On the rack, both galvanized pipe manufactured according to EN 10255 and ASTM A53 standards appear to be the same; however, there are some variations in diameters and in the systems of making threads that make it impossible to ensure that the fitting from one group would serve fastening to the pipe from the other group due to leakage. The procedure of galvanizing steel pipes comprises dipping the carbon steel pipes in molten zinc in order to produce pipes that fulfill either ASTM A53 or EN 10255 standards with plain ends or threaded ends. It is used intensively in water, firefighting, and irrigation supply systems in the UAE. Other welded products are on the carbon steel welded pipes and tubes hub.
Where Galvanized Pipe Is Used
- Potable and service water in plants, camps and buildings
- Firewater and sprinkler systems, subject to the fire protection standard
- Irrigation and landscaping networks
- Compressed air and low-pressure utility lines
- Structural uses: handrails, fencing, scaffolding tube and supports
Galvanizing protects against atmospheric and mild water-side corrosion. It is not a substitute for a corrosion-resistant alloy in seawater or aggressive process service.
ASTM A53 vs EN 10255: Sizes and Threads Compared
DN | ASTM (NPS) OD (mm) | EN 10255 OD (mm) | Same OD? |
|---|---|---|---|
|
15 |
21.3 (1/2) |
21.3 |
Yes |
|
20 |
26.7 (3/4) |
26.9 |
No |
|
25 |
33.4 (1) |
33.7 |
No |
|
32 |
42.2 (1-1/4) |
42.4 |
No |
|
40 |
48.3 (1-1/2) |
48.3 |
Yes |
|
50 |
60.3 (2) |
60.3 |
Yes |
|
65 |
73.0 (2-1/2) |
76.1 |
No |
|
80 |
88.9 (3) |
88.9 |
Yes |
|
100 |
114.3 (4) |
114.3 |
Yes |
The DN 65 difference is large enough that grooved couplings and flanges for one system will not fit the other. The smaller differences at DN 20 to DN 32 matter mostly for threads: A53 pipe is normally threaded NPT to ASME B1.20.1, while EN 10255 pipe is threaded to ISO 7-1 (BSP taper) under EN 10226. The two thread forms have different angles and pitches, so an NPT fitting on a BSP thread may start but will not seal reliably.
Worked example: checking a firewater order
A project buys EN 10255 medium pipe, DN 65, for a firewater ring, and grooved couplings from a US-standard supplier. The couplings are sized for 73.0 mm OD; the pipe is 76.1 mm. They will not fit. Specifying one system for pipe, fittings, couplings and valves from the start avoids this, and the enquiry should state which system is intended.
Zinc Coating and Base Steel
The pipe is hot-dip galvanized after manufacture, coating both the outside and the bore. For EN 10255 pipe, the zinc coating is specified to EN 10240, which defines coating quality levels; for A53, the coating requirements are set in A53 itself. State the required coating standard or quality on the order.
Base steel strength depends on the standard: A53 Grade B has 240 MPa minimum yield, while EN 10255 steel S195T has a lower minimum yield of 195 MPa. Where pressure rating matters, confirm which standard the design is based on.
Galvanized Pipe in Gulf Conditions
- Coastal air: zinc gives good protection in inland atmospheres, but salt-laden coastal air consumes the coating faster, so exposed coastal systems benefit from an additional paint system.
- Buried pipe: galvanizing alone is limited protection in aggressive soils; buried lines usually need wrapping or coating.
- Hot water: at water temperatures above roughly 60 °C, zinc can lose its protective effect on steel, so galvanized pipe is not the best choice for hot water circuits.
- Storage: bundles left wet can develop white storage stain; keep pipe dry and ventilated.
Welding and Sour Service
Galvanized pipe is normally joined by threading or grooved couplings. Welding burns off the zinc and releases hazardous fumes, so any welding needs fume extraction and the damaged area must be repaired with zinc-rich paint. Galvanized pipe is not used in sour process service; for H2S duty, pipe must meet NACE MR0175 / ISO 15156-2, which is a different product altogether.
Galvanized Pipe Price Factors
- Standard (A53 or EN 10255) and series or schedule
- Welded or seamless base pipe
- DN or NPS and length
- Threaded and coupled or plain ends
- Coating standard or quality
- Quantity and stock availability versus a mill order
- Certification (EN 10204 3.1 or 3.2) and third-party inspection
- Incoterm and destination port
Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.
What to send for a quotation: standard, DN or NPS, series or schedule, end type and thread standard, length, quantity, coating requirement, certification, inspection, destination port and required date.
Certificates and Inspection
Galvanized pipe is supplied with EN 10204 3.1 certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. Certificates cover the base pipe properties and the zinc coating results. See the MTC and EN 10204 certification guide.
Related Products
- ASTM A53 welded pipes
- Carbon steel forged fittings for threaded systems
- Carbon steel fittings and flanges hub
Galvanized pipe is widely used in desalination and water treatment and plant utilities across oil and gas sites.
Galvanized Steel Pipe FAQ
What is the difference between EN 10255 and A53 galvanized pipe?
EN 10255 pipe (formerly BS 1387) uses metric medium and heavy series walls, slightly different outside diameters at several sizes, and ISO 7-1 threads. A53 pipe uses ASME schedules and NPT threads.
Can NPT fittings be used on BSP-threaded galvanized pipe?
Not reliably. NPT and BSP taper threads have different angles and pitches, so the joint may not seal. Keep pipe and fittings in one thread system.
Is DN 65 galvanized pipe the same size in both standards?
No. EN 10255 DN 65 is 76.1 mm OD, while ASTM NPS 2-1/2 is 73.0 mm OD, so couplings and fittings are not interchangeable.
Can galvanized pipe be welded?
It can, with fume extraction and zinc-rich repair of the weld area, but it is normally threaded or grooved instead.
Is galvanized pipe suitable for hot water?
Not ideal. At water temperatures above roughly 60 °C, zinc can lose its protective effect on steel.
What should I send for a quotation?
Send the standard, size, series or schedule, end type and thread standard, length, quantity, coating requirement, certification, inspection, destination port and required date.
Request a Quote for Galvanized Steel Pipe
Send the standard, size, series or schedule, thread type and quantity. Every enquiry is checked before the offer is prepared, so a mix of EN 10255 pipe with NPT fittings, or DN 65 pipe with ASTM couplings, is raised at the start.