SH 316 Double Hex Nut Clamp
Advanced Coupling Clamp Specifications
A clamp consists of two half-shells joined by a hinge and closed by a tightening mechanism. On a tri-clamp connection, sealing is achieved by compressing the gasket between the two ferrule faces. The clamp holds this compression and determines how it is distributed around the gasket circumference.
This version combines three features: two adjustable-length swing bolts, hex nuts, and shouldered eye bolts that prevent accidental opening. Six sizes, from 2 1/2″ to 5″, for a maximum allowable pressure of 50 bar to 30 bar.
Adjustable-length shouldered eye bolts, 2 1/2″ to 5″, DN50 to DN125
Safety clamp with two swing bolts and hex nuts, 316 stainless steel body, two segments hinged by cold-formed rivets, polished finish. Six sizes from 2 1/2″ to 5″, i.e. DN50 to DN125, compatible with DIN 32676, ISO 2852 and ASME BPE ferrules. Maximum allowable pressure from 50 bar at 2 1/2″ to 30 bar at 5″. Controlled torque tightening, tool-operated opening, accidental opening prevented.
Three constraints addressed together
A process point can combine three requirements: repeatable, recorded tightening; an opening that cannot be done by hand by mistake; and uniform compression on a diameter where the lever arm starts to matter. Each can be handled separately with a different clamp. This one handles them in a single reference.
Two diametrically opposed bolts for symmetrical tightening. Hex nuts to apply and record a torque. Shouldered eye bolts so that the clamp cannot open until the nuts have been loosened by the specified number of turns.
This is the version that naturally appears on qualified points of a high-risk line: steam connections, solvent transfers, sampling points on hot circuits, connections subject to periodic requalification.
The hex nut is not a mere fastener detail
A wing nut is tightened by hand. The torque achieved depends on the operator, how strong they are that day and how accessible the point is. It is neither measurable nor repeatable, and therefore cannot be included in a qualification file.
The hex nut requires a wrench. The consequence is twofold: the torque becomes a value that is applied, read and recorded, and opening is no longer possible without a tool. On a high-risk point, this second property is worth as much as the first.
With two bolts, tightening is carried out in alternating passes, as on a flange. Each bolt receives the same travel, and gasket compression remains balanced over the full 360 degrees throughout the torque build-up.
The shouldered eye bolt
The shoulder is held in its seat and cannot pivot until the nut has been loosened by the specified number of turns. An impact, a vibration, partial loosening: the clamp does not open. On a line that is still under pressure or still hot, this margin is what separates an operation from an accident.
The nuts do not need to be fully removed to open the clamp. Normal operation remains quick; only unintentional opening is prevented.
The effective length of each bolt is adjustable. This makes it possible to take up the accumulated tolerances of the two ferrules and to obtain the same tightening travel on both bolts, a prerequisite for symmetrical compression.
Construction
Two segments hinged by cold-formed rivets, investment-cast body, polished finish. 316L stainless steel body.
The clamp remains outside the process and comes into contact neither with the fluid nor with internal CIP solutions. It is, however, exposed to floor washdowns, ambient steam, splashes of alkaline detergents and, in microelectronics, acidic atmospheres. Grade 316L limits the onset of crevice corrosion in the overlapping areas of the hinges.
The anti-galling option is available. On a clamp torqued with a tool, a galled thread forces you to strain, which distorts the torque value even before it compromises opening.
Pressure rating
The maximum allowable pressure depends on the diameter and follows the values of the SH range. It applies to the clamp alone.
| Diameter | DN equivalent | Flange A (mm) | MAWP (bar) |
| 2 1/2″ | DN50 (ISO) | 77,5 | 50 |
| 3″ | DN65 | 91 | 40 |
| 3 1/2″ | DN80 | 106 | 40 |
| 4″ | DN100 (DIN) | 119 | 35 |
| 4 1/2″ | DN100 (ISO) | 130 | 30 |
| 5″ | DN125 | 144,4 | 30 |
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 are the mechanical limit of the clamp at ambient temperature, not that of the connection. The two bolts do not increase the MAWP: they determine the quality and repeatability of compression, not the allowable load.
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.
Depending on the case, the associated tubes conform to DIN 11850, EN 10357 series A to C, DIN 11866 or ISO 2037. The hygienic classes H3, H4 and H5 of DIN 11866 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 selected 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.
A tightening torque only makes sense in combination with a given gasket material and thickness. The same torque applied to EPDM and to PTFE does not produce the same compression. Any value recorded in a qualification file must specify the gasket reference.
On hot lines, it is also the gasket that governs the risk on opening. A gasket that has crept can stick to the faces and release its stress all at once when it comes loose. The shouldered eye bolt holds the assembly together during this phase.
Overall dimensions
Band width of 19 mm across the entire range. Overall length from 124 mm to 194 mm depending on size. Flange diameter from 77.5 mm to 144.4 mm. As the two bolts are diametrically opposed, allow wrench clearance on both sides of the fitting, not just one.
Applications
Pharmaceutical and biotechnology industries, high-risk process lines, steam circuits and hot points, solvent distribution, chemicals, microelectronics, food processing.
This version is chosen for points that combine qualification and operator exposure. Periodic inspections by third-party bodies. Clamps calibrated from batch to batch to ensure consistent fit on the ferrule. Packed in cardboard, plastic-free.
Technical specifications
| Characteristic | Value |
| Type | Safety SH double bolt, 2 hinged segments |
| Body material | 316 stainless steel |
| Manufacturing | Investment casting, cold-formed rivets, polished finish |
| Fasteners | 2 adjustable-length shouldered eye bolts, hex nuts |
| Option | Galling-resistant fastener version |
| Size range | 2 1/2″ to 5″ (DN50 to DN125) |
| Flange diameter | 77.5 mm to 144.4 mm |
| Band width | 19 mm across the entire range |
| MAWP | 50 bar at 2 1/2″ to 30 bar at 5″ |
| Compatible ferrules | DIN 32676 series A, B, C, ISO 2852, ASME BPE |
| Tightening | To torque, in alternating passes on both bolts |
| 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 DN100 tube fitted with a DIN ferrule takes a clamp with a 119 mm flange; the same DN100 fitted with an ISO ferrule takes a clamp with a 130 mm flange. 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
This version combines safety, recorded tightening and symmetry. The others meet narrower needs.
| Version | Closure | Use |
| Safety double bolt, hex nuts | 2 shouldered eye bolts, wrench | Qualified points in hazardous areas, 2 1/2″ to 5″, from 50 to 30 bar |
| Safety single bolt type SAF, 4 levels | 1 shouldered eye bolt, 2 pins | Safety only, DN8 to DN300, quicker operation |
| SH double bolt, wing nut | 2 adjustable swing bolts | Symmetrical tightening without a safety requirement, 2 1/2″ to 10″ |
| SH single bolt, double hinge | 1 bolt, 2 pins | Standard connections from 50 to 10 bar, DN8 to DN300 |
| Reinforced SSH | 2 bolts, 2 separate segments | High pressure, from 75 to 20 bar depending on diameter |
| Three segments | 1 bolt, 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 |
Frequently asked questions
Why does the range stop at 5″?
Only six sizes, from 77.5 mm to 144.4 mm flange. Beyond that, refer to the single-bolt safety clamp, available up to 12 5/8″. Below 2 1/2″, a single bolt achieves the same compression more quickly, as the lever arm stays short.
Two bolts: does it withstand more pressure?
No. The MAWP is identical to that of the single-bolt clamp of the same diameter. The second bolt provides symmetry and repeatability of tightening. To go higher in pressure, you need a reinforced clamp.
How does it differ from the single-bolt safety clamp with hex nut?
The single-bolt clamp covers the same safety and traceability need over the entire DN8 to DN300 range. This one adds symmetrical tightening, useful from a 77.5 mm flange upwards, at the cost of longer operation and a shorter range.
How should tightening be carried out?
In alternating passes on both bolts, up to the specified torque. Fully tightening one bolt before the other crushes the gasket on one side and creates a leak that subsequent turns cannot fix.
What is the bolt length adjustment for?
To take up the accumulated tolerances of the two ferrules and obtain the same tightening travel on both bolts. Useful when the two ferrules do not come from the same standard or the same supplier.
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 DN100 exists with a 119 mm ferrule and with a 130 mm ferrule, depending on the standard.
Which pressure should be used for a technical file?
That of the gasket under its actual operating conditions. The stated MAWP value applies to the clamp alone, at ambient temperature.