Guillemin, DSP, Camlock: which quick coupling to choose for your application?

Guillemin, DSP, Camlock: these three families of quick couplings are found in the same sectors — agriculture, industry, fluid transfer, firefighting — and yet they are not interchangeable. A wrong choice translates concretely into a leak under pressure, a coupling unusable for suction, or a dimensional incompatibility with existing equipment. The aim of this article is not to present side-by-side technical data sheets, but to provide operational decision criteria for choosing the right family based on the actual specifications of the installation. Browse our full range of couplings on Multitanks.

🔧 GUILLEMIN AND DSP: THE TWO SYMMETRICAL COUPLINGS IN BRIEF

The Guillemin and the DSP share a fundamental property: their two halves are identical, which simplifies stock management and eliminates any risk of orientation error during assembly. That is where the similarity between the two families ends, and it is precisely this that structures the choice between them.

The Guillemin relies on a flat gasket and a locking ring or lock, generally tightened with a wrench to ensure a perfect seal. It works both in suction and discharge, making it the versatile coupling par excellence in agricultural and industrial installations. It is sized in metric DN (from DN20 to DN150) and covered by standards NF E29-572 / NF EN 14420-8, as well as NF S61-701 for firefighting applications. For a complete overview of how it works, we refer you to the dedicated article in this series.

The DSP, visually similar to the Guillemin, is distinguished by a lip seal whose sealing performance increases with pressure in the discharge direction. The direct consequence: it cannot be used for suction. Its locking mechanism, which snaps the lock into the notches, requires no wrench, which speeds up connection. Like the Guillemin, it falls within the scope of standard NF S61-701 for equipping emergency services and firefighting vehicles. The key point that structures the rest of this article is therefore: the Guillemin works in both directions, the DSP only in discharge.

🔧 THE CAMLOCK: OPERATION, STANDARDS AND SIZING

The Camlock is the cam and groove coupling: the male part carries a peripheral groove, the female part is fitted with two spring-loaded cam arms that lock into this groove by simple manual folding. No tool is required to connect or disconnect, which fundamentally distinguishes it from the Guillemin, whose optimal sealing requires a wrench.

Unlike the two previous families, the Camlock is not symmetrical: there is a male part and a female part, available in several standardised configurations designated by letters. Types A, B, C, D, E, F, DC and DP correspond to different combinations of threading, hose shank, or plug and dust cap. This non-symmetry requires more rigorous stock management and careful attention when ordering: the exact type of each end to be connected must be precisely identified.

From a standards perspective, the Camlock originates from the American military specification Mil-C-27487, replaced in 1999 by the federal standard A-A-59326A, since updated to A-A-59326D. In Europe, standard EN 14420-7, which came into force in 2004 replacing the former DIN 2828, adopts the specifications of the American federal standard, making couplings compliant with both reference frameworks interchangeable. One point to note: these standards cover the coupling connection itself, but not necessarily the levers, bolts, rings and gaskets, whose specifications may vary between manufacturers.

Camlock sizing is in inches (generally from 1/2" to 8"), unlike the metric DN system used for Guillemin and DSP. For a given nominal size, the exact dimensions of the male and female parts differ slightly by design, to allow coupling. As for working pressure, it varies significantly depending on the material: aluminium and plastics are generally not suitable for high-pressure applications, while stainless steel effectively handles higher pressures. Working pressure also decreases as temperature increases. Available materials cover a wide spectrum: aluminium, stainless steel (304 or 316), brass, polypropylene, glass fibre reinforced nylon.

🔧 COMPARISON TABLE: THE CRITERIA THAT MATTER

The table below summarises the key differences between the three families. It is not a list of characteristics to be read column by column, but a decision grid: each row corresponds to a criterion that can, on its own, rule out one family or make another mandatory.

🔧 HOW TO READ THIS TABLE TO MAKE A DECISION

The first question to ask is about suction. If the installation needs to operate in suction — pumping from a tank, vacuum filling, any circuit where fluid is drawn rather than pushed — the DSP must be ruled out immediately. Its lip seal, which is its strength in discharge, becomes a structural weakness as soon as pressure reverses. Both the Guillemin and the Camlock remain usable in suction as well as discharge.

The second question concerns regulatory compliance. If the installation must comply with French fire standard NF S61-701 — equipping emergency services, firefighting vehicles, fire water networks — the choice is restricted to the Guillemin or the DSP. The Camlock, whose reference standards are American (A-A-59326D) and generic European (EN 14420-7), does not fall within this regulatory scope. Using a Camlock in a context where NF S61-701 is required constitutes non-compliance, regardless of the intrinsic quality of the coupling.

The third question concerns the speed and frequency of connection operations. If the priority is to connect and disconnect without any tools, particularly for repeated operations — tanker loading and unloading, frequent configuration changes on a tanker truck or agricultural machine — the Camlock offers a real operational advantage. The DSP, also tool-free, is faster than the Guillemin in this regard, but remains limited to discharge. The Guillemin, whose perfect sealing requires a wrench, is less suited to very frequent connections where tooling becomes a constraint.

The fourth question, often overlooked when ordering, is that of the sizing system. If the existing installation is already standardised in metric DN — which is the case for almost all French agricultural and fire networks — introducing Camlock couplings sized in inches requires adapters, with the associated risks of pressure drop and incompatibility. Conversely, an industrial or petrochemical installation already fitted with Camlock inch couplings has no reason to introduce DN couplings without a regulatory requirement.

🔧 PRAGMATIC SUMMARY: THREE DESIGN PHILOSOPHIES

These three families are not ranked: none is strictly superior to the other two. They respond to different design philosophies, stemming from distinct industrial histories. The Guillemin was born from late 19th-century firefighting and was adopted by French agriculture and industry for its versatility and robustness. The DSP shares this firefighting heritage but opted for a lip seal that optimises sealing in discharge at the expense of reversibility. The Camlock, originating from the American military world and adopted by the global oil and chemical sector, prioritised connection speed and configuration diversity at the expense of symmetry.

The right choice therefore depends on the actual specifications of the installation: flow direction, regulatory requirements, frequency of operations, existing equipment and the fluid being transferred. Multitanks offers a complete range of couplings covering these three families, with materials suited to each application. For installations also requiring shut-off elements, stainless steel butterfly valves effectively complement a circuit fitted with quick couplings.