纸机管理.docx

1、纸机管理A. PAPER MACHINE CLEANING MANAGEMENTABSTRACT This paper discusses the importance of paper machine cleaning management. It explains the process of determining cleaning management status for existing machines and setting up goals for improvements. This process, cleaning management audit, helps pap

2、ermakers detect cleaning problems that are affecting the machines efficiency, paper quality and safety. A post-audit report includes suggestions for improving the mills cleaning management practices, which after implementation need to be followed up to ensure sustainable gains. With the state-of-the

3、-art paper machines cleaning management is taken into consideration by the design of the machine. Paper mills improving their cleaning management processes have been able to increase productivity. This has been achieved by eliminating breaks in certain areas, shortening down time, increasing runnabi

4、lity, improving paper quality and improving safety INTRODUCTION Paper machine cleanliness has an impact on paper machine efficiency, paper quality and safety. With right practices, equipment and training it is possible to positively affect these areas. The importance of this is acknowledged in the p

5、aper industry and in the recent years a lot of effort has been put in to developing paper machine cleaning management processes. The development is ongoing and new technology is delivered with new machines and as smaller projects to help existing machines. CLEANING AUDIT - THE KEY TO IMPROVEMENT WIT

6、H EXISTING MACHINES The purpose of paper machine cleaning audit is to determine those areas on an existing paper machine where better cleaning management will enhance the machine productivity. The audit starts with pre-study and is completed only when results of improvements have been recorded, figu

7、re 1. AVNurJEr.gif (5.94 KB)PAPER MACHINE CLEANING MANAGEMENT2006-11-1 10:37Figure 1. Cleaning audit principle. Pre-Study and Gathering of Information In the pre-study phase all relevant information regarding the up coming project is gathered. This includes drawings of e.g. shower locations in wet e

8、nd and other related equipment such as mist collectors, information of mill cleaning management practices including e.g. fabric change intervals, doctor data, machine and production data, etc. With the gathered data it is possible to beforehand make plans on how to carry out the audit and what would

9、 be the potential areas where special attention needs to be paid during the audit. Carrying out the Audit The audit is carried out while the machine is in operation and completed when the machine is down. While the machine is operating the machine is thoroughly checked. The equipment is evaluated as

10、 are the practices of the mill operations. Functioning of showers, doctors, trim-squirts etc. is recorded. Overall cleanliness of the machine will be taken into special consideration. Any structure going across the machine has a potential of causing runnability and efficiency hazards when gathering

11、build-up. Also structures such as catwalks and walkways will be evaluated from safety point of view. During breaks the mills cleaning practices will be recorded, and later on compared to the mill instructions. It is important to complete the observations with photos. These photos added in the final

12、report will later on make it easier for the reader to understand the situation, figure 2. M164ZOqZ.gif (55.29 KB)PAPER MACHINE CLEANING MANAGEMENT2006-11-1 10:37Figure 2. Photo showing defected nozzles in hp-shower and build-up on mist collector causing a break hazard. On a down day a similar full m

13、achine approach is taken as when the machine is running. This time there are possibilities to look into places where it was impossible to get to during the production: inside save-alls, air exhaust ductwork, complete check-up of doctors, etc. Again the mill operation practices are monitored and late

14、r compared to mill instructions. The audit can include the whole machine or for instance just the wet end, if thats the place where most improvement is needed. Before auditor leaves the mill a meeting is held where the mill is updated with preliminary results of the audit. Report and Benchmark An im

15、portant part in preparing the cleaning management audit report is comparing and benchmarking the studied mill with the industry. With comprehensive databases it is possible to position the mill in relation with others including the best, which helps the auditor in pointing out the potential for the

16、mill and setting up goals. These databases are only used by the auditor to help him guiding the mill to the right direction. The information in the databases includes e.g.: _ Production (t, t/d, kg/cm/d) _ Average basis weight (g/m) _ Average speed (m/min) _ Efficiency (%) _ Shut downs (%, interval,

17、 duration, planned, unplanned) _ Breaks (%, # of breaks/d, wet end, dry end) _ Broke (%) _ Trim loss (%) _ Wash-up procedures during shut downs (interval, duration) _ Machine clothing shock cleaning procedures during shut downs (interval, duration) Normal machine cleaning procedures during run (inte

18、rval, duration) _ Doctor maintenance (blade change intervals, wash-up procedures) _ Clothing change (interval, duration) When the report is ready it is presented at the mill and plans for improvements are made based on the report. Improvements The report identifies two different areas of improvement

19、s: those under direct control of mill maintenance and operating personnel, and those affected by design and equipment. Improving the areas under direct control of maintenance and operations can be achieved by proper training and implementing correct procedures. This can be very cost effective yet yi

20、elding good results. For example washing the doctors from front side to back and neglecting the back side can cause accumulated build-up which will eventually create problems; quite often the case in the mills. The equipment and the design will affect cleanliness of the machine. In the new machine a

21、nd component design special emphasis has been put on the prevention of build-up accumulation and taking care of the problems at the source. There are also cases where new equipment is not needed only relocating and readjusting the current is enough. For instance in some cases relocating high pressur

22、e showers in the forming section can cure mist and buildup problems. Training Training is an essential part of planting the improvements. To ensure good results all levels of the organization should be included in the training. Part of the training is classroom type training and part of it is hands

23、on at the machine. Recording the Results It is important to follow up with the improvements and record the results. This way it can be made sure the goals are met. This will also help determining whether further studies in cleaning management area or other areas will be needed. NEW MACHINES - CLEANI

24、NG MANAGEMENT BY DESIGN This chapter will very shortly introduce some design features in the new machines affecting cleaning management. With new high speed machines the speed alone is not the key to high production. High efficiency is needed, which in turn is created by good runnability and minimum

25、 shut down time. Cleaning management has a significant impact on these factors which has been taken into consideration for example in the design of new former, figure 3. In this design for instance all the water drained is directed into closed channels helping to keep the former clean by avoiding sp

26、lashing and misting on the save-all pans. The ventilation has evolved from overall ventilation into target ventilation thus eliminating soiling points. Forming roll as the first drainage element provides high retention, which enhances wet end cleanliness. The main design is such that maintaining and

27、 keeping it clean is easy including quick fabric change.V0sKZs5y.gif (30.46 KB)PAPER MACHINE CLEANING MANAGEMENT2006-11-1 10:39Figure 3. New former design with features helping to keep it clean. The idea of removing moisture and mist at the location, where it is born is applied also in the new press

28、 section design. In the dryer section for instance the frame leg has been designed to hide hydraulic, pneumatic and electric piping behind a cover plate. That makes the construction roomy and easy to keep clean. Also other equipment such as dryer felt cleaners are located so that build-up on them is

29、 avoided. EXAMPLES OF PROCESS IMPROVEMENTS WITH EXISTING MACHINES In the forming section high pressure showers can create mist which accumulates as build-up on structures. The mist can also prevent visual inspection of the machine while the machine is running. These will create break and safety haza

30、rds unless taken care of. In such a case a mist elimination system can give good benefits. A newsprint mill in Norway installed mist elimination system for top and bottom fabric which reduced the wet end breaks 50%, from 3 breaks per day to 1.5 breaks per day. With the high speed machines producing

31、lighter grades it is important to complete the mist elimination system with felt drying equipment. Studies with the pilot machine have shown that as much as 90g/m/s of water can be removed from the fabric with the fabric drying equipment. This would equal 70m/h removed water on a 10m wide machine in

32、 production running at 22m/s (1320m/min). If not removed this water including e.g. fillers and fines will partially get thrown into the structures and accumulate build-up. As seen in figure 4 the wet streaks caused by high pressure showers will also be eliminated with this system, which is important

33、 with lighter grades as the steaks will show in the paper moisture profile. EPoSFp43.gif (16.77 KB)PAPER MACHINE CLEANING MANAGEMENT2006-11-1 10:42Figure 4. Inner fabric conditioning system in forming section with mist removal and fabric drying. Doctoring is part of the paper machines cleaning management. The area with lot of potent