How Many Bolts in 132kV Transmission Tower? Complete Count Guide

A typical 132kV transmission tower contains 1,200 to 2,500 bolts depending on tower type, height, and configuration. Suspension towers require 1,200-1,500 bolts, angle towers need 1,800-2,200 bolts, and dead-end towers use 2,000-2,500 bolts. The distribution includes main leg bolts (400-600), bracing member bolts (500-800), cross-arm assembly bolts (200-350), and foundation anchor bolts (16-24).

Here's the quick breakdown:

Tower Type	Height Range	Typical Bolt Count	Primary Use
Suspension	25-35m	1,200-1,500	Straight line sections
Angle	30-40m	1,800-2,200	Direction changes
Tension/Strain	30-40m	1,600-2,000	Conductor tension points
Dead-end	35-50m	2,000-2,500	Line termination

After manufacturing over 8,000 tons of transmission line towers since 2008, we've documented exact bolt counts across hundreds of 132kV projects. This guide shows you the real numbers.

Why Bolt Count Varies So Much

The 1,300-bolt difference between tower types isn't random. Three factors drive this variation.

Tower structural load: Dead-end towers resist the full conductor tension from one direction, requiring reinforced connections throughout. That means more bolts at every joint. Our engineering team adds roughly 400-600 additional bolts to dead-end designs compared to suspension towers.

Height extensions: Each 3-meter section adds 80-120 structural bolts. A standard 132kV tower at 28 meters uses the base count. Extend it to 40 meters with two 6-meter sections, and you're adding 320-480 bolts to your material list.

Circuit configuration: Double circuit towers carry six conductors instead of three. The extra cross-arm assemblies, wider base structure, and additional bracing mean 300-400 more bolts than single circuit equivalents.

Bolt Count Breakdown by Tower Type

Let's get specific. Here's what you'll actually order for each tower type.

Suspension Towers: 1,200-1,500 Bolts

These are your workhorse towers for straight-line sections. The bolt distribution looks like this:

Component	Bolt Count	Percentage	Common Sizes
Main leg connections	400-450	33%	M20, M24
Bracing members	500-600	42%	M16, M20
Cross-arm assemblies	200-300	21%	M16, M20
Miscellaneous hardware	50-80	4%	M12, M16
Total	1,200-1,500	100%	—

Foundation anchor bolts (16-20 bolts, typically M24-M30) are counted separately since they're embedded in concrete before tower assembly.

Angle Towers: 1,800-2,200 Bolts

Line direction changes create lateral loads that demand reinforcement. You'll see the difference in these areas:

• Reinforced leg connections: 500-650 bolts (vs. 400-450 in suspension)
• Additional K-bracing: 700-850 bolts (vs. 500-600 in suspension)
• Strengthened cross-arms: 250-350 bolts (vs. 200-300 in suspension)
• Hardware and gussets: 80-120 bolts (vs. 50-80 in suspension)

The angle size matters too. Small angle towers (2-10° deviation) sit at the lower end of this range. Large angle towers (30-60° deviation) hit the upper limit or exceed it.

Tension and Dead-End Towers: 1,600-2,500 Bolts

These towers handle the highest loads. Dead-end towers at major substations top the count because they:

• Use double-bolted connections at critical joints (where suspension towers use single)
• Include stub angle assemblies at the base (adds 100-150 bolts)
• Feature redundant bracing in the tower body (adds 200-300 bolts)
• Support heavier strain insulator assemblies (adds 80-120 bolts)

When we built 132kV dead-end towers for a Southeast Asian project in 2022, the 45-meter towers required 2,380 bolts each. The same customer's 28-meter suspension towers used 1,420 bolts.

Component-by-Component Bolt Distribution

Understanding where the bolts go helps you catch errors in material estimates. Here's the complete breakdown.

Foundation Anchor Bolts: 16-24 Per Tower

These don't count toward the "tower body" total, but you still need to order them.

Each tower leg needs 4-6 anchor bolts embedded in the concrete foundation. Standard configuration:

• Four legs × 4 bolts each = 16 anchor bolts (minimum)
• Four legs × 6 bolts each = 24 anchor bolts (heavy-duty)

Size: M24-M30, Grade 8.8 or ASTM A394 Type 1. Our galvanizing factory applies 86 microns minimum coating thickness on anchor bolts since they're partially buried.

Main Leg Connections: 400-600 Bolts (35-40%)

The tower legs use lap-splice connections every 3-6 meters of height. Each splice joint requires:

• 8-12 bolts for single angle sections
• 16-24 bolts for double angle (back-to-back) sections

On a 30-meter tower with splices at 0m, 6m, 12m, 18m, 24m, and 30m, that's six splice locations × four legs = 24 splice joints. At 12 bolts per joint average, you're at 288 bolts just for leg splices.

Add the base-to-stub connections and cross-bracing attachment points, and you reach 400-600 total for this component.

Horizontal and Diagonal Bracing: 500-800 Bolts (40-45%)

This is your largest bolt category. The tower body uses K-bracing, X-bracing, or combined patterns. Each connection point typically needs:

• Diagonal members: 4-6 bolts per connection (both ends)
• Horizontal members: 3-4 bolts per connection
• Secondary bracing: 2-3 bolts per connection

Count the connection points on your tower drawings, multiply by bolts per connection, and you'll land in this range. Angle towers and dead-end towers sit at the upper end due to doubled bracing in high-stress panels.

Cross-Arm Assemblies: 200-350 Bolts (15-20%)

Cross-arms support the conductor insulators. A 132kV tower typically has:

• One top cross-arm (for top phase conductor)
• One middle cross-arm (for middle phase conductor)
• One bottom cross-arm (for bottom phase conductor)
• Ground wire peak assembly

Each cross-arm assembly requires:

• Main connection to tower body: 12-20 bolts
• Bracing members: 16-24 bolts
• Insulator attachment brackets: 8-12 bolts

Total per arm: 36-56 bolts. Three arms = 108-168 bolts. Add the ground wire assembly (40-60 bolts) and equipment mounting brackets (50-80 bolts), and you're at 200-350 bolts total.

Double circuit towers double the cross-arm bolts since you need six conductor positions instead of three.

Miscellaneous Hardware: 50-100 Bolts (3-5%)

Don't forget these:

• Step bolts for climbing: 20-40 bolts (one every meter of height)
• Anti-climbing device bolts: 8-16 bolts (around 3-meter height)
• Danger sign bolts: 4-8 bolts
• Tower number plate bolts: 4-8 bolts
• Equipment mounting: 10-20 bolts

Bolt Size and Grade Distribution for 132kV Towers

Not all bolts are the same size. Here's the actual distribution from our production records.

Size Distribution by Percentage

Bolt Size	Percentage of Total	Primary Applications	Typical Length Range
M12	5%	Step bolts, light brackets	40-80mm
M16	40%	Secondary bracing, cross-arm members	50-100mm
M20	35%	Horizontal bracing, diagonal members	60-120mm
M24	15%	Main leg splices, critical joints	70-140mm
M30+	5%	Heavy-duty connections, foundations	80-180mm

For a 1,400-bolt suspension tower, that means:

• 70 × M12 bolts
• 560 × M16 bolts
• 490 × M20 bolts
• 210 × M24 bolts
• 70 × M30+ bolts

Grade Requirements by Application

Foundation anchor bolts:

• Grade 8.8 (DL/T 248-2021) or ASTM A394 Type 1
• Yield strength: 640 MPa minimum
• Always hot-dip galvanized per ASTM A153

Main structural bolts:

• Grade 6.8 (most common in Asian markets)
• Grade 4.8 acceptable for secondary members
• All galvanized to 70-86 microns coating thickness

Special application bolts:

• Step bolts: Grade 8.8 minimum for safety
• Equipment bolts: Stainless steel or weathering steel where specified

We source our tower steel fittings including bolts from ISO-certified suppliers. Every batch gets tested for tensile strength, galvanizing thickness, and thread dimensions before assembly.

How Tower Height Affects Your Bolt Count

Height directly impacts your material requirements. Here's how to calculate it.

Base Height Bolt Count

Standard 132kV towers use these baseline heights:

• 25-30 meters: Base bolt count applies (1,200-2,200 depending on type)
• 30-35 meters: Add first extension section
• 35-40 meters: Add second extension section
• 40-50 meters: Add third extension section (rare, special applications)

Extension Section Impact

Each 3-meter extension section adds approximately:

• Leg extension bolts: 32-48 bolts (8-12 per leg × 4 legs)
• Bracing bolts: 40-60 bolts (additional panels)
• Connection hardware: 8-12 bolts

Total per 3m extension: 80-120 bolts

Quick Calculation Formula

Total Bolts = Base Tower Count + (Extension Height ÷ 3m × 100 bolts)

Example 1: Suspension tower, 28m height (no extensions)
= 1,400 bolts (base count)

Example 2: Suspension tower, 34m height (6m extension)
= 1,400 + (6m ÷ 3m × 100)
= 1,400 + 200
= 1,600 bolts

Example 3: Angle tower, 40m height (10m extension)
= 1,900 + (9m ÷ 3m × 100)
= 1,900 + 300
= 2,200 bolts

This formula gets you within 5% accuracy for material estimation. For final procurement, always verify against actual tower drawings.

Height vs. Bolt Count Reference

Base Height	Extension	Added Bolts	Suspension Total	Angle Total
25m	0m	0	1,200	1,800
28m	0m	0	1,400	1,900
31m	3m	100	1,500	2,000
34m	6m	200	1,600	2,100
37m	9m	300	1,700	2,200
40m	12m	400	1,800	2,300

International Standards for 132kV Tower Bolts

Specifications matter. Here's what to reference in your procurement documents.

North American Standards

ASTM A394-08(2024) covers transmission tower bolts with:

• Type 0: Hot-dip zinc-coated, low/medium carbon steel (most common)
• Type 1: Hot-dip zinc-coated, quenched and tempered (high-strength applications)
• Type 3: Bare weathering steel (special applications)

Thread sizes: 1/2", 5/8", 3/4", 7/8", 1" (metric equivalents: M12, M16, M20, M22, M24)

Galvanizing per ASTM A153: Minimum 86 microns (610 g/m²) coating weight

Chinese Standards

DL/T 248-2021 specifies:

• Grades 4.8J, 6.8J, 8.8J, 10.9J
• Thread sizes: M12, M16, M20, M24, M30, M36
• Galvanizing per GB/T 13912-2002: Minimum 70 microns

Material requirements:

• Grade 6.8: 35K or 45# steel
• Grade 8.8: 35K, 45#, or 40Cr steel (quenched and tempered)

Indian Standards

IS 12427:2001 covers mushroom head and hexagon head transmission tower bolts:

• Steel grades: 5.8, 8.8
• Galvanizing per IS 2629
• Dimensional tolerances per IS 1367

European Standards

EN 14399 for structural bolting:

• Property classes 4.6, 5.6, 8.8, 10.9
• Hot-dip galvanizing per EN ISO 1461: 70-85 microns minimum

Most power transmission tower projects we export specify a combination of standards. African projects typically reference British Standards (BS). Southeast Asian projects use a mix of ASTM and Chinese standards. European projects strictly follow EN standards.

Always confirm which standard applies to your project before ordering. Bolt threads aren't interchangeable between standard systems.

Total Weight of Bolts in a 132kV Tower

Weight affects shipping costs and tower design calculations. Here's what the bolt assembly weighs.

Weight by Bolt Size

Bolt Size	Approximate Unit Weight	Typical Quantity	Total Weight
M12	25g	70 bolts	1.8 kg
M16	50g	560 bolts	28.0 kg
M20	90g	490 bolts	44.1 kg
M24	150g	210 bolts	31.5 kg
M30	280g	70 bolts	19.6 kg
Bolts Subtotal	—	1,400 bolts	125 kg

Add nuts (same weight as bolts) and washers (10% of bolt weight):

• Nuts: 125 kg
• Washers: 12.5 kg
• Total hardware weight: 262.5 kg

For a complete 132kV suspension tower weighing 5,500-7,000 kg, the bolt assembly represents approximately 3.8-4.8% of total weight.

Weight Considerations for Project Planning

Shipping: Bolts ship separately from tower steel. Plan for 0.25-0.35 tons of hardware per tower.

Handling: Bolt packages arrive in boxes of 50-100 bolts by size. A full tower's hardware fills 15-20 boxes weighing 10-20 kg each.

Inventory: Store bolts by size and grade. Mixing different standards creates assembly problems.

Single Circuit vs. Double Circuit Bolt Requirements

Circuit configuration significantly changes your bolt count. Here's the comparison.

Specification	Single Circuit	Double Circuit	Difference
Base tower body	800-1,000 bolts	900-1,150 bolts	+100-150
Cross-arm assemblies	200-300 bolts	350-500 bolts	+150-200
Foundation bolts	16-20 bolts	20-24 bolts	+4
Suspension total	1,200-1,500	1,500-1,900	+300-400
Angle total	1,800-2,200	2,100-2,600	+300-400

Why Double Circuit Adds Bolts

Cross-arm complexity: Six conductor positions instead of three means:

• Double the number of insulator brackets
• Wider cross-arm spans requiring more bracing
• Heavier assembly creating higher connection loads

Tower base width: Supporting six conductors requires wider tower bases. Base width increases from 3.5-4.0 meters to 4.5-5.5 meters. The wider geometry adds:

• Extra horizontal bracing members
• Additional diagonal bracing for stability
• More connection points throughout the structure

Foundation requirements: Heavier loads mean 4-6 anchor bolts per leg instead of 4 bolts per leg.

How to Calculate Bolt Requirements for Your 132kV Project

Follow this process to generate accurate material estimates.

Step 1: Identify Your Tower Types

Review your transmission line design. Count:

• Number of suspension towers
• Number of angle towers (note the angle degrees)
• Number of tension towers
• Number of dead-end towers

Example project: 80 km line with towers every 350 meters = 229 total towers

• 210 suspension towers
• 12 small angle towers (2-10°)
• 5 medium angle towers (10-30°)
• 2 dead-end towers

Step 2: Determine Heights and Extensions

Check tower spotting profiles. List:

• Standard height towers (count)
• Towers with 3m extension (count)
• Towers with 6m extension (count)
• Towers with 9m+ extension (count)

Example: Out of 210 suspension towers:

• 170 towers at 28m (standard)
• 30 towers at 31m (3m extension)
• 10 towers at 34m (6m extension)

Step 3: Check Circuit Configuration

Single or double circuit? This affects every tower.

Step 4: Calculate Base Bolt Count

Use these baseline numbers:

Tower Type	Single Circuit	Double Circuit
Suspension	1,400	1,700
Small angle (2-10°)	1,800	2,100
Medium angle (10-30°)	2,000	2,300
Large angle (30-60°)	2,200	2,500
Dead-end	2,300	2,600

Step 5: Add Extension Bolts

For each tower with extensions:

• 3m extension: +100 bolts
• 6m extension: +200 bolts
• 9m extension: +300 bolts
• 12m extension: +400 bolts

Step 6: Calculate Project Total

Example calculation for our 229-tower project:

Suspension towers (210 total):

• 170 × 1,400 bolts = 238,000
• 30 × 1,500 bolts = 45,000
• 10 × 1,600 bolts = 16,000
• Suspension subtotal: 299,000 bolts

Angle towers (17 total):

• 12 × 1,800 bolts = 21,600
• 5 × 2,000 bolts = 10,000
• Angle subtotal: 31,600 bolts

Dead-end towers (2 total):

• 2 × 2,300 bolts = 4,600

Project total: 335,200 structural bolts

Foundation anchor bolts: 229 towers × 20 bolts = 4,580 anchor bolts

Step 7: Add 15% for Spares and Wastage

Structural bolts: 335,200 × 1.15 = 385,480 (round to 386,000)

Anchor bolts: 4,580 × 1.15 = 5,267 (round to 5,300)

Step 8: Break Down by Size

Apply the standard distribution percentages:

Size	Percentage	Structural Bolts	Anchor Bolts	Total to Order
M12	5%	19,300	—	19,300
M16	40%	154,400	—	154,400
M20	35%	135,100	—	135,100
M24	15%	57,900	2,650	60,550
M30	5%	19,300	2,650	21,950
Total	100%	386,000	5,300	391,300

This gives you a complete procurement list broken down by size. For our 40,000 tons annual capacity manufacturing facility, this represents about 3.5 tons of hardware—a typical month's bolt consumption for our 132kV transmission tower production line.

Cost and Procurement Considerations

Understanding costs helps you budget accurately. Here's what to expect.

Typical Bolt Costs (2024 Pricing)

Prices vary by order quantity, but these ranges apply for bulk orders:

Bolt Size	Price Range (USD per bolt)	1,000-Bolt Price	10,000-Bolt Price
M12	$0.40-$0.80	$0.60	$0.45
M16	$0.50-$1.20	$0.85	$0.60
M20	$0.80-$1.80	$1.30	$0.95
M24	$1.50-$3.00	$2.20	$1.70
M30	$2.50-$5.00	$3.75	$3.00

Total bolt cost per suspension tower: $1,500-$2,800 (depending on specifications)

Total bolt cost per angle tower: $2,200-$4,000

For a 100-tower project, hardware costs range from $150,000 to $400,000. That's 5-8% of total tower steel costs.

Procurement Best Practices

Order in bulk: Negotiate better pricing by ordering for your entire project at once. We manufacture 180 tons of tower steel monthly, and we order six months of bolts at a time to lock in pricing.

Specify galvanizing clearly: Standard hot-dip galvanizing adds 15-20% to bolt costs compared to plain steel. But it's essential. Specify minimum 70 microns coating thickness (ASTM A153 or equivalent).

Verify standards compliance: Request mill certificates showing:

• Chemical composition
• Mechanical properties (tensile strength, yield strength, elongation)
• Galvanizing thickness test results
• Thread dimension verification

Check thread compatibility: ASTM and DIN threads differ. Mixing standards creates field assembly problems. Specify one standard system for your entire project.

Plan for lead times: Standard bolts ship in 2-4 weeks. Custom sizes or special coatings need 6-8 weeks. Order early.

Quality inspection matters: We reject 2-3% of bolt shipments during incoming inspection for:

• Insufficient galvanizing thickness
• Thread damage
• Dimensional variations
• Wrong grade markings

Having backup suppliers prevents project delays.

Maintenance and Replacement Factors

Bolt maintenance extends tower service life. Here's what field crews need to know.

Inspection Requirements

Visual inspection schedule:

• New towers: After 1 year in service
• Normal conditions: Every 3-5 years
• Coastal/industrial areas: Every 2-3 years
• After severe weather events: Within 6 months

What to check:

• Galvanizing condition (white rust is acceptable; red rust is not)
• Bolt loosening (check critical connections with torque wrench)
• Thread damage or shearing
• Missing nuts or washers

Common Replacement Scenarios

Corrosion replacement: Coastal installations lose 5-10 microns of galvanizing per year. After 7-10 years, some bolts need replacement. Priority order:

1. Foundation anchor bolts (ground contact accelerates corrosion)
2. Lower tower bolts (splash zone from ground moisture)
3. Cross-arm bolts (bird dropping acid)

Retrofitting additions: Adding equipment to existing towers (telecom antennas, monitoring equipment) requires 20-50 new mounting bolts per tower.

Storm damage repair: Lightning strikes and high winds create localized failures. Keep spare kits on hand with:

• 50 × M16 bolts
• 50 × M20 bolts
• 30 × M24 bolts
• 100 matching nuts and 200 washers

Recommended Spare Inventory

For a 100-tower transmission line:

Item	Quantity	Purpose
M16 structural bolts	500-1,000	Most common size
M20 structural bolts	400-800	Second most common
M24 structural bolts	200-400	Critical connections
M30 anchor bolts	50-100	Foundation repairs
Nuts (all sizes)	Match bolt quantities	—
Washers (all sizes)	2× bolt quantities	—

This represents about 3-5% of project total, stored at maintenance depots along the line.

Our substation structure projects require similar spare inventories. We recommend clients order spares at the time of original tower procurement to ensure batch consistency.

Real-World Project Example: 132kV Line in Southeast Asia

Here's how the numbers worked on an actual project our team completed in 2023.

Project details:

• 95 km transmission line
• 272 total towers
• Terrain: Mixed (flat agricultural + 15 river crossings)
• Circuit type: Single circuit

Tower breakdown:

• 240 suspension towers at 28m height
• 18 suspension towers at 34m height (river crossings)
• 8 small angle towers at 30m height
• 4 medium angle towers at 32m height
• 2 dead-end towers at 38m height

Bolt calculation:

• Suspension 28m: 240 × 1,400 = 336,000 bolts
• Suspension 34m: 18 × 1,600 = 28,800 bolts
• Small angle 30m: 8 × 1,900 = 15,200 bolts
• Medium angle 32m: 4 × 2,100 = 8,400 bolts
• Dead-end 38m: 2 × 2,500 = 5,000 bolts
• Total structural: 393,400 bolts
• Foundation anchors: 272 × 20 = 5,440 bolts
• Project total: 398,840 bolts

Order quantity (with 15% spare):

• Structural: 452,410 bolts
• Anchors: 6,256 bolts
• Final order: 458,666 bolts total

Breakdown by size:

• 22,930 × M12 bolts
• 180,964 × M16 bolts
• 158,344 × M20 bolts
• 67,862 × M24 bolts
• 28,566 × M30 bolts

Total hardware weight: 98 tons (bolts, nuts, washers)

Project cost: Tower steel: $2.8M | Hardware: $185,000 (6.6% of steel cost)

The customer's initial estimate was 380,000 bolts based on generic calculations. Our detailed engineering increased the order by 78,666 bolts (21% increase). That prevented a mid-project shortage that would have cost far more than the additional hardware.

Frequently Asked Questions