Flanges – Tips for an easy life.

The Golden Rules of Stainless Steel Flange supply

Flanges are amongst the most critical components in a pipeline. They are used as connections for pumps, valves, strainers etc. and for pipework which has to be regularly dis-assembled and re-assembled.

It is critical that the correct flanges are supplied that can cope with the pressure of the system and are compatible with all the components which are connected in the pipeline. A flange is specified by the nominal pipe size and the pressure rating. However, there are distinctly different types of flanges depending on the plant design. In the offshore, petro-chemical, power and nuclear power industries they are generally designed in the USA, UK or Germany. There are of course flanges required for the paper pulp, water, brewery industries etc. but the rules of suitability remain the same.

Those who are regularly involved in the buying and selling of flanges, will be all too aware of how easy it is to supply the wrong flange if the correct questions are not asked. In this short piece we outline the do’s to supply the correct flange which will avoid delay, frustration and most importantly costly mistakes!

Listed is a short tick list of the relevant questions for the correct identification of a flange

Golden rules for flange identification

  1. Stainless Steel Grade: 304L, 316L, 1.4306, 1.4404, 31803, 254SMO, UNS 31254 etc.
  2. Pipe Size: NB (Nominal Bore), NPS (Nominal Pipe Size), DN (Diameter Nominal)
  3. Dimensional specification: ASME B16.5, EN1092-1, BS4504, BS10, API605 etc.
  4. Pressure Ratings: 150#, PN16, Table E etc.
  5. Type of Face: RF (Raise Face), FF (Flat Face), RTJ (Ring Type Joint) etc.
  6. Quantity Required


  • There is no such thing as a ‘better grade’ of steel, and a higher price does not mean better quality or performance. Instead steel is manufactured to internationally recognised specifications to fulfil a particular application. Material grades may or may not be interchangeable, but it is essential that the grade of steel is fit for purpose. You must find out exactly what grade of material is acceptable before supplying or purchasing a stainless steel flange.
  • Flanges of different dimensional specifications and pressure ratings are not interchangeable.
Image of Stock Services Chris Price puzzling over a weld neck flange.
What’s this then? I think it is written on the side Chris?

Flange manufacturing materials

Dimensions Base Material Pressure Rating
ASME B16.5 ASTM A182 (Forgings) ASTM A240 (Plate) 150#. 300#. 400#. 600#. 900#. 1500#. 2500#.
API 605 ASTM A182 (Forgings) ASTM A240 (Plate) 150#. 300#. 400#. 600#. 900#. 1500#. 2500#.
ASME B16.47series A & B ASTM A182 (Forgings) ASTM A240 (Plate) 150#. 300#. 400#. 600#. 900#. 1500#. 2500#.
EN1092-1 ASTM A182 (Forgings) PN2.5. PN6. PN10. PN16. PN25. PN40. PN63. PN100. PN160. PN250. PN320. PN400.
BS4504 BS970 (Bar)ASTM A240 (Plate) ASTM A182 (Forgings) PN2.5. PN6. PN10. PN16. PN25. PN40. PN63. PN100. PN160.
BS10 BS970 (Bar)ASTM A240 (Plate) ASTM A182 (Forgings) Table D. Table E. Table F. Table H. Table J. Table K. Table R. Table S. Table T.


Typical Stainless Steel 18/8 Grade Designations

304 304S15 X5 Cr Ni 18 10 1.4301
304L 304S11 X2 Cr Ni 18 9 1.4307
316 316S31 X5 Cr Ni Mo 17 12 2 1.4401
316L 316S11 X2 Cr Ni Mo 17 13 2 1.4404
321 321S31 X6 Cr Ni 18 10 1.4541
316Ti 320S31 X6 Cr Ni Mo Ti 17 12 2 1.4571
SMO 254SMO X1 Cr Ni Mo Cu N 20 18 7 1.4547


The information contained in this article is intended to help you to supply the correct flanges contained in the golden rules. It is not intended as a comprehensive guide to all the flanges that are available.


Should you like to send you next enquiry for stainless steel flanges to Stock Services, please send us an email.

Large PN flanges available on quick manufacture times
It’s another flange…a little bigger than the last.

Air freight

Where can I get big stainless steel fittings and flanges from?

On many occasions you will quote a job, and then be asked for a re-offer (or three) before a job eventually goes live. Just when you think you are about to get your order, another engineer decides to have a look pushing the job back a couple of weeks or months.

As is normally the case, a job that seemed relatively simple at the outset, can become a huge rush, and the supply of materials may be problematic. When your client cannot wait for 2-3 months for delivery, the only option remaining to them, is to pay a premium price for the required material to be manufactured locally on a quick lead time.

Stock Services have been delivering material for just these type of scenarios for many years. We have expertise in supplying large volume, or non standard and oversized products manufactured on quick lead times from a variety of our approved mills in China.

Image of an Equal Cross (seamless) that are available to order from Stock Services
Seamless Equal Crosses manufactured and delivered in 3 weeks by Air freight

How does air freight work?

Sending goods by air freight, is not really any different to sending goods by sea fright. Materials still abide by the standard INCOTERMS, and require a bill of lading, go through the same customs entry process with duty, VAT and handling fees added. The benefit of air freight is purely speed.

Although air freighting goods is considerably more expensive than sea freight, goods can be manufactured and then shipped by air anywhere in the world often within one week of a product being completed.

Stock Services have long standing relationships with a number of mills producing fittings and flanges, meaning we can quote you very quickly, and have materials produced on short lead times of 10-25 days ex mill China. This service has allowed many of our clients to win jobs before their competitors have even been able to make a bid.

How expensive is it to send goods by air freight?

There is no real rule of thumb, as both the volume (size of package) and gross weight will need to be considered when calculating an air freight fee. You will also need a reliable agent to clear your goods once they arrive into a port.

There are a number of costly errors that people can make when organising air freight, often these come in the form of paying high deferment fees, (which can often be charged at a percentage rate of your overall order value) or by instructing mills to ship goods by air on CIF terms. By instructing a mill to ship your goods, you have no control over the carrier used, delivery time can be longer than anticipated if a shipment travels on multiple flights to a location, and fees charged by import agents when goods arrive may be un-negotiable.

Image of 180 short radius return bends. Avaiable for purchase from stock services
8 NPS short radius return bends manufactured in Grade 304H. Air freighted to client within 5 weeks of order.


How can Stock Services help?

  • Stock Services have become experts in air freighting goods by making all the mistakes listed above (and more besides). We offer quick, competitively priced air freight services to the UK, Europe and elsewhere.
  • We fix the price meaning there are no unwelcome additional costs when the goods arrive at your works. The price we offer is the price you pay, inclusive of all handling and duty fees.
  • We can offer you prices next day for your fitting and flange requirements in many grades and sizes, and delivery can often be made in 15-40 days to your works depending on requirement.
  • Once you have placed your order you can rest assured that it will be delivered on time as per your order requirements.

If you would like to send us your next urgent enquiry, send us an email.

Seamless Reducing Tees - Non standard sizes available from stock services.
Non standard stainless steel seamless reducing tees via air freight

Thanks for reading 🙂