Product Description Electro polishing (EP), also known as electrochemical polishing, anodic polishing, or electrolytic polishing is an electrochemical treatment performed on the metal surface to remove the impurities and microscopic imperfections. The process leaves a shiny, smooth, ultra-clean surface finish. A double packaging EP tube is an electro polished tube protected by a two-layer cleanroom packaging system: after ultrasonic cleaning, ultra high purity hot nitrogen purging and drying, each tube is end capped and sealed in two independent polyethylene bags before being placed in a wooden box. This double packaging treatment is essential because the value of an EP tube lies in its ultra-clean, smooth inner surface — a single damaged or punctured bag during long-distance transport, warehousing or site handling would allow dust, moisture and particles to re-contaminate the bore, destroying the cleanliness achieved by the entire EP process. The second bag acts as an independent barrier, keeping the tube in as-shipped clean condition until the moment of installation. Why Double Packaging Matters

The cleanliness of an EP tube must be preserved all the way to the point of use. Double packaging provides:
✓  Two independent polyethylene barriers against dust, moisture and particles
✓  Protects the electro polished bore from re-contamination during transport and storage
✓  Inner bag remains sealed and clean even if the outer bag is removed or damaged
✓  Maintains nitrogen-purged, dried condition until installation
✓  End caps prevent foreign matter ingress and protect tube ends
✓  Ideal for export shipments and projects with long logistics chains

Application

Double packaging EP tubes are recommended wherever tube cleanliness must be guaranteed through long transport and storage cycles:
Semiconductor Industry High Purity Pipeline
Ultra High Purity (UHP) Gas Supply Lines
Pharmaceutical & Biotechnology
Food & Beverage Processing
Medical Equipment
Precision Instruments
Laboratory Gas Pipeline
Overseas / Export High-Purity Projects

Product Detail

Parameter	Value
Product Name	Double Packaging Electro Polishing Tube (Double Packaging EP Tube)
Material	TP316L (Ni ≥ 12%）
Outside Diameter	1/4" ~ 1" (6.35mm ~ 25.4mm)
Wall Thickness	0.035" ~ 0.083" (0.89mm ~ 2.11mm)
EP Lines	10
Daily Output	2,000 m
Inner Roughness	Ra ≤ 0.2µm
Outer Roughness	Ra ≤ 0.6µm

Material Grade

Grade	UNS	ASTM	EN
304L	S30403	304L	1.4307
316L	S31603	316L	1.4404
2205	S31803	S31803	1.4462
Hastelloy C-22	N06022	N06022	2.4602

* TP316L (Ni ≥ 12%) is the primary material for EP tubes.

Production Standard

Standard	Description
ASTM A269	Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service
ASTM A270	Seamless and Welded Austenitic Stainless Steel Sanitary Tubing
ASTM B912	Standard Specification for Passivation of Stainless Steels Using Electropolishing

Process

Surface Preparation (Acid Cleaning) → Electro Polishing → Surface Passivation → Pure Water Treatment → Hot Nitrogen Drying → Clean Room Packaging
EP tube is derived from BA (bright annealing) pipe through electrochemical polishing, following ASTM B912 standard. Every tube is then protected by the double packaging system described in the Packing section below.

Dimension Tolerance

Outside Diameter (OD)	Tolerance OD (mm)	Tolerance WT (%)
1/4" ~ 1"	±0.1	±10

Nominal Length: 6 meters / each, or customized.
If higher outside diameter tolerance is required, welcome to contact us.

Roughness

EP Roughness:
✓  Inner: Ra ≤ 0.2 µm
✓  Outer: Ra ≤ 0.6 µm
Lower roughness (e.g. Ra ≤ 0.13 µm inner) is available upon request.

Specification / Size Sheet

Standard length is 6 meters. Custom lengths are available upon request.

Outside Diameter (OD)		Wall Thickness (WT)		Unit Weight
Inch	mm	Inch	mm	kg/m
1/4	6.35	0.035	0.89	0.12
		0.049	1.24	0.16
3/8	9.53	0.035	0.89	0.19
		0.049	1.24	0.26
		0.065	1.65	0.33
1/2	12.7	0.035	0.89	0.26
		0.049	1.24	0.36
		0.065	1.65	0.46
3/4	19.05	0.049	1.24	0.55
		0.065	1.65	0.72
		0.083	2.11	0.90
		0.095	2.41	1.01
		0.105	2.67	1.10
1	25.4	0.065	1.65	0.98
		0.083	2.11	1.23

Final Inspection

Surface Quality
OD & WT, Length, Straightness, inner & outer surface roughness and endoscopy.
Chemical Composition
Spectrum analysis.
Mechanical Test
Tensile, Yield, Elongation (%), Hardness (HRB)
NDT (Non-Destructive Testing)
ET (Eddy Current testing).
PMI (Positive Material Identification)
Direct-reading spectrometer.
Marking and Color Coding
Marking and color coding available if required.
Optional Tests (Upon Customer Request)
According to customer requirements, the following additional tests can be performed on the sample(s):
✓  Chromium-iron ratio (Cr/Fe) and chromium oxide / iron oxide ratio
✓  Surface adsorption contamination
✓  Oxide layer thickness
✓  Surface defects
✓  Surface contamination
✓  Surface roughness
✓  Pitting temperature (CPT) test

Packing

EP tubing is ultrasonically cleaned then purged and dried with ultra high purity hot nitrogen before packing in the cleanroom. Each tube is end capped and bagged in double polyethylene bags to ensure the product's cleanliness. Finally the tubes are placed in wooden boxes for maximum protection during shipment.
1. Ultrasonic Cleaning — Tubes are ultrasonically cleaned to remove any residual particles.
2. Nitrogen Purge & Dry — Purged and dried with ultra high purity hot nitrogen.
3. Cleanroom Packaging — End capped, double-bagged in polyethylene, placed in wooden boxes.