torques

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EI 042 COLLECTION -------------------------

METALLIC BRANCH

IF-MA N° 286 ISSUE: I APPLICATION SHEET FITTING AND TIGHTENING OF BOLTS AND SCREWS

SUMMARY OF THE MODIFICATION Standard document added for surface treatments codes PR designations update

CREATED :

INQUIRED ON :

DISTRIBUTED UNDER EDS :

07/09/1971

07/09/1971

--/--/----

WRITER DIPLM1 WRITER :DIQL

SIGNING : Signed

NAME: GELY

(At the creation)

SIGNING :

NAME :

(At the creation)

MODIFICATION :

ISSUE :

17/11/2009

I

DISTRIBUTED UNDER EDS :

8/12/2009

WRITER EDDLM

NAME : C. PRUD’HOMME

SIGNING : Signed

WRITER EQTDL

NAME : O. MOLINAS

SIGNING : Signed

WORK GROUP : LMP MANAGERS

Original language: French DOCUMENT(S) WITH EQUIVALENCE : none

PRODUCTION

QUALITY

Signed

Signed

D. LECURU

M.PIERANTONI

ORIGINAL SIGNE : EDDLM INTERNAL INTERNAL DISTRIBUTION : EDMS COLLECTION EI-042 EXTERNAL DISTRIBUTION: DISTRIBUTION: YES

This document is the property of EUROCOPTER, no part of it shall be reproduced or transmitted without the express prior written authorization of EUROCOPTER; and its contents shall not be disclosed. « Copyright EUROCOPTER 09/1971. All rights reserved

CONTENTS

I

GENERAL I.1 I.2 I.3 I.4 I.5 I.6

II

MEANS II.1 II.2 II.3 II.4 II.5 II.6

III III

PURPOSE SCOPE OF APPLICATION TIGHTENING OF MULTIPLE BOLTS HOW TO HOLD A TORQUE WRENCH TERMS USED APPLICABLE DOCUMENTS

TORQUES WRENCHES USE OF ADAPTERS SETTING FIXTURES TABLE OF CONVERSIONS ASN (Table of Standard Torques) ASN (Table of Correction Factors)

PROC PROCED EDUR URE E III.1 III.2

PREPARATION OF THE WORK TYPES OF ASSEMBLIES 3.2.1 3.2.2 3.2.3

III.3

SETTING THE WRENCH 3.3.1

III.4 III.5 III.6

Dry With lubricants With interfacing compound

Setting periodicities

PRELIMINARY SETTING TORQUING SAFETYING

IV

CAST CASTEL ELLA LATE TED D NUTS NUTS

V

FINAL CHECK

VI

CHECKING CHECKING A TIGHTENIN TIGHTENING G TORQUE TORQUE

I -GENERAL

I.1 PURPOSE

Specify the preliminary precautions to be taken and the procedure to be applied for screw-type assemblies and more specifically for tightening to the torque specified on the drawing.

Quality control: Proper control of the exactness of the tightening torques applied to the threaded elements of helicopter assemblies depends on: -

adequate and properly maintained tooling (a torque wrench is a measuring instrument).

-

perfect knowledge of the function of each operator in the design, manufacturing and inspection process. These functions and associated means are briefly called out in the following table:

DESIGN OFFICE

PRODUCTION PREPARATION

Torque value specified on drawing

Recording of torque values, including any possible corrections to TS and to other working documents

INSPECTION

MANUFACTURE Tightening using torque wrench or screwdriver

Sample verification using torque wrench or screwdriver as per para 6

Torque as per ASN 501.17 + Ditto lubricant, if required

Ditto

Ditto

No torque or interface product indicated on drawing

Tighten using ordinary wrench or screwdriver

Visual and tactile check

Indication: tighten (without torque wrench) on working documents

I.2 SCOPE OF APPLICATION

This document applies to all standard bolts and screws, calibrated or not, and to assembling elements with a threaded section. ISO METRIC THREADS (ROLLED OR MACHINED THREADS)

Unless otherwise specified on drawing, a tightening torque can only be applied after a counterbored flat, washer has been inserted or a lockwasher has been placed under the nut or under the screw head for screw head tightening. -

After tightening, the threaded section end shall protrude from the nut and the nut locking device by at least 1 thread, rounded section and lead-out chamfer of thread excluded.

Note:

Whatever the type of safetying device (cotter pin, lockwire or lock plate), safetying must be performed immediately after torquing. When marking with a paint line is required on the drawing, this marking must be applied immediately after torquing.

Tightening to a given torque makes possible to: -

prevent the assembled parts of tensile loaded assemblies from separating under the effect of the load.

-

increase the peening and shear strength of the assembly

-

avoid fretting corrosion

-

increase the fatigue strength of the screw or bolt.

I.3 TIGHTENING OF MULTIPLE BOLTS

Unless otherwise specified on drawing, tightening of facteners on a given part must be performed starting from the center and distributing the loads outwards. EXAMPLE: Follow the chronological sequence.

11

3

1

5

9

7

8

10

6

2

4

12

1 5

8

3

4

6

7

2

I.4 HOW TO HOLD A TORQUE WRENCH

Since the position of the torque wrench has a direct effect on the torque applied, it is essential to: -

hold the wrench by the middle of the handle,

-

the thumb shall not extend beyond the handle

-

keep your wrist straight

-

hold the wrench with your arm perpendicular to the wrench

-

do not jerk ; the motion imparted to the wrench shall be smooth and regular

-

stop the motion after the wrench release has actuated.

INCORRECT

CORRECT

INCORRECT

This phenomenon applies particularly when setting the wrench on ACRATORK. Pay special attention to this operation.

HOLD FIRMLY IN THE BOLT HEAD RECESS

I.5 USED TERMS

Torquing:

Tightening action to a specified torque

Tightening:

General term = sensitive tightening action without torque value

Calibration:

Periodic inspection of means (wrench and ACRATORK) by the Measuring Department.

Setting:

Adjusting a wrench to a given torque value using an ACRATORK

Nominal torque:

Value specified on drawing (e.g. 25 ±1) or average value of the range specified on drawing (e.g. 28 to 32 mdaN; nominal = 30 mdaN).

Checking:

Check performed during or after torquing

Working documents:

TS, MRV, work cards etc.

I.6 APPLICABLE DOCUMENTS

ASN 501.17 at the latest issue + STANDARDIZATION NOTICE dated 26.03.96 CAL.34021 Iss. B. NFL 09-752 and 753 NFE 74-325 IFMA No 527-35 MP 71.28.11 MP 71.28.13 IGC 04.62.130 IGC 04.14.100 IGC 04.62.140

II- MEANS

II.1 TORQUE WRENCHES

Before first use, torque wrenches shall be tested, calibrated and stamped by the calibration Department (Measuring Department). Torque wrenches shall be submitted to a periodic inspection (IGC 04.14.100) and shall only be used within their validity limits. In all cases, if during setting, the value read on "ACRATORK" exceeds the set value by ± 15% of the indicated value, the wrench shall be recalibrated. Dial or vernier type torque wrenches shall be exclusively reserved for measurement, test and checking operations. Wrenches with automatic release, declutching or break action are the most used. They can be used with or without an adapter.

Loosening using a torque wrench: 1°) Release wrench, without ratchet: Loosening is possible provided the adapters are inverted by 180° so that the load applied on the wrench is always in the same direction. Otherwise, the setting is lost. A new setting is required before any new torquing operation.

2°) Release wrench with ratchet: Loosening is possible after ratchet has been inverted but with loss of adjustment. In this case, the wrench has to be readjusted before any new torquing action.

In all the cases the maximum capacity of the wrench must not be exceeded.

SELECTION OF THE TORQUE WRENCH

a)

The value of the torque to be applied shall be within the top 80% of the scale. Example:

torque wrench scale

80% of (5 - 0.5)

USABLE RANGE

b) The minimum and maximum values of the torque to be applied shall be readable on the graduated scale of the wrench. Example: setting value = 32 WRENCH A

0

10

20

30

40

50

0

10

20

30

40

50

WRENCH B

Only wrench B provides correct setting. Make sure that the wrench has been submitted to the periodic inspection as well as the ACRATORK used for its setting.

Note: The other tools (such as flat wrench, ratchet, screwdriver, screwing machine, if permitted), will be used to tighten when no specific torque is required. These tools shall be used without adapters (e.g. extension, larger screwdriver handle etc.).

II.2 USE OF ADAPTERS

Extensions or adapters can only be used if they have been set along with the wrench, on ACRATORK. -

All adapters shall be shorter than the wrench.

-

The maximum axial offset shall be 15°. 15° max.

15° max.

Page FITTING AND TIGHTENING

IF-MA No 286 10

OF BOLTS AND SCREWS

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2.3 SETTING FIXTURES

"ACRATORK" adjusting fixtures are permanent workshop equipment. They are submitted to periodic inspection. Limit date is displayed on top. Never adjust a wrench on an instrument whose limit date has expired. Immediately inform the workshop supervision for appropriate remedial action. The "ACRATORK" torquemeter accuracy is 2.5% of its full scale. Note: The "ACRATORK" must not be used with dynamic screwing sets like pneumatic screwer. For this kind of tool a specific torquemeter must be used. Selection of the ACRATORK: a)

The value of the torque to be set shall be within the range authorized by the Manufacturer, if specified. If no indication is given, the value shall be greater than 10% of full scale. Example: The "ACRATORK" is graduated from 0 to 570. The unusable range is 0 to 57. 0

550

570 cmN

PROHIBITED RANGE : 0 to 57 b)

The value of the torque to be set shall be readable on the ACRATORK graduated scale. Example: Setting value = 32 ACRATORK A

ACRATORK B

0

0

10

20

10

Only ACRATORK B provides correct setting.

20

30

30

40

40

50

50


IF-MA No 286 11

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II.4 TABLE OF CONVERSIONS

In most torquing cases, the three components required for performing the operation are expressed in different measurement units. -

Set of drawings in: Manufacturing files (TS): Torque wrenches in: ACRATORK in:

mdaN mdaN cm/kg mN or mdaN

Theoretical equivalence: 1 kilogram force = 9.81 NEWTON Commonly accepted equivalence: 1 kgf = 1 daN

TORQUES OBTAINED IN mkg

cmkg

mdaN

mN

cmN

mkg

1

100

1

10

1000

REQUIRED

cmkg

0.01

1

0.01

0.1

10

TORQUES

mdaN

1

100

1

10

1000

mN

0.1

10

0.1

1

100

cmN

0.001

0.1

0.001

0.01

1

Example: Torque required: 1.5 mdaN 1°) Setting value for the wrench expressed in cm/kg 1.5 mdaN = 150 cm/kg (mdaN * 100 = cm/kg) 2°) Calibration on ACRATORK expressed in mN 150 cm/kg = 15 mN. (cm/kg * 0.1 = mN)


IF-MA No 286 12

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II.5 ASN 501.17 TABLE OF STANDARD TORQUES (in mdaN for dry torquing)

These torques are applicable to ISO M and ISO MJ hardware. These tables have been extracted from AS.N 50.17. They are provided for information purposes, the ASN remains the reference document for these values.

I

Standard screws and bolts are coded as per NFL 09-752 for materials codes and NFL 01-753 for surface treatment codes. 35NC6 30NCD16 T-A6V

= BC ( L / M / T ) = BE ( L / M ) = TK ( X / XA )

ORDINARY NUT AND CADMIUM-PLATED STEEL ALLOY BOLT THREAD

35NC6

30NCD16

SELF-LOCKING NUT AND CADMIUM-PLATED STEEL ALLOY BOLT 35NC6

30NCD16

ø

PITCH

MIN.

MAX.

MIN.

MAX.

MIN.

MAX.

MIN.

MAX.

4

0.70

0.20

0.25

0.25

0.30

0.25

0.30

0.30

0.35

5

0.80

0.30

0.40

0.40

0.50

0.40

0.50

0.50

0.60

6

1

0.60

0.75

0.75

0.90

0.75

0.90

0.90

1.10

7

1

1.00

1.25

1.25

1.50

1.25

1.50

1.50

1.75

8

1 and 1.25

1.50

1.90

1.90

2.30

1.90

2.30

2.30

2.70

10

1.25 and 1.50

3.40

4.10

4.10

4.80

4.10

4.80

4.80

5.50

12

1.25 and 1.50

6.30

7.50

7.30

8.50

7.30

8.50

8.30

9.50

14

1.50

10.00

12.00

11.50

13.50

11.50

13.50

13.00

15.00

16

1.50

16.00

19.00

18.00

21.00

18.00

21.00

20.00

23.00

Note : For "Nylstop" and "castellated" nuts, the torque is determined by the Design Office and marked on the drawing.


IF-MA No 286 13

OF BOLTS AND SCREWS

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Tightening torques for TA6V titanium bolts (in m.daN)

These torques are applicable only to conventional nuts (ordinary nuts or with elliptical deformation locking). The values provided below apply to dry assembly with bolts coated with "MoS 2". ORDINARY NUT D

PITCH

mm

mm

4

SELF-LOCKING NUT with "MoS2" coating

MIN.

MAX.

MIN.

MAX.

0.70

0.13

0.16

0.18

0.21

5

0.80

0.27

0.32

0.37

0.42

6

1.00

0.46

0.55

0.66

0.75

7

1.00

0.75

0.90

1.00

1.15

8

1 and 1.25

1.10

1.30

1.50

1.70

10

1.25 and 1.50

2.20

2.60

2.90

3.30

12

1.25 and 1.50

4.00

4.80

5.00

5.80

14

1.50

6.50

7.50

8.00

9.00

16

1.50

9.50

11.50

11.50

13.50

Tightening torques for INCONEL 718 bolts :

The torque value is determined by the Design Office and is marked on the drawing.


IF-MA No 286 OF BOLTS AND SCREWS

14

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NOTE: For countersunk head screws, unless a specific fit is required (bore H or G), the values of these tables shall be increased by 18% if the tightening is via the bolt head.

The tightening torque is determined by the smallest diameter. Examples:

SHOULDERED BOLT

II.6 ASN 501.17 TABLE OF CORRECTION FACTORS

NOTE:

WAISTED BOLT OR SCREW


IF-MA No 286 15

OF BOLTS AND SCREWS

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For PR, refer to chapter III.2.3. Mastinox and Loctite compounds are not lubricants (use values for dry torquing). Unless otherwise specified on the drawing, no lubricating compound is required with T-A6V screws since they are initially lubricated with MoS2. These factors do not apply to nuts with nylon or fiber locking which have to be dry assembled. AIR Std NATO Code Type or usage Manufacturer Designation COEF 4247 S.720 Graphite grease for 0.50 threads 4205 G.359 Mineral grease 0.50 III.1 4206 G.355 Graphite mineral 0.40 WORK PREPARATION grease 4207 G361 Grease for wide 0.55 temperature range "extreme pressure, III.2 ester type TYPES OF ASSEMBLY 4210 G.354 Grease with low 0.50 freezing point and III.2.3Multi-purpose mineral 4215 III.2.2G382 0.50 III.2.1 WITH LUBRICANTgrease OR DRY II.6 INSULATING PRODUCT 4222 G395 Synthetic hydrocarbon 0.50 DETERMINE THE (replaces grease CORRECTION FACTORS 4217) 3565 S.753 Mineral petrolatum 0.75 (for electrical bonding) Sealant Without Sealing and Kerosene PR 1222 */ 1.60 II.1.a and bLe joint français CHOOSE THE TORQUE WRENCH 1321 ** / 1436*** * PR 1222 replaced by PR 1829B2 ** PR 1321 replaced by PR 1773 B2 III.3 *** PR 1436 GB2 replaced by MC ADJUST 780 B1 orTHE 1776 B2 – And 1436 GS replaced by 1776 S WRENCH

WRENCH Mastinox and Loctite compounds: no correction factor. Tightening torque value: dry assembly.

III.3.1 ADJUSTMENT FREQUENCY

III.4 by the correction factor of the product. The specified tightening value shall be multiplied PRE ASSEMBLY IF SPECIFIED

(to draw down into contact) The use of a product whose correction factor is unknown is prohibited . III.5.B.b MEASUREMENT OF SAFETYING TORQUE IF REQUIRED

III - PROCEDURE: GENERAL CASE

III.5 For all threaded components with specified tightening torques, it is advised to have them torqued by TIGHTEN TO THE REQUIRED qualified personnel. TORQUE III.6 SAFETYING if required



16

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III.1 PREPARATION OF THE WORK

-

Before any assembly, the operator must check the part numbers of the nuts and bolts to avoid any possibility of mixing between ISO M and ISO MJ standards. − The operator shall also ensure that the parts and their hardware are free from : . .

burrs scratches



. . .

17

/ 25

damaged threads corrosion traces paint runs and other dirt or foreign matter.

-

The operator shall know the required tightening values and the correction factors to be apply.

-

All cleaning products commonly used in workshops can be used except on Titanium fasteners and fasteners with a surface treatment other than cadmium-plating.

-

Screws and bolts shall be installed without being stressed. Unless particular cases specified on the drawing, the head shall always be placed upwards or towards the nose of the aircraft. Similarly for all rotating parts, the nut shall be installed on the trailing edge side.

III.2 TYPES OF ASSEMBLIES III.2.1 Dry

A dry assembly is an assembly made without any product being applied on the threads. Only an insulating product (such as Mastinox) is allowed on plain sections.

III.2.2 With lubricants



18

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Unless otherwise specified on the drawing, a lubricant is a product applied on the threaded section. In this case, the product will be applied on the nut, not on the screw. (To determine the torque, use the table of correction factors as per the standard if no indication is provided on the drawing). These indications shall be entered in the working documents. MASTINOX AND LOCTITE PRODUCTS ARE NOT CONSIDERED AS LUBRICANTS. NUTS WITH NYLON OR FIBER LOCKING SHALL IN NO CASE BE LUBRICATED.

III.2.3 With insulating compounds (Curing type)

After application of insulating compound (e.g.: PR) the tightening torque must be applied as soon as possible and before the compound has cured (refer to the IF specific to the products). To determine the torque value, use the table of correction factors as per the standard, if no indication is provided on the drawing.

III.3 SETTING THE WRENCH

Since wrench setting is highly dependent on the operator (position of the arm, torquing rate, sensitivity), the operator will have to perform his setting himself. To perform wrench setting, the operator will adhere as closely as possible to the working configuration. He will install the adapters, if any, on the wrench. He will have to reset the ACRATORK before installing the wrench. He will perform setting smoothly and regularly (without jerking), keeping his wrist straight and his arm perpendicular to the wrench during the motion. Important note: The wrench shall be set to the required nominal value.


IF-MA No 286 19

OF BOLTS AND SCREWS

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2250 mm x

ADJUSTMENT

DO NOT USE WITHIN THE RANGE 0 TO 200

permissible adjustment range

USE

F

1F

PROHIBITED

III.3.1

F

Setting periodicity

-

Before each operation and for each wrench, take 3 measurements (at 20%, 60% and 100% of the wrench capacity).

-

Each time the wrench configuration is changed (extension).

-

In case of impacts on the wrench.

-

In case of any doubt arising about setting.

III.4 PRELIMINARY SETTING

If specified on working documents:

-

Bring the components to be assembled into contact in the unstrained condition.

-

Screws and bolts shall be fitted without forcing.

-

Nuts without internal locking shall be tightened by hand until mating faces are in contact.

-

Perform one or more tightening actions to nominal torque followed by a loosening action, without separating the components (about 1/8 turn).

Caution: do not tighten a given self-locking nut more than three times.

III.5 TORQUING

A) GENERAL CASE FOR NUTS WITHOUT INTERNAL LOCKING



20

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-

In all cases, tightening values shall be within the permissible tolerances.

-

Using a torque wrench, tighten to the nominal torque value as per the procedure defined in paragraphs I.3 and I.4

NOTE:

Values are given for torquing the nut or the bolt head if no specific fit indication is required and in case of dry assembly. When torquing a countersunk head screw, this torque shall be increased by 18%. When torquing a nut, hold the bolt head using a wrench or equivalent, if required. When torquing a locknut (rod), hold the nut already torqued using an appropriate wrench and apply the same torque to the locknut.

B) NUT WITH INTERNAL LOCKING

After an internal safetying nut has been torqued three times, it shall be replaced.



21

/ 25

a) General case

The safetying torque value shall be included in the values specified in working documents This value should be given on the drawing (set of working documents). The safetying torque value is given in applicable standards. b) Specific cases

Measurement of the actual value of the safetying torque may be required. This requirement shall be explicitly mentioned on the set of drawings and therefore on the working documents.

Since this procedure is extremely long, its application shall be limited as far as possible.

The total torque to be applied shall in such cases be calculated as follows: total torque = tightening torque + safetying torque

Tightening torque: read off the production document (specified on the drawing).

Safetying torque: to be measured by the operator on each nut and at each tightening action (if pre-assembly is required). Total torque = torque value to be set on the wrench.

Measuring procedure for safetying torque: Fully engage nut and safetying device. Tighten using a dial type torque wrench providing torque reading. The value to be considered is the constant load value after break-away. Apply total torque as per chapters I.3 and I.4

III.6 SAFETYING

Safetying shall be performed immediately after torquing.


IF-MA No 286 22

OF BOLTS AND SCREWS

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IV - CASTELLATED NUTS

It is advisable to use a wrench that allows the both safetying system and the nut position on the bolt to be seen in order to avoid going beyond the position of the cotter pin. In case of improper pin positioning, the tightening cycle shall be repeated. The requirement to align one castellation with a cotter hole must in no case cause the maximum torque value to be exceeded. PROCEDURE III.4 PRE ASSEMBLY if required

III.5.B.b MEASUREMENT OF SAFETYING TORQUE

if required

III.5 TIGHTEN TO MIN. VALUE

TORQUE TIGHTEN

TIGHTEN FROM MIN. VALUE WITHOUT EXCEEDING MAX. VALUE

LOOSEN FULLY OR CHANGE THE NUT (see NOTES 2 and 3)

HOLE OUT OF POSITION

(check hole position)

HOLE IN POSITION (see NOTE 1)

III.6 SAFETY if required NOTE 1: Whenever the tolerance range or the type of assembly makes it possible (bolt with two holes), apply the highest possible torque value before safetying. NOTE 2: Castellated nuts with nylon or fiber locking shall be replaced (discarded) after 3 tightening actions provided that a minimum locking torque is maintained. NOTE 3: The components of non self-locking nuts (see § VII "Case of reuse") shall be replaced if proper positioning cannot be obtained after several tightening attempts. NOTE 4: Nuts with nylon or fiber internal locking provision shall systematically be replaced.



23

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V - FINAL CHECK

Upon completion of operation, the operator will remove any excess compound, whatever its nature, and will check for satisfactory workmanship: -

twisted lockwire, tensioned in the appropriate direction and unmarked (MP 71.28.11)

-

cotter pin secured (IGC 04.62.140)

-

lockplate properly positioned, bent over and unmarked (MP 71.28.13)

-

adequate thread protrusion from the nut

-

Etc.

VI - CHECKING A TIGHTENING TORQUE

This checking procedure is designed to make sure that the minimum torque value is maintained. Important note : Never check tightening torque by loosening the nut. Within the context of sample inspection, checking a tightening torque will be made according to IGC 04 . 62 . 130 as follows: 1° Use of a dial-type torque wrench:

Remove safetying components (for lockplates, bend the tab). With an ink or paint line, mark the position of the bolt nut and the washer on the fixed section (or on the bolt head, washer and fixed section in case of bolt head torquing). Lock the end opposite the bolt head or nut, as applicable. Important note: For checking, loosen only one fastener at the same time to prevent separation of the parts. Re-tighten until the minimum prescribed torque. -

If the mark on the nut or bolt does not reach that on the fixed section, complete tightening until the two marks coincide. In case of lockplate, replace it systematically before completing tightening operation.

-

If the mark on the nut or bolt moves beyond that on the fixed mark (min. torque), replace the bolt/nut assembly and re-tighten as per chapter III.5 or IV , depending on the type of nut.

Modif.

I

17.11.2009

This document is the property of EUROCOPTER, no part of it shall be reproduced or tra nsmitted without the express prior written authorization of EUROCOPTER; and its c ontents shall not be disclosed. « Copyright EUROCOPTER 09/1971. All rights reserved



-

24

/ 25

In case of an internally locked nut (nylon or fiber), systematically replace it and retighten it according to Chapter IV.

After inspection and verification, restore initial configuration. In all cases, safetying elements (pin, lockplate, etc.) shall systematically be replaced. Safetying will be achieved in compliance with IFMA 527-25. 2° Use of a release-type torque wrench

Remove all safetying components (for lockplates, bend the tab). With an ink or paint line, mark the position of the nut and washer on the fixed section (or on the bolt head, washer and fixed section in case of bolt head torquing). Lock the end opposite the bolt head or nut as applicable. Important note: For checking, loosen only one fastener at the same time to prevent separation of the parts.

Using a wrench set to the minimum permissible torque, tighten until release of the wrench.

-

If after release of the wrench, the mark on the nut or bolt does not reach that on the fixed section, complete tightening until the marks coincide. In the case of lockplate, replace it systematically before completing tightening operation.

-

If the mark on the nut or bolt moves beyond that on the fixed mark (min. torque), replace the bolt/nut assembly and re-tighten as per chapter III.5 or IV , depending on the type of nut.

-

In case of a nut with internal locking (nylon or fiber), replace it systematically and retighten according to Chapter IV.

After inspection and verification, restore initial configuration. In all cases, safetying elements (pin, lockplate, etc.) must systematically be replaced. Safetying will be achieved in compliance with IFMA 527-25.

Modif.

I

17.11.2009




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Case of Application of Interfaying Compound On dry product: (See IFMA specific to the product). On fresh product:

The bolt + nut assemblies fitted with non-cured interfaying compound shall be retightened. Failing that preloading could be definitively lost after curing. This condition results from the fact that the compound does not squeeze out instantaneously. Retightening shall be made: At the earliest: within 5 to 10 minutes following first tightening. At the latest: before the end of the pot life of the compound (time limited by curing: see applicable IFMA). VII – REUSE OF BOLTS AND NUTS Resuse of bolts and nuts

Reusing bolts and nuts results in the following: - Decrease of the pre-load due to a lesser efficiency of the lubricant. - Local degradation of the protection on the bolts and nuts which may induce further corrosion (cadmium-plated steel hardware) or seizing (stainless steel hardware). - Risk of degradation of the bearing surfaces - Decrease in the tightening torque. Bolts and nuts can be reused provided that: - The protection of the components is not degraded. - The prescribed tightening torque is met. - The surface condition is conform (for fasteners without surface protection), absence of: bending, torsion and striction deformations tear-off and scratches wear, modifying the dimensions of the parts beyond tolerances corrosion pittings. For lubricated nuts, restore lubrication (see table in paragraph II.6)

Modif.

I

17.11.2009


torques

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