- Sizes 1″ to 8″ (25 mm – 200 mm).
- Pressures 19 – 1450 psig (1.3 – 100 bar).
- 80% operating ratio.
- ± 5% Burst Tolerance.
- Flat Seal.
- Metal-to-Metal “bite type” seal.
- Tension loaded.
- Minimal fragmentation.
- Liquid and Gas service.
- Extended life.
- Easy Installation.
- No vacuum support needed.
The Nu-SafT System introduces a new concept that combines the benefits of advanced technology with the simplicity of a basic style. Reliable overpressure relief is assured with components which cover a wide range of applications and service pressures.
Overpressure relief from 19 psig (1.3 bar) to 1450 psig (100 bar) is assured in a range of sizes from 1 inch (25 mm) to 8 inch (200 mm).
The Nu-SafT System consists of an inlet and an outlet of the NX-7R Safety Head plus the XN or LCN Rupture Disk, depending on the pressure required. Refer to Figure 1.
The XN Rupture Disk (Bursting Disc) incorporates precision scoring technology in a metal, tension loaded design. The precision scoring design minimizes the possibility of disk fragmentation. Operating pressure may be extended to 80% of the disk’s burst rating without the risk of metal fatigue and subsequent reduction in normal service life. The new design exhibits no premature failure or fatigue cracks after extended pressure cycle testing from vacuum to 80% of the disk’s burst rating. The XN Rupture Disk (Bursting Disc) design can withstand full vacuum without the need for a vacuum support.
For the lower pressure ranges the LCN Rupture disk is available. This is a composite disk comprised of three parts: (1) A slotted metal top section is the pressure controlling element. (2) A fluoropolymer seal isolates the top section from the process. (3) The slotted metal bottom section will withstand vacuum. The flat design minimizes the possibility of disk damage during installation.
The simplicity of the NX-7R Safety Head design incorporates several features which allow easy installation. The Quick-Sert Safety Head with its reduced diameter fits inside the studs of two companion flanges. Asymmetric alignment pins in the Safety Head mate with location holes in the rupture disk (bursting disc), thus eliminating incorrect installation and slippage. The flat set design in combination with a metal-to-metal “bite-type” seal provides a leak-tight system. The NX-7R Safety Head and rupture disk (bursting disc) are easily pre-assembled with side lugs.
XN Precision Scored Rupture Disk (Bursting Disc)
- Solid Metal
- Precision Scored
- Minimal fragmentation
- Can withstand vacuum without support
- Operates up to 80% of the disk’s rated pressure. (Consult factory for tighter operating ratio and manufacturing ranges.)
- Liquid and gas service (acceptable for liquid service with compressible gas pocket between liquid and disk.)
- Disks damaged or installed incorrectly will burst at rated pressure or lower.
- Can be used in pressure cycling conditions.
How a Tension Loaded Disk Works
As the pressure increases on the tension-loaded disk, the seating design allows the dome to thin out until it can no longer withstand the pressure. The disk ruptures. Metal segments fold back against the walls of the fitting in an irregular pattern to provide a full opening. The ultimate tensile strength of the metal determines its failure point when loaded in tension.
Standard Manufacturing Ranges
When you order a rupture disk (bursting disc), a manufacturing range is automatically assigned to the burst pressure you specify. The following table gives the standard manufacturing ranges. A manufacturing range eliminates the necessity for the manufacturer to stock all possible thicknesses of all materials, nearly 100,000 thicknesses in all, to make all burst pressures.
For example, if you order a B Disk to burst at 80 psig, BS&B will enter the order to the shop with the standard manufacturing range (+9,-5), or 75 to 89 psig. BS&B will try for your requested pressure of 80 psig, but will ship the lot of disks if the marked pressure falls between 75 to 89 psig. Once the disk is rated and marked 78 psig, the burst tolerance of ±5% now applies to this stamped pressure.
The standard manufacturing ranges shown in the following table can be reduced by 1/2 or 1/4 for an additional cost. Hastelloy C-276 / Alloy C-276 is available only with standard manufacturing range and 1/2 range.