Attachment 5 TO-31-10-12.PDF

TO 31-10-12

TECHNICAL MANUAL

AIR FORCE COMMUNICATIONS

COMMAND

(E-1 STANDARD)

STANDARD

INSTALLATION PRACTICES

METAL DUCTS AND CONDUITS

Prepared By: Automated Technical Order Sys-tem (ATOS)

DISTRIBUTION STATEMENT - Distribution author-ized to U.S. Government Agencies and their contractors, Administrative or Operational Use, 20 May 1997. Other requests for this document shall be referred to OC-ALC/LIIS-T, Tinker AFB, Oklahoma 73145-3029.

WARNING - This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751 et seq.) or the Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401, et seq.

Violation of these export-control laws is subject to severe criminal penalties. Dissemination of this document is controlled under DoD Directive 5230.25.

HANDLING AND DESTRUCTION NOTICE - Comply with distribution statement and destroy by any method that will prevent disclosure of contents or reconstruction of the document.

Published under authority of the Secretary of the Air Force

15 JULY 1973

CHANGE 3 - 1 JUNE 1999

Attachment 5

INSERT LATEST CHANGED PAGES. DESTROY SUPERSEDED PAGES.

LIST OF EFFECTIVE PAGES

NOTE: The portion of the text affected by the changes is indicated by a vertical line in the outer margins of the page. Changes to illustrations are indicated by miniature pointing hands. Changes to wiring diagrams are indicated by shaded areas.

Dates of issue for original and changed pages are:

Original ..................0 ................ 15 July 1973 Change ...................1 ................15 May 1985 Change ...................2 ............ 29 March 1995 Change ...................3 ................. 1 June 1999

TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS

88, CONSISTING OF THE FOLLOWING:

Page *Change Page *Change No. No. No. No.

Title .............................. 3 2-17 - 2-18 A................................... 3 2-18.1 - 2-18.7 Added. 3 B Added....................... 3 2-18.8 Blank Added ... 3 C Blank Added............ 3 2-19 - 2-20 i - iv .............................. 3 2-21 - 2-22 1-1 - 1-2 ........................0 2-23 1-3................................ 3 2-24 1-4 Blank..................... 3 2-24.1 - 2-24.2 2-1 - 2-4 ....................... 3 2-25 2-4.1 Added................. 3 2-26 2-4.2 Blank Added...... 3 2-27 - 2-28 2-4.3 Added................. 3 2-28.1 Added 2-4.4 Blank Added...... 3 2-28.2 Blank Added ... 3 2-5 - 2-6 ........................1 2-29 2-7 - 2-8 ....................... 3 2-30 - 2-35 2-9.................................0 2-36 - 2-37 2-10...............................1 2-38 2-11 - 2-12 ................... 3 3-1 2-12.1 Added............... 3 3-2 - 3-4 2-12.2 Blank Added ... 3 3-5 2-13 - 2-14 ....................0 3-6 - 3-8 2-15...............................1 3-9 2-16...............................0 3-10

*Zero in this column indicates an original page

A Change 3 USAF

LIST OF EFFECTIVE PAGES

Page *Change Page *Change No. No. No. No.

3-11 3-12 - 3-14 3-15 - 3-16 3-17 3-18 Index 1 - Index 3 Index 4 Blank

*Zero in this column indicates an original page

Change 3 B/(C Blank)

TABLE OF CONTENTS

Section/Para Page

I GENERAL ............................................................... 1-1

1-1 Purpose .................................................. 1-1 1-3 Scope ...................................................... 1-1 1-5 Safety Precautions ................................ 1-1 1-12 List of Applicable

Publications .......................................1-3 1-14 Installation Tools .................................. 1-3

II CONDUIT................................................................ 2-1

2-1 Description............................................. 2-1 2-4 Types of Conduit ................................... 2-1 2-5 Rigid Conduit ........................................ 2-1 2-8 Flexible Metal Conduit ......................... 2-2 2-11 Thin Wall Conduit ................................ 2-3 2-13 Storage and Use. ................................... 2-3 2-14 Storage of Conduit ................................ 2-3 2-16 Number of Conductors in

Conduit...............................................2-3 2-18 Routing................................................... 2-4 2-22 Conduit Entrances ................................ 2-4 2-23 Point of Entrance .................................. 2-4 2-24 Sealing Wall Penetrations................. 2-4.1 2-27 Fabrication............................................. 2-8 2-28 General................................................... 2-8 2-29 Measuring Conduits.............................. 2-8 2-31 Cutting Conduit .................................... 2-9 2-36 Power Hacksaw ................................... 2-11 2-37 Hacksaw Blades .................................. 2-11 2-40 Removing Burrs .................................. 2-12 2-41 Threading Conduit .............................. 2-13 2-45 Bending Techniques............................ 2-14 2-50 Hydraulic Bender ................................ 2-18 2-51 Use of Hydraulic Bender .................... 2-18 2-56 Conduit Supports ................................ 2-20 2-59 Wooden Battens for

Protection.........................................2-21 2-60 Conduit Spacers .................................. 2-22 2-68 Assembling and Securing

Conduit.............................................2-25 2-71 Conduit Fittings .................................. 2-27 2-72 Threaded Fittings................................ 2-27 2-73 Non-Threaded Fittings ....................... 2-27

Change 3 i

TABLE OF CONTENTS - Continued

Section/Para Page

2-74 Outlet Boxes, Pull Boxes, and Cabinets....................................2-28

2-75 General................................................. 2-28 2-76 Outlet Boxes ........................................ 2-28 2-82 Knockouts ............................................ 2-31 2-85 Cutting Holes ...................................... 2-34 2-90 Terminating......................................... 2-36 2-94 Flexible Conduit .................................. 2-37

III METAL DUCTS ...................................................... 3-1

3-1 General................................................... 3-1 3-3 Wireways ............................................... 3-1 3-6 Installation ............................................ 3-2 3-9 Hangers.................................................. 3-3 3-14 Wireway Fittings................................... 3-4 3-18 Steel Underf loor Raceways .................. 3-4 3-20 Installation ............................................ 3-5 3-24 Steel Underf loor Raceway

Fittings...............................................3-6 3-29 Concrete Raceways................................ 3-7 3-33 Metal Surface Raceways....................... 3-8 3-35 Floorduct ................................................ 3-8 3-39 Wiremold................................................ 3-9 3-48 LA-IN Raceways.................................. 3-13 3-49 General................................................. 3-13 3-51 Installation .......................................... 3-14

LIST OF ILLUSTRATIONS

Figure Title Page

1-1 Warning Signs ............................................ 1-2 2-1 Common Types of Conduit......................... 2-2 2-2 Bench and Storage Rack ............................ 2-4 2-2.1 Metal Conduit and Conduit

Fittings, 1/2″ to 2″ ...............................2-4.3 2-3 Conduit Measurement................................ 2-9 ii Change 3

LIST OF ILLUSTRATIONS - Continued

Figure Title Page

2-4 Tube Cutter............................................... 2-10 2-5 Cutting With Hand Hacksaw .................. 2-11 2-6 Common Misuses and the

Correct Usage of Hacksaw Blades ....................................................2-12

2-7 Typical Reamer ......................................... 2-13 2-8 Conduit Hickey ......................................... 2-16 2-9 Manual Conduit Bending......................... 2-17 2-10 Use of Hydraulic Conduit

Bender ...................................................2-19 2-11 Bending Conduit with Wheel and Block Sheet 1 of 2 .........................2-20 2-11 Bending Conduit with

Jackscrew Sheet 2 of 2 .........................2-21 2-12 Conduit Support Intervals ....................... 2-22 2-13 Wooden Batten Supports for

Conduit ..................................................2-23 2-14 Pipe Straps and Clamp ............................ 2-24 2-14.1 Conduit Mounting Details

(Cement Surfaces)..............................2-24.1 2-14.2 Conduit Mounting Details

(Drywall or Fiber Board)...................2-24.2 2-15 I-Beam Clamps ......................................... 2-25 2-16 Supporting Conduit Beneath

Cable Rack ............................................2-25 2-17 Support of Conduit to Cable

Rack .......................................................2-26 2-18 Supporting Conduit from

Framing Bar or Lipped Channel .........2-27 2-19 Typical Threaded Fittings........................ 2-28 2-20 Threadless Fittings................................... 2-29 2-21 Outlet Boxes.............................................. 2-30 2-22 Pull Boxes.................................................. 2-31 2-23 Cabinets and Panel Boxes ....................... 2-33 2-24 Removing Ordinary Knockouts................ 2-33 2-25 Removing Concentric

Knockouts..............................................2-34 2-26 Hole Saw ................................................... 2-35 2-27 Forming Knockout with Drill

Holes ......................................................2-36 2-28 Securing Threaded Conduit ..................... 2-37

Change 3 iii

LIST OF ILLUSTRATIONS - Continued

Figure Title Page

2-29 Installing Insulating Bushing.................. 2-38 2-30 Flexible Conduit Connector ..................... 2-38 3-1 Wireway Section ......................................... 3-1 3-2 Wireway Fittings ........................................ 3-2 3-3 Underf loor Raceway

Installation..............................................3-5 3-4 Concrete Raceway Installation .................. 3-7 3-5 Overf loor Raceway Installation................. 3-8 3-6 Overf loor Raceway Fittings..................... 3-10 3-7 Wiremold Raceway and

Supports ................................................3-11 3-8 Wiremold Fittings..................................... 3-12 3-9 La-in Surface Raceway............................. 3-14 3-10 Mitered Turn............................................. 3-16 3-11 Mitered Inside Bend................................. 3-17 3-12 Mitered Outside Bend .............................. 3-17

LIST OF TABLES

Number Title Page

1-1 Installation Tools........................................ 1-3 2-1 Permissible Number of

Conductors in Conduit ...........................2-7 2-2 Minimum Radius of Conduit

Bend.......................................................2-23 2-3 Permissible Number of

Conductors in Outlet Box.....................2-32 iv Change 3

SECTION I

GENERAL

1-1 . P U R P O S E .

1-2. Methods and other information contained herein -are intended as guides for installations personnel to assure standardization and provide a reference for verification and quality assurance inspections.

1 -3 . S C O P E .

1 - 4 . T h i s p u b l i c a t i o n c o v e r s i n f o r m a t i o n a n d methods per t inent to the proper se lect ion, use, and installation of conduits and ducts.

T h i s p u b l i c a t i o n i s d i v i d e d i n t o t h r e e s e c -t i o n s a s f o l l o w s :

a. Section I contains introductory material, the safety precautions to be observed, a list of applicable publications, and a tabulation of tools required to perform the procedures described in this manual.

b. Section II contains information for routing. fab-rication, measuring, threading, cutting, and install-ation of a conduit system.

c. Section III contains information pertinent to the various types of ducts and fittings, their application, and their installation.

1-5. SAFETY PRECAUTIONS.

1-6. The following general safety precautions shall be observed by installation personnel when performing the operations detailed in this manual.

a. When working from ladders, always face them.

Do not lean to the sides.

b. Tools are not to be placed on the top step of a ladder. Use the too l shel f that is provided or a pouch. When leaving a ladder, even temporarily, take the tools with you.

Change 1 1-1

1-7. The base of extension ladders should be set a distance from the wall equal to one-fourth the height of the ladder.

1-8. When working from a crew chief’s stand, be certain that the brake is set. After the stand is ele-vated to the desired height, verify that the safety pin has been inserted.

1-9. A steel tape is never used in an operating site or near energized equipment.

1-10. Stand on an insulated platform of dry wood when working on electrical apparatus. The notion that rubber mats are always safe is not necessarily true since they may contain a large amount of elec-trically conducting carbon black.

1-11. WARNING SIGNS. Warning signs, such as those in f igure 1-1, should be posted at the base o f s t ruc tures car ry ing h igh vo l tage.

Suitable guards are required whenever neces-sary to prevent personnel from coming in contact wi th h igh vo l tage.

Figure 1-1. Warning Signs

1-2 Change 1

1-12. LIST OF APPLICABLE PUBLICATIONS.

1-13. Requirements and procedures contained in this manual are based upon or are to be used in conjunction with information appearing in the following publications:

a. OSHA 1910.268 Telecommunications

b. 31-10-6 Cable Racks, Troughs and

Their Supports

c. 31-10-13 Cabling for Fixed Ground

C-E-M Equipment

d. MIL-STD-188-124B Grounding, Bonding and

Shielding

e. MIL-HDBK-419 Grounding, Bonding and

Shielding for Electronic Equipment and Facilities

1-14. INSTALLATION TOOLS.

1-15. The tools listed in table 1-1 are included for reference purposes to aid in determining those items required to install metal ducts and conduits.

Table 1-1. Installation Tools

TOOL

Bender, elect., conduit Bender, elect., conduit, thin wall, 1/2 in.

Bender, elect., conduit, thin wall, 3/4 in.

Bender, elect., conduit, thin wall, 1 in.

Bending Mach., Pipe and Conduit, Hyd., Hand Blade, hand, hacksaw Blade, hole saw, 3/4 in. Reamer, hand, pipe Blade, hole saw, 7/8 in. Rule, folding, wood, 6 ft.

Blade, hole saw, 1 in. Saw, hand, hack Blade, hole saw, 3 in. Saw, power, hack Blade, hole saw, 4 in. Tape, measuring, linen, 100 ft.

Blade, power, hacksaw Tape, measuring, steel, 100 ft.

Cutter, pipe Thread, cutter, 6 die heads Drill, elect., port., 1/2 in. Vise, mach., table, 4 in.

File, hand, rd. Vise, pipe, hinged jaw, 1/8-2-1/2 in.

Hammer, hand, ball-peen Vise, pipe, hinged jaw, 1/8-4-1/2 in.

Wrench, pliers

Change 3 1-3/(1-4 Blank)

SECTION II

CONDUIT

2-1. DESCRIPTION.

2-2. Conduit is a tubular raceway through which insulated conductors are pulled. This tubing not only protects the conductors from mechanical injury, but it also permits easy removal and replacement of the conductors. It is used to conceal conductors whose exposure would constitute a hazard or be otherwise objec-tionable. The conduit system can be employed for both exterior and interior work and can be constructed to meet a variety of weather and climatic conditions.

2-3. Conduit is available in many different materials. The type used is dependent upon installation and location requirements. Certain installation factors often make it necessary to use a particular conduit having definite charac-teristics. This is generally determined and specified in advance during the engineering or planning phase.

2-4. TYPES OF CONDUIT. Three types of con-duit commonly used are f lexible, rigid, and thin wall. These are shown in figure 2-1.

2-5. RIGID CONDUIT. Rigid conduit is made from steel, aluminum, or copper alloy tubing and non-metallic materials such as PVC. Such tubing, with diameters ranging from 1/2 to 6 inches, may be either galvanized or non-galva-nized. Galvanized conduit is widely used where it will be exposed to weather conditions. It is also used when excessive dampness is present and when conduit is to be imbedded in concrete.

Non-galvanized conduit is used for general inte-rior work.

Change 3 2-1

2-6. Because of its heavy construction, rigid conduit is usually threaded for use. This will insure a more permanent installation. Rigid conduit may be used with threadless fittings as the bushing in each fitting will grip a threaded as well as non-threaded end. Because of the gripping action of the threadless fitting, it is not necessary to scrape off any coating which may be on the conduit in order to obtain an electrical connection to a threadless fitting.

Figure 2-1. Common Types of Conduit

2-7. Rigid conduit is moisture proof and fire-proof and can withstand severe mechanical injury. It is approved for both exposed and con-cealed work and can be used in nearly all clas-ses of buildings. There are no restrictions on voltage or wire size.

2-8. FLEXIBLE METAL CONDUIT. This type of conduit possesses great f lexibility and high mechanical strength. It is made from a strip of steel that is spirally wound and interlocked on itself. It is used mainly in conjunction with rigid conduit, when extending to vibrating equipment such as motors, engines, etc.

2-2 Change 3

2-9. Because of its unique characteristics, f lex-ible conduit is often preferred to rigid conduit.

Its f lexibility is important where cramped wir-ing makes it diff icult or impossible to use rigid conduit.

2-10. Flexible conduit is approved for both exposed and concealed work, but it is not to be used on circuits exceeding 600 volts. It is not to be imbedded in concrete, used in battery rooms, or used in hazardous locations. Sizes of f lexible conduit range from 3/8 to 3 inches.

2-11. THIN WALL CONDUIT. This type of con-duit is similar to rigid conduit but is fabricated with a thinner wall. It is made of steel, alumi-num, or copper alloy tubing with diameters ranging in size from 1/2 to 6 inches.

2-12. There are no restrictions on wire size, but the conductor must not exceed 600 volts. It is approved for both concealed and exposed work in dry locations. It will not withstand severe mechanical shock or corrosive vapors unless made from special materials. Because of its thin wall construction, it cannot be threaded and, therefore, is used only with threadless fittings.

2-13. STORAGE AND USE.

2-14. STORAGE OF CONDUIT.

2-15. Conduit should be stored in an orderly manner. A rack and bench may be constructed out of discarded packing case lumber as illus-trated in figure 2-2.

2-16. NUMBER OF CONDUCTORS IN CONDUIT.

2-17. The rules governing the permissible size and number of wires in a conduit are the same for rigid, thin wall, and f lexible conduit. The proper size of conduit necessary for a particular installation can be determined from table 2-1.

Change 3 2-3

2-18. ROUTING.

2-19. Conduits are to be routed in accordance with the detail plans or engineering directives and the general rules stated in the following paragraphs.

2-20. All exposed runs of conduit shall be run parallel with or at right angles to the walls and f loors of the building as far as practicable.

Figure 2-2. Bench and Storage Rack

2-21. The clearance between any conduit and a bare live conductor or connection shall be a minimum of 1 inch.

2-22. CONDUIT ENTRANCES.

2-23. POINT OF ENTRANCE. The location of the conduit entrance into a building is governed primarily by the location and nature of the

2-4 Change 3 outside plant facility. The conduit entrance point location will be governed secondarily by the nature and disposition of existing conduit layout within the building. Generally, the outside plant facility is routed to the building in the simplest and most direct manner. However, the routing of the outside plant facility may be extended as necessary to minimize the need for any interior cable runs.

2-24. SEALING WALL PENETRATIONS. The hole must be sealed once the conduit f ixtures have been put in place with cement grouting or an approved crack filler. Cement grouting, used to seal holes in concrete block and brick, is a mixture of 1 part cement, 2 or 3 parts sand, and water as needed.

2-25. Grout is generally mixed by hand in small quantities. As little water as practicable is used so that the mixture will be dry.

Dampen the inner surface of the hole being grouted to ensure a good bond. Dress the grout-ing f lush with the surface, using a putty knife.

A smooth finish may be attained by dipping the putty knife in clear water before each applica-tion. The grout will set after a few hours, pro-viding a weatherproof and permanent bond.

Change 3 2-4.1/(2-4.2 Blank)

Figure 2-2.1. Metal Conduit and Conduit Fittings, 1/2″ to 2″

Change 3 2-4.3/(2-4.4 Blank)

Table 2-1.

Change 1 2-5

2-6 Change 1

Change 3 2-7

2-26. Caulking compound, a putty substance furnished in handy tube form, is used to seal conduit entrances in wood. It is squeezed into place around the conduit or f ixture until all the crevice and openings are filled. It later hard-ens, providing an air-tight and weatherproof seal.

2-27. FABRICATION.

NOTE

Before proceeding with fabrication, observe figure 2-2.1 for metal con-duit and conduit f ittings in this technical order.

2-28. GENERAL. Fabrication procedures (cut-ting, bending, threading) are essentially the same for rigid, thin wall, and f lexible conduit.

Specialized fabrication techniques pertinent to any one class of conduits are covered, where necessary, under appropriate headings else-where in the instructions.

2-29. MEASURING CONDUITS. When making measurements in preparation for cutting a desired length of conduit, take into considera-tion fittings (bends, els, etc.) that are to be used. Temporarily support these fittings in position before the measurement for the conduit is made. Since the fittings are apt to vary in dimension, use the same fittings that the mea-surements were made with. Measure length of conduit (f igure 2-3) to connect two fittings as follows:

a. Measure the distance M between centers of the conduit f ittings.

b. Measure the distance from the centers to the end of each fitting, F1 and F2, and add these dimensions.

2-8 Change 3

Figure 2-3. Conduit Measurement

c. Subtract the sum of F1 and F2 from M, and add twice the distance S by which the conduit penetrates into the fitting to obtain N, the length of conduit to be cut.

2–30. If linen tape is used for measuring purposes, the space and the conduit should be measured with the same tape. This may minimize any errors due to tape stretching.

2-31. CUTTING CONDUIT.

2–32. GENERAL. Conduit, rigid or thin wall, a tube cutter, hand hacksaw, or power hacksaw.

is cut with a hand hacksaw or armor cutters.

Note may be cut with Flexible conduit

Lubricant shall not be used on the saw blade or conduit, when cutting conduit.

2–33. TUBE CUTTER. The following procedure should be used in order to cut conduit with a tube cutter.

2-9

a. Place the conduit between the roller and the cutting wheel as shown in figure 2-4.

b. Tighten the clamping jaw until the cutting wheel rests lightly against the conduit at the point where the cut is to be made.

c. Rotate the cutter around the conduit while keep-ing a light even pressure on the cutting wheel by means of the screw adjustment. Continue this proc-ess until the conduit is cut.

Figure 2-4. Tube Cutter

2-34. Conduit cutting with a tube cutter is preferable to the use of a hacksaw. A tube cutter insures per-fectly square ends, with no external burrs and little internal burring.

2-35. HAND HACKSAW. The following procedure should be followed in order to cut conduit with a hand hacksaw.

a. Clamp the conduit in a horizontal posi-t ion in a p ipe or bench v ise . Do not c lamp t h e c o n d u i t s o t i g h t t h a t i t w i l l b e d e -formed.

2-10 Change 1

b. Saw squarely through the scribed cut mark with hacksaw, taking care not to rock or bend the saw blade.

c. Cut through the conduit with long smooth cutting strokes, utilizing the entire cut-ting length of the blade. Do not saw too fast or exert too much pressure; this will cause the blade to weaken and break. Figure 2-5 illus-trates the manner in which the hack-saw should be held when cutting.

Figure 2-5. Cutting With Hand Hacksaw

2-36. POWER HACKSAW. The power hacksaw is most effective when a number of conduit can be cut at the same time. It is important to check the printed instructions before placing the machine in operation. When the power hack-saw is used, be sure parts are properly lubrica-ted and the blade installed correctly. It is important to note if the cutting power is exerted on the forward or return stroke. Whichever is the case, the blade (teeth) shall be installed in the direction of cutting stroke.

2-37. HACKSAW BLADES. Care should be given to the proper selection of hacksaw blades.

It should be remembered that the distance between two adjacent teeth of the blade should always be less than the thickness of the mater-ial being cut.

Change 3 2-11

2-38. A fine tooth blade should be used when sawing thin material. If a coarse tooth blade is used on thin material, the teeth will break off.

A coarse tooth blade should be used when cut-ting heavy material. A fine tooth blade will f ill with material when used on heavy material.

Figure 2-6 illustrates and explains common mis-uses and the correct usage of hacksaw blades.

Figure 2-6. Common Misuses and the Correct Usage of Hacksaw Blades

2-39. The blade shall be inserted so that the teeth point away from the handle of the hack-saw. When in use, the blade should be drawn up tight in the frame to prevent it from buck-ling under pressure of stroke. On the other hand, do not strain blade so much that slight canting of the frame will break it.

2-40. REMOVING BURRS. After cutting, check all conduit ends for burrs. Internal burrs

2-12 Change 3 must be removed to prevent damage to the con-ductor insulation. Remove internal burrs with a round file or hand reamer. Figure 2-7 shows a typical hand brace operated reamer. However, there may be other types available, such as those equipped with ratchet operated handles.

External burrs are undesirable, and should be removed, as they can severely cut the hands.

Remove external burrs with a f lat f ile.

Change 3 2-12.1/(2-12.2 Blank) with either a round file or reamer. External burrs should be removed, if only for the reason that they present a hazard while handling. The reamer illus-trated in figure 2-7 is typical of the type used with a standard brace. However, there may be other types available, such as those equipped with ratchet operated handles.

Figure 2-7. Typical Reamer

2-41. THREADING CONDUIT.

2-42. DIES. Conduit is threaded using adjustable round split screw and bolt threading die. Such dies consist of a piece construction with adjustments be-ing made by splitting the die between two of its lands (cutting portion between grooves) and expanding or contracting it. Dies are available to cut both right and left hand threads.

2-43. CUTTING THREADS. The following proced-ure is to be used when threading conduit.

a. Select a die having the proper thread count but which is slightly larger than desired.

b. Secure the die in place in the stock.

c. Place the die on the conduit face first. The side of the die with the chamfered threads is referred to as the face of the die.

2-13

d. Turn die stock carefully, insuring balance at all times and insuring that the die cuts into the conduit squarely.

e. Cut a few threads, and back the die off the conduit.

f. Test the threads with correct size nut and read-just the die, if required, to the correct diameter.

g. Proceed with threading, but back off 1 or 2 turns after several forward turns. This action will allow shavings to fall free and will prevent clogging.

2-44. THREADING LUBRICANT. A lubricant shall be used when threading conduit. The use of a lubri-cant will insure a smoother, cleancut thread. Lard oil is generally preferred on steel. Kerosene is used on aluminum or aluminum alloy.

2-45. BENDING TECHNIQUES.

2-46. GENERAL. Conduit from fitting to fitting or outlet shall contain no more than 4 quarter bends (90 degrees). If more bends are required, pull boxes shall be inserted. Care must be exercised when making bends to prevent injury to conduit or reduction of the internal diameter of the conduit.

2-47. CONDUIT HICKEY. A hickey is a hand lever having a slot at one end wherein the conduit to be bent may be held. Only the hickey head is furnished so that the handle must be fabricated from available conduit or pipe stock. This is usually a piece of pipe about four feet long. The hickey head is tapped to receive the threaded end of the handle which should be engaged the full depth of the threads in the hickey.

2-48. A conduit hickey (figure 2-8) will conveniently bend conduit up to 1" in diameter, either by holding the hickey stationary and applying pressure on the conduit or by holding the conduit stationary and applying leverage on the hickey.

2-49. RIGHT ANGLE BENDS. See figure 2-9, Sheets 1 and 2, for procedures to follow when forming right angle bends in conduit with conduit bending tools. Pro-ceed as follows:

2-14

a. See f igure 2-9 , sheet 1 o f 2 . From the w a l l , make a mark on the floor “XY” which is the outs ide d is tance the condui t i s to be bent . See (A).

b . But t the condui t aga ins t the wai l . P lace the condui t aga ins t the wal l . S tand on the condui t jus t ins ide the “XY” mark on the f loor and pu l l the h ickey and condui t to an angle of about 20 degrees. See (B).

c. While standing on the conduit, move the hickey along the conduit toward the wail about one inch. Bend the condui t a b i t fur -t h e r . C o n t i n u e t h i s u n t i l t h e o u t s i d e o f t h e bend is perpendicular to the mark on the f loor . Use the hand le o f the h ickey to f in ish of f the bend to f ina l pos i t ion. See (C) .

d . For th in wal l condu i t (EMT) see f igure 2-9, sheet 2 of 2 and proceed as follows:

(1) For a typical 12-inch, 90 degree bend in 1/2-inch conduit, measure 7 inches from the end of the conduit and mark the point w i t h c h a l k .

(2) Using a combination 1/2-inch and 3/4-inch bender , p lace i t so that the ins ide of the hook is at the mark on the conduit.

(3 ) P lace your foo t on the pressure po in t on the bender and pull the hand lever unti l you have the desired 90-degree bend. The difference between the 7-inch mark on the conduit and the 12-inch bend is the 5-inch take-up for the rad ius of the bend.

Change 1 2-15

Figure 2-8. Conduit Hickey

2-16

Figure 2-9. Manual Conduit Bending (Sheet 1 of 9)

Change 3 2-17

Figure 2-9. Manual, Conduit Bending (Sheet 2 of 9)

2-50. HYDRAULIC BENDER. Conduit sizes 1 1/4 to 4 1/2 inches are generally bent with the hydraulic bender (f igure 2-10). The hydraulic bender is available with different size castings to bend different size conduits.

2-51. USE OF HYDRAULIC BENDER. The bender is prepared for use as follows:

a. Set in place the bending shoe (casting) corresponding to the conduit size.

b. Set in the radius required by adjusting the two pivoted shoes. The adjustment is made by using the six large holes in the horizontal bars of the frame.

2-18 Change 3

Figure 2-9. Manual Conduit Bending (Sheet 3 of 9)

Change 3 2-18.1

Figure 2-9. Manual Conduit Bending (Sheet 4 of 9)

2-18.2 Change 3

Figure 2-9. Manual Conduit Bending (Sheet 5 of 9)

Change 3 2-18.3

Figure 2-9. Manual Conduit Bending (Sheet 6 of 9)

2-18.4 Change 3

Figure 2-9. Manual Conduit Bending (Sheet 7 of 9)

Change 3 2-18.5

Figure 2-9. Manual Conduit Bending (Sheet 8 of 9)

2-18.6 Change 3

Figure 2-9. Manual Conduit Bending (Sheet 9 of 9)

Change 3 2-18.7/(2-18.8 Blank)

CAUTION

Figure 2-10. Use of Hydraulic Conduit Bender

In making radii adjustment, care should be taken when tightening the nuts on the pivot to insure enough space to allow the shoe to oscillate.

c. Insure that curvature o f the condui t is at the desired point and mark the place where the bend is to occur. This mark should corre-spond wi th the scr ibed center l ine on the shoe.

2-52. Prior to making a bend on 3“ or larger condu i t , app ly a grease to the sur face o f the pivoted shoes where they come in contact with the condui t . Th is a ids cons iderab ly in re-d u c i n g f r i c t i o n a t t h e s e p o i n t s .

2-53. WHEEL & BLOCK. See figure 2-11, sheet 1 of

2. Small size conduits may be bent by using a grooved metal wheel fastened to a handle. The conduit is held firmly between two blocks of wood. A downward pres-sure is exerted on the handle causing the grooved wheel to bend the conduit to a desired radius.

Change 1 2-19

Figure 2-11. Bending Conduit with Wheel and Block (Sheet 1 of 2)

2-54. JACK SCREW. See figure 2-11, sheet 2 of

2. A jack screw may be used for conduit bending when a hydraulic bender is not avail-able. This bending rig can be set up in a doorway or between any two strong posts.

2-55. PERMISSIBLE RADIUS. Bends shall be made with as large a radius as practicable. This is done to avoid reducing the internal diameter of the conduit. Table 2-2 shows the allowable radius of the inner edge of any field bend.

2-56. CONDUIT SUPPORTS.

2-57. GENERAL. Pipe straps are generally used to support conduit on surface runs. There are also other supports available for specific applications such as "U" bolts for use with framing, I-beam clamps, etc.

2-58. INTERVAL OF SUPPORT. Securely fasten

2-20 Change 1

Figure 2-11. Bending Conduit with Jackscrew (Sheet 2 of 2) conduit runs (rigid and thin wall) at intervals of 10 feet maximum. Conduit is fastened securely within three feet of each outlet box, junction box, cabinet or f itting. Generally, each individ-ual piece of conduit should have a minimum of one support. Figure 2-12 illustrates an example of support intervals for conduit secured to lipped channel (Unistrut).

2-59. WOODEN BATTENS FOR PROTECTION.

See figure 2-13. Wooden battens are used to protect f inished plaster surfaces when support-ing conduits. Offset bends are eliminated at the point of conduit termination. Battens are fabri-cated as follows:

a. Select strips or blocks of hard wood and cut to size dependent upon the number and sizes of conduits to be supported.

b. Sandpaper the exposed surfaces to a smooth finish and bevel the edges with a plane.

c. Paint the batten before mounting to the wall or mount the unpainted batten using a backing of heavy paper extending six inches from the edges on all sides. After the paint is dry, cut the excess paper with a razor blade.

Change 3 2-21

Figure 2-12. Conduit Support Intervals

2-60. CONDUIT SPACERS. Conduit spacers are used in much the same way as wooden bat-tens. They are of malleable iron and are used with one-hole straps and screws to mount to various surfaces. Conduit spacers permit the spacing of conduit away from its mounting sur-face, reduce corrosive moisture traps due to damp or wet walls, and eliminate the need for offset bends (dog legs) when entering or leaving conduit f ittings.

2-61. Five sizes of conduit spacers are available.

2-22 Change 3

Figure 2-13. Wooden Batten Supports for Conduit

Table 2-2. Minimum Radius of Conduit Bend

Radius-Inches Radius-Inches Size of Conduit (Conductors not (Lead Covered in Inches Lead Covered) Conductors)

½ 4 6

¾ 5 8 1 6 11 1¼ 8 14

1½ 10 16 2 12 21

2 ½ 15 25

3 18 31 3 ½ 21 36 4 24 40 4 ½ 27 45

5 30 50 6 36 61

2-62. PIPE STRAPS OR CLAMPS. Pipe straps or clamps (figure 2-14) are available with two mounting holes and with one mounting hole. When installing multiple conduit runs, the dimensions of the clamps should be considered in the layout of the job.

2–63. I-BEAM CLAMPS. There are many styles of I-beam clamps available for supporting conduit. A typical I-beam clamp is shown in figure 2–15. The principal advantage of this clamp is that it draws the conduit up closely against the I-beam and grips it firmly. If the clamps are used to support conduits lying close together, or when this type of clamp is used for multiple runs of conduit, stove bolts should be used in preference to studs, because they can be easily drawn up with a screw driver.

2-23

Figure 2-14. Pipe Straps and Clamp

2-64. Another type of beam clamp which permits conduit to be run parallel with the beam, cross-wise, or at any horizontal angle, is illustrated in figure 2-14. When using this clamp for conduit run-ning at right angles to the beam, the clamp placement should be in a back-to-back manner on the first and each succeeding pair of beams. This alternating placement is expected to reduce their shifting when conduit is secured.

2-65. A few conduits may be supported under cable racks by means of U-bolts, iron bars, and J-bolts. Figure 2-16 illustrates the method of supporting under cable racks.

2-66. Suppor t hor izonta l condui t a t r ight ang les to hor izonta l cab le racks and ver t ica l conduit to edge of horizontal cable rods as shown in f igure 2-17. Insta l la t ion of condui t to cement surfaces is shown in f igure 2-14A;

i n s t a l l a t i o n o f c o n d u i t t o d r y w a l l o r f i b e r board is shown in f igure 2-14B. Catalog num-bers are examples only.

2-24 Change 1

Figure 2-14.1. Conduit Mounting Details (Cement Surfaces)

Change 3 2-24.1

Figure 2-14.2. Conduit Mounting Details (Drywall or Fiber Board)

2-24.2 Change 3

Figure 2-15. I-Beam Clamps

2-67. CONDUIT SUPPORTED BY FRAMING BARS OR

LIPPED CHANNEL. Conduit is secured to framing bars w i th U-bo l ts , ch ips and nuts . Condu i t can be secured to l ipped channel (Unis t ru t ) by using one hole pipe clamps. A threaded pla te nut is Inser ted in the channel . The pipe clamp is then secured to the plate nut wi th an appropr ia te bo l t or screw.

2-68. ASSEMBLING AND SECURING CONDUIT.

2-69. GENERAL. A conduit system is assembled

Figure 2-16. Supporting Conduit Beneath Cable Rack

Change 1 2-25

Figure 2-17. Support of Conduit to Cable Rack with conduit fittings, outlet boxes, pull boxes, and cabinets. Hardware can be adapted to threaded, non-threaded, and flexible conduit.

2-70. COUPLINGS. Couplings are used to join lengths of conduit in a straight run. Couplings may also be used to join different types of conduit such as threaded, non-threaded, or a combination of flexible and non-threaded conduit.

2-26

Figure 2-18. Supporting Conduit from Framing Bar or Lipped Channel

2-71. CONDUIT FITTINGS. Conduit f ittings are applicable to many different types of instal-lation. A tee may be used to extend a vertical conduit run from a horizontal run. An elbow may be used in a similar manner. Conduit f it-tings can be obtained in a wide variety of styles to f it threaded and non-threaded conduit (see figure 2-19.1).

2-72. THREADED FITTINGS. Threaded conduit fittings are joined to conduit by threading the conduit into the threaded hole. It is then fast-ened tightly in place, using a wrench to turn the conduit. Some typical threaded fittings are shown in figure 2-19.

2-73. NON-THREADED FITTINGS (f igure 2-20).

The fitting and the conduit are joined by inserting the conduit in the fitting hole and tightening the locknut. The concentric rings within the fitting hole are forced into the con-duit metal as the nut is turned. To prevent the fitting from turning, a spare piece of conduit may be inserted in the other conduit f itting hole while tightening.

Change 3 2-27

Figure 2-19. Typical Threaded Fittings

2-74. OUTLET BOXES, PULL BOXES, AND

CABINETS.

2-75. GENERAL. Outlet boxes, pull boxes, and cabinets are constructed so that conduit can easily be secured to them by mechanical means.

Such devices are used for conduit termination points and conduit junction points for outlets and switches. They also provide a suitable space to electrically interconnect the various conductors within the system.

2-76. OUTLET BOXES. Outlet boxes (f igure 2-21) are used to mount switches and outlets or to provide a junction point. Such boxes are made in different shapes and sizes. Table 2-3 lists the dimensions and the maximum numbers of conductors allowed in an outlet box.

2-28 Change 3

Figure 2-19.1. Metal and Conduit Fittings, 1/2″ to 2″

Change 3 2-28.1/(2-28.2 Blank)

Figure 2-20. Threadless Fittings

Note

The following points should be kept in mind when using Table 2-3. Wires belonging to attached fixtures are not considered as con-ductors when making an outlet box conductor count. A conductor running through the box, or a conductor terminated within the box is counted as only one conductor. If the box contains a fixture stud, switch receptacle, or cable clamp, one conductor less than that shown in Table 2-3 is permitted.

2-77. Outlet boxes can be mounted with the box cover flush with the surface or mounted exposed, depending on the kind of conduit system being used. The sum of the conductor cross sectional areas must not exceed 20 per cent o f the in ter ior area at any one cross sect ion. Mount ing ho les are prov ided for securing the box to a surface.

Change 1 2-29

Figure 2-21. Outlet Boxes

2-78. PULL BOXES. Pull boxes of the type illus-trated in figure 2-22 are used for pulling a number of heavy wires and cables.

2-79. A pull box should be inserted in place of an elbow or a bend when there is a requirement for more than 3 right angle turns in a conduit run carrying heavy wires. In many cases, one pull box can take the place of several elbows. A large pull box can be used as a convenient junction box where several conduit lines intersect. Wires can be pulled in more readily when a pull box is included in an installation.

2-80. Pull boxes are usually fabricated from sheet steel. They may be obtained with or without standard knockouts.

2-81. CABINETS AND PANEL BOXES. Cabinets and panel boxes (figure 2-23) are used to mount con-trol switches, terminal boards, and protective

2-30

Figure 2-22. Pull Boxes devices (fuses, etc.). They may be obtained either for flush or surface mounting.

2-82. KNOCKOUTS.

2-83. GENERAL. Knockouts are usually for outlet, pull, and panel boxes to permit flexibility and ease for attachment of conduit. Knockouts are provided in different sizes either as single or concentric knockouts. Concentric knockouts are employed to permit the selection of hole sizes that may be used.

2-31

Table 2-3.

2-32

Figure 2-23. Cabinets and Panel Boxes

2-84. REMOVING KNOCKOUTS. An ordinary knock-out can be removed by striking it a sharp blow with a hammer as shown in figure 2-24, or a sharp blow with a hammer and twisting off with pliers. Concen-tric knockouts are removed as follows:

a. Place the cutting edge of a cold chisel on the inner knockout as indicated in figure 2-25.

Figure 2-24. Removing Ordinary Knockouts

2-33

Figure 2-25. Removing Concentric Knockouts

b. Tap the handle of the chisel with a hammer, displacing the material so that it may be gripped firmly with a pair of pliers.

c. Twist out one knockout size at a time as they are needed, with the pliers, starting with the smallest size first.

2-85. CUTTING HOLES.

2-86. GENERAL. If knockouts are not provided, access holes must be cut in metal cabinets, boxes, etc. The holes are usually cut with a hole saw driven by an electric drill equipped with guide han-dles.

2-87. HOLE SAW. A hole saw consists of a continu-ous circular saw blade constructed of tungsten alloy high speed steel. In use, the mandrel of the hole saw is chucked up in the electric drill, and a guide hole is drilled with the integrally mounted pilot drill.

Figure 2-26 shows a typical hole saw with the round disc removed after cutting.

2-34

Figure 2-26. Hole Saw

2-88. ELECTRIC DRILL. When using an electric drill to drive a hole saw, replace the removable handles with apiece of pipe about 3 feet long with the same diameter and thread size. The longer handles give the workman greater leverage to overcome the large drill torque existing when the hole saw is caught in the metal. When sawing a hole, the saw must be held perfectly vertical to the surface being cut to guard against wedging the blade.

2-89. DRILLING HOLES. If a hole saw is not avail-able, a large hole may be cut by means of the “series of small holes” method. The holes should be laid out as shown in figure 2-27. Such a hole should be pre-pared as follows:

a. Outline the holes to be drilled with a center punch.

b. Drill each hole.

c. Knock the disc out.

2-35

Figure 2-27. Forming Knockout With Drill Holes

d. File off the rough metal projections.

Note

Where the hole itself will not be visible, being covered with washers or bushings after a conduit is connected, it is not always neces-sary to finish off the irregular edges left by the small drill.

2-90. TERMINATING.

2-91. GENERAL. The procedure necessary to terminate conduit at cabinets, pull boxes, etc., are dependent upon the type of conduit.

2-92. METHOD OF TERMINATING THREADED

CONDUIT. A length of threaded conduit is terminated to an outlet (figure 2-28) as follows:

a. Punch out the circular knockout on the outlet box .

b. Thread locknut onto the conduit.

c. Insert the conduit into box knockout opening.

d. Thread a second locknut onto the conduit and run up t ight .

e . Pu l l the condui t out unt i l the second locknut bears on the box.

2-36 Change 1

Figure 2-28. Securing threaded Conduit f . T i g h t e n t h e o u t s i d e l o c k n u t u n t i l i t I s t ight against the box.

g. Fasten insu la t ion bushing on the condui t and run up t ight .

2–93. METHOD OF TERMINATING THREADLESS CON-

DUIT. Threadless connectors are used for terminating thread-less or threaded conduit to an outlet box. The connector and con-duit are fastened in the following manner:

a. Remove the locknut from the fitting.

b. Insert the threaded end of the fitting through the knockout hole.

c. Replace the locknut on the threaded fitting and tighten until secured in place.

d. Insert the threadless conduit in the fitting.

e. Tighten the nut to secure the conduit in place.

2-94. FLEXIBLE CONDUIT.

2-95. CUTTING FLEXIBLE CONDUIT. Technical Manual, Cabling for Fixed Ground C-E Equipment covers the procedure for cutting flexible conduit with a hand hacksaw or armor cutters.

2–96. BENDING FLEXIBLE CONDUIT. The inner edge of any bend shall not be less than five times the diameter of the conduit.

2-97. SUPPORT OF FLEXIBLE CONDUIT. Secure flexible metal conduit at intervals not exceeding 4½ feet and within 12 inches of every outlet box or fitting with approved staples, straps or hangers. Examples of the support interval not applying would be when flexible conduit is fished or when it is run with other cables on cable racks or troughs. When flexibility is re-quired, such as terminating the conduit to a motor, adequate support must not exceed 36 inches.

Change 1 2-37

2–98. TERMINATION OF FLEXIBLE CONDUIT. After the cutting process has been completed and the section of armor removed, an insulating bushing is placed between the conductors and armor (figure 2-29). More information about this procedure can be found in Technical Manual, Cabling for Fixed Ground C-E Equipment.

Figure 2-29. Installing Insulating Bushing

2–99. Flexible conduit is secured to an outlet box by using a special connector (figure 2-30). It is fastened to a box or other termination point in the same manner as a threadless connector. A clamp on the connector holds the flexible conduit in place. Various types of flexible conduit connectors are available, however, they should be of such design that the insulating bushing is visible for inspection.

Figure 2-30. Flexible Conduit Connector

2-38

T.O. 31-10-12

SECTION III

DUCTS

3-1. General

3-2, Ducts constitute another style of raceway through which insulated conductors may be run.

Such raceways, whether formed of metal, plastic, or concrete, offer suitable protection to conductors. While such ducts serve the same purpose as conduits, they are limited in their usage. Ducts are classified as metal, plastic, or concrete trench ducts. Metal ducts should not be subjected to severe mechanical shock or corro-sive vapors. They should be used in a dry, non-hazardous location.

3-3. WIREWAYS

3-4. General. A wireway is a sheet metal or plastic-having a cover in which a large number of conductors may be located in one run. It is used where a flexible means of sup-plying branch circuits are necessary. A typical wireway section is shown in figure 3-1. Wire-way is available in variable lengths and cross sectional area depending on the manufacturer and application. The side of the ducts are pro-vided with closely spaced knockouts for the attachment of conduit.

Figure 3-1. Wireway Section

Change 2 3-1 provided with closely spaced knockouts for the attachment of conduit.

3-5. RESTRICTION OF USE. A wireway system is restricted to circuits not exceeding 600 volts. At no time must the sum of the conductor cross sectional areas used exceed 20 per cent of the interior area at any one cross section. Where taps and splices are made, it must not fill the wireway to more than 75 per cent of its area.

3-6. INSTALLATION.

3-7. GENERAL. Wireway sections are joined to-gether and secured in place by the use of special fit-tings and support attachments (figure 3-2). The use

Figure 3-2. Wireway Fittings

3-2 of wireway fittings and following paragraphs.

TO 31-10-12

attachments is covered in the

3-8. COUPLING. A wireway coupling (figure 3-2) is universally used to join adjacent sections of wire-way. In use, the hinged collar of the coupling is swung away and the two wireway sections inserted into the coupling. The wireway sections are posi-tioned so that their fabricated sheet metal depres-sions are engaged by the raised portions of the coupling. The hinged coupling collar is now swung back into place and secured with attachment bolts.

The coupled wireway sections may be fastened to a support hanger with bolts or screws passing through mounting holes in the base of the coupling unit.

3-9. HANGERS.

3-10. GENERAL. Special hangers are used to sup-port wireway. Hangers should be located every five feet, but this spacing may be increased to ten feet if closer support is not feasible. The hangers are attached to the wireway coupling with attachment hardware.

3-11. BRACKET TYPE HANGERS. A bracket hanger (figure 3-2) is designed for mounting wire-ways on side walls. Attachment holes are provided which correspond to the placement of the bolt holes in the base of the coupling. The hanger is secured to the coupling with nuts and bolts.