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This bulletin focuses on the important aspects of brick installation in rotary kilns. In particular, special attention will be given to the proper procedures for closing brick rings using a hydraulic jack and how to correctly install key brick and shims. It is important that each ring of brick is laid as tightly as possible, and that they are kept perpendicular to the longitudinal axis of the kiln. These procedures should be used in conjunction with any customer supplied guidelines. For conflicts, the customer supplied guidelines should be followed. 1. General Information: Before brick are installed the following issues should be addressed. a. Kiln Shell: Both the internal and external surfaces of the shell should be inspected. Any kiln shell abnormalities should be noted and plans to deal with them discussed with the customer (see examples later in this bulletin). The inside of the kiln should be free of all debris including used refractory, cement or lime products, and any loose surface dust or scale. The brick must be seated firmly on the shell with tight brick-to-brick contact. b. Tools: All tools should be inspected and checked to make sure they are in working condition. This includes all pneumatic equipment such as shim drivers. Only leather, wood or rubber mallets should be used to set brick. c. Brick Rig and Ramp: Harbison-Walker Refractories prefers a pneumatic brick rig for installations in cement and lime kilns. The rig and ramp should be checked for functionality and for all safety considerations. d. Jack: A pneumatic or hydraulic jack is preferred to assist in the jacking and closing out of each brick ring. The jack should have a pressure dial capable of reading up to 4000 psi. e. Brick Storage: All Harbison-Walker refractory brick should be kept dry and under cover. If the brick become wet inadvertently, either in transit or storage, individual pallet loads should be dismantled and the brick spread out and exposed to ambient air. Wet brick should be separated allowing large volumes of air flow around them at normal ambient temperatures. Wet brick should not be exposed to temperatures above 50°C (120°F) as this will promote hydration (re: Technical Bulletin: Hydration Resistance of MAGNEL RS Catalogue No. C&L TB 102). 2. Kiln Preparation a. Drawing Review: Before installation begins, a thorough review of the installation drawings with the customer, installer, and refractory supplier is recommended.
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b. Longitudinal Reference Lines: A longitudinal reference line should be established on the lowest part of the shell (6 o’clock position) along the length of the area to be bricked. A spirit level laid across the kiln at several points (See Figure 1) is an accurate method to locate this line. This longitudinal reference line must be perpendicular to the axis of the kiln shell and will be used to start laying brick for each ring. Additional parallel lines at 1.5 meter intervals should also be drawn on the shell.
Spirit level
Figure 1. Spirit level.
c. Circumferential Reference Lines: Reference lines are essential for determining the accuracy of the installation and to help keep rings straight while maintaining tight joints. Existing weld joints may be used as circumferential reference lines (see Figure 2)but it may also be helpful to add additional reference lines at set intervals around the entire internal circumference of the shell.
Figure 2. Rotary kiln reference lines.
3. Brick Installation: Brick are always installed starting at the downhill end of the section to be lined. As brick are laid, they should be tapped into place with a leather or rubber hammer. Key points during brick laying: a. Joint Bonding: Standard ISO and VDZ brick should be installed (Figure 3) in a bonded fashion. Joints should be staggered by ½ a brick width from ring-to-ring. If bricking with Rotary Kiln Blocks (RKBs), the joints (Figure 4) should be staggered by ⅓ to ¼ of the brick width.
1 /2
N BO
Figure 3. Bonding of ISO and VDZ brick.
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D 1 /3
OR
1/4
N BO
Figure 4. Bonding of Rotary Kiln Blocks.
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b. Initial Brick Rings: From the reference lines along the bottom of the kiln, brick are laid with bonded joints in rings up both sides. Several rings of brick should be laid up to the spring-line of the kiln maintaining as closely as possible the recommended mixing ratio for the kiln. Depending on the diameter of the kiln and the condition of the shell, the general guidelines are a 1:1 ratio for ISO brick and a 2:1 or 3:1 ratio for VDZ brick as depicted in Figure 5. Dramatic deviations from these ratios may indicate problems with the kiln shell Figure 5. Correct 2:1 ratio. or that the wrong combination of brick are being used. The initial brick rings should be closely inspected to make sure that the brick are squarely seated against the shell and not ‘tilting’ up or down. c. Brick Orientation: The notch on the end of the brick indicates the hot face. All brick are to be installed with the notch facing inward towards the center of the kiln. Any brick installed upside down need to be removed and replaced in the correct orientation. See Figure 10. d. Laying Brick: Brick should be tapped or hammered down-kiln with a leather mallet to tighten the joints between the rings. With proper installation, each brick will remain in its original position throughout its entire life. Tight joints between the rings also will prevent down-kiln movement. e. Brick Runout: Brick rings should be measured to the nearest circumferential reference line at least every 4 feet of kiln length. Minor corrections should be made with mortar in subsequent rings to compensate for deviations greater than ½”. f. Taper Issues: Stepping or hacking at the brick hot face indicates that corrections for taper are needed. Insertion of a shim or mortar across the radial joint will correct the alignment. For brick with too much taper, where the brick turns a diameter too small for the kiln shell (see Figure 6), a correction to the hot face is required. If two shapes are being used, install more of the larger size kiln brick. For brick with too little taper, where the brick turns too large a diameter (see Figure 6), a correction to the cold face is required. In twoshape construction, more of the smaller size kiln brick should be used.
STEPS STEPS SHELL
SHELL
TOO MUCH TAPER
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TOO LITTLE TAPER
Figure 6. Brick taper issues during installation.
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g. Notes on Mortar: With Basic brick, tight brick-to-brick contact provides the strongest and most stable lining. Mortar use within rings of Basic brick is not recommended. Mortar may be used between rings to correct for runout with Basic brick. Mortar or castable may be used to help support Basic brick placed over rivets or deformed areas of the kiln shell as illustrated in Figure 7. For Fireclay and High Alumina brick, corrections may be made with the appropriate mortar. With Basic brick, corrections to taper or spiraling should be made with steel shims.
FILL WITH MORTAR OR CASTABLE
FILL WITH MORTAR OR CASTABLE
Figure 7. Bricking over shell irregularities.
4. Jacking Procedure: Before each brick ring can be closed, an appropriate amount of pressure must be applied to the lining to ensure that it is as tight as possible. For this purpose, Harbison-Walker Refractories recommends the use of a pneumatic or hydraulic jack with a pressure gauge. a. Lay up the brick work in the ring to be closed to about the 11 o’clock position holding each brick in place with the pneumatic cylinders. The gap at the key up location should be 6-8 brick wide (Figure 8.) b. Place the jack into the key up area. To avoid point loading on the brick, a hardwood block, metal plate or large rubber boots, as shown in Figure 8, should be used. Apply 500 psi pressure to tighten the ring and release the pneumatic cylinders holding the brick. RUBBER BOOT OR HARDWOOD BLOCK
JACK
Figure 8. Jacking of ring to tighten lining.
c. Keeping the pressure on the jack, set the brick down kiln and against the shell, especially at the 3 o’clock and 9 o’clock positions, using the rubber/leather mallet.
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d. Increase the pneumatic jack pressure to 1000 psi and repeat the process of tapping the brick down kiln and against the shell. Continue this process until the jacking pressure reaches 3200 to 3600 psi. The jacking pressure should not exceed 80% of the brick’s cold crushing strength. e. Reapply the pneumatic cylinders to hold the brick on the shell and slowly release the air pressure on the jack. 5. Keying and Shimming or Closing the Ring: The gap remaining in each ring is closed and keyed by selecting and inserting an appropriate combination of standard kiln liners, special keying brick and steel plates or shims as shown in Figure 9. a. Measure the top of the key area. This will give the key size required for keying up the ring. Fit the brick to approximate the gap size as closely as possible. b. Close out the ring with the correct ratio of standard kiln liners and the necessary keys to fit the gap as tightly as possible. c. Do not cut key brick which weakens the brick. d. Do not place 2 key brick next to each other. e. Do not drive the key brick into the ring during closure. Fit and exchange brick as necessary so that the gap between the key brick and the adjacent brick is ¼” or less. METAL SHIMS
KEY BRICKS
Figure 9. Proper installation of key brick and shims.
f. If the key brick are loose, install shims as required to tighten the lining. Do not install 2 shims in the same brick joint (Figure 9). Bent shims are not recommended.
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g. A properly installed lining will require the use of a pneumatic shim driver to install the shims. h. After insertion of the proper combination of keying shapes, continue to drive the brick down-kiln while tightening the ring with the steel shims. i. After all the rings are tightened and closed in this way, remove the installation equipment and, if possible, rotate the kiln several times. Check the lining again for tightness and, if necessary, insert additional steel shims to tighten the ring. j. Cold turning of the kiln should be limited to that required to check the lining for tightness. 6. Cut Rings: General guidelines for cut rings are as follows: a. No cut brick should be less than ½ brick in width. b. All Basic brick are to be cut dry. Alumina brick may be wet cut. c. If a cut ring is required on the downstream side of a retaining ring it is to be placed one full ring away from the retaining ring. d. The first upstream ring of brick at a retaining ring should be a full brick never a cut ring. e. Cut rings should be one full ring away from an existing lining left in place. 7. Expansion Allowance: Harbison-Walker’s basic brick are supplied with suitable longitudinal expansion allowance. This expansion material is in the form of a cardboard strip glued to one end of each brick (Figure 10). This expansion allowance should not be removed without prior approval by Harbison-Walker. All brick should face the same direction in the kiln so that the expansion cardboard is facing up kiln. Do not provide for any radial expansion between brick within each ring during installation.
EXPANSION CARDBOARD
BRICK HOT FACE and MARKINGS
Figure 10. Typical VDZ kiln brick showing hot face identification and longitudinal expansion allowance.
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8. Heating and Cooling: The refractory lining of any high temperature furnace, such as a rotary kiln, will give longer life if it is always brought to operating temperature with great care. Please see the Harbison-Walker Refractories Technical Bulletin on Heating and Cooling Rate Recommendations Catalogue No. C&L TB 113 for more detailed information. a. To minimize thermal and mechanical stresses, the heating rate should conform as closely as possible to that provided by the refractory supplier. b. For various kiln systems, equipment manufacturers will specify recommended preheat schedules that should preferentially be followed to avoid the risk of equipment damage. c. Thermal cycling occurring during repeated kiln shutdowns has a cumulatively adverse effect on refractories. The two most damaging situations in kiln start-ups are an incorrect or too rapid heat-up curve and burning zone temperatures that are too high prior to the entry of the feed into the burning zone. d. If extensive monolithic repairs are made it is recommended that a separate dry-out for those areas be conducted prior to heating up the kiln proper. Please contact your Harbison-Walker Refractories Representative for dry-out schedules and information.
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