DN100 (4") flanged expansion bellows — PN16 bolt-up, UK stock
What the UKGP-FEB-04 DN100 (4") flanged expansion bellows does
The UKGP-FEB-04 is a DN100 (4") single-sphere EPDM rubber bellows with PN16 carbon-steel flange rings drilled to EN 1092-1 — a complete bolt-up assembly that fits between any pair of matching PN16 pipe flanges with full-face gaskets and standard M16 bolts. Flanged expansion bellows absorb pump vibration, thermal expansion (up to 19 mm axial) and minor flange misalignment (up to 13 mm lateral) in a single short, serviceable fitting.
Why bolt-up flanged construction beats screwed or grooved
Screwed (BSP) and grooved (Victaulic) expansion couplings limit you to small DNs and create a leak path at every joint. A flanged expansion bellows like the UKGP-FEB-04 bolts straight to standard PN16 pump flanges, butterfly valves and strainers — no adapters, no thread sealing, no proprietary couplings. Installers fit a pair (suction + discharge) on every commercial inline pump in the UK exactly because of this: one part code, one gasket pattern, one bolt set, drops in on any plant room.
Installation: gaskets, bolts and torque
Use full-face EPDM or graphite-faced gaskets (1.5–3 mm) — the bellows' moulded sealing bead doesn't need extra rubber gaskets but inserting them is harmless. Torque M16 bolts in a star pattern to 60 Nm (PN16) in three passes. Don't over-tighten: the most common warranty claim on flanged expansion bellows is a crushed sealing bead caused by torquing past the rated value. Where pipework is not anchored either side of the bellows, fit our tie-bar restraint kit — pressure thrust on a DN100 bellows at 16 barg is roughly 13 kN.
Pump-decoupling: the standard UK flanged bellows application
Fit a DN100 (4") flanged expansion bellows on the suction and discharge of every commercial inline pump (Grundfos TPE, Wilo Stratos GIGA, Armstrong DE) to drop airborne plant-room noise by 6–10 dB(A), absorb start-up water-hammer and decouple the steel pump body from the rigid header. This is why a single-sphere flanged bellows is the most-ordered fitting in our range: simple part code, fast delivery, standard PN16 drilling.
Drilling, materials and rating
Standard stock: EN 1092-1 / BS 4504 PN16 drilling, hot-dip galvanised carbon-steel flange rings, EPDM single-sphere body. PN25 (BS 4504 Table E), stainless flange rings, NBR (oil-resistant) bodies and ANSI 150 / JIS 10K drilling are available to order. Operating envelope: 16 barg at 16 °C, 10 barg at 110 °C — covers virtually every UK commercial heating, chilled water, condenser and DHW duty.
Price and lead time on the UKGP-FEB-04
The UKGP-FEB-04 DN100 (4") flanged expansion bellows is £275 ex VAT, in UK stock for same-day dispatch on orders placed before 3 pm Mon–Fri. PN25 flanging, NBR bodies and ANSI drilling are quoted within one working day.