Process Pipes

Q: What does RST pipe mean?

RST is the Finnish abbreviation for stainless steel (ruostumaton teräs). An RST pipe is therefore a pipe made of stainless steel. In process applications the most common grades are 304L and 316L.

Q: Which should I choose, 304L or 316L?

304L is sufficient indoors and in processes with a low chloride content. Choose 316L for outdoor use, coastal locations and applications where the pipe is in contact with chloride-bearing liquids or cleaning chemicals.

Q: Which standards do the process pipes meet?

Our welded process pipes are manufactured to EN 10217-7 and the American ASTM A312 standard. Material certificates are available on request.

Q: What does DN 50 mean in millimetres?

DN 50 is a nominal size. The actual outside diameter of the pipe is 60.3 mm. The wall thickness is chosen according to pressure and application, typically 2.0 mm in process use.

Q: How quickly are the pipes delivered?

The delivery time depends on size, grade and quantity. State the DN size, wall thickness, grade and quantity in your quotation request and we will confirm the delivery time.

Our stainless steel process pipes are of the highest quality in the industry and are used by our customers for very demanding applications, including radiators, dairies and pulp mills

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Virtually invisible weld seam — no internal finishing required. Cut and assemble straight from delivery.

Certified to EN 10217-7 and ASTM A312 — documentation ready when your QC team asks for it.

Eddy current and hydrostatic testing available on request for critical applications.

Consistent chemical composition — reliable corrosion resistance, batch after batch.

Grades: when to choose 304L and when 316L

AISI 304L (EN 1.4307) is the most common stainless steel pipe for indoor use and for processes with a low chloride content. AISI 316L (EN 1.4404) contains molybdenum, so it resists chlorides, salt water and cleaning chemicals better. Choose 316L when the pipe is outdoors, in a coastal location or in contact with chloride-bearing liquids. The differences between the grades are explained in more detail in the article AISI 304 vs AISI 316.

Common stainless steel pipe sizes

Reference table of standard dimensions (outside diameters to EN ISO 1127). This is a general reference, not a stock list; availability is confirmed in the quotation.
DN 15: OD 21.3 mm, typical wall 2.0 mm - instrumentation, small lines
DN 25: OD 33.7 mm, typical wall 2.0 mm - process lines
DN 40: OD 48.3 mm, typical wall 2.0 mm - process lines
DN 50: OD 60.3 mm, typical wall 2.0 mm - process and water lines
DN 80: OD 88.9 mm, typical wall 2.0 mm - main lines
DN 100: OD 114.3 mm, typical wall 2.0 mm - main lines
DN 150: OD 168.3 mm, typical wall 2.6 mm - large lines
Tell us the size, wall thickness and length you need in your quotation request and we will confirm availability. Full dimension and weight table: article Stainless steel tube sizes.

Delivery and documentation

We deliver process pipes from our Tallinn distribution centre, and the delivery time is confirmed in the quotation. Material certificates (EN 10204 3.1) are available on request. For critical applications, eddy current and pressure testing can be arranged on request.

Frequently asked questions

Answers to common questions about stainless steel process pipes: grades, standards, sizes and delivery.

What does RST pipe mean?

Which should I choose, 304L or 316L?

Which standards do the process pipes meet?

What does DN 50 mean in millimetres?

How quickly are the pipes delivered?