Galvanized Welded Round Steel Pipe
Zinc coated welded round pipe from 21.3mm to 660.4mm outside diameter
Specifications
Specifying Galvanized Tube for Greenhouse and Solar Structures
Galvanized tube is the frame of a greenhouse and the mounting structure under a ground mounted solar array.
This page is an engineering application brief built from published product data.
It is not a record of a delivered customer project and contains no customer name, quantity or date.
The Application
What the Material Has To Do
Galvanized tube is the frame of a greenhouse and the mounting structure under a ground mounted solar array. It forms hoops arches purlins posts side rails and gutter supports in a greenhouse, and posts beams rails and cross bracing in a solar table. The duty is unglamorous and unforgiving: the structure sits outdoors for its whole life, it is loaded by wind and snow rather than by anything the operator controls, and half of it is in or near the ground. Round tube from 21.3mm to 660.4mm outside diameter with 1.5 to 22.2mm wall covers most greenhouse framing, while square and rectangular sections carry the flat connections a solar mounting rail needs.
The Challenge
Where Specifications Usually Go Wrong
These structures fail at the zinc long before they fail at the steel. A post that is galvanized to the same specification as a roof purlin will still corrode first, because the soil line and the humid greenhouse interior attack the coating in a way an open air roof does not. The specification trap is that buyers concentrate on section size and wall thickness, which are easy to compare between quotations, and treat the coating as a single word. The second trap is length: a structure designed around a 6 meter bay and ordered in a random length family generates an offcut at every bay, and on a large array that offcut is paid for twice, once as steel and once as site labor.
Pain Points
What Buyers Run Into
Coating Treated as a Yes or No
Galvanized describes a process not a quantity. The coating designation and the galvanizing route hot dipped or electro have to be on the order, because they are what decides whether the structure is still sound in ten years.
Cut Ends and Drilled Holes Left Bare
Every cut and every hole made at site exposes bare steel at exactly the point where water collects. Ordering tube cut to length and punched before galvanizing removes most of that exposure from the job.
Section Size Chosen by Availability
A greenhouse hoop and a solar post do different work. Round tube suits bent hoops and arches, square and rectangular sections suit bolted flat connections, and choosing by what a supplier had last time forces a connection detail that does not fit.
Random Length Against a Fixed Bay
Standard length runs 0.3 to 18 meters on welded round tube and 5.8m 6m fixed 12m fixed or 2-12m random on square and rectangular sections. Matching the length to the bay spacing takes the offcut out of every repeat.
Ground Contact Not Separated From the Rest
The posts in the soil and the rails above the array are not the same corrosion problem, and specifying one coating for the whole structure means overpaying on the rails or underprotecting the posts.
Specification Logic
Narrowing To the Right Grade and Size
Split the Structure Into Duty Zones
Posts in ground contact, frame members in the humid interior or under the array, and rails and bracing in open air. Each zone gets its own section and its own coating decision, which is where most of the cost and most of the life is decided.
Pick the Section Shape From the Connection
Round galvanized tube suits bent hoops arches and pipe fittings. Galvanized square pipe and galvanized rectangle pipe suit bolted plate connections and rail interfaces. Solar mounting usually mixes the two in one order.
Set Diameter and Wall Together
Welded round tube covers 21.3mm to 660.4mm outside diameter with 1.5 to 22.2mm wall. Square and rectangular sections are supplied across the same schedule family, with wall from 1.65mm to 80mm on the XS range or customized. Wall thickness is what carries wind and snow load, not the outside dimension alone.
Name the Steel Grade
Welded galvanized tube is supplied in ASTM A53 GR A and GR B, EN S275 S275JR S355JRH and S355J2H and GB Q195 Q215 Q235 and Q345. Galvanized square and rectangle pipe also cover ASTM A36 and A106 GR.A GR.B, JIS SS330 SS440 SS490 SPHD and SPHE and EN BS S185 S235 and S235JR.
State the Coating Requirement Explicitly
Say which coating designation the structure is designed to and whether hot dipped or electro galvanizing is acceptable. On the coil side coating classes run G20 G30 G40 G60 and G90 and Z40 through Z350, and the equivalent requirement for the tube should be confirmed with the quotation rather than assumed.
Fix Length and Processing Before Galvanizing
Decide the cut length and the hole pattern up front so the tube is processed and then coated, instead of being cut and drilled on site through a finished coating.
Material Options
Grades Worth Comparing
| Galvanized Welded Round Steel Pipe | Use when: Greenhouse hoops arches side posts and purlins, and any member that will be bent to a radius. Trade-off: The most economical section for framing at 21.3mm to 660.4mm outside diameter, and it needs a saddle or a fitting where a flat bolted connection is wanted. |
|---|---|
| Galvanized Square Pipe and Galvanized Welded Square Steel Pipe | Use when: Solar mounting posts beams and any joint where a plate bolts flat onto the member. Trade-off: Simple square connections and clean bolt detailing, at a higher cost per meter than round tube of comparable capacity. |
| Galvanized Rectangle Pipe and Galvanized Welded Rectangle Steel Pipe | Use when: Purlins and rails spanning between posts where stiffness is needed in one direction only. Trade-off: Efficient use of steel where bending is in one plane, and it has to be installed the right way up which matters on a site crew doing hundreds of repeats. |
| Galvanized Seamless Steel Pipe | Use when: Members carrying pressure or higher load where no longitudinal weld is wanted, in A53 Gr A and Gr B A106 GR.A GR.B A333 GR1 GR3 GR6 or S355JR. Trade-off: No longitudinal weld and the widest wall range by schedule, at a higher price than welded tube for the same structural duty. |
| Zn-Al-Mg Steel Coil | Use when: Roll formed purlins rails and mounting components in the same structure where a coated coil is formed rather than a tube being used. Trade-off: Corrosion resistance stated at 10 to 20 times that of hot dip galvanized steel coil with a self healing effect at scratches and cut edges, and weldability is slightly worse than a hot rolled or cold rolled sheet so the joining method has to suit it. |
Getting It Right
Processing Quality and Packing
Processing Notes
- Order tube cut to the bay length and punched to the connection drawing so that cutting and drilling are not done through the coating at site.
- Round tube bends to a hoop radius, and the bend should be agreed before galvanizing rather than after.
- Where the structure mixes round posts with square rails, keep the two on separate lines of the enquiry so each is priced on its own section family.
- Give the length family you can transport and erect, as welded round tube is supplied from 0.3 to 18 meters and square and rectangular sections as 5.8m 6m or 12m fixed or 2-12m random.
- Where a repair coating will be used at site for field cuts, plan it into the erection method statement rather than leaving it to the crew.
Quality Notes
- The certificate on galvanized welded tube is EN 10204 3.1, and the standards covered are ASTM A53 EN10217 DIN 2458 IS 3589 JIS G3452 and BS1387.
- Testing available covers chemical component analysis, ultimate tensile strength yield strength and elongation, flattening bending blow and impact tests, exterior size inspection and hydrostatic testing.
- Certification held covers ISO9001 BV SGS and RoHS, and the mill test certificate is issued against the ordered grade.
- Confirm the coating requirement in writing on the purchase order so the certificate and the structural design refer to the same thing.
- Check section dimensions and wall thickness against the order before erection starts, since a wall thickness shortfall on a repeated member multiplies across a whole array.
Packing Notes
- Bundle by member type rather than by section size so an erection crew can take one bundle per bay instead of sorting on the ground.
- End protection is checked before loading because a crushed tube end has to be cut off, which loses both length and coating.
- Mark the bundles with section wall and grade so the crew can identify a post from a rail without paperwork.
- State the destination port and whether the tube ships in a container, since length above container length decides the loading method for the whole order.
- Confirm the bundle size your site handling can lift, as greenhouse and solar sites often unload without a heavy crane.
Before You Ask For a Price
What To Send With Your Enquiry
- The structural drawing or the bill of quantities with section sizes and member lengths
- The steel grade or its equivalent such as Q235 S275JR ASTM A53 GR B or SS400
- Outside diameter or section size with wall thickness for each member type
- Quantity in meters or tons and the number of repeat bays or tables
- Destination port and the bundle size your site can unload
- The coating requirement galvanizing route and whether cut lengths and punched holes are needed before coating
Materials
Products For This Application
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Galvanized Tube for Greenhouse and Solar Structures FAQ
What sizes of galvanized tube can you supply?
Welded round tube runs from 21.3mm to 660.4mm outside diameter with 1.5 to 22.2mm wall. Galvanized square and rectangular sections are supplied across the schedule family with wall from 1.65mm to 80mm on the XS range or customized. Send the member schedule and each section can be quoted against its own duty.
Should we use round or square tube?
Round tube suits greenhouse hoops arches and any bent member. Square and rectangular sections suit bolted flat connections and solar mounting rails. Most orders mix the two, and the connection detail rather than the price should decide which goes where.
How should we specify the coating?
Name the coating designation your structure is designed to and whether hot dipped or electro galvanizing is acceptable, and we will confirm it against the quotation. Coating is what decides the life of a greenhouse or solar structure, so it belongs on the purchase order in the same detail as the wall thickness.
Can the tube be cut and punched before it is coated?
Tell us the cut length and the hole pattern with the enquiry. Processing done before coating avoids the bare steel that a site cut or a site drilled hole leaves at the point where water collects.
What lengths are available?
Welded round tube is supplied from 0.3 to 18 meters. Galvanized square and rectangular sections come as 5.8m or 6m fixed, 12m fixed or 2-12m random or customized. Match the length to the bay spacing and the offcut disappears from every repeat.
Is there a more corrosion resistant option than standard galvanizing?
For roll formed members Zn-Al-Mg coated coil is stated at 10 to 20 times the corrosion resistance of hot dip galvanized steel coil, with a self healing effect that covers scratches and cut edges. Its weldability is slightly worse than hot rolled and cold rolled sheet, so the joining method has to be planned around it.
Specifying Material For Galvanized Tube for Greenhouse and Solar Structures
Start with the structural drawing or the bill of quantities with section sizes and member lengths. With that plus the quantity and destination we can put real numbers against each grade.