Dye Penetration Test
(Liquid Penetrant Testing — NDT)

Surface crack detection in metals using liquid penetrant dye — identifying surface-breaking defects including cracks, porosity, laps and seams in steel, cast iron, aluminium and non-ferrous metals.

Overview

What is the Dye Penetration Test (DPT)?

The Dye Penetration Test (DPT), also known as Liquid Penetrant Testing (LPT), uses a coloured or fluorescent penetrant liquid that is applied to a cleaned metal surface and drawn into surface-breaking defects by capillary action. After excess penetrant is removed and developer applied, indications appear as bright red marks on a white background revealing all surface discontinuities.

Conducted as per IS 3658 and ASTM E165, DPT is one of the most widely used surface NDT methods for metals. It requires no special surface preparation beyond cleaning and works on any non-porous material — steel, cast iron, aluminium, copper, titanium and plastics. Global Lab's certified Level II DPT technicians conduct both visible dye and fluorescent penetrant testing.

Surface Defect Detection

Detects cracks, porosity, laps, seams and cold shuts on any non-porous surface.

Visible & Fluorescent Options

Visible red dye (daylight) or fluorescent (UV light) penetrant per project requirement.

All Metal Types

Steel, cast iron, aluminium, stainless steel, titanium and non-ferrous metals tested.

Level II Certified Technicians

NABL-certified DPT technicians per ASNT SNT-TC-1A Level II requirements.

NABL Certified Reports

All results on NABL-accredited letterhead with photographic defect records.

Weld Inspection

Butt welds, fillet welds and heat affected zones inspected per IS 3658.

Test in Action

Dye Penetration Test (DPT) — Site Images

Red Dye Penetrant Applied to Weld

Developer Reveals Surface Cracks

Crack Indication Photographed and Mapped

Test Procedure

How the Dye Penetration Test (DPT) is Conducted

1

Surface Cleaning

Metal surface cleaned with solvent cleaner (Method C) to remove oil, grease, paint and rust.
2

Penetrant Application

Red visible dye penetrant spray applied uniformly. Dwell time: 5–30 minutes per IS 3658.
3

Excess Penetrant Removal

Excess penetrant wiped with dry cloth followed by solvent dampened cloth — not flooded.
4

Developer Application

White developer spray applied. Developer draws penetrant from defects within 7–30 minutes.
5

Inspection & Report

Surface inspected under adequate visible light (≥1000 lux). Red indications on white background photographed and mapped. NABL report within 24 hours.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 3658	Code of Practice for Liquid Penetrant Flaw Detection	DPT Standard	Indian Standard
ASTM E165	Standard Practice for Liquid Penetrant Examination for General Industry	Penetrant Testing	ASTM
ASNT SNT-TC-1A	Personnel Qualification and Certification in Nondestructive Testing	Technician Qualification	ASNT
IS 2595	Code of Practice for Radiographic Testing	NDT Reference	Indian Standard

Applications

Where is the CAPO Test Used?

Weld quality inspection on structural steel fabrication and pressure vessels

In-service crack detection on machinery components and shafts

Casting quality inspection — porosity and cold shut detection in cast iron components

Turbine blade and aerospace component surface inspection

Heat exchanger tube and shell weld inspection

Lifting equipment and crane hook periodic inspection

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid IS 3658 NDT certificates for all structural and statutory requirements.

Level II Certified TechniciansASNT SNT-TC-1A Level II qualified DPT inspectors.

Photographic EvidenceAll indications photographed and included in NABL report.

Combined Metal NDTDPT + Thickness measurement + MPI offered as complete surface NDT package.

Pan-India CoverageNDT teams at all 7 lab locations for rapid site deployment.

Fast 24-Hour ReportResults and photographic NABL report within 24 hours.

Dye Penetration Test(Liquid Penetrant Testing — NDT)