Ligament: Tube Pitch 1.25 to 2 times tube OD

Component Specifications

Definition

In industrial engineering, a ligament is a critical structural element found in tube sheets and headers of heat exchangers, boilers, and pressure vessels. It refers to the material section between adjacent tube holes, which maintains precise spacing, prevents tube vibration, and distributes mechanical loads. Ligaments are designed to withstand thermal expansion, pressure differentials, and corrosive environments while ensuring leak-proof tube-to-tube sheet joints. Their geometry and strength directly impact the equipment's efficiency, safety, and longevity.

Working Principle

Ligaments function by creating a rigid framework between tubes in a tube sheet or header, transferring loads from tubes to the surrounding structure. They resist bending and shear forces caused by internal pressure, thermal cycling, and fluid flow, maintaining tube alignment and preventing fatigue failure. The ligament efficiency—calculated as the ratio of ligament width to tube pitch—determines the component's ability to handle stress without deformation or cracking.

Materials

Common materials include carbon steel (ASTM A516), stainless steel (ASTM A240 grades 304/316), alloy steels (e.g., ASTM A387 for high-temperature applications), copper alloys (e.g., C12200 for corrosion resistance), and titanium for aggressive environments. Material selection depends on factors like temperature, pressure, corrosion potential, and compatibility with tube and shell materials.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Hardness	150-250 HB for carbon steels
Tube Pitch	1.25 to 2 times tube OD
Surface Finish	125-250 microinches Ra for sealing surfaces
Ligament Efficiency	40-60% (typical range for pressure vessels)
Minimum Ligament Width	As per ASME BPVC Section VIII (e.g., 1/4 inch or 6.35 mm minimum)

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 16812, ASME BPVC Section VIII, TEMA Standards, DIN 28180

Parent Products

This component is used in the following industrial products

Tube Sheets / Headers

Structural components that secure and distribute fluid flow in heat exchanger tube bundles.

View Product Details

Engineering Analysis

Risks & Mitigation

Ligament cracking due to thermal fatigue
Corrosion-induced thinning reducing structural strength
Improper alignment causing tube leakage
Overpressure leading to ligament deformation

FMEA Triads

Trigger: Cyclic thermal stress from temperature variations
Failure: Crack propagation in ligaments, leading to tube sheet failure and fluid leakage
Mitigation: Use materials with high thermal fatigue resistance, design for adequate ligament efficiency, and implement regular non-destructive testing (e.g., ultrasonic inspection)

Trigger: Erosion-corrosion from aggressive fluids
Failure: Thinning of ligaments, compromising structural integrity and pressure containment
Mitigation: Select corrosion-resistant materials, apply protective coatings, and monitor thickness during maintenance

Trigger: Insufficient ligament width during manufacturing
Failure: Reduced load-bearing capacity, causing distortion under pressure
Mitigation: Adhere to ASME standards for minimum ligament dimensions, conduct quality checks via dimensional verification

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Ligament width tolerance: ±0.5 mm per ISO 16812; tube hole alignment within 0.2 mm of true position

Test Method

Non-destructive testing (UT, PT), dimensional inspection per ASME BPVC, pressure testing per Section VIII Div. 1

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Ligament

Manufacturer profiles associated with Ligament.

Sourcing Ligament from China?

Tell us your specification and target quantity — we will match it against manufacturer records and come back with the factories that fit.

Request manufacturers We manufacture this

Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

Related Components

Upper Tool (Punch)

Upper Tool (Punch) is the active forming component in metal plate bending machines that applies precise downward force to create bends in sheet metal.

Main Frame

The main frame is the primary structural component of a hydraulic press, providing rigidity and stability to withstand high compressive forces during metal forming operations.

Shaft Bearing

Precision component supporting rotating shafts in vibration motors to reduce friction and maintain alignment.

Seal Groove

Precision-machined groove in aluminum bearing housings designed to accommodate sealing elements for fluid containment and contamination prevention.

Frequently Asked Questions

What is ligament efficiency in tube sheet design?

Ligament efficiency is a design parameter representing the ratio of the ligament width (distance between adjacent tube holes) to the tube pitch. It indicates the structural strength of the tube sheet; higher efficiency (typically 40-60%) ensures better load distribution and resistance to pressure-induced stresses.

How do ligaments prevent tube failure in heat exchangers?

Ligaments maintain precise tube alignment, reduce vibration from fluid flow, and distribute thermal and mechanical loads evenly. This prevents stress concentration, fatigue cracking, and tube loosening, thereby extending equipment life and preventing leaks.

What materials are best for ligaments in corrosive environments?

For corrosive environments, stainless steel (e.g., 316L), duplex steels, nickel alloys (e.g., Inconel), or titanium are preferred due to their high corrosion resistance. Material choice should match tube and shell materials to avoid galvanic corrosion.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Ligament