Millwright Module 15402 Troubleshooting and Repairing Conveyors Copyright © 2023 by N C CE R, Alachua, F L 32615. Published by Pearson. All rights reserved. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Maintaining and Repairing Conveyors Objective 1. Explain how to maintain and repair various types of conveyor systems. a. State general considerations and safety practices related to conveyor system maintenance and repair. b. Explain how to maintain and repair belt conveyors. c. Identify factors that affect conveyor belt tracking and explain how to correct tracking problems. d. Explain how to maintain and repair chain conveyors. e. Explain how to maintain and repair screw conveyors. f. Explain how to maintain and repair pneumatic conveyors. Module 15402 – Troubleshooting and Repairing Conveyors Performance Tasks 1. Create a splice between two sections of belting using a mechanical fastening system. 2. Complete an instructor-selected mechanical repair on a belt, chain, screw, or pneumatic conveyor system. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0–1.1.0 Maintaining and Repairing Conveyors (1 of 2) Over time, mechanical parts become worn, loose, or misaligned and require the skills of an industrial maintenance specialist or millwright. • Timely lubrication and accurate alignment is necessary to minimize the effects of friction. • Problems must be identified and resolved as soon as possible to minimize downtime. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0–1.1.0 Maintaining and Repairing Conveyors (2 of 2) • The needs of a conveyor system depend on the type of conveyor, the scope of usage, and its environment. • PM prolongs equipment life and improves reliability. • Craft professionals become attuned to the sound and feel of normal operation. Module 15402 – Troubleshooting and Repairing Conveyors 1.1.1 Troubleshooting and Repair Processes (1 of 2) Troubleshooting and repair activities can be broken down into five basic steps: 1. Verifying or observing the symptoms 2. Considering probable and possible causes 3. Investigating the possible causes and testing 4. Making the repairs, replacing parts as necessary 5. Operational testing and confirming that the problem has been solved Module 15402 – Troubleshooting and Repairing Conveyors 1.1.1 Troubleshooting and Repair Processes (2 of 2) • Observing the conveyor system operating correctly makes brainstorming the possible causes of a problem much easier. • If the system is not operational, troubleshooting can be more difficult because the symptoms may no longer be visible or audible. • Never hesitate to contact someone who understands and can interface with the electrical and control systems when troubleshooting conveyors! Module 15402 – Troubleshooting and Repairing Conveyors 1.1.2 Conveyor Safety (1 of 5) • The American Society of Mechanical Engineers (ASME) is an essential resource for conveyor safety. • Emergency stop controls are required on all powered conveyors! • Some conveyors have red cords or cables in addition to, or instead of, an Emergency Stop button. Module 15402 – Troubleshooting and Repairing Conveyors 1.1.2 Conveyor Safety (2 of 5) CAUTION The Emergency Stop control should not be used outside of emergency situations. Many conveyor systems are interlocked with other equipment and systems. In that case, a specific shutdown sequence may be bypassed when the Emergency Stop button is used, in the interest of immediate stoppage. For this reason, it is best to use the normal conveyor controls to shut down a system in the absence of a true emergency. Module 15402 – Troubleshooting and Repairing Conveyors 1.1.2 Conveyor Safety (3 of 5) Basic safety practices to remember when working on or near a conveyor include: • Inform operating personnel when you need to shut down a conveyor. • After turning off the power, always lock out and tag (LOTO) the power source. • Keep the work area clean and uncluttered. As work is completed, collect and inventory all your tools. • Reinstall all guards and reset all safety devices before the conveyor is restarted or tested. Module 15402 – Troubleshooting and Repairing Conveyors 1.1.2 Conveyor Safety (4 of 5) • Follow all OSHA and local LOTO procedures as you restore power. • Pay close attention to how the conveyor operates when it starts. Listen as well as watch. • Inform management and the operators of the status of the conveyor before you leave the area. Module 15402 – Troubleshooting and Repairing Conveyors 1.1.2 Conveyor Safety (5 of 5) Specific hazards to be aware of when working around conveyors include: • Unguarded moving parts • Shifting or protruding loads • Damaged parts • Overheated components • Moving surfaces and pinch points • Bolt tension and stored energy Module 15402 – Troubleshooting and Repairing Conveyors 1.2.0 Maintaining and Repairing Belt Conveyors • The easiest way to prevent conveyor problems is to ensure that regular, scheduled PM is performed on the conveyor. Ideally, potential problems are found during PM inspections and resolved before a breakdown occurs. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.1 Belt Conveyor Maintenance (1 of 3) The following inspection items are common for belt and roller conveyors: • Test the Emergency Stop switch. • Inspect all rollers and idlers. • Examine all exposed drive shafts. • Inspect sprockets. • Brush grit and debris from drive chains. • Examine drive sheaves and belts. • Ensure all bearings that require lubrication are serviced. • For sliding bed conveyors, inspect the bed. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.1 Belt Conveyor Maintenance (2 of 3) WARNING! To prevent injury, keep away from the rotating parts of an operational conveyor. Most maintenance is performed with the conveyor off, and all energy sources locked out and tagged. While working, keep your tools collected in a bin or toolbox, rather than laid haphazardly on the conveyor itself. Regardless of the conveyor’s status, never wear loose clothing, jewelry, unbuttoned sleeves, or untucked shirttails around machinery. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.1 Belt Conveyor Maintenance (3 of 3) • Both roller and belt conveyors may rely on drum motors as a drive option. • Drum motor maintenance is simple compared to conventional drives, but some maintenance is required: • Clean any deposits on the rollers. • Look for signs of damage on the drive motor, the small belts that transfer power, and the wiring connections. • Ensure all mounting hardware is secure. • Ensure the manufacturer’s lubrication schedule is being followed and that the correct lubricant is being used. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.2 Maintaining and Replacing Rollers (1 of 3) • The drive rollers, tail rollers, and rollers in a center-drive arrangement are critical to the operation of the conveyor. • Drive rollers are usually larger than any of the other rollers. They are generally found on conveyors that do not require a lot of belt tension. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.2 Maintaining and Replacing Rollers (2 of 3) • Some tail rollers have a winged design that help dislodge debris that adheres to the bottom of the belt, called carryback. • Take-ups provide the means to properly tension a conveyor belt. • The correct tension is that which is sufficient to move the maximum design load without slipping on the drive roller. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.2 Maintaining and Replacing Rollers (3 of 3) • Systems with light loads require less belt tension. • To replace a drive roller, the drive components must be disassembled and removed. • Before shutting down the system for repairs, carefully evaluate the task and have everything on hand. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.3 Belt Repair • Some belt damage can be repaired. • Repair kits are available from a variety of sources and can be used to repair large gouges, holes, or tears. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.4 Conveyor Belt Splicing (1 of 4) Conveyor belts are expensive and time-consuming to replace. • Splicing a belt to replace a damaged section is one way to get the expected service life from a belt. • Vulcanizing is generally the best approach for belts made of rubber and rubbery materials. • Mechanical splicing is much faster than vulcanizing. However, due to the stress applied to some thick and heavy belts, mechanical splicing may not be a practical solution. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.4 Conveyor Belt Splicing (2 of 4) • Cutting the end of a belt in a pattern increases the line of contact between the two pieces. • Fastening solutions include Clipper® Wire Hooks, Alligator® Staples, bolted solid-plate fastening systems, riveted-plate fasteners, and fasteners with hinged plates. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.4 Conveyor Belt Splicing (3 of 4) • When choosing a fastening system, consider the diameter of the rollers and the tension rating of the belt. • Not every mechanical splice is created on the full thickness of the belt. Skiving is often required to lower the profile of the splice. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.4 Conveyor Belt Splicing (4 of 4) • A belt skiving tool can be used to ensure the cut is of the proper width and depth. • Belt products and fastening systems vary widely, so it is vital to follow the belt manufacturer’s guidance and the fastening system’s instructions. Module 15402 – Troubleshooting and Repairing Conveyors 1.2.5 Replacing Conveyor Belts The method for replacing a conveyor belt is determined by the length of the belt and the complexity of the conveyor. • Conveyor belts are usually received on rolls. • To join an old and new belt, a roll of new belt material is typically placed near the tail roller where a temporary splice is created. • After the old belt has been removed, the ends of the new belt are spliced and aligned. • Rolls of conveyor belting are rolled at the factory with the load-carrying side of the belt on top. Module 15402 – Troubleshooting and Repairing Conveyors 1.3.0 Conveyor Belt Tracking Making the necessary adjustments so that a belt consistently runs along the center of its bed is called training a belt. • Poor belt tracking can result in wear, damage, and product spillage. • Adjusting the tail roller take-ups should only be done to correct a tracking problem if all other possible causes have been eliminated or resolved. Module 15402 – Troubleshooting and Repairing Conveyors 1.3.1 Equipment Problems That Affect Belt Tracking (1 of 3) Equipment-related factors include: • Belt curvature • Belt cupping • Damaged or out-of-square belt splice • Conveyor structure that is bent, twisted, or misaligned • Misaligned or damaged return, idler, and snubber rollers Module 15402 – Troubleshooting and Repairing Conveyors 1.3.1 Equipment Problems That Affect Belt Tracking (2 of 3) • Belt curvature is often caused by improper storage. Ideally, belts should be suspended by the core for storage. • Excessive tension coupled with head and tail roller misalignment can also cause curvature to develop during operation. • When a belt forms an undesirable trough, it is referred to as belt cupping. Cupping is often caused by excessive heat, excessive tension, or chemical attacks. • A belt-splice that is separating or not square can cause significant wandering. Module 15402 – Troubleshooting and Repairing Conveyors 1.3.1 Equipment Problems That Affect Belt Tracking (3 of 3) A conveyor structure must be square in all planes. • The structure should be level from end to end, unless designed for a specific incline. • Rollers must be square to the belt path and parallel to the other rollers. • Rollers must rotate freely and be kept clean. Module 15402 – Troubleshooting and Repairing Conveyors 1.3.2 Operational Problems That Affect Belt Tracking Some tracking problems are related to how the conveyor is operated and managed. • Material stuck to the belt (carryback) can affect belt tracking. • Devices featuring solid or segmented blades may be used to scrape the belt clean as it passes by, but it must be inspected regularly. • Uneven loading of heavy materials can impact the belt. This can’t always be addressed through adjustments to the conveyor. Instead, changes must be made to the chute position or design. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.0 Maintaining and Repairing Chain Conveyors • Chain conveyors are versatile and can carry material above, beside, or below the conveyor. • Chain conveyors can withstand extreme heat and temperature changes. • The main components are the chains, carrying devices, sprockets, shafts, bearings, and take-up devices. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.1 Chain Conveyors Maintenance PM for chain conveyors is similar to PM for belt and roller conveyors. • The conveyor chain should be inspected daily. Any debris should be removed, and the lubrication should be applied as needed. • Weekly inspections should include cleaning and any needed lubrication. • Always check the chain tension as conveyor chains elongate over time. • More significant maintenance must occur each quarter, including a close inspection of the drive components. • Some components will likely require more maintenance than the chain. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.2 Conveyor Chain (1 of 4) Most products are assembled by inserting a pin through two links and securing the pin with a clip, cotter pin, or similar hardware. • Most chain products in the United States are built to American National Standard Institute (ANSI) standards. • ANSI products have an assigned number for identification. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.2 Conveyor Chain (2 of 4) • Other components must often be attached to the chain using K, F, L, and spigot pin attachments. • These attachments are standardized but there are many variations in chain construction. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.2 Conveyor Chain (3 of 4) Chain elongation can be determined using measurement and math. • Conveyor chain is often larger and heavier than standard roller chain. • Chain will often be disassembled while it remains on the conveyor. • There must be slack in the chain before it can be taken apart. • Determining how much a chain has elongated helps determine when it needs to be replaced. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.2 Conveyor Chain (4 of 4) When assembling a chain link, the pins must be secured using riveted links, pin clips, cotter pins, or nuts and bolts. WARNING! Common cable-equipped come-alongs are not safe to pull and hold heavy chain. They should not be used for this purpose to avoid possible injury from a sudden release. Ratcheting-chain hoists have a superior braking and holding mechanism. The cable-equipped device shown in Figure 48 is designed specifically for pulling chain and is rated to handle ANSI roller chain sizes #80 through #240. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.3 Chain Conveyors Sprockets (1 of 3) • Sprockets may wear faster than chain. • Cast iron and steel sprockets are standard but there are unique types as well. • Split sprockets and segmented sprockets make maintenance and repair easier. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.3 Chain Conveyors Sprockets (2 of 3) • Sprocket wear is common on the drive side of each tooth, and along the sides of the teeth. • Balanced wear on both sides of a sprocket is considered normal. • The criteria to determine sprocket replacement is not standardized— consult the manufacturer. Module 15402 – Troubleshooting and Repairing Conveyors 1.4.3 Chain Conveyors Sprockets (3 of 3) • Most manufacturers allow the sprocket to be reversed, which can nearly double its service life. • After completing repairs on chain, sprockets, or other drive components, testing is required. • Always monitor the operation of the conveyor for multiple revolutions to ensure it operates as expected. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.0 Maintaining and Repairing Screw Conveyors A basic screw conveyor consists of a drive motor, an auger, and the trough. • Screw conveyors are typically simpler and shorter than other types. • Clogs and jams are the most common problems. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.1 Lubrication Bearings at the end of each auger shaft require lubrication. • Many augers have hanger bearings that also require lubrication. • Be sure to use the oil or grease product recommended for each component. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.2 Drive Components Screw conveyors use a variety of drive arrangements. • Service and inspect drive components according to the manufacturer’s guidance. Bearings should rotate freely and smoothly without play. • Refer to NCCER Module 15311, Installing Belt and Chain Drives; Module 15209, Introduction to Bearings; and NCCER Module 15306, Removing and Installing Bearings. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.3 Augers and Auger Shafts (1 of 2) • Augers are often shipped in multiple pieces and assembled using compatible couplings. • The outer edge of the flights is a critical area. • Auger removal or replacement begins at the end opposite the drive. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.3 Augers and Auger Shafts (2 of 2) A screw conveyor jam often needs to be cleared manually. • Clogs in screw conveyors moving granular material are often due to moisture in the material. • Tapping the sides of the trough with a rubber mallet can often dislodge clogged material. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.4 Shaft Seals and Stuffing Boxes Auger shafts pass through trough end plates. • Penetrations through the end plates may be fitted with seals. • Conveyors with shaft seals may have stuffing boxes with rings of packing. Some may have lantern rings. Module 15402 – Troubleshooting and Repairing Conveyors 1.5.5 Troughs The trough must be kept clean and aligned along its entire length. • Alignment should be checked before the flange bolts are tightened and before the trough is anchored in place. • The tolerance for trough alignment is specified by the manufacturer. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.0 Maintaining and Repairing Pneumatic Conveyors Pneumatic conveyors use air to blow (positive airflow) or vacuum (negative airflow) product from one point to another. • There are two primary classes of pneumatic conveyance: dilute phase systems and dense phase systems. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.1 Dilute Phase Systems Dilute phase systems generate a continuous airstream, pushing airborne material down the line. • The material-to-air volume ratio is low compared to dense phase systems. • Dilute phase systems generate a lower pressure difference between the inlet and the outlet, but the air velocity is much higher than dense phase systems. • They can operate at a positive or negative pressure and generally move product through tubing. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.2 Dense Phase Systems These systems rely on a pressure differential to move product. • Product movement down the pipe occurs in slugs. • There is a lot of product in motion in a small volume of air. • Dense phase systems have a compressor with an accumulator instead of a blower. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.3 Pneumatic Conveyor Maintenance Maintenance focuses on two main areas: the air source and the receiving vessel. • Filter receivers generally represent the destination of the conveyed product. • The filters can load very quickly. To prevent this, they usually have an automated cleaning system to assist. • Filters can virtually remain in service until they begin to come apart. • Periodic maintenance must include an inspection for air leaks along the line. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.4 Pneumatic Conveyor Troubleshooting and Repair (1 of 3) • If receiver filters don’t seem to be cleaning properly, check the differential pressure and air pressure. Ensure each control valve is opening on command. • In dense phase systems, a great deal of force is applied when the product changes direction. • Worn or binding flappers can cause a blockage. • Sliding diverter valves can eliminate many of the problems associated with flapper-type diverters, but they cost more. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.4 Pneumatic Conveyor Troubleshooting and Repair (2 of 3) • Clogs can develop from improper operation and control, component failure, or changes in the product. Disassembly of the tubing or pipe is required to clear significant clogs. • When troubleshooting blower and system pressure issues, start with the system pressure gauges. • A steady but low-pressure reading can indicate that there isn’t enough product entering the system. • A steady but high-pressure reading indicates a blockage. • A pressure reading that fluctuates indicates wear and/or air leakage through the rotary valve. Module 15402 – Troubleshooting and Repairing Conveyors 1.6.4 Pneumatic Conveyor Troubleshooting and Repair (3 of 3) Rotary valves cause as many problems as all other sources combined. • They are not easily accessed for inspection, so they are scheduled for replacement based on prior experience. • Worn valves often cause a reduction in the volume of conveyed product. Module 15402 – Troubleshooting and Repairing Conveyors Trade Terms (1 of 2) : Conveyed material that fails to unload at the end of a conveyor belt, adhering to or embedding itself in the belt and traveling back to the head of the conveyor on the underside. : Any material that falls from or escapes a conveyor system, including dust, and doesn’t reach the intended destination. : The removal of one or more layers of a conveyor belt to accommodate a splice to avoid a significant change in belt thickness. Module 15402 – Troubleshooting and Repairing Conveyors Trade Terms (2 of 2) : Using heat or chemicals along with pressure to create a conveyor belt splice. Hot vulcanization relies on direct heat, while cold vulcanization relies on chemicals to develop the necessary heat and bond. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 1 1. Which of the following statements about Emergency Stop controls is correct? a. An Emergency Stop control should only stop the conveyor for a few seconds. b. For consistency, only a large red button can be used as an Emergency Stop control. c. An Emergency Stop control may bypass important interlocks with other equipment. d. Using the Emergency Stop control is the best way to shut down a conveyer in every situation. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 1 Answer 1. Which of the following statements about Emergency Stop controls is correct? a. An Emergency Stop control should only stop the conveyor for a few seconds. b. For consistency, only a large red button can be used as an Emergency Stop control. c. An Emergency Stop control may bypass important interlocks with other equipment. d. Using the Emergency Stop control is the best way to shut down a conveyer in every situation. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 2 2. Which of the following statements about belt conveyors is correct? a. Counterweight take-ups are usually found on longer conveyors with heavier belts. b. Belt conveyors perform at their best with the belt tension set as high as possible. c. The correct belt tension for all belt conveyors is roughly the same, regardless of the load or application. d. When adjusting belt tension, begin with the conveyor belt loaded to its maximum rated product load. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 2 Answer 2. Which of the following statements about belt conveyors is correct? a. Counterweight take-ups are usually found on longer conveyors with heavier belts. b. Belt conveyors perform at their best with the belt tension set as high as possible. c. The correct belt tension for all belt conveyors is roughly the same, regardless of the load or application. d. When adjusting belt tension, begin with the conveyor belt loaded to its maximum rated product load. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 3 3. Which of the following steps is best to protect rolls of belting that must be stored on the floor? a. Rotate the roll 90 degrees every 90 days. b. Unroll and then roll the belt back up in the opposite direction every 90 days. c. Stand the roll on its end, changing ends every 90 days. d. Alternate between standing the roll on its end and laying it on the floor every 90 days. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 3 Answer 3. Which of the following steps is best to protect rolls of belting that must be stored on the floor? a. Rotate the roll 90 degrees every 90 days. b. Unroll and then roll the belt back up in the opposite direction every 90 days. c. Stand the roll on its end, changing ends every 90 days. d. Alternate between standing the roll on its end and laying it on the floor every 90 days. Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 4 4. What is the percentage of elongation for an ANSI-standard #120 conveyor chain that measures 387 mm across 10 pitches, as shown in the figure provided? a. 3.72 percent b. 2.62 percent c. 2.04 percent d. 1.57 percent Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 4 Answer 4. What is the percentage of elongation for an ANSI-standard #120 conveyor chain that measures 387 mm across 10 pitches, as shown in the figure provided? a. 3.72 percent b. 2.62 percent c. 2.04 percent d. 1.57 percent Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 5 5. Screw conveyor shaft seals that require a cooling fluid introduce the fluid into the seal through a . Fill in the blanks a. labyrinth seal b. secondary seal c. lantern ring d. perforated packing ring Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 5 Answer 5. Screw conveyor shaft seals that require a cooling fluid introduce the fluid into the seal through a . Fill in the blanks a. labyrinth seal b. secondary seal c. lantern ring d. perforated packing ring Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 6 6. A dilute phase pneumatic conveyor generates a constant stream of product moving at speeds up to 40 mph 65 kph . a. True b. False Module 15402 – Troubleshooting and Repairing Conveyors 1.0.0 Section Review Question 6 Answer 6. A dilute phase pneumatic conveyor generates a constant stream of product moving at speeds up to 40 mph 65 kph . a. True b. False Module 15402 – Troubleshooting and Repairing Conveyors Next ellipsis Review for Module Testing Complete the Review Questions at the end of the module and prepare for the Module Test.
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