK-2300 Cs=3.e. is that the mill. Also worth to mention was that the blade transmitter was installed using a separate pump loop to maintain a stable flow velocity. The mill is located in Maine. Foundation for successful Refiner Control to optimize Paper Machine runnability and profitability Fig 40: MEK for refiner control F M EK -2300 Valve pos Cs C O N S I S T E N C Y T R A N S MI T T E R BWCS Valve input SP Actual BW C O N S IS T E N C Y T R A N S MIT T E R M EK-2300 VBW-10 MEK-2300 RET-5300 Machine chest In the second example the situation was very similar. the paper must contain min. The produced paper quality specification states that to keep the required properties. fig.Much lower sensitivity for different fiber types. fiber type. including the statistical uncertainty. high pH. knots.Better control ability. and other types of consistency transmitters can hardly be successfully used here. Fig 45: Comments to fig. heavy vibrations.Robust design. Short dead time between dilution and measurement results in considerably better ability to attenuate incoming disturbances and provide a smooth stable consistency control. stones and metal pieces. Improves pulp mill economics Three examples from the chemical pulp mill. All of these applications are very difficult. 44. conductivity. 44 Why does MEK provide a superior result in the pulp mill? .Really measures pulp consistency. . Withstands badly cooked woodchips.Virtually no flow sensitivity. fig.in the pulp or ambient etc. washer or refiner • Transmitter really operates reliable in the very tough measuring conditions (MC. high temp. 46 and fig. Blow tank consistency control (Or HD storage chest) Fig 46: Blow tank consistency control 17 © BTG 2003 P2007en . . Changing from mechanical groundwood to kraft pulp or from pine to blend kraft stock only meant a very small shift in transmitter signal. Can control disturbances and changing conditions very well. consistency control after the continuous digester. etc. impurities) Enables better over-all control of the digester.fig. backflows. small influence of disturbance factors. high pressure. 48. varying flow. high temperatures . air content. seal Fig 43: Consistency proof and savings • 25 bar (300 psi) flange with deflector Pulp mill applications: • Stabilizes blow line Kappa no. . Installation directly in-line without expensive pump by-pass arrangements. retention time) • Enables accurate yield and production rate calculations Special model MEK-2315 • 30% higher torque • Special MC-sensing element and mech. freeness. Virtually insensitive (or to a very small degree only) for flow variations. after the blow tank and inlet to the bleach plant are described .Excellent controllability. Continuous digester Consistency Control Fig 44: Continuous digester consistency control Continuos digester Consistency Control Medium consistency 8-16% • Enables early consistency control in process • Improves digester stability (level control. highly concentrated pulp jams. In the recycled fiber pulp mill the application after the pulper is shown . and optimizes the internal washing • Prevents hang-up in digester and plugging in the blow line. pressure. 50. .Why did the result in the two cases become so much better using MEK? . The shift was so small that it was difficult to detect using ordinary lab methods. but for various reasons. Data sheets. 48 P2007en Additional information: . 254 SMO or Hastelloy C Fig 49: Comments to fig. Consistency 2-8% • Optimizes production capacity and eliminates risk for plugging in screens and cleaners • Can withstand the very tough process conditions. Available from BTG. available from BTG. A handbook on consistency measurement in pulp and paper processing. 50 Bleach plant consistency control For medium Consistency 8-16% (MC) • For accurate consistency control and dry tonnage calculation • Is insensitive for variations of air/pressure or conductivity in pulp. Seal • No propeller The only reliable transmitter available for the application. Proven in many installations • Enables early consistency control which stabilizes the subsequent steps in process • Enables a high optimal consistency without risk for plugging in the screen and pump. • Is virtually insensitive for changes in flow velocity Special model MEK-2310/-2312 • 30% higher torque Brings the reliable foundation for correct chemical dosing. Optimize screen and cleaner operation Batch pulper consistency control – recycled fiber Fig 47: Comments to fig. . TAPPI and Paptac. 46 Fig 50: Batch pulper consistency control Batch pulper consistency control For special applications Consistency 1-10% • For the most demanding pulper applications.“Accurate Consistency”. Proven in hundreds of installations • Insensitive for variations of air/pressure or conductivity in pulp. Special model MEK-2308 • Is virtually insensitive for changes in flow velocity • Deflector to protect from debris • Extra sturdy mech. manuals. papers. © BTG 2003 18 . Special model MEK-2320 • Specially designed to prevent hang-up and spinning • Standard MEK-2200/MEK-2300 for less demanding pulper applications • Cone protects from spinning • Special anti-spinning sensing element Optimizes pulper and cleaner production for maximum capacity and runnability • Clean-flushing with water Bleach plant consistency control Fig 48: Bleach plant consistency control Fig 51: Comments to fig. articles etc. Minimizes chemical costs and improves pulp quality • Flange for 10 or 25 bar pressure • Special MC sensing element • Wetted parts in 316 SS.Blow tank consistency control For special applications.