If you have a fitting in your hand and need to know what it is, this page will get you there. Measure the part, match the measurement to a table, order the right adapter.
Nominal sizes are misleading across all of these standards — a "2½ inch" BSP thread does not measure 2½ inches, and a "Storz 65" is not 65mm across the lugs. Measure, then match.
Storz couplings
Storz is symmetrical: there is no male or female half. Two couplings of the same size mate together; different sizes will not.
To identify the size, measure lug centre to lug centre across the face.
| Storz size | Lug-to-lug distance |
|---|---|
| 25 | 31 mm |
| 38 | 51 mm |
| 50 | 66 mm |
| 65 | 81 mm |
| 75 | 89 mm |
| 90 | 105 mm |
| 100 | 115 mm |
| 125 | 148 mm |
| 150 | 160 mm |
Storz is also sometimes designated by letter rather than number — D, C, B and A in ascending size. Letter and number designations are not always used consistently between suppliers, so the measured lug distance is the reliable identifier.
BSP threads
Nearly every firefighting adapter is built as coupling-to-BSP rather than coupling-to-coupling. BSP is the common thread that lets a manageable range of parts cover a large number of combinations — so identifying the thread correctly matters as much as identifying the coupling.
Male thread — measure across the outside
Female thread — measure across the inside
| Nominal size (BSP) | Male — outside Ø (AG) | Female — inside Ø (IG) |
|---|---|---|
| ¾ inch (19 mm) | 26.4 mm | 24.1 mm |
| 1 inch (25 mm) | 33.2 mm | 30.3 mm |
| 1½ inch (38 mm) | 47.8 mm | 44.8 mm |
| 2 inch (50 mm) | 59.6 mm | 56.7 mm |
| 2½ inch (65 mm) | 75.2 mm | 72.2 mm |
| 3 inch (75 mm) | 87.9 mm | 84.9 mm |
| 4 inch (100 mm) | 113.0 mm | 110.1 mm |
| 5 inch (125 mm) | 138.4 mm | 135.5 mm |
| 6 inch (150 mm) | 163.8 mm | 160.9 mm |
These are ISO 228 parallel thread dimensions. A male and female of the same nominal size mate together; the male outside diameter runs roughly 3 mm larger than the female inside diameter.
Note on thread type. BSP comes in parallel (G) and tapered (R/Rc) forms. Firefighting adapters are usually parallel, sealing on a gasket or washer rather than on the thread. If a fitting seals by tightening metal-to-metal, check whether it's tapered before assuming a parallel adapter will suit.
NOR (Norlas) couplings
NOR is symmetrical like Storz — two lugs, no male or female half — so it is identified the same way: measure lug centre to lug centre. The diagram above applies.
Note that the number in a NOR designation is the lug spacing, not the bore. A "NOR 66" is NOR 2, with a 50 mm nominal bore.
| NOR size | Lug spacing | Nominal bore |
|---|---|---|
| NOR 1 (Las 1) | 83 mm | 65 mm |
| NOR 2 (Las 2) | 66 mm | 50 mm |
| NOR 3 (Las 3) | 50 mm | 40 mm |
NOR is standard on Norwegian, Danish and other Scandinavian-flagged vessels, and is the rarest of the four standards in Australian waters. Bronze is the usual material, chosen for seawater resistance.
Nakajima and BIC
These two are identified by type and fit rather than by a single face measurement, so they are set out here for comparison rather than as a measurement table.
| Nakajima (JIS F-7335) | BIC (BS 336) | |
|---|---|---|
| Type | Instantaneous interlocking | Instantaneous pressure-seal |
| Region | Japan, Asia, marine | UK and Commonwealth |
| Standard sizes | 40A, 50A, 65A | 65 mm |
| Hose internal Ø | 40 mm, 50 mm, 65 mm | approx. 65 mm |
Nakajima is a rigid quarter-turn interlocking coupling. It resembles other instantaneous types at a glance and is not interchangeable with BIC despite the similarity. Sizes are written in the JIS convention — 50A is nominally 2 inch, 65A nominally 2½ inch.
BIC — the British Instantaneous Coupling — seals under pressure rather than by interlock, and is the Commonwealth standard still fitted across older tonnage and much Australian shore-side equipment. Under BS 336 the marine size is 65 mm.
Not sure which you have? Send us a photo of the coupling face along with the hose bore measurement and we will confirm it. Between the visible lug or slot arrangement and the bore size, the two are straightforward to tell apart.
International Shore Connection
The ISC flange is fixed by SOLAS and does not vary — that is the entire point of it. There is nothing to measure and no size to select: any compliant ship-side half bolts to any compliant shore-side half, anywhere in the world.
If a flange does not match the standard dimensions, it is not an ISC, however well made.
Still not sure?
Send us the measurement and, if you can, a photo of the fitting face. Thread size and coupling type are usually enough for us to confirm the right adapter.
Fire Equip holds BIC, Storz, Nakajima and NOR adapters, International Shore Connections and complete ship-shore kits in Australian stock.