Straub Flex 2

Date Posted:22 August 2025 

Straub® Flex 2 & Open-Flex 2 – 172–2032 mm

Straub Flex 2 coupling Straub Open-Flex 2 technical view

Large-diameter flexible couplings for plain-end pipes. Absorb axial expansion/contraction and angular deflection while saving space versus expansion joints. Install with a torque wrench — no hot work.

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  • Working pressure
    Flex 2: 26–67 bar (2,600–6,700 kPa)
    Open-Flex 2: 5–29 bar (500–2,900 kPa)
  • Temperature
    −30 °C to +100 °C
  • Materials
    316L housing; AISI 301 rings (Flex 2); EPDM / NBR / FKM seals (to 180 °C by compound)
  • Angular deflection
    Up to 4° (size dependent)

Overview

Flex 2 is the standard large-diameter flexible coupling for new installs and general duty. Open-Flex 2 is the split, wrap-around version used for live-line access and repairs where you can’t dismantle the pipe. Both are non-axial restraint couplings — provide external restraint/fixed points.

Technical specifications

Size range 172–2032 mm
Working pressure Flex 2: 26–67 bar; Open-Flex 2: 5–29 bar (varies by size)
Temperature range −30 °C to +100 °C
Housing 316L stainless steel (Open-Flex 2: split two-part housing)
Rings AISI 301 stainless (Flex 2)
Seals EPDM (standard), NBR, FKM (up to 180 °C by compound)
Angular deflection Up to 4° (size dependent)
Standards DIN 86128; ASTM 1476
Design life 25+ years

Non-restrained: provide fixed points/external restraint.

Applications

  • Large diameter mains & water distribution
  • Industrial process & power generation
  • Chemical plants & mining operations
  • Marine and utility infrastructure

Model comparison

Model Purpose Working pressure (bar) Housing Notes
Flex 2 General install; expansion compensation 26–67 (by size) 316L, low-profile Lightweight vs flanged; works on rough pipe surfaces
Open-Flex 2 Live-line/repair; no disassembly 5–29 (by size) Split two-part 316L Wrap-around installation; ideal for weld/pitting/short crack repairs

Notes

  • All Flex/Open-Flex couplings are non-pull-out — use external restraint/fixed points.
  • Test pressure = 1.5 × PS; Burst pressure ≈ 2 × PS.
  • Strip inserts supplied with all couplings sold in Australia.

Request a quote

Tell us your pipe OD, medium, pressure and operating temperature and we’ll size the correct Flex 2 / Open-Flex 2 model.

Request a quote Email sales@dewaterproducts.com.au