Preliminary Requirements

Procedure

1. SUBTASK 70-41-01-400-001 Table of Contents

   Safety Precautions		Step
   Introduction		Step
   Equipment and Material		Step
   Use of Torque Wrenches		Step
   Use of Power Wrenches		Step
   Application of Torque		Step
   Lubrication		Step
   Cleaning		Step
   Sealing Compounds		Step
   Tightening Sequence		Step
   Self-locking Fasteners		Step
   Torque Loading of Fluid Fittings and Blanking Plugs		Step
   Assembly of Face Tooth Joints		Step
   Minimum Thread Projection Requirements		Step

2. SUBTASK 70-41-01-860-002 Safety Precautions

   1. 

      WARNING

      IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURER'S MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS, THESE CONTAIN INFORMATION SUCH AS, HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

      The operator shall provide adequate procedures and training to ensure manual manipulation and handling comply with local regulations.

3. SUBTASK 70-41-01-860-003 Introduction

   1. 

      CAUTION

      UNIVERSAL JOINTS MUST NOT BE USED WITH TORQUE WRENCHES BECAUSE INCORRECT TORQUE VALUES CAN BE SHOWN.

      

      CAUTION

      HANDLE EXTENSIONS MUST NOT BE USED ON TORQUE WRENCHES.

      This specification gives torque tightening procedures and standardized torque loads for use on V2500 engines in order to ensure consistent assembly of bolted joints.

   2. The torque limits given in this specification apply to threaded assemblies when the specification is referenced on the drawing or in a document referenced on the drawing. Torque limits specially shown on the drawing or in a document referenced on the drawing shall take priority over the torque limits listed in this specification.

      For a small number of bolts at moderate torque loads (for example, 3 or 4 bolts at up to 125 lbf/inch), use a suitable manual wrench; the use of a power tool is not appropriate.

4. SUBTASK 70-41-01-860-008 Equipment and Material

   1. Standard equipment.

      1. Generally good quality commercial tooling; some specific type-approved power wrenches are given in Table 1, (Step).

   2. Consumable materials used in the overhaul process.

      CoMat 01-124 ISOPROPYL ALCOHOL	Isopropyl alcohol
      CoMat 04-004 JOINTING COMPOUND, LIGHT GRADE	Jointing compound
      CoMat 04-005 JOINTING COMPOUND, MEDIUM GRADE	Jointing compound
      CoMat 04-006 JOINTING COMPOUND, HEAVY GRADE	Jointing compound
      CoMat 10-039 ENGINE OIL	Lubricant (Engine oil)
      CoMat 10-040 LUBRICANT (ENGINE OIL)	Lubricant (Engine oil)
      CoMat 10-077 APPROVED ENGINE OILS	Approved engine oil
      NOTE To identify the consumable materials, refer to the PCI.

5. SUBTASK 70-41-01-860-005 Use of Hand Torque Wrenches

   1. Flexible Beam Type.

      1. To get the correct torque indication, the handle must be held lightly with one hand. The wrench must be pulled at right angles (90 degrees) to the center line of the wrench. The handle must be free to move on the pivot-point. This will make sure that the concentration of the force or load is at the correct position (refer to Figure. The position of the hand must not be changed to a position that will change the concentration of the force from the pivot-point to a different position on the handle. Interchangeable sockets, adapters and extension bars are supplied with all wrenches to suit a variety applications.

      2. Use a torque wrench which will show the necessary torque value in the higher range of the scale; this will make sure of an accurate torque indication. The first and last quarter of the scale must not be used for mandatory loads. This is because the torque value shown for small loads can not be read accurately in the first and last quarter. Some flexible beam type wrenches do not show the first and last quarter of the scale. Wrenches must be set to zero before they are used.

      3. Do a test on wrenches on a setting rig at regular times to make sure they give an accurate torque indication. If necessary, adjust the wrench specified in the manufacturer's instruction book.

   2. Screwdriver Type.

      1. Hold the tool the same as a screwdriver handle; this will make sure of an accurate torque indication. The handle must be turned smoothly until the necessary torque value is shown (refer to Figure.

      2. Do a test on screwdriver-type wrenches to make sure they give an accurate torque indication. When the screwdriver-type wrenches are not used they must read zero on the scale. If necessary, adjust the wrench as specified in the manufacturer's instruction book.

   3. Torque Multiplier.

      1. The torque multiplier is a mechanical gearbox or hydraulic unit and must be used with a torque wrench. Higher torque values are possible with a torque multiplier than are possible with the usual range of torque wrenches. The torque wrench must have the correct scale for the ratio of the unit that is used. The torque multiplier must be calibrated at regular times and kept serviceable as specified in the applicable instructions.

   4. NOTE

      The length of extensions, adapters, and wrenches must be shown on the tools, or measured correctly before they are used.

      Torque Wrenches and Extensions.

      1. When an extension is used with a torque wrench, it will change the length that has an effect on the load. The corrected torque value that is necessary to give a specified torque value for a part must be calculated when extensions are used (refer to Figure. The procedure to calculate the corrected torque value that is necessary on the torque wrench is as follows:

         T = Specified torque for a part.

         E = Length of extension or adapter.

         L = Length of torque wrench.

         A = Distance through which force is given to a part.

         R = Corrected torque value.

         	R =	L x T		=	L x T
         		A			L + E

      2. Example:

         A specified torque of 1440 pound-inches (163 Nm) is necessary on a part. An extension of 3 inches (76 mm) from center to center of its holes is used. The torque wrench used has a length of 15 inches (381 mm) from center of handle or handle swivel pin to center of its square adapter. The extension or adapter and torque wrench are used in a straight line.

         Then:

         	R =	L x T		=	15 x 1440		= 1200
         		L + E			15+3

         To get the specified torque (T) of 1440 pound-inches (163 Nm) the corrected torque value (R) that is necessary is 1200 pound-inches (136 Nm).

6. SUBTASK 70-41-01-860-006 Use of Power Wrenches

   1. 

      CAUTION

      DUE TO THE SPEED OF POWER TORQUE WRENCHES, HEAT CAN BE GENERATED, THIS HEAT CAN AFFECT THE TORQUE VALUE. IF YOU DO NOT ALLOW THE FASTENERS TO COOL BEFORE APPLYING THE FINAL TORQUE YOU CAN DAMAGE THE FASTENERS.

      

      CAUTION

      DO NOT USE POWER TOOLS TO TIGHTEN FASTENINGS ON JOINTS THAT CONTAIN "CRUSH GASKETS" BECAUSE THE GASKET CAN BE DAMAGED BY INAPPROPRIATE TIGHTENING TECHNIQUE.

      Air-driven power wrenches must give a constant load irrespective of the airline pressure.

   2. Maintenance and Calibration.

      1. Power tools must be maintained to an adequate standard to ensure satisfactory operation. The following apply:

         1. The accuracy of the torque applied must be within +/- 10 percent of the necessary setting.

         2. Power wrenches must be checked when they are drawn from the stores and at regular intervals at the discretion of the Quality department concerned.

         3. Power wrenches must be identified by affixing a label endorsed "This wrench is set to ....lbf/inch (....Nm)" and the power setting must not be changed with authority of the appropriate department.

         4. Power tools must not be used with universal joints which can move through an angle greater than 25 deg from vertical.

   3. Power Wrenches.

      1. NOTE

         * These tools are complex and not appropriate for general use. Facilities introducing these tools with no previous experience must seek manufacturer's recommendations for their appropriate application.

         All power tools approved for final torque tightening must have demonstrated calibrated accuracy of +/- 5% of the tightening torque. Table 1 contains a sample list of tools that have been assessed and approved.Other torque wrenches can be used provided it can be demonstrated that they meet the calibration requirements of this specification.

         Tool Manufacturer and Tool Part Number		Torque Range	Power Source
         Atlas Copco ETB6		9 to 53 lbf/in (1 to 6 Nm)	Battery
         Atlas Copco ETB10		26 to 90 lbf/in (3 to 10 Nm)	Battery
         Atlas Copco BTB12		95 to 105 lbf/in (10 to 12 Nm)	Battery
         Atlas Copco LTV008 R07-6		31 to 62 lbf/in (3.5 to 7 Nm)	Pneumatic
         Atlas Copco LTV18 R15-6		53 to 132 lbf/in (6 to 15 Nm)	Pneumatic
         Atlas Copco LTV28 N22-10		96 to 192 lbf/in (11 to 22 Nm)	Pneumatic
         Atlas Copco LTV28 R28-10		120 to 252 lbf/in (14 to 28 Nm)	Pneumatic
         Atlas Copco LTV38 N31-10		156 to 276 lbf/in (18 to 31 Nm)	Pneumatic
         Atlas Copco LTV37 SR005		180 to 372 lbf/in (20 to 42 Nm)	Pneumatic
         Atlas Copco LTV38 N55-10		265 to 486 lbf/in (30 to 55 Nm)	Pneumatic
         Atlas Copco Tensor S7*		45 to 1770 lbf/in (5 to 200 Nm)	Electric
         Atlas Copco Tensor ST*
         Atlas Copco Tensor SL*
         Desoutter CVI 11 with ERP 10L		26 to 90 lbf.in (3 to 10 Nm	Electric
         Desoutter CVIS with ERP 10L		26 to 90 lbf.in (3 to 10 Nm	Electric
         Desoutter CVI 11 with ERP 20L		45 to 177 lbf.in (5 to 20 Nm	Electric
         Desoutter CVIS with ERP 20L		45 to 177 lbf.in (5 to 10 Nm	Electric

   4. Other Power Wrenches.

      1. Power torque tools with accuracy of at least +/-10% of the required setting can be used to aid faster assenbly but not for applying final tightening torques. These tools must be set to approximately 50% of the final tightening torque value. The full final torque being applied with an approved torque tool having the +/-5% calibration accuracy.

7. SUBTASK 70-41-01-400-010 Application of Torque

   1. It is recommended that you turn the nut and not the bolt wherever possible. If the bolt is to be turned, obey the instructions that follow to make sure correct tension can be achieved and that there will be no scoring of the bolt, the bolt-hole or bearing surfaces.

      1. The bolt, which includes close tolerance shank bolts, must pass freely through aligned holes.

      2. Where the flange material is soft, an engineering-specified washer must be under the bolt head.

      3. The bolt head bearing must be lubricated.

8. SUBTASK 70-41-01-400-002 Lubrication

   1. Unless specified differently, torque values given in this specification must apply when at least one of each pair of surfaces that will experience rubbing contact during the torquing process are lubricated. These faces are the screw threads and bearing surfaces of the mating fasteners.

   2. The lubricant must be clean CoMat 10-077 APPROVED ENGINE OILS unless an alternative antigalling compound is approved either on the fastener drawing, or on some other Engineering Document.

   3. The application of both oil and antigalling compounds on the same pair of surfaces must not be used unless specifically authorized.

   4. Torque limits given in this specification for parts coated with antigalling compound, apply specially to the compounds given in CoMat 10-077 APPROVED ENGINE OILS. If other compounds are used, the torque must be as specified on the drawing or on other applicable documentation.

9. SUBTASK 70-41-01-400-003 Cleaning

   1. Tooling, Mating fasteners and components to be assembled to this standard must be free from all contamination (such as, foreign material, machining chips, dirt, and grease).

10. SUBTASK 70-41-01-400-004 Sealing Compounds

    1. When CoMat 04-004 JOINTING COMPOUND, LIGHT GRADE or CoMat 04-005 JOINTING COMPOUND, MEDIUM GRADE or CoMat 04-006 JOINTING COMPOUND, HEAVY GRADE is specified, the oil lubrication must be ignored, and a minimum of 10 minutes air drying time must be allowed before assembling components. Torque values must be as those specified in Figure for oil-lubricated fasteners.

11. SUBTASK 70-41-01-400-005 Tightening Sequence for Circular and Split Casing Flanges

    1. For engine components where close-pitch bolting occurs and in applications where it is necessary to seal the joint, the tightening sequence must be carried out in a symmetrical pattern to make sure that strain is not added to the structure.

    2. Do not immediately tighten adjacent fasteners on flanges to the necessary torque load. Lightly tighten (nip) two fasteners approximately opposite to each and then another pair approximately at 90 degrees to the first pair. This process is repeated by selecting the next pair of fasteners by bisecting the resulting angular spaces until all fasteners in the flange are lightly loaded (nipped) and the joint faces are in light contact. When the faces are in light contact with all the positions lightly loaded (nipped up), apply the specified torque in a similar sequence. No special requirements apply for horizontal build except face tooth joints (curvics) (refer to Step).

       1. When using non type-approved power wrenches, the torque setting must not exceed 50 percent of the final torque (refer to Step).

    3. An illustration of the numbered sequence of tightening bolts in a circular pattern is shown in Figure.

    4. For rectangular-shaped flanges, and joints at half casing split lines, a similar procedure must be followed, but the bolts at the central positions must be tightened first as illustrated in Figure.

       1. On half-casing split lines, use the same method but tighten the mid-section positions first and then work outwards from the center.

    5. Sequence tightening of flanges with 50 or more fastenings.

       1. It is recognized that, when flanges contain 50 or more fastenings, it is not practical to apply a standard tightening sequence, and it is permitted to instead tighten adjacent fasteners in groups of 4 to simplify and speed up the assembly process. For such flanges, do the procedures that follow:

          1. Lightly nip 4 adjacent fasteners, and then 4 fasteners approximately opposite them.

          2. Then lightly nip another group of 4 fasteners at 90 deg to the first set. Then lightly nip another group 4 approximately opposite to this (3rd set) of fasteners.

          3. Bisect the resulting angles and do as before.

          4. When the faces are in light contact with all fasteners lightly nipped up, apply the specified tightening torque in the same sequence.

          5. A final check around in a clockwise order must be made, to make sure when you obeyed the above tightening sequence, a fastener position was not missed.

12. SUBTASK 70-41-01-400-006 Self-Locking Fasteners

    1. Torque loads.

       1. This section gives torque loads and build requirements for bolts assembled with standard self-locking nuts, self-locking helical coil inserts and miscellaneous self-locking fasteners such as riveted anchor nuts (plate nuts), clip-on nuts, and flange-restrained nuts (shank nuts). For torque limits on wiring harness temperature probe nuts and junction box terminal nuts, see below.

       2. If oil lubricant is applied to the part, use the torque values of Figure.

       3. If one of the antigalling compounds given in SUBTASK 70-41-02-410-002, is applied, either by engineering drawing instruction or specified by another engineering document, use the torque values of Figure.

       4. If the fastener is for either the wiring harness temperature probe terminal or junction box terminal and is oil-lubricated, use the torque value of Figure.

    2. Re-use of self-locking fasteners.

       1. Self-locking (general torque) fasteners must be approved for use. That is, meeting the minimum torque limits listed in Figure.

       2. Self-locking torque must be made sure at re-assembly with the locking feature fully engaged and the fastener unseated so that only the frictional hold on the screw thread is measured.

       3. For sizes below 0.1900, acceptance can be checked by the fingers, unless specified differently.

       4. For sizes 0.1900 and 0.2500, acceptance can be checked if the locking device cannot be fully engaged when tightened as hard as possible with the fingers, unless specified differently.

       5. Sizes above 0.2500 must be checked by measuring the self-locking torque, which must not be less than that given in Figure.

    3. Definitions.

       1. Self-locking torque (general torque).

          The torque necessary to overcome kinetic friction between the fastener mating threads with the locking element fully engaged and with no axial load in the assembly.

       2. Breakaway torque.

          The torque necessary to overcome static friction between the fastener mating threads with the locking element fully engaged and with no axial load in the assembly.

    4. Thread protrusion of bolts through self-locking nuts.

       1. There must be a small amount of thread after the chamfer protruding through the nut.

13. SUBTASK 70-41-01-400-007 Torque Loading of Fluid Fittings and Blanking Plugs

    1. Preparation of fittings and mating surfaces.

       1. All tapped holes must be free from dirt and damage and the screw threads must be of sufficient quantity.

       2. Fitted plugs must be leak-proof under pressure test conditions specified on the assembly drawing. Damage at the joint face which would cause failure of the seal must be carefully removed before the plugs are fitted.

       3. Engine oil must be applied to the screw threads before torque loading.

    2. Torque loading of thrust wire union nuts.

       1. In order to reduce the union turning, during tightening of the union nut, a lower torque load for the union nut must be applied as given in Figure. These values are based on the practice of tightening the union to a value of 20 percent higher than that for the union nut.

       2. When fitting tube assemblies, a 'bedding-in' procedure is necessary to give a good seal as follows:

          1. A suitable wrench must be used to prevent the union from turning.

          2. The nut threads and ferrule must be lubricated with clean engine oil as given in SUBTASK 70-41-02-410-002.

          3. The ferrule and nut must be aligned with the union without too much straining of the assembly.

          4. The nut must be tightened to the value given in Figure, unless specified differently on the Engineering Drawing.

          5. The nut must be untightened approximately half a turn.

          6. The nut must be tightened and untightened again a further two times.

          7. The nut must be tightened finally to the specified tightening torque, refer to Figure, without a pause being made before reaching the applicable torque value.

    3. Torque loadings - Unions and blanking plugs.

       1. NOTE

          Some parts have male threads which are 0.003inch (0.0762 mm). undersize. This will give the fitting a loose feel but is intended and will allow the abutment faces to 'square up' for the sealing.

          The torque values in Figure are applicable to standard unions, and blanking plugs of the type shown in Figure.

    4. Torque loading of double seal fluid connections.

       1. The torque values in Figure are applicable to coupling nuts for double seal (performed packing and 37 degree cone, dual seal) fluid fittings.

14. SUBTASK 70-41-01-400-008 Assembly of Face Tooth Joints

    1. General.

       1. This subtask is used for the assembly of face-toothed joints to get a high degree of balance consistency and applies at all times where two parts of a face tooth joint are brought together, for example engine build, mating modules, balancing (with engine and slave components).

       2. These procedures are applied to curvic couplings, hirth couplings and all other forms of face tooth joint.

       3. The tightening torque values are applicable to both self-locking fasteners.

    2. Assembly procedure.

       1. Immediately before bringing together the face-toothed joint, examine the teeth to be sure that they are free from burrs or damage and fully clean by brushing with a soft brush (nylon for example), with CoMat 01-124 ISOPROPYL ALCOHOL or by swab degreasing to the SPM TASK 70-11-26-300-503.

       2. Whichever cleaning agent is used, the brushing process must be followed by a clean air blast.

          1. Failure to observe these cleaning instructions and the following tightening sequence, will affect the seating of the joint and can lead to serious unbalance of the rotor assembly.

          2. After cleaning, care must be taken to prevent conditions which could lead to corrosion. Oil must not be applied before assembly of the coupling unless there are specific instructions to do so.

       3. For a horizontal engine build, bring the two parts together with sufficient accuracy to get an even mating of the teeth and to prevent shear loads on the teeth.

       4. Fastener threads and the bearing surface of the nut or bolt, whichever is to be wrenched, are to be lubricated with engine oil, and the threads engaged, but not run down.

       5. Tightening sequence.

          1. Each bolt hole must be identified by a number, which shows the sequence for tightening of the nut/bolt combination, or in the case of small size couplings with 10 or less bolts, the tightening sequence will be specified on the related Engineering Drawing.

          2. If the joint is being assembled with its axis horizontal, position holes 1 and 2 on the horizontal axis. If there is an odd number of bolts, hole number 1 is to be on the horizontal axis.

          3. Start with the nut/bolt combination in hole 1 and continue in numerical sequence to tighten to the initial torque value specified in Figure.

          4. Follow the same sequence (without loosening) and tighten each nut/bolt combination to the intermediate torque values specified in Figure.

          5. Without loosening, follow the sequence again, and tighten each nut/bolt combination to the final tightening torque values specified in Figure, unless other values are specified on the related Engineering Drawing or Torque Tightening Schedule.

          6. Start with the nut/bolt combination in hole 1 and continue in a clockwise direction, checking each nut/bolt combination in turn to the torque value specified in Figure, unless other values are specified on the related Engineering Drawing or Torque Tightening Schedule.

15. SUBTASK 70-41-01-400-009 Minimum Thread Projection Requirement

    1. Control of the projection of an externally threaded bolt, screw or stud through its nut is important:

       1. To get full thread contact between parts.

       2. To develop the maximum strength of the assembly.

       3. To make sure the locking feature of a self-locking nut operates correctly.

    2. Thread projection must meet the minimum requirements as shown in Figure.

Figure: Flexible beam torque wrench

Flexible beam torque wrench



Figure: Screwdriver torque wrench

Screwdriver torque wrench



Figure: Calculate corrected torque value

Calculate corrected torque value



Figure: Torque limits for oil-lubricated fasteners

Torque limits for oil-lubricated fasteners



Figure: Example of tightening sequence for circular flanges and split casing flanges

Example of tightening sequence for circular flanges and split casing flanges



Figure: Torque limits for fasteners coated with antigalling compound

Torque limits for fasteners coated with antigalling compound



Figure: Torque limits for temperature probe and junction box terminal fasteners

Torque limits for temperature probe and junction box terminal fasteners



Figure: Self-locking torque limits for re-use of fasteners

Self-locking torque limits for re-use of fasteners



Figure: Torque loads for thrust wire union nuts

Torque loads for thrust wire union nuts



Figure: Standard unions and blanking plugs

Standard unions and blanking plugs



Figure: Torque loads for unions and blanking plugs

Torque loads for unions and blanking plugs



Figure: Torque limits for oil-lubricated double seal fluid connections

Torque limits for oil-lubricated double seal fluid connections



Figure: Initial, intermediate, and final torque values

Initial, intermediate, and final torque values



Figure: Minimum thread projection requirements

Minimum thread projection requirements