October 11, 2001
Written in a question-and-answer format, this article offers tips for inspecting and correcting damage to coil reels. Descriptions of several tests are offered, including arbor or reel runout, lost motion, final indicator, and segments straightness tests. Frequently encountered problems such as coilers that break constantly, telescoping coils, and marred material are also addressed.
Q. What is the most common type of failure encountered with payoff or take-up reels?
A. The most common failure is overload failure, which occurs when the reel is loaded with coils that exceed the OEM's weight rating. Often, this failure is not evident with a catastrophic event such as breakage; instead, overload affects the shaft strength, coiler arms, slide surfaces, bearings, and reel alignment. When the reel is overloaded, the arbor shaft bends and/or cracks develop that may not be noticeable until the reel breaks down totally. Overload also causes premature component wear, which contributes to metal fatigue. This premature wear can cause tolerances to open up to an unsafe level, causing hazardous operating conditions.
Q. When a reel is overloaded, has it been damaged even if severe failure has not occurred?
A. Several simple tests can be performed by maintenance or engineering personnel to determine if overload has occurred. If regularly performed, these tests can help track the wear patterns and the condition of reels.
1. Arbor or reel runout tests. This test can be accomplished with a dial indicator. Dial indicator readings are taken at the outboard, middle, and inboard sections of the reel with the unit in the expanded and collapsed positions. These readings are recorded and compared. Readings that show more than 0.015 inch runout (TIR) should be investigated further for possible damage. Excessive runout indicates a bent, broken, or fractured reel shaft, or other damage, and should be corrected immediately.
2. Lost-motion test. To determine if reel components are wearing prematurely, perform a lost-motion test. An indicator is placed above the arbor, on center to the expansion segments or arms. Readings should be taken in both the expanded and collapsed positions. When the indicator is set at zero, a pry bar or small jack is used to try to lift the segment. The amount of movement of the segment is reflected in the indicator reading and recorded. A reading exceeding 0.015 inch should be investigated and corrected because it indicates an out-of-tolerance condition.
3. Final indicator test. This test measures a component's horizontal movement. After placing the dial indicator on the end of each segment, a pry bar is used to attempt to move the segment horizontally. This should be done on each segment, and the readings should be recorded. Corrective maintenance should be done when movement of more than 0.025 inch is noted. The arbor shaft also should be checked for horizontal movement in the same manner, both during rotary motion and with pressure applied to the end of the shaft. Corrective action should be taken when indicator readings above 0.010 inch are present.
4. Segments straightness test. Segments of the reel should be inspected periodically for straightness because bent segments are an obvious sign of overload. With a common straight edge or precision scale that is at least as long as the segment being tested, check for flatness. By laying the straight edge across the centerline of each segment and passing a feeler gauge under the straight edge, an inboard, center, and outboard flatness reading can be obtained. Out of flatness beyond 0.015 inch indicates overload. The reel arbor and segments should be disassembled and nondestructively tested for cracks. Out-of-flat conditions should be repaired.
Q. The segments on coilers break constantly. What causes this, and can anything be done to eliminate this problem?
A. Broken reel segments are a common complaint among reel users. The most frequent causes of these breaks are loading coils that are smaller in width than the reel was designed for and overexpanding the coiler. Most coilers rely on linkage or sloped surfaces called wedges to create the expand and contract diameters of the reel. These expansion devices are located at even dimensions across the underside of each segment. When a metal coil is wound over an unsupported area of the segment that is not directly above an expansion device, the coil puts a deflective load on the segment. If the reel is then expanded or the coil is tensioned, the deflective load is increased, often breaking the segment.
This scenario can be eliminated by loading the coils directly above the support areas on the segments. If this is not possible, the other alternative is to modify the reel with higher-strength segments. This can be done by a reputable machine rebuilder with engineering capabilities.
Q. Two product-related problems that cause customers to reject product are telescoping coils and marred material on the first few wraps. What maintenance tips can help to eliminate these problems?
A. Both of these problems are not only common but relate directly to reel maintenance. The main cause of telescoping coils, which create a great deal of scrap, is tapered and/or loose segments on the reel in the expanded position. To check for taper on the reel, expand it to the fully expanded position. With a caliper and scale, check the reel inboard, middle, and outboard for taper, and record the readings. If the taper is more than 0.025 inch, the telescoping could be caused by the tapered condition. Remachining the expanded segments will correct the taper.
Loose segments also cause telescoping coil. By performing the indicator and lost-motion tests as described previously, loose segments can be documented. Once again, if the tolerances noted are exceeded, telescoping coils could result.
Marred material on the first few wraps, or the bore, of the coil ruins many coils. Marred product is usually caused by a reel that is out of tolerance, which causes egg-shaped bores, or by the transfer of a poor surface finish from a marred segment to the inner surface of the coil. Indicator readings, along with the caliper dimension readings, can indicate any out-of-tolerance condition that might cause egg-shaped coils. Carefully examining the surface finish of the segments will reveal which marrs are being transferred from the segments to the metal coil.
Rebuilding the reel will solve both of these problems. Another solution is to slide urethane or rubber sleeves over the collapsed segments to eliminate the transfer of scars from the segments to the coil.
Q. Where can replacement parts be obtained for reels and coilers built by companies now out of business?
A. The best place to find replacement parts is a qualified machine rebuilder whose capabilites include fabricating, machining, and assembly and whose staff is familiar with the type of equipment you own. The most important element to look for in your source for replacement parts is qualified engineering and sales staffs who clearly understand the tolerances, design, and rebuilding of reels. Firms that qualify can reverse-engineer even the most intricate components from a broken or worn sample.
Q. Is it possible or advisable to increase a 30,000-pound-capacity reel to a 50,000-pound-capacity one?
A. A reel's capacity can be upgraded. Whether it is feasible or cost-effective can be determined from a cost evaluation and engineering study. Once again, this should be done only by qualified engineering and machinery building specialists with background and experience in this field. Material specification, loads, speed, bearings, and overhang are among the many items that must be analyzed to redesign a coiler properly.