SELECTION GUIDE
KC Nipple Types: Clamped or Crimped
The choice is not really between part numbers. It is between two ways of holding the nipple in the hose, and everything else follows from that.
| Clamped assembly | Crimped assembly |
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| Nipple series | FDKP plated carbon steel, FDKS SS304 | FDK5N KC grooved, FDK6N |
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| Shank | Serrated | Long-lead KC serration profile |
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| Retained by | Band, bolt clamp or interlocking clamp | F60 slotted ferrule or F70 external swage collar |
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| Size range | 1/2" – 12" | 1-1/2" – 6" |
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| Threads | NPT or BSP SCH120 | NPT or BSP |
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| Assembled | On site or at a hose shop, with hand tools | On a crimping machine |
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Series names, sizes and thread standards above are from our 2026 catalogue. New to KC nipples? Our guide What Is a King Nipple? covers the other names, NPT and BSPT thread data by size, and how to install one. Two companion guides cover how to tell NPT from BSP king nipple threads and choosing zinc-plated or stainless king nipples.
What Sets the Working Pressure of a KC Nipple Assembly
Our FDKP and FDKS king nipples are rated to 200 psi maximum working pressure for the fitting. That figure describes the fitting in isolation. It is not the rating of the finished assembly, and it is not the figure to design to, because the assembly is limited by whichever of three things gives first.
The hose. Its own working pressure is almost always the governing figure, and no fitting raises it.
The retention method. A band or bolt clamp on a serrated shank will release before a crimped ferrule will. That is the reason higher-pressure service moves from a clamped FDKP or FDKS to a crimped FDK5N with an F60 slotted ferrule or an F70 swage collar.
The fitting material and wall thickness. This only becomes the governing limit at the top of the range.
Where we do publish a figure, it is against the component that sets the limit: the F70 external swage ferrule with collar is rated to 300 psi maximum working pressure, which is why it is specified for wire-braid and spiral-reinforced hose.
To quote an assembly we need the hose ID and OD, the hose’s own working pressure, the thread standard, and whether it will be clamped or crimped.
Where a KC Nipple Should Not Be Used
A serrated shank held by a band or bolt clamp is a mechanical grip, not a restraint against stored energy. Two exclusions follow from that, and neither is negotiable by going up a material grade.
Steam. Not for steam service, in any size or material.
High-pressure and heavy-duty compressed gas. Not for compressed air, nitrogen or other stored-energy gas in heavy-duty service, and particularly not at 1-1/4" and above, where the barb can blow off under load. Gas duty belongs on a crimped termination, not a clamped one.
Both exclusions are about what happens at failure, not at working pressure. A liquid line that lets go drops pressure immediately; a gas line stores the energy and releases the fitting with it.
KC Nipple Application Guide
Clamped — FDKP and FDKS. Water transfer, irrigation and agricultural lines, construction site discharge and general suction and discharge. The serrated shank with a bolt clamp can be rebuilt with hand tools, which is what matters when a hose is cut down or repaired in the field.
Crimped — FDK5N with F60 or F70. Oil suction and discharge, dock and marine loading, L.P. gas, anhydrous ammonia and acid chemical transfer, on wire-braid and spiral-reinforced hose.
Material. Plated carbon steel for water, air and general industrial duty. SS304 where the medium or the washdown regime would attack a plated surface.
