**Process Specification for Lockwiring**

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| **Engineering Directorate**                                           |
|                                                                       |
| **Structural Engineering Division**                                   |
|                                                                       |
| January 2007                                                          |
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| ![](media/image1.png){width="1.3944444444444444in"                    |
| height="1.113888888888889in"}                                         |
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| National Aeronautics and                                              |
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| Space Administration                                                  |
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| **Lyndon B. Johnson Space Center**                                    |
|                                                                       |
| Houston, Texas                                                        |
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**Process Specification for Lockwiring**

+--------------+-----------------------------------+-----+------------+
| **Prepared   |                                   |     |            |
| by:**        |                                   |     |            |
+--------------+-----------------------------------+-----+------------+
|              | Jay E. Bennett                    |     | Date       |
|              |                                   |     |            |
|              | Materials and Processes Branch    |     |            |
|              |                                   |     |            |
|              | ES4                               |     |            |
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|              |                                   |     |            |
+--------------+-----------------------------------+-----+------------+
|              |                                   |     |            |
+--------------+-----------------------------------+-----+------------+
|              |                                   |     |            |
+--------------+-----------------------------------+-----+------------+
| **Approved   | Bradley S. Files, Chief           |     | Date       |
| by:**        |                                   |     |            |
|              | Materials and Processes Branch    |     |            |
|              |                                   |     |            |
|              | ES4                               |     |            |
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|              |                                   |     |            |
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  ----------- --------------------------------------------- ---------------
  REVISIONS                                                 

  VERSION     CHANGES                                       DATE

  \--         Original version                              5/15/96

  A           Revised Section 4, 8                          7/30/99

  B           Changed Division name. Revised Section 3.1    10/2004
              (Work Instructions) and moved to Section 6.1, 
              restructured Section 6, removed process       
              qualification requirement in Section 7.0.,    
              revised Section 8.0, and revised Section 9.0  
              (Training).                                   

  C           Updated document number in Section 4.0        1/2007
              (References)                                  

                                                            
  ----------- --------------------------------------------- ---------------

**1.0 [SCOPE]{.underline}**

This process specification establishes the requirements for lockwiring
fasteners used in flight hardware manufactured by JSC.

**2.0 [APPLICABILITY]{.underline}**

This specification shall be applicable whenever a lockwire application
is invoked per section 3.0, "Usage".

**3.0 [USAGE]{.underline}**

This process specification shall be called out on the engineering
drawing (reference JPG 8500.4) by using a drawing note. For example**:**

**LOCKWIRE PER NASA/JSC PRC-9005.**

**4.0 [REFERENCES]{.underline}**

The following references were used to develop this process
specification:

SOP-007.1 *Preparation and Revision of Process Specifications*

JPR 8500.4 *Engineering Drawing System Manual*

The following documents are called out as an extension of the
requirements

given in this specification:

NASM 33540 *Safety Wiring and Cotter Pinning, General Practices for*

NASM 20995 *Wire, Safety and Lock*

**5.0 [MATERIAL REQUIREMENTS]{.underline}**

No special materials are needed for this process.

6.  **[PROCESS REQUIREMENTS]{.underline}**

**6.1 WORK INSTRUCTIONS**

All work shall be performed to written procedures. The work instructions
shall contain sufficient detail to ensure that the manufacturing process
produces consistent, repeatable products that comply with this
specification.

For work performed at JSC facilities, these work procedures consist of
Detailed Process Instructions (DPI's).

For contracted work, the contractor shall be responsible for preparing
and maintaining, and certifying written work procedures that meet the
requirements of this specification.

**6.2 GENERAL REQUIREMENTS**

All lockwiring shall be performed according to the installation
requirements of NASM 33540.

1.  **[PROCESS QUALIFICATION]{.underline}**

None required.

**8.0 [PROCESS VERIFICATION]{.underline}**

Self verification shall be performed by the installer to ensure that the
following steps, in accordance with NASM 20995 and NASM 33540 were
performed:

a.  Verify the use of proper safety wire material (per table, NASM
    20995)

Inconel, Monel natural

Copper yellow

Aluminum alloy blue

b.  Verify the use of proper diameter safety wire as called out in NASM
    33540, Section 2.a-c.

c.  Verify the use of proper safety wire configuration geometry as
    depicted in NASM 33540, Figure 1. Ensure that the lockwire shall be
    put in tension when the part tends to loosen, and that the lockwire
    is tight but not overstressed.

d.  Verify that where it is necessary to break the wire quickly, (for
    securing emergency devices) only copper wire is used.

e.  Verify the use of the proper method according to application:

  ------------ ----------------------------- -----------------------------
  Method       Geometric Configuration       Usage Application

                                             

  Single wire  Use for closely spaced, (2"   Use for shear and seal
               between centers, max) closed  wiring, and in electrical
               geometric patterns (triangle, systems.
               rectangle, circle, etc).      

                                             

  Double twist Must use for \> 2" spacing,   All others, and especially:
               and for screws in closely     to secure hydraulic or air
               spaced geometric patterns for seals, hold hydraulic
               usage applications described. pressure, or in critical
                                             areas of clutch mechanisms
                                             and superchargers.
  ------------ ----------------------------- -----------------------------

f\. Verify that safety wire pigtail has been bent back or under to
prevent snagging per NASM 33540, Section 5.

**9.0 [TRAINING AND CERTIFICATION OF PERSONNEL]{.underline}**

This process shall be performed by personnel qualified through training
or experience and certified by their supervision to conduct the process.

**10.0 [DEFINITIONS]{.underline}**

None.