Attachment_09_FOSOV_Work_Instruction-Bonding_for_Mobile_Systems_1Jun11.pdf

FOSOV 10-01 REV A

FOSOV

WORK

INSTRUCTION

TITLE:

Bonding Requirements

NUMBER:

FOSOV 10-01

REVISION: A

DATE: 1 June 2011

1. PURPOSE: To prescribe bonding requirements for integrated Command, Control, Communications, Computers, and Intelligence (C4I) systems to reduce the likelihood of electromagnetic interference (EMI) and signal exploitation, and to promote electromagnetic compatibility (EMC) among system components.

2. SCOPE: This work instruction is applicable to C4I systems on all USSOCOM Family of

Special Operations Vehicles (FOSOV). It provides a brief explanation of bonding theory, and describes specific bonding practices and procedures to be implemented in FOSOV designs. The use of standard EMI/EMC practices does not guarantee satisfactory integrated system performance or the elimination of interference. EMI testing shall be conducted where necessary to ensure adequate system performance.

NAME/TITLE SIGNATURE DATE

REVIEW

SCR FOSOV Lead Engineer X

REVIEW

SCR FOSOV Production Engineer

FINAL

APPROVAL

SCR FOSOV Program Engineer

3. REFERENCE DOCUMENTS : The documents cited below provide instructions, guidelines, and requirements applicable to various aspects of EMI/EMC. Where applicable to FOSOV processes these standards are referenced in the appropriate sections.

3.1 Handbooks

MIL-HDBK-235-1B – Electromagnetic (Radiated) Environment Considerations for Design and

Procurement of Electrical and Electronic Equipment, Subsystems and Systems

MIL-HDBK-237B – Electromagnetic Environmental Effects on Platforms, Systems, and

Equipment

MIL-HDBK-241B [notice] – Design Guide for EMI Reduction in Power Supplies

MIL-HDBK-274 – Electrical Grounding for Aircraft Safety.

MIL-HDBK-454A – General Guidelines for Electronic Equipment

MIL-HDBK-1512 – Electro-explosive Subsystems, Electrically Initiated, Design Requirements and Test Methods

MIL-HDBK-1857 – Grounding, Bonding and Shielding Design Practices

3.2 Standards

MIL-STD-188-124B – GROUNDING, BONDING AND SHIELDING for Common Long

Haul/Tactical Communication Systems Including Ground Based Communications-Electronics

Facilities and Equipments.

MIL-STD-188-125-2 – High-Altitude Electromagnetic Pulse (HEMP) Protection for Ground-

Based C4I Facilities Performing Critical, Time-Urgent Missions – Part 2. Transportable Systems.

MIL-STD-461E – Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment

MIL-STD-464A – Electromagnetic Environmental Effects Requirements for Systems

MIL-STD-1310G – Shipboard Bonding, Grounding, and Other Techniques for Electromagnetic

Compatibility and Safety.

MIL-STD-1377 – Effectiveness of Cable, Connector, and Weapon Enclosure Shielding and

Filters in Precluding Hazards of Electromagnetic Radiation to Ordnance, Measurement of.

MIL-STD-1541A – Electromagnetic Compatibility Requirements for Space Systems.

MIL-STD-1542B – Electromagnetic Compatibility and Grounding Requirements for Space

System Facilities http://www.interferencetechnology.com/emcstandards/northamerica/mil-hdbk-235-1b.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-hdbk-237b.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-hdbk-241b.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-hdbk241b-Notice%201.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-hdbk-1512.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-hdbk-1857.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-std-461e.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-std-464.pdf http://www.interferencetechnology.com/emcstandards/northamerica/mil-std-1542b.pdf

MIL-STD-1686C – Electrostatic Discharge Control Program for the Protection of Electrical and

Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive

Devices).

3.3 Instructions

TI 5820-25/22A – U.S. Marine Corps Technical Instruction, Electromagnetic Environmental

Effects Procedures for Installation of Communication Equipment on United States Marine Corps

Platforms

3.4 Specifications

A-A-59313 – Commercial Item Description, Thread Compound; Antiseize, Zinc Dust-

Petrolatum

4. REVISION/CHANGE INFORMATION:

Rev No Description Date

- Original 08/20/10

A 1) Removed paragraph letter designations assigned to reference documents, and corrected references to these documents in the text.

(Para 3)

2) Added accommodations for bonding irregular metal surfaces by using unpainted areas under washers on both sides of bolted surfaces. (Para

5.5.1c)

3) Clarified instructions for equipment such as FFCS that have existing bonding surfaces. (Para 5.5.1f)

4) Removed the “conductive” descriptor from A-A-59313 anti-seize compound. (Para 5.5.2d and attachments)

5) Replaced MIL-S-8802 sealant with Permatex Form-A-Gasket No. 2, PN 80010 (CAGE 01232; NSN 8030-00-849-0071), in accordance with the latest guidance from MIL-STD-1310H. (Para 5.5.2g and attachments)

6) Clarified discussion of shock-mount bond straps to specify Type III straps. (Para 5.5.5)

7) Added instructions for bonding temporary equipment. (Para 5.5.10)

8) Revised “Standard Bonding Notes for Drawings.” (Attachment 2).

9) Corrected document number in page footer.

06/01/11

5. DISCUSSION:

5.1. Introduction. All electrical and electronic equipment and systems create and emit electromagnetic emissions. Both deliberate emissions and byproducts may cause interference with other electronic or electrical systems and under certain conditions could risk system performance, personnel safety, equipment damage, or signal exploitation. Good engineering design takes into consideration the possible adverse effects of electromagnetic emissions and minimizes them by incorporating appropriate bonding, grounding, shielding, filtering, and equipment placement. These practices can mitigate the effects of undesirable noise by reducing radiated or conducted emissions between equipment.

Figure 1 portrays the outputs from one piece of equipment and how it can affect collocated or remote equipment or systems. The green signals with adjacent checks represent desired signals and the red signals with adjacent X represent unwanted emanations or by-products. Equipment E of the diagram represents a system that can exploit by-product emanations. Electrical or electronic equipment by-products include; the electrical noise of an electric motor, the higher order harmonics generated by an RF amplifier, and signals or voltage variations fed back to a power supply by the activities of an electronic device.

EMI and EMC are the general terms used to define the unintended interaction between electrical/electronic equipment. EMI is defined as electromagnetic energy from sources external or internal to electrical or electronic equipment that adversely affects equipment by creating undesirable responses (degraded performance or malfunctions) or adverse impact. EMC is the ability of a system or equipment to operate in the expected EMI environment and/or not to generate EMI that will adversely affect the performance of other systems and equipment collocated with it.

Equipment AEquipment B Equipment C

Equipment E

Equipment D

Figure 1. All electronic and electrical systems emit electrical emanations, some desired and some undesired.

Integrated System

The reference documents cited have information that provides bonding, grounding, and shielding guidance for a wide range of applications. The standards specifically applicable to FOSOV system integration are cited where appropriate in this document.

5.2 EMI/EMC Theory. MIL-HDBK-1857 provides a good discussion of EMI/EMC emanation theory, and methods of EMI/EMC mitigation, much more than can be covered in this instruction.

Engineers/designers are encouraged to read and understand the concepts of EMI/EMC discussed in this handbook. EMI emanations or emissions have four principal modes of propagation or conveyance from one piece of equipment to another. They are:

1) Common impedance coupling – This conducted EMI occurs where two electrical circuits (or equipments) share common impedance. This occurs most often with a shared power source where the current of one circuit affects the other circuit or where there is improper or inadequate grounding. Figure 2 illustrates common impedance coupling through a shared power source. In this example, the shared impedances are the internal impedance of the power supply, and the impedance of the power cables that connect the source to the distribution panel.

As can be seen in Figure 2, the voltage fluctuation seen by both pieces of equipment are the result of the current fluctuation of both, thus electronic activity of one piece of equipment may be superimposed on the other piece of equipment. Common impedance power coupling can be minimized by selecting a power source with minimum internal impedance, placing the distribution panel as close to the source as possible, by increasing the size of the cables to reduce their resistance, and by twisting the source and return cables together so that their inductive magnetic flux fields are self canceling. Filters can also be effective in dampening voltage fluctuations or ripples. Power line magnetic field cancellation may also reduce the flux field EMI on the platform to devices such as fluxgate or magnetic compasses and degaussing systems.

2) Electromagnetic radiation – This is energy propagated through free space or through a material medium in the form of electromagnetic waves. With communication equipment, radio frequency

(RF) electromagnetic radiation is normally an intended objective, but spurious RF emissions outside the desired band can be generated by non-linearities in RF amplifiers, over-driving of the

RF amplifiers, or by improper bonding. A poor metal to metal bond with significant impedance can exhibit non-linear behavior and generate harmonics of the basic RF to which it is exposed.

These harmonics can operate in the frequency bands of nearby communications systems -- either directly on the center channel or intermediate frequencies (IF). Many radios exhibit decreased performance when in the presence of other communications receivers/transmitters due to limited filtering and selectivity on receiver front ends, and limited filtering on outputs to suppress spurious

Equipment A ZLINE

ZLINE

Zs

Equipment B

Power

Source

IA

BI

BI

I A

Common (shared) Impedances

IA+B

Figure 2. Common Impedances in a shared power source.

emissions. When including these radios in an integrated system, adding external filters is often required to mitigate spurious emissions.

3) Electrical field coupling– This results when the electric field of one conductor affects another electrically isolated (or insulated) conductor. Electrical field coupling is a relatively near-field phenomenon and is normally negligible outside the range of an integrated circuit.

4) Magnetic field coupling – This occurs when magnetic flux fields of an electrical/electronic equipment or device affects a neighboring device. Magnetic flux fields are generated by current flow. When these fields intersect another conductor with varying intensity, they induce current flow in that conductor. In this way one signal can be inadvertently superimposed on another signal.

Magnetic field coupling is also a relatively near-field phenomenon. Magnetic field coupling can be minimized through shielding and signal conductor separation. The most effective magnetic flux shielding material is ferrous metals which often take the form of ferrite cores, rings, and windings that enclose cabling.

5.3 General Bonding Practices. Proper bonding practices help mitigate potential EMI problems by minimizing impedances between metallic surfaces. Bonding is incorporated on all conductive equipment chassis, mounts, metallic racks, console components, and assemblies to achieve a single unified ground potential with the vehicle chassis. Figure 3 illustrates this bonding approach. Direct electrical bonds can be made by welding or brazing, called Class A bonds in MIL-STD-1310, or by mechanically fastening the metallic structures together (Class B & C) bonds. MIL-HDBK-1857 classifies the following bonds:

Direct - Mating or fayed surfaces of each structure are welded or physically fastened together

Indirect - Bonds are joined by an intermediate bond strap.

Equipment is bonded to shelves; shelves are bonded to racks; racks are bonded to vehicles. Following these practices throughout the system ensures minimum impedances between components and mitigates EMI problems.

Bonds involving dissimilar metals can promote galvanic action and metallic corrosion. These effects are minimized by reducing the electromotive force between the metals and by physically preventing moisture from penetrating to the bonded surfaces. The galvanic actions are reduced by treating the mating surfaces of dissimilar metals with corrosion protective compounds. Moisture is

Figure 3. Bonding joins all conductive chassis and structure into one electrically contiguous mass.

Blank Plate

Equipment Shelf

Equipment B

Equipment A

Standard 19" Rack

Equipment C

Conductive Vehicle Chassis, Boat Hull or Bonded Foundation

Bonding

Straps (2)

Front Panel

Bonding to Rack

Bonding straps (2) around shock mounts

Joints or fayed surfaces subject to galvanic and electrolytic corrosion

B

C

A

Bonding joints and fayed surfaces minimizes impedance between bodies and joint/fayed surface corrosion.

Theory

Practice prevented from penetrating between the bonded surfaces by using sealant around the perimeter of bonds exposed to the environment.

5.4 Verifying Proper Bonds. Guidance provided in the standards (MIL-STD-464A and MIL-HDBK-

1857) specifies the following maximum direct current (DC) resistance across bonded surfaces:

a. 10 milliohms or less from the equipment enclosure or chassis to the system structure or mounting surface, including the cumulative effect of all faying surface interfaces.

b. 15 milliohms or less from cable shields to the equipment enclosure, including the cumulative effect of all connector and accessory interfaces.

c. 2.5 milliohms or less across individual faying interfaces within the equipment, such as between subassemblies or sections.

5.5 Detailed Bonding Instructions. The following bonding practices shall be followed on FOSOV platforms.

5.5.1 All conductive equipment chassis, metallic rack components, console assemblies, equipment mounts and brackets, antenna mounts, metal cableways, and other metallic components shall be bonded together and to the vehicle chassis to achieve a single unified ground potential. Bond components using the following practices:

a) Bond metal components where practical by physical fusion of surfaces, i.e. welding. In general, welding in the field or during vehicle electronics installations is not practical. For FOSOV systems, welding will primarily be used for pre-fabricated metalwork.

b) Bond metal components and electronic equipment, where possible, by direct contact between unpainted metal surfaces which come into contact when the items are bolted together. Bond straps should be used only when direct bonding between metal surfaces of equipment and metalwork is not practical.

c) For equipment and metalwork bonded by bolting components together, the area of unpainted contact between mating surfaces shall be as large as practical, i.e. the bottom surface of an antenna mount, or the entire mounting flange of a bracket. For example, Figure 4 illustrates typical antenna mounts with unpainted areas covering the entire mating area for the antenna base, and the entire mating surface with the vehicle. Figure 5 illustrates the corresponding unpainted mating surfaces on the vehicle. However, the area of bonding surface may be limited by practical considerations. For example, it may not be practical to remove several square feet of paint from the floor of a vehicle to support bonding with the bottom surface of a large equipment rack or component. In these instances, a minimum of two, unpainted 3” x 3” squares shall be provided as bonding surfaces on the base of the mounted item as shown in Figure 6, and the mounting surface as shown in Figure 7 (USMC TI 5820-25/22A). There may also be instances that it is not practical to bond the entire area of irregular vehicle surfaces and metal components. In these instances a minimum of two, unpainted circles shall be provided under the flat washers used on both sides of bolted surfaces. Unpainted circles shall extend a minimum of 1/16” beyond the diameter of the washers.

d) When bonding antennas to existing mounts on a vehicle, inspect the mounts to ensure they are properly bonded to the vehicle chassis. If not properly bonded, remove the mount, prepare bonding surfaces, and properly bond the mount to the vehicle in accordance with section 5.5.2 of this SOP.

e) For racks or assemblies with multiple metal components, all mating surfaces between each component shall be bonded where possible.

f) For components with surfaces the manufacturer has specifically left unpainted in order to support bonding requirements, these surfaces may be used for bonding provided they are properly treated with MIL-DTL-5541 Class 3 chemical conversion coating (chem-film) or equivalent. For example, the VIC-3 Full Function Crew Station (FFCS) has unpainted surfaces on the back-side of its mounting flanges. These components may be bonded by clearing a matching unpainted area on the FFCS mounting bracket or platform mounting surface.

5.5.2 Bonding shall be accomplished in accordance with the following instructions.

a) Bonding surfaces shall be bare metal, cleared of paint and other non-conductive finishes.

When the entire surface such as a flange mates with a larger surface such as a shelf, the shelf shall be cleared of paint over an area that extends at least 1/16 inch beyond all sides of the bonded area.

b) Mating surfaces shall be thoroughly cleaned before joining to remove dust, grease, oil, moisture, non-conductive protective finishes, and corrosion products.

c) Cleaned aluminum surfaces shall be treated with MIL-DTL-5541 Class 3 chemical conversion coating (chem-film) to protect from corrosion.

d) Bonding surfaces exposed to the outside environment shall be coated with A-A-59313 anti-seize prior to bonding.

e) All fasteners shall be torqued in accordance with manufacturer specifications.

f) Bolts, washers, and other hardware exposed to the weather shall be protected by coating thoroughly with anti-seize.

g) Bonds exposed to the outside environment shall be sealed around the edges of joined surfaces to create a waterproof seal which prevents water intrusion or loss of anti-corrosive compound.

Sealant shall be Permatex Form-A-Gasket No. 2, PN 80010 (CAGE 01232; NSN 8030-00-

849-0071).

h) Measure DC resistance of bonds to verify compliance with the requirements in Section 5.4.

i) Follow the detailed procedures in Attachment A for preparing surfaces, bonding components, and measuring resistance.

5.5.3. Rack-mounted equipment shall be bonded to the rack through an unpainted surface on the back of the equipment front panel, and an unpainted mounting surface on the rack mounting rails. If necessary, paint or non-conductive coatings shall be removed from the back of equipment front panels or mounting rails to ensure proper bonding. The compression bond created by bolting the mating surfaces of the equipment mounting flange and the unpainted mounting rails typically provides an acceptable bond between equipment and rack.

5.5.4. Compression bonds between copper conductors or between aluminum alloys located in easily accessible areas not subject to weather exposure, corrosive fumes, or excessive dust do not require sealing or anti-seize (For example crimped lugs, terminal strips, and standard 19” rack-mounted equipment).

5.5.5. Install MIL-DTL-24749A(SH) Type III bond straps across shock isolation mounts as shown in

Figure 8. Also use Type III bond straps as shown in Figure 9 when direct bonding between metal surfaces of equipment and racks is not practical, and the equipment provides a ground stud. Figure 10 provides the general design for a MIL-DTL-24749A(SH) Type III bond strap. Bond straps shall be obtained from qualified vendors that fabricate them, or by specifying bond strap design to be fabricated at a general purpose machine shop. Bond straps shall be as short as possible and attached using appropriate corrosion resistant stainless steel hardware. Bond straps should have a width to length ratio of approximately 1-to-5 and thickness of approximately 0.020 inches. Paint shall be removed from the shelf or other attachment points to allow direct contact with the bond strap. Anti-seize shall be applied to the mating surfaces. Braided bond straps shall not be used except where the movement, rotation, sliding, or temporary nature of a mount or fixture requires the bond strap be flexible, or separation between surfaces is too great for a Type III strap. Braided bond straps shall be as short as practical.

5.5.6. Minimize modifications to COTS equipment where possible. Equipment may require inclusion of a ground strap for bonding to a shelf or mounting bracket. These modifications may require replacing hardware from the chassis and the removal of paint and powder coat. These altered items require an altered item drawing and must be modified before being integrated in the system.

5.5.7. Ensure proper bonding of connector feed-thru interface panels or Signal Entry Panels (SEPs):

a) The mating surfaces around the edge of the shelter cut-out and around the interface panel mounting flange shall be completely free of paint, cleaned and treated with a corrosion protective MIL-DTL-5541 Class 3 chemical conversion treatment.

b) A conductive gasket (e.g. nickel wire impregnated) shall be used to provide both a weather seal around the mounting flange and to provide a proper bonding contact.

c) Panels shall have unpainted mating areas to accommodate mating surfaces of connectors and flanges.

d) Conductive EMI/RFI gaskets should be used where applicable for military flange-mount connectors.

5.5.8. Ensure all cable shields are properly grounded to connectors by using a termination method that grounds the shield 360 degrees around the perimeter of the connector. Shields shall NOT be terminated by using a soldered conductor and terminal lug clamped to the connector backshell or strain relief.

5.5.9. Identify bonding requirements on system integration drawings. Address bonding requirements using a combination of the following:

a) Convey specialized bonding needs for fabricated items (for example, showing no-paint zones and bonding straps on shock isolation mounts)

b) Include notes to address general bonding installation techniques (for example, cable shield termination methods, and standard antenna mounting methods). The top-level installation and assembly drawings need to include descriptions of bonding requirements in order to reinforce best practices. Standard bonding notes to be used on FOSOV drawings are provided in

Attachment 2.

c) Design documentation may either contain details of bond strap fabrication, an example being

Figure 10, or shall be identified by nomenclature as described in paragraph 6.6 of MIL-DET-

24749A(SH).

5.5.10. Equipment temporarily installed on FOSOV platforms shall be properly bonded to the vehicle.

All internal metal components of the temporary equipment shall be bonded together and grounded to the equipment chassis or frame. Where possible a single ground stud shall be provided on the temporary equipment to support bonding. A bond strap shall be used to bond the temporary equipment chassis to the vehicle chassis. Connection to the vehicle chassis may be at any location convenient, but the bond strap shall be as short as possible and in compliance with paragraph 5.5.5.

Figure 4. Unpainted areas on a typical antenna mounting base

Figure 5. Typical unpainted areas prepared for antenna mounts on a vehicle

Figure 6. Typical radio mounting tray bonding

Figure 7. Typical radio mount support bracket

Figure 8. Installation of Solid Bond Straps on Shock Mounts

Figure 9. Recommend Bond Strap Installation for Rigid Mounts

Remove all paint from mounting surfaces

Figure 10. Type III Bond Strap Conforming to MIL-DTL-24749A

6. RECORDS.

System bonding and grounding will be a topic at the Preliminary Design Review (PDR) and will be readdressed at Critical Design Review (CDR) including verification/validation requirements.

Records of the PDR and CDR meeting minutes will include bonding and grounding decisions. Design documentation (drawings) including installation and interface control drawings (ICDs) will detail bonding, grounding, cable routing and shielding. Results of required EMI/EMC, TEMPEST, and bonding tests will be included in the project records.

0.5"

L

W

D

ROUND

CORNERS

0.5" RADIUS

0.02"

TOP VIEW

SIDE VIEW

NOTES:

1. Bond straps for electronic equipment will be fabricated from flat copper meeting ASTM B 152.

2. Length (L), width (W) and hole diameter (H) of bonding straps will be specified in the project’s design documentation.

3. The length to width ratio shall be no greater than 5:1 and the bond strap width shall not be less than 1.0 inch.

Figure 4. Type III Bond Strap Conforming to MIL-DTL-24749A

Attachment 1

FOSOV Standard Procedures for Metal-to-Metal Bonds

1. Remove paint as indicated on the integration drawings to support proper bonding

a. Use tools that will not damage metal substrate. For examples, wire brush, sandpaper, angle grinder with scotch-britetm pads, or Dremmel tool with sanding drum attachments. Avoid using a grinding stone.

b. Gently run the tool across the surface until the metal surface is completely exposed and free of debris.

2. Clean the surface free of all corrosion or contaminants.

a. Clean the surface with a moistened abrasive pad.

b. Wipe the substrate with a damp lint-free cloth.

c. Allow surface to dry.

3. Apply chemical film to the exposed metal to protect against corrosion using an Alodinetm 1132 pen applicator.

a. To activate, hold the pen upright, pop off the cap, and then hold the pen tip down on a clean surface to begin the flow of solution to the tip. Do not twist or turn to remove the cap since this may result in the pen leaking.

b. Press the pen tip down on the prepared surface until the solution fills the pen tip. Apply the solution to the metal surface with firm, smooth, even strokes, covering all edges.

Over-lap each stroke and allow the solution to dry. Frequent short jabs to rewet the application tip are preferred to maintain constant coating weights and avoid over-wetting the felt tip.

c. Within 5 minutes of the first coat, apply a second coat at a 90o angle to the first coat with the same smooth, firm stroke.

d. Allow the coating to air dry thoroughly.

e. Immediately replace the cap when not in use to avoid evaporation and contamination.

4. Apply A-A-59313 anti-seize to the exposed metal.

a. The surface should be thoroughly cleaned before application.

b. Open the anti-seize container and apply to a small acid brush or similar applicator.

c. Using the brush or applicator, apply a thin film of anti-seize to the exposed metal.

Cover metal substrate completely using short strokes.

d. Wipe off any excess with a damp rag and alcohol.

5. Repeat steps 1-4 to the mating surface as applicable.

6. Mate the two surfaces, and apply anti-seize to hardware.

a. Apply a thin coat of anti-seize to the threads and flats of the nuts and bolts with a small acid brush or other applicator.

b. A thin coating is all that is required to prevent seizing. In the case of blind holes, the application of an excessive amount of the compound may prevent proper seating of components. Under low temperature conditions, the compound hardens and is difficult to apply. It should be kept at room temperature for 24 to 48 hours prior to use.

7. Complete assembly by installing hardware.

a. Wipe off any excess anti-seize at the joint with a damp rag and alcohol.

8. Apply Permatex Form-A-Gasket No. 2 sealant, PN 80010 (CAGE 01232; NSN 8030-00-849-0071) or equivalent non-acidic sealing compound.

a. Temperature should be above 40o F at time of application to assure proper curing.

b. Apply sealant around the perimeter of the mating surfaces and mounting hardware.

c. Use finger or orangewood stick to contour and mold sealing compound to the edges of the material around the mating surfaces.

d. Wipe off excess sealant.

e. Assembly is operational after 4 hours; final cure time is 24 hours.

9. Measure the resistance of the bond using a low resistance ohm meter.

a. Example of a suitable meter is the Megger DLRO10HD. It provides a high power setting with a 10A output, a resistance range of 0 to 250.00 mΩ and a resolution of 10 μΩ.

b. The meter should be used on the high power setting.

c. The bond resistance must measure 10 milliohms or less from the component to the vehicle chassis ground point including the cumulative effect of all metal surface and bond strap interfaces.

Attachment 2

FOSOV Standard Bonding Notes for Drawings

1. Typical note used when bonding unpainted surfaces that will not be exposed to weather. (For example, interior fabricated metalwork components that already have no-paint zones on their mating surfaces.)

Bond metal subcomponents of assemblies in accordance with FOSOV Bonding Requirements

Work Instruction FOSOV 10-01. Ensure that paint has been removed from components extending at least 1/16” beyond all mating surfaces. Ensure that all unpainted aluminum surfaces have been treated with MIL-DTL-5541, Class 3 chemical film coating. Clean mating surfaces and fasten components together using indicated hardware.

2. Typical note used when bonding unpainted surfaces that will be exposed to weather. (For example, exterior fabricated metalwork components that already have no-paint zones on their mating surfaces.)

Bond metal subcomponents of assemblies in accordance with FOSOV Bonding Requirements

Work Instruction FOSOV 10-01. Ensure that paint has been removed from components extending at least 1/16” beyond all mating surfaces. Ensure that all unpainted aluminum surface have been treated with MIL-DTL-5541, Class 3 chemical film coating. Clean all mating surfaces and apply a thin coat of A-A-59313 anti-seize compound. Fasten components together using indicated hardware. After assembly coat mounting hardware with anti-seize and apply Permatex

Form-A-Gasket No. 2 sealant, PN 80010 (CAGE 01232; NSN 8030-00-849-0071) around the perimeter seams of all mating surfaces.

3. Typical note used when surfaces require paint removal and will not be exposed to weather.

(For example, mounting brackets with no-paint zones that are bolted to a vehicle interior surface that is already painted.)

Bond component to indicated location in accordance with FOSOV Bonding Requirements Work

Instruction FOSOV 10-01. Remove paint from intended mounting surface to create an unpainted bonding area. Ensure paint is removed from mounting area extending at least 1/16” beyond all mating surfaces of the component to be mounted. Clean all mating surfaces prior to installation.

Treat bare aluminum area with MIL-DTL-5541, Class 3 chemical film coating. Install component using indicated hardware.

4. Typical note used when surfaces require paint removal and will be exposed to weather. (For example, mounting brackets with no-paint zones that are bolted to a vehicle exterior surface that is already painted.)

Instruction FOSOV 10-01. Remove paint from intended mounting surface to create an unpainted bonding area. Ensure paint is removed from mounting area extending at least 1/16” beyond all mating surfaces of the component to be mounted. Treat bare aluminum area with MIL-DTL-

5541, Class 3 chemical film coating. Clean all mating surfaces and apply a thin coat of A-A-

59313 anti-seize compound. Install component using indicated hardware. After installation coat mounting hardware with anti-seize and apply Permatex Form-A-Gasket No. 2 sealant, PN 80010

(CAGE 01232; NSN 8030-00-849-0071) around the perimeter seams of all mating surfaces.

5. Typical note used for ground strap installation where no bonding point has been provided.

(For example, equipment bond straps or shock-isolation mount bond straps.)

Install ground straps on items indicated using specified bond strap and hardware. Create a bonding point at location indicated, a minimum of one inch diameter, by removing paint and drilling hole in the center to accommodate noted mounting hardware. After removing paint, clean surface and treat with MIL-DTL-5541, Class 3 chemical film coating. Treat mating surfaces of the strap and shelf with A-A-59313 anti-seize compound and install bond strap.

6. Typical note used for existing vehicle components that must be checked and reworked to provide acceptable bonding. (For example, existing antenna mounts on the vehicle.)

Instruction FOSOV 10-01. Verify proper bonding of existing antenna mounts by removing mount and inspecting. Ensure paint is removed from both antenna mount and mounting area extending at least 1/16” beyond mating surfaces. If not properly bonded, remove paint from mount and vehicle. Treat bare aluminum surfaces with MIL-DTL-5541, Class 3 chemical film coating. Clean all mating surfaces and apply a thin coat of A-A-59313 anti-seize compound.

Reinstall mount using existing hardware. Coat mounting hardware with anti-seize and apply

Permatex Form-A-Gasket No. 2 sealant, PN 80010 (CAGE 01232; NSN 8030-00-849-0071) around the perimeter seams of all mating surfaces.

7. Typical note used when paint removal from a large mating surface is not practical. (For example, a radio mount with unpainted base is bolted to a shelf that is painted.)

Instruction FOSOV 10-01. Remove paint to create an unpainted bonding area on mounting surface as indicated in Detail (X). Treat bare aluminum surfaces with MIL-DTL-5541, Class 3 chemical film coating. Clean surfaces on installed component and mounting surface. Install component using indicated hardware.