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Galvanized tubes


Zinc coated precision steel tubes (galvanized tubes) are destined for hydraulic and pneumatic pressure distribution (so called HPL tubes), production of automobile components, utility vehicles as well as for production of machine products such as fittings and joints.

Cold drawn precision tubes are used as the semi-finished product and they are made from rolled seamless tubes. Precision tubes HPL types are made from carbon and alloyed steel.

Galvanized tubes

Dimensions of zinc coated tubes

OUTER DIAMETER (OD)4,0 – 42,0 mm
WALL THICKNESS (WT)1,0 – 4,0 mm
EUROPEAN STANDARDSEN 10305-4,
DIN 2391-1,
STN/ČSN 42 6711,
STN/ČSN 42 6712
Dimensional standard SIZES (OD x WT) Dimensional table
EN10305-44.0 x 0.5 – 80.0 x 12.5 mm
DIN2391-14.0 x 0.5 – 80.0 x 12.5 mm
DIN2445-24.0 x 0.5 – 80.0 x 12.5 mm
ČSN42 67114.0 x 0.5 – 80.0 x 12.5 mm
ČSN42 67124.0 x 0.5 – 80.0 x 12.5 mm
NF A49-3304.0 x 0.5 – 80.0 x 12.5 mm
BS74164.0 x 0.5 – 80.0 x 12.5 mm
PN – H742454.0 x 0.5 – 80.0 x 12.5 mm
UNI79454.0 x 0.5 – 80.0 x 12.5 mm
ASTMA8226.35 x 0.51 – 120.65 x 9.53 mm [0.250 x 0.020 – 4.750 x 0.375 in] [25 – 3/8 GA]
JISJOHS-10210.5 x 1.7 – 114.3 x 9.5 mm

Steel grades of galvanized tubes

EN 10305-4E235+N, E355+N
DIN 2391-2CSt 35
DIN 1630St 37.4, St 44.4, St 52.4
JIS JOHS 102OST1, OST2, STPG370, STS370
ASTM A 822A 822

Standard TDC Steel grade (open product) Dimensional standard
BS74167416
PN – H74 24574245
NF A49-33049-330
UNI79457945
DIN1630 / 2445-22445-2
UNI79457945
ČSN42 026042 6712
BS74167416
ČSN42 026042 6711
PN – H74 24574245
NF A49-33049-330
UNI79457945
BS74167416
DIN1630 / 2445-22445-2
NF A49-33049-330
EN10305-410305-4
PN – H74 24574245
DIN2391-2C / 2445-22391-1
STN42 026042 6711
ČSN42 026042 6711
DIN1630 / 2445-22445-2
EN10305-410305-4
STN42 026042 6711
ČSN42 026042 6712
STN42 026042 6712
UNI79457945
UNI79457945
STN42 026042 6712
EN10305-410305-4
ASTMA822/A450A822
JISJOHS-102JOHS-102
JISJOHS-102JOHS-102
JISJOHS-102JOHS-102
JISJOHS-102JOHS-102

Length of zinc coated tubes

LengthDiameter
6000 mm + 100 mm4 – 16 mm
6000 mm + 50 mm18 – 42 mm

Tubes testing and coat resistence testing

Non specific or specifific testing.flattening test or drift expanding test
leak tightness test (NDT)
  • eddy current (STN 01 5054, PRP 02-74, SEP 1925, ASTM E 309, EN 10246-3 Gr.E3),
  • stray flux (STN 01 5047, ČSN 01 5047, SEP 1913, ASTM E 570, EN 10246-5 Gr.F3),
  • ultrasound (STN 01 5028, ČSN 01 5028, SEP 1915, ASTM E 213, EN 10246-7 Gr.U3),

Other tests according to standard.

Zinc coated tubes ends

The tubes with deburred ends or ends customized for welding.
The tubes with deburred ends or ends customized for welding.
The ends are vertical to the longitudinal axis and are without burrs.
The ends are vertical to the longitudinal axis and are without burrs.

Ends of the tubes are smooth and are enclosed by plastic plugs

Tolerances of zinc coated tubes

Tolerances of the outside diameter:

diameter between 4 – 30 mm±0,08 mm
diameter between 32 – 38 mm±0,15 mm
diameter between 32 – 38 mm±0,20 mm

Tolerances of the inside diameter are according to EN 10305-4
Tolerance of the wall thickness ± 10%

Delivery condition of zinc coated tubes

Tubes are delivered as cold drawn and normalized NBK (acc. to DIN standard), +N (acc. to EN standard), N (acc. to ASTM standard). Overview of other conditions can be found here. Coarseness of the outer and inner surface (starting with 15 mm of the inside diameter) is Ra <= 4 micrometers (0.004mm).

Packaging of zinc coated tubes

(a) tubes bound with a steel band,
(b) tubes wrapped in plastic sheets, burlap,
(c) tubes in wooden crates.

Tube are supplied in packages with a circular or hexagonal outline with maximum weight of 2 000 kg

Packaking-STANDARD-tubes bound with a steel band
Packaking-STANDARD-tubes bound with a steel band
Packaking-STANDARD-bundle tied down by steel strap underlaid by paper
Packaking-STANDARD-bundle tied down by steel strap underlaid by paper
Packaking-STANDARD-PLUS-paper tape and polyethylene foil
Packaking-STANDARD-PLUS-paper tape and polyethylene foil
Packaking-STANDARD-PLUS-the bundle placed into a wooden box
Packaking-STANDARD-PLUS-the bundle placed into a wooden box
Packaking-PREMIUM-B-into a wooden box in which the tubes are wrapped in foil
Packaking-PREMIUM-B-into a wooden box in which the tubes are wrapped in foil
Packaking-PREMIUM-C-the bandles are wraped into and plastic foil
Packaking-PREMIUM-C-the bandles are wraped into and plastic foil
Packaking-PREMIUM-D-placing the whole shipment into foil+vacuum sealed
Packaking-PREMIUM-D-placing the whole shipment into foil+vacuum sealed

Marking of zinc coated tubes

a) Marking of metallic zinc coatings as it is described in DIN 50979

  • thin passivation (transparent) is colorless or slightly rainbow color. It is marked as A,
  • strong passivation (rainbow – iris) it has a rainbow tint. It is marked as C,
  • surface without sealing – there is no code. A sealed surface has T2 code.

Example of surface marking Fe / Zn8 / A / T2
(it means – steel, zinc 8 micrometers, transparent passivation, with sealing)

(b) marked by the InkJet along the whole length acc. to customer requirements

Tube bundles are marked by tags.

Marked by a label
Marked by a label
Marked with spray either by a white or black color using InkJet
Marked with spray either by a white or black color using InkJet
Marked by stamping the data
Marked by stamping the data

Certified test reports of zinc coated tubes

EN 10 204:

2.2 nonspecified testing (only mandatory tests),
3.1 specific testing,
3.2 after agreement.


Straightness of zinc coated tubes

The allowable straightness for the whole length of the tube is 0.0015 multiple of the tube length, allowed straightness of one meter is 3 milimeters.

Allowable pressure for hydraulic and pneumatic lines

The highest allowable pressure for hydraulic and pneumatic lines in relationship to steel and tube testing. Calculation was done according to DIN 2413.

Steel 37.4 (E235) without specific testing according to 3.1.B (3.1)

Steel 37.4 (E235) with specific testing according to 3.1.B (3.1)

Steel 52.4 (E355) without specific testing according to 3.1.B (3.1)

Steel 52.4 (E355) with specific testing according to 3.1.B (3.1)

Surface condition of zinc coated tubes

First layer: electrolitically leached zinc (Zn) – acts as anode and in a corrosive environment it corrodes first and the base metal is cathodically protected against corrosion. The zinc layer thickness may be in the range of 5 to 30 micrometers (µm).

Second layer: based on the valency of used chrome is called either: passivation or chromating. For chromating in the past the Cr+6 salts were used. Nowadays the term chromating is no longer used, but passivation, or based on the number of chromites (salts Cr3+) we are talking about chromiting.

Third layer: for the overall increase of coating resistance, we use as the last layer the layer of organic substances on the Si base that stabilizes the chrome layer. This process is called impregnation or sealing.



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