T 275 sp-02
STANDARD PRACTICE – 1998
REVISED – 2002
2002 TAPPI
The information and data contained in this document were prepared
by a technical committee of the Association. The committee and the
鄙夷不屑的意思Association assume no liability or responsibility in connection with
the u of such information or data, including but not limited to any
liability under patent, copyright, or trade cret laws. The ur is
responsible for determining that this document is the most recent
edition published.
Approved by the Standard Specific Interest Group for this Test Method
TAPPI
CAUTION:
This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of the is to alert the ur of the method to safety issues related to such u. The ur is responsible for determining that the safety precautions are complete and are appropriate to their u of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the u, disposal, or both, of chemicals which may prent rious health hazards to humans. Procedures for the handling of such substances are t forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the u of this method, the ur must determine whether any of the chemicals to be ud or dispod of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe u and disposal of the chemicals.
Screening of pulp (Somerville-type equipment)
1.
Scope
1.1 The purpo of this method is to parate contaminants such as shives in mechanical pulp, and macro stickies, plastics, sand, metal pieces, and flakes in recycled fiber from pulp fibers for subquent examination and/or quantification. This method employs a screening device and the paration is bad on size difference between fibers and contaminants. However, depending on their flexibility and/or geometry, not all of the contaminants that are larger in size than fiber can be captured by the screen.
1.2 The dimensional limits that parate contaminants from fibers, as well as the time length of screening are arbitrary.
1.3 Screen plates of various slit widths such as 0.10 mm, 0.15 mm, 0.20 mm, and 0.25 mm have been ud in parating contaminants. Only the u of 0.15 mm slit is covered in detail in this method.
2. Significance
如何添加目录2.1 The adaptation of TAPPI UM 242 “Shive Content of Mechanical Pulp (Somerville Fractionator),” to the screening of other pulps such as recycled pulp is common. In the adaptation process, screening procedure variations were introduced. It is imperative that a common practice is defined so that the outcomes of the paration are comparable.
2.2 Contaminants such as shives, stickies, and plastics adverly affect paper machine operation and down grade final product. Qualitative and/or quantitative measurements of the contaminants are thus critical in evaluating the effectiveness of a process or a piece of equipment, as well as final product quality. This method provides a way to isolate the contaminants for the purpos of qualification and quantification.
3. Apparatus
3.1 Somerville-type of screen (e Figs. 1 and 2)
3.1.1 From top down, the screening device consists of a rectangular screen box, a screen plate, a diaphragm chamber with a weir box attached, and a stand. The diaphragm chamber is attached to th
e stand. Before each run the screen plate is cured between the diaphragm chamber and the screen box by locking clamps. Gaskets above and below the screen plate make the asmbly water tight.
健身的意义3.1.2 The inside dimensions of the screen box must not be over sized and at the same time must be such that no slits in the screen plate are obstructed by the structure of the box. The screen box must also be tall enough so that a water
level of 102 mm ± 2 mm over the screen plate can be maintained.
3.1.3 The screen plate is made of 316 stainless steel. There are 756 slits in the screen plate arranged in 6 columns of 126 slits each. Slit pitch within a column is 2 mm. The entire slit pattern on the screen plate must not exceed an area measuring 250 × 300 mm. The slits are 45 ± 0.5 mm long by 0.15 + 0.005 / -0.01 mm wide (0.140 to 0.155 mm). Some of the slits will actually be shorter than 45 cm due to the nozzle ho and mounting. This may vary with the manufacturer.
3.1.4 A spray nozzle with 12 equally spaced horizontal holes is mounted at the center of the screen plate. The holes are equal in size and are positioned 2 mm (measured from center of hole) above the screen plate surface. The spray nozzle is calibrated for a flow of 8.6 ± 0.2 liter / minute at a water
supply of 124 ± 5 kPa.
3.1.5 A rubber diaphragm in the diaphragm chamber is connected to an eccentric mechanism which in turn is driven by a motor. The eccentric runs at 700 ± 10 rpm and creates a vertical movement of 3.2 ± 0.1 mm maximum amplitude for the diaphragm.
3.1.6 At the flow rate of 8.6 liters/minute, the height of the weir in the weir box is adjusted to maintain the water level inside the screen box at 102 ± 2 mm above the screen plate surface.
3.2 Other lab equipment
3.2.1 Standard disintegrator as specified in TAPPI T 205, or in TAPPI T 262 for mechanical pulp.
3.2.2 Apparatus as specified in TAPPI T 240 for consistency determination.
3.2.3 Sample containers of 10 liter capacity.
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3.2.4 Lab
4. Procedure
4.1 If a sample is not in slurry form, follow the procedures in ctions 6 and 7.1 of T 205 to transform the sample to pulp slurry. The disintegration time is one minute (or 3000 revolutions). In ca of mechanical pulp, follow the procedures of T 262 to develop the latency properties of pulp.
4.2 Dilute a pulp sample (originally in slurry form or disintegrated in step 4.1) to a consistency of no more than 1%.
4.3 Determine the consistency of the diluted pulp in accordance to T 240.
4.4 Weigh into sample container(s) the amount of the diluted pulp equivalent to 50 ± 0.2 gram oven-dry material and record the exact weight to the nearest 0.1 gram.
NOTE 1:Depending on the contaminant concentration, the amount of oven-dry material ud to run a test may be more or less than 50 grams. Always record the exact amount of diluted pulp weighed out. It is not recommended to u more than 80 or less than 20
grams of oven-dry material in a test.
4.5 Asmble the device by putting the screen plate and the screen box in position, followed by clamping the screen box and plate, and connecting the spray nozzle to water supply.
4.6 Add water into the screen box until the water level is about 25 mm above the screen plate surface.
4.7 Add the sample weighed out in step 4.4 into the screen box; rin the sample container with small amounts of water and add the rin water into the screen box.
4.8 Turn on the water supply to the spray nozzle and adjust the water pressure to 124 ± 5 kPa.
4.9 Start the motor when overflow occurs at the weir.
4.10 Stop the motor at the end of 20 ± 1 min.
4.11 Drain the screen box and rin all the debris remaining on the walls of the screen box as well as on the spray nozzle and the connecting ho to the screen plate.
4.12 Disconnect the water ho and un-clamp the screen box; then remove the screen plate.
4.13 Wash all the debris on the top surface of the screen plate to a sample container.
4.14 The suspended debris in the container is now ready for further processing (such as forming a pad for obrvation or quantification).
4.15 Clean the screen after each run. Do not u hard objects such as feeler gauges, tweezers, and discting needles to clean the slits. A pressure washer is recommended for the purpo of cleaning the screen plate.
5. Calculation比的应用题
Calculate the amount of oven-dry materials added into the device as follows:
W = C×R / 100
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where
W= The amount of oven-dry materials added into the screen, grams;
C= consistency of the sample added into the screen as obtained in step 4.3, %;
R= the amount of pulp slurry added into the screen as recorded in step 4.4, grams.
Fig. 1. Screen plate slit pattern.
6. Report
Report W, the amount of oven-dry materials added into the screen, to the nearest 0.01 gram.
If, for a particular reason or purpo, slit width other than 0.15 mm is employed, report the actual slit size ud as well as the tolerances.
7. Precision
A precision statement is not applicable for this Standard Practice.
8. Keywords
Fiber debris, Shives, Stickies, Plastics, Mechanical pulps, Recycling, Reclaimed fibers, Screening, Separation.
9. Additional information
9.1 Effective date of issue: October 29, 2002.
9.2 This method is an upgrade of UM 242.
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Your comments and suggestions on this procedure are earnestly requested and should be nt to the TAPPI Director of Quality and Standards.g
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