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Table of Contents - Chapter F Drawworks BrakesIntroduction........................................................................................................................................F-3I. Maintenance Procedures.................................................................................................................F-4II. Brake Linings (Blocks)...................................................................................................................F-5 III. Brake Bands.................................................................................................................................F-5 IV. Brake Rims (Flanges)....................................................................................................................F-6 V. Brake Linkage..............................................................................................................................F-20 VI. Company Policy.........................................................................................................................F-20Chapter FDrawworks BrakesThe IADC Drilling Manual is a series of reference guides for use in field operations covering a variety of subjects related to drilling operations.The contents of this (these) volume (s) are assembled by a wide range of members of the drilling industry inter-ested in providing information to field personnel to encourage proper operations, maintenance and repair of equip-ment and training and safety of personnel.It is not intended that the contents of this manual replace or take precedence over manufacturer's, operators or individual drilling company recommendations, policies and/or procedures. In those areas where local, state and federal law is in conflict with the contents then it is deemed appropriate to adhere to suer laws. IADC has endeav-ored to insure the accuracy and reliability of this data, however, we make no warranties or guarantees in connec-tion with these recommendations.As technology continues to develop this manual will be updated. It is important that the user continue to update their knowledge through research and study.The following industry representatives have contributed to the development and updating of this chapter:MEMBERS OF THE TASK GROUP:Bill Brannon Grey Wolf Drilling CompanyG. Otis Danielson ConsultantNorman Dyer LTV Energy ProductsJames Jones S & J Rig PartsPaul Price National OilwellJack Reeve IRI International Corp.IntroductionThe information contained in this section of the Drilling Manual is for use by field personnel as a guide in the maintenance of a drawworks brake system to insure proper function, safety and economy of operation. Drawworks brakes are highly engineered mechanical systems. Manufacturers of drawworks generally furnish complete maintenance instructions. Owners and operators of rigs should look first to the equipment manufacturer for the complete and specific details of maintenance and safety considerations. Field personnel need to be in-formed of the basic maintenance and safety concepts necessary to make proper judgements in carrying out maintenance procedures at the well site.Fortunately, the signals indicating the need for most maintenance functions are cumulative and easily recognized. Since adjustments and replacement of linings are very routine with rig crews, the precautions and planning involved are largely just normal care and common-sense.As a practical matter, the overriding concern in brake system maintenance is the proper monitoring of the various parts to assure that wear or deterioration does not progress beyond safe limits.Operating Cautions: WARNINGBrake handle kick can be dangerous and can result in bodily injury. Causes of brake handle kicks which involve rapid brake handle movement and potentially large forces may include:1) sudden hoisting speed with brakes engaged with little or no hook load,2) band rollers/springs missing or out of adjustment,3) brake blocks stuck to the brake rims,4) bent or damaged brake bands, and5) worn or loose dead-end linkage.WARNINGSudden application of the brakes while the block is going up in the mast or derrick can cause the wire line on the drum spool to backlash and the wireline clamp to unseat or loosen. Such practice is hazardous to both equipment and personnel. Any time such wireline backlash does occur, rig personnel should inspect the wireline clamp to insure it is still properly installed.Only mechanical band brake systems are discussed in this section; however, caliper brake systems are presently being developed. Therefore, refer to the equipment manufacturer's literature for information on maintenance and safety considerations.I. Maintenance ProceduresThe following maintenance procedures are recommended:1) scheduled lubrication and visual inspection,2) adjustment of brake handle position,3) adjustment of band rollers and springs,4) inspection of lining (blocks) and brake rims for wear,5) inspection of cooling system,6) inspection of bands, especially when blocks are replaced, and7) inspection of linkage (live and dead end) for wear.The timing of these activities should be influenced by the experience of the operation, rig conditions and usage, and recommendations of the equipment manufacturer. Special or more frequent inspections may be dictated by any unusual braking action or performance of the equipment, as well as anticipated requirements for the braking system. Most of these items are a part of daily rig operation, and problems discovered in the inspection will be solved by the experienced rig crew. All inspection and repairs should be reported. Problems of an unusual or serious nature may require special attention.Item 4 inspection may dictate replacement of linings and calls for an evaluation of the equipment by the inspections in items 4 through 7 and other related parts of the brake system, as needed. A lengthy idle period and possibility of deterioration will call for an evaluation of the braking system before restarting rig use. In all cases, good mainte-nance records must be kept, and will help to provide a safe brake system.II. Brake Linings (Blocks)As with other equipment expendables, drawworks brake lining wear and replacement should be monitored and recorded. If, when inspected, the worn blocks are giving good service and have adequate wear remaining, the evaluation is likely to be "Don't change it." If service life has been shortened by non-uniform wear, etc., lining should be replaced and the cause(s) should be determined and corrected.Brake linings for all manufacturers' drawworks are readily available from a number of suppliers in a variety of materials. Due to health concerns, some equipment manufacturers are discontinuing the use of asbestos lining on new drawworks. As to the selection of replacement linings, there are many choices available. Considerations include friction factors, fade, wear, service compatibility, equipment manufacturer's recommendations, as well as health and safety of the rig crew.With the proper supervision, inspection, tools and care, the rig crew can install a new set of brake blocks at the rig site. The brake bands must meet minimum acceptance criteria as outlined below in order to be re-lined.Replacement linings delivered to the rig installed on a set of used brake bands on an exchange basis could be dangerous. Use them only if the exchange bands have been properly inspected prior to re-lining.Brake linings and blocks should be stored in a clean dry place and protected from high heat or strong sunlight to minimize aging and deterioration.III. Brake BandsBrake band failure can be catastrophic. Proper maintenance and periodic inspection are critical to safe and reliable rig operations.WARNINGField personnel should be constantly alert to the severe consequences of brake band failure and should follow manufacturer's recommendations for brake band maintenance.Probably the largest contributor to wear on brake rims and linings, other than normal usage, is bent, flattened, or twisted brake bands. Special care must always be taken when handling, storing, or transporting brake bands, especially if brake blocks are installed on bands. When a band is distorted from its proper shape it not only pro-motes rapid wear, but causes the brake lever to "kick" when released. Operation of damaged brake bands can also cause brake band failure and/or damage to or failure of other brake linkage components.When removing a brake band for any reason, proper care should be taken to prevent damage of the brake band.Similar care should be taken during installing a new or relined brake band. Jerking the brake band assembly with the cat line or the hoisting line can cause kinking and distortion.Brake bands, as reinstalled on the drawworks, should conform to the following:1) Blocks properly bolted and secured in place on a surface that is clean and free from rust and paint.2) Bands inspected for roundness and proper curvature. Bands free of bends, flattening, twists, kinks or other distortions.3) Bands with the same material strength and other mechanical properties as the original equipment bands.4) Bands free from cracks around holes, rivets, welds, and at any other areas of stress concentration. All bands should have been examined prior to relining by technically qualified personnel using generally accepted inspection methods, such as magnetic particle inspection, dye penetrant examination, or other method for the detection of fatigue cracks and other defects. Bands with fatigue cracks should be removed from service and destroyed.5) Bands free from nicks, gouges, dents or other surface irregularities which act as stress risers. These should have been removed by filing and smoothing prior to relining.6) Bands free from any weld repair. Make no attempt to repair a brake band by welding or any other means. If bands are not in reasonably "as good as new" condition, they should not be put into service.As a word of caution, it is an accepted fact that end connector welds that run straight across the band width act as stress risers and can cause fatigue cracks.New or replacement brake bands should be stored flat and on a level surface to minimize distortion while in storage.IV. Brake Rims (Flanges)IntroductionBrake rims are designed to have a prescribed amount of wear (reduction in thickness) before they should be replaced. Wear generally accelerates rapidly once the hardened layer or surface has been worn away, and further usage will result in more rapid wear and an unsafe condition.Each time brake linings are replaced, brake rim wear should be measured. By keeping accurate records of the cumulative amount of rim wear, field personnel can predict when to replace the brake rims in order to get the maximum safe allowable service from each set. Timely measurement of brake rims must be made to assure that safe wear limits are not exceeded.A. Measuring for WearWear measurements can be made in several ways. The examples shown in Figure F-1 (as well as ultrasonic measurements) are used because they can be made with the brake bands in place and with only a short interrup-tion in rig operations.Figure 1-1 Brake Rims MeasurementsThe procedure used in Figure F-1 obtains the measured distance "M" (using a depth gage) which is used to calculate the greatest amount of brake rim wear "W". Compare this amount of wear to the permissible amount of wear, Wi or W2, in each manufacturer's table, included herein, to determine the appropriate action.Ultrasonic thickness instruments may also be used to accurately measure remaining brake rim thickness, which, as shown in Figure F-1, is used to figure the amount of wear "W". All drill pipe inspection companies routinely use this method.Dimension "L" should be measured and recorded before each brake rim is put into service.Information in the Table F-xx is not meant to be a substitute for information that is available from the drawworks manufacturer or other suppliers.Tables Related to Brake Rim Wear: T ables F-xxIt should be noted here that hardness tests of the worn brake rim surface will indicate if the wear has progressed into the underlying "soft" metal below the hard surface overlay. The brake rim manufacturer should be consulted in this. Many machine shops have portable hardness testing equipment. A variation of 10 to 15 points or more on the Rockwell C scale indicates wear into the softer base metal.B. Inspection of RimsEach time that bands are removed, wear should be measured and recorded and rims rotated to make a full 360 degree inspection for visible defects and wear, such as:1) Grooving and/or uneven wear. Measurement for greatest wear should be made at the point where grooving or uneven wear is greatest.2) Transverse or other cracks which propagate across the rim.3) "Cross checking" heat cracks are normal for hard metal overlay rims; however, if the cracks join or intersect adjoining crack patterns, it is possible for such cracks to propagate or enlarge to the point that the brake rim becomes unsafe.4) If operating conditions or the condition of the brake rim so indicate, further inspection by non-destructive means, such as magnafluxing, should be made.Remachining of brake rims for the purpose of correcting warpage or uneven wear can be performed by any machine shop with the appropriate machining capability. The finished diameter of the rim should fall within the wear guidelines recommended by the manufacturer.C. Replacement Brake RimsThe use of rebuilt or resurfaced brake rims is economically viable in certain circumstances, as long as the integrity of the product meets original equipment standards. Generally, large diameter rims or rims with complex geometries such as those with counterbored bolt flanges are good candidates. Rims with excessive wear or rims made of highly hardened material are not safe candidates for resurfacing.Hard surfaced brake rims are common, and are increasing in popularity both as new, original equipment rims, and as replacement equipment. New or rebuilt hard surfaced brake rims are generally harder than through hardened brake rims, and have a thicker hardened surface than flame hardened or induction hardened brake rims. The weld overlayed surface generally differs in appearance from other rims, being characterized by a cross-checking of shallow cracks. These characteristic cracks are not detrimental, and in fact indicate proper weld overlay applica-tion and relieving of residual stresses. These cracks should never extend into the base metal nor should they ever propagate into adjacent areas of the base metal.New or replacement rims should be stored flat and on a lever surface to minimize distortion while in storage.D. Water Jacket ScaleThe formation of scale in water jackets can cause brake overheating. Brake rims should be descaled when inspection reveals a significant scale build-up. Water used as a brake coolant should always be checked for hardness and treated as needed. Never use salt water to cool brake rims.V. Brake LinkageGiven enough time and usage, the contact surfaces in the brake system linkage will wear, resulting in noticeable slack. This affects adjustment of the linkage, operation of the brakes, response time, braking force, etc. This wear can be accelerated by several factors, including infrequent lubrication, selection of improper greases, accumulated grit and extremes in operating temperatures.Inspection and replacement or repair of the affected parts should be scheduled. Parts should be regularly inspected for fatigue cracks as well as for wear. The drawworks manufacturer should be consulted to determine if safe wear limits have been exceeded.VI. Company PolicyLong term economy of operation, within the bounds of sound safety practice, is probably the bottom line of most company policy. For the average drilling contractor, this is best accomplished by supervisors and operating person-nel educating themselves to the task and by calling on the expertise of knowledgeable and reliable manufacturers and suppliers. Our most important skill is knowing how to ask the right questions. Company policy must spell out the safe limits and must schedule the necessary monitorings and inspections.The use of remanufactured brake system components will always be an option and the test of this should be the assurance of quality as represented by the vendor and, or course, performance. The product must perform with the same degree of safety as incorporated in the original design of the drawworks.This Page Left Intentionally BlankChapter G: Chains and Sprockets Chapter GChains and SprocketsInternational Association of Drilling ContractorsG-1。