SAFETY 316 SAF Clamp with Wing Nut
Advanced Coupling clamp specification
A clamp consists of two half-shells connected by a hinge and closed by a tightening mechanism. On a tri-clamp connection, sealing is ensured by compressing the gasket between the two ferrule faces. The clamp holds this compression and determines how it is distributed around the gasket circumference.
The Safety design takes the geometry of the SH clamp and adds a shouldered eye bolt that prevents opening until the nut has been loosened by the specified number of turns. Four safety levels are available. The clamp’s maximum allowable pressure ranges from 50 bar at 1/2″ to 10 bar at 12″.
Shouldered eye bolt, 4 safety levels, 1/2″ to 12 5/8″, DN8 to DN300
The SAFETY clamp is a double-hinge safety clamp with a 316 stainless steel body and a shouldered eye bolt. Four safety levels, from simple anti-opening up to a padlock lockout device. Diameters from 1/2″ to 12 5/8″, i.e. DN8 to DN300, compatible with DIN 32676, ISO 2852 and ASME BPE ferrules. Maximum allowable pressure from 50 bar at 1/2″ to 10 bar at 12″. Patented design, anti-galling option across the whole range.
The delayed-opening mechanism
On a standard clamp, the screw pivots as soon as the nut stops bearing on it. An impact, a vibration, an operator who loosens a quarter turn and turns away: the clamp can open while the line is still under pressure or still hot. The gasket blows, the fluid escapes, and the operator is right in front of it.
The shouldered eye bolt eliminates this scenario. The shoulder is retained in a grooved housing and cannot pivot until the nut has been loosened by the specified number of turns. During these turns, gasket compression decreases gradually: any residual pressure shows up as an audible, controlled leak before the clamp can open. The operator is warned before being exposed.
Complete removal of the nut is not required for opening. Normal operation remains quick; only accidental opening is prevented.
The four safety levels
The level is chosen according to the nature of the risk, not the pressure. A point with 3 bar steam at 140 °C justifies a higher level than a cold process line at 20 bar.
| Level | Designation | Composition | Use |
| 1 | SAF | Shouldered eye bolt | Accidental opening prevented, hand operation |
| 2 | SAFX | Shouldered eye bolt, hex nut | Tool-only opening, traceable torque tightening |
| 3 | SAFS | Shouldered eye bolt, hex nut, cover | Restricted nut access, thread protection |
| 4 | SAFL | Shouldered eye bolt, hex nut, cover, lockout device | Points included in a padlock lockout procedure |
Level 4 accepts a lockout padlock. The clamp then becomes part of the LOTO procedure in the same way as an isolator or a valve: the line cannot be reopened by a third party during an intervention.
Two versions complete the range: a double-screw version for connections from 2 1/2″ to 5″, and a three-segment version in 304L for points with frequent opening.
Material and surface finish
316 stainless steel body. The clamp remains outside the process and is in contact neither with the fluid nor with internal CIP solutions. It is, however, exposed to floor washing, ambient steam, splashes of alkaline detergents and, in microelectronics, acidic atmospheres. The 316 grade limits the onset of crevice corrosion in the overlapping areas of the hinges.
The anti-galling option is available across the whole range. On a safety clamp, a galled thread turns a controlled opening into an angle-grinder job, which defeats the purpose of the device. On hot points and circuits subject to repeated SIP, this option is not a luxury.
Wing nuts are available in coloured versions, to visually identify a network or fluid class on an installation that has several.
Pressure rating
The maximum allowable pressure depends on the diameter and uses the values of the SH clamp from which its geometry is derived. It applies to the clamp alone.
| Diameter | DN equivalent | Flange A (mm) | MAWP (bar) |
| 1/2″ to 2 1/2″ | DN8 to DN50 | 25.4 to 77.5 | 50 |
| 3″ and 3 1/2″ | DN65 and DN80 | 91 and 106 | 40 |
| 4″ | DN100 (DIN) | 119 | 35 |
| 4 1/2″ to 6″ | DN100 (ISO) to DN125 | 130 to 167 | 30 |
| 6 5/8″ | DN150 | 183 | 25 |
| 8″ and 8 5/8″ | DN200 | 217.4 and 233.5 | 20 |
| 10″ and 10 5/8″ | DN250 | 268 and 286.1 | 16 |
| 12″ and 12 5/8″ | DN300 | 319 and 338 | 10 |
The allowable pressure of the complete assembly depends on the gasket, its material, the operating temperature and the ferrule tolerances. The values in the table represent the mechanical limit of the clamp at ambient temperature, not that of the connection. The entire range has been pressure-tested by a third-party body; reports are available on request.
Standards compatibility
The clamp is defined by the outside diameter of the ferrule face, not by the tube DN. It therefore applies equally to ferrules made to DIN 32676 series A, B and C, ISO 2852 and ASME BPE, provided the flange diameter matches.
The associated tubes fall, depending on the case, under DIN 11850, EN 10357 series A to C, DIN 11866 or ISO 2037. The DIN 11866 hygienic classes H3, H4 and H5 make it possible to trace the correspondence between tube, fitting and internal surface finish.
Gasket selection
The clamp is independent of the gasket. The elastomer material, EPDM, silicone, FKM or PTFE, is chosen based on chemical compatibility and operating temperature, then on the food or pharmaceutical compliance requirements applicable to the project. It is this choice that sets the allowable temperature of the connection, not the clamp.
On hot lines, it is also the gasket that governs the risk on opening. A gasket that has crept or aged thermally can stick to the sealing faces and release its stress all at once when it comes away. The shouldered eye bolt holds the assembly together during this phase.
Dimensions
Band width of 17 mm on single-screw versions, 19 mm on the double-screw version. Flange diameter from 25.4 mm to 338 mm. Levels 3 and 4, cover and lockout device, increase the radial footprint around the nut: to be checked on insulated lines and tight pipe racks.
Fields of application
Hazardous process lines, steam circuits and hot points, solvent distribution, pharmaceutical and biotechnology industries, chemicals, microelectronics, food processing.
This type of clamp is specified by name in the internal standards of several pharmaceutical groups, on frequently dismantled connections in hazardous areas. Patented design. Periodic inspections by third-party bodies. Clamps calibrated between batches to ensure consistent fit on the ferrule. Packed in cardboard, plastic-free.
Technical characteristics
| Characteristic | Value |
| Type | Safety SH, double hinge, shouldered eye bolt |
| Safety levels | 4, from the shouldered bolt alone to the lockout device |
| Body material | 316 stainless steel, 3-segment version in 304L |
| Fasteners | Shouldered eye bolt, wing nut or hex nut, anti-galling option |
| Size range | 1/2″ to 12 5/8″ (DN8 to DN300) |
| Flange diameter | 25.4 mm to 338 mm |
| Band width | 17 mm single-screw, 19 mm double-screw |
| MAWP | 50 bar at 1/2″ to 10 bar at 12″ |
| Compatible ferrules | DIN 32676 series A, B, C, ISO 2852, ASME BPE |
| Options | Coloured wing nuts for network identification |
| Delivery | Assembled, ready to install |
| Packaging | Cardboard, plastic-free |
Dimensional drawing key: A flange diameter (ferrule face), B opening radius, C overall length, W band width.
Clamp and ferrule correspondence
The clamp flange diameter A corresponds to the outside diameter of the ferrule face, not to the tube DN. A DN25 tube fitted with a 1″ ferrule takes a 50.5 mm flange clamp. The same DN25 fitted with a DIN ferrule takes a 34 mm flange clamp. The table below gives the equivalence between clamp size, ferrule size and tube diameter for the ASME BPE, DIN 32676 and ISO 2852 standards.
Other clamp versions
The safety clamp is essential at risk points. The other versions address different constraints.
| Version | Closure | Use |
| Safety, 4 levels | 1 shouldered eye bolt, 2 axes | Points where accidental opening under pressure must be prevented, 1/2″ to 12 5/8″ |
| SH single-screw, double hinge | 1 screw, 2 axes | Standard connections from 50 to 10 bar depending on diameter, frequent dismantling |
| Double hex nut | 1 screw, 2 nuts | Controlled and traceable tightening torque |
| Reinforced double-screw SSH | 2 screws, 2 segments | High pressure, from 75 to 20 bar depending on diameter |
| Three segments | 1 screw, 3 riveted segments | Frequent one-handed opening, from 21 to 12 bar, 1″ to 4″ |
| Polymer, single-use | Quick closure | Bags, filters and disposable lines, -70 °C to 60 °C |
Single-use polymer clamps cover a standard range of -70 °C to 60 °C, freezing down to -80 °C, autoclaving up to 134 °C for 30 minutes and gamma sterilisation up to 50 kGy.
Frequently asked questions
What is the difference from a standard SH clamp?
The geometry and pressure rating are identical. Only the closing mechanism changes: the shouldered eye bolt cannot pivot until the nut has been loosened by the specified number of turns. The clamp therefore does not open under an impact or partial loosening.
Which safety level should be chosen?
Level 1 at points where only accidental opening needs to be prevented. Level 2 when opening must require a tool and tightening must be recorded. Level 3 to restrict access to the nut. Level 4 at points included in a lockout procedure. The criterion is the nature of the risk, not the operating pressure.
How do I choose the size?
The choice is based on the outside diameter of the ferrule, dimension A. The tube DN is not enough: a DN25 exists with a 34 mm ferrule and with a 50.5 mm ferrule depending on the standard.
Wing nut or hex nut?
The wing nut is suitable for connections dismantled by hand in production. The hex nut is chosen when a tightening torque must be applied and recorded, and when opening must require a tool. This is what distinguishes level 1 from level 2.
Is the anti-galling option necessary?
On hot points and circuits subject to repeated SIP, yes. A galled thread forces a destructive opening, which removes the benefit of the safety device and immobilises the line.
What pressure should be used for a technical file?
That of the gasket under its actual operating conditions. The MAWP value stated corresponds to the clamp alone, at ambient temperature.