One difference, stated plainly
Seamless and welded pipe differ in one respect that this site can state plainly: welded pipe is formed by welding, each welded line by a different route, while seamless pipe is formed without a welded seam. The welded lines on this site are ERW, SSAW and LSAW, formed by electric resistance welding, spiral submerged arc welding and longitudinal submerged arc welding respectively. Seamless pipe has no welded seam to name. That single difference is the whole basis of the comparison on this site, and no specification table is added to it.
The size ranges listed on the company About page differ between seamless pipe and each welded line, and they are given on the line pages as the About page lists them: seamless at OD 1/8 to 36 inch (10.3 to 914.4 mm), ERW at OD 1/2 to 26 inch (21.3 to 660 mm), SSAW at OD 8 to 120 inch (219.1 to 3048 mm), and LSAW at OD 14 to 64 inch (219.1 to 1626 mm). Those ranges are starting points for an enquiry, not guarantees that every size inside any range is available for any particular order. A buyer who needs a particular size should name it in outside diameter terms, together with the application and the quantities.
Application directions for each kind
Both kinds are discussed on this site through the same five application directions named on the company About page: petroleum and gas pipelines, water pipelines, construction and building, dredging projects and piling projects. The application pages describe each direction and the lines discussed for it, and neither application page assigns one kind to one direction as a matter of fact. A pipeline job, a water job and a construction job can each be discussed through either kind, and the choice between kinds for a particular job is settled by the job detail carried in the enquiry, not by any assignment on this site.
Within those directions, seamless pipe is most often raised where a buyer wants a pipe without a welded seam and where that difference is part of the job description itself. Welded pipe is most often raised where a buyer wants a welded route and where the route name is part of the job description. Neither framing is a specification, and neither page states pressure, temperature, coating or jointing facts for any pipe. A buyer whose job depends on any of those points should name the point in the enquiry, for the items named.
Questions that decide between seamless and welded
The questions that decide between seamless and welded pipe for a particular job are job questions, not catalogue questions. They include the size wanted, the quantities, the destination, any date by which the pipes are needed, and any site conditions that affect handling and jointing. They also include whether the absence of a welded seam is itself a job requirement, stated plainly where it is, and any further point the job depends on, stated in plain terms for the items named. A buyer who answers those questions in the enquiry gives the supplier a job that can be answered, while a buyer who asks only which kind is better, without describing a job, will receive only a general answer.
Those questions should be asked together, in the same message, for the same items, together with quantity terms, timing, trade terms, payment method and documents. This site uses only the general wording that certificates are available upon request, and any document question should name the items it concerns. Splitting the questions across separate messages produces fragmented answers that are hard to check against the order, while gathering them produces a single reply that can be checked as a whole. That discipline is the same for every comparison on this site.
From comparison to enquiry
A buyer who has read this page should next read the line page for the kind favoured, then the welded pipe guide for the three welded lines together, and then the enquiry checklist page, which collects the questions in order. A buyer who already knows the kind can skip directly to the enquiry page, naming kind, line, application, size, quantities, destination and date in the first message. Either path ends at the same place: an enquiry that states the job in full and asks for quantity terms, timing, trade terms, payment method and documents to be confirmed together for the items named.
No comparison on this site settles an order. The catalogue narrows the choice, and the enquiry settles the order, and that division is kept on every page. A buyer who treats a comparison page as an order confirmation will be disappointed, because no catalogue wording can cover quantities, timing and terms for items that have not yet been named. The enquiry pages are therefore written as the working end of the catalogue, not as an afterthought, and the comparison pages point to them at every step.
Certificates available upon request. Please confirm the minimum order quantity in your inquiry before placing an order. Please confirm the lead time with the supplier before placing an order. Please confirm the trade terms and payment method before confirming an order.