BS&B SKR-U Reverse Buckling Disk

Introduction

The SKR-U™ rupture disk (bursting disc) is partnered with the UR-2 safety head to provide high integrity reverse buckling rupture disk (bursting disc) technology in a threaded union type holder. The SKR-U™ rupture disk (bursting disc) uses Saf™ technology (structural apex forming) to accurately control its burst pressure making it insensitive to the assembly torque variations that will occur in a threaded type holder.
The UR-2 safety head is available in three standard nominal sizes: 1/2 " / 15mm,3/4_" / 20mm, and 1" / 25mm. Standard inlet & outlet female threads are 1/2 ", 3/4 ", and 1" NPT. Custom thread configurations are available. The SKR-U™ rupture disks (bursting discs) are identified SKR-U™1/2" / 15mm, SKR-U™3/4" / 20mm, SKR-U™ 1" / 25mm and are all supplied with permanently attached 3-D metal identification tags.

Table of MNFA, NRA, KR

MDR and burst tolerance are additive. In the European PED & ISO cases, the burst tolerance and MDR are combined. In the ASME case, the ‘marked burst pressure’ must be a value within the agreed manufacturing design range & then the burst tolerance is applied.

Safety Head Design – Rupture Disk (Bursting Disc) Installation

The UR-2 safety head contains 4 metal components: inlet, holdown ring, outlet, and hexagon assembly nut. The SKR-U™ rupture disk (bursting disc) is pre-assembled to the safety head between the inlet and the holdown ring using two capscrews. This locates and centers the disk, ensuring the correct direction of installation: these two capscrews and a single locating pin in the UR-2 inlet have an asymmetric layout that matches three holes in the SKR-U™ disk flange.
This pre-assembly feature ensures that the disk can be easily installed even where the piping flow path may not be ‘vertical up’. The inlet/disk/holdown subassembly is fixed to the UR-2 threaded outlet by a hexagon nut. It is the hexagon nut that provides the sealing load to the safety head assembly (the capscrews are for preassembly only).
As an option, the UR-2 safety head can be provided with a threaded connection on the outlet side to enable the connection of a ‘tell-tale’ assembly.

Torque Drive Adapter

Accurate torque control on a large hexagon can be difficult. BS&B Safety Systems can provide a Torque Drive Adapter for use with all UR-2 safety heads (one adapter for all sizes). This adapter permits the use of a standard torque wrench for control of installation load.

Leak Tightness

The SKR-U™ safety head incorporates a ‘bite-type’ seal. This concentrates the holder assembly load to cut an impression in the SKR-U™ rupture disk (bursting disc) flange that ensures a leak tight installation.
A gasket (compressed non asbestos fiber) is placed inside the UR-2 safety head between the holder outlet and the disk holdown ring to ensure a good seal on the downstream side of the installation after assembly of the two holder halves. This gasket is supplied with each SKR-U™ rupture disk (bursting disc), and should be replaced with each new disk.

Pressure Rating of Holder

The design pressure of the UR-2 holder is 1,000 psi / 68.95 Bar. This far exceeds the maximum burst pressure of the SKR-U™ rupture disk.

Codes & Standards

The SKR-U™ & UR-2 are manufactured in conformance with the following international codes and standards:
ASME Section III & VIII (UD stamped)
ISO 6718
BS2915
TUV AD Merkblatt A1
SVTI
Stoomwezen

Address, International logo, ISO & UD logos, printed in the USA, 9.2000
Products, specifications and all data in this literature are subject to change without notice. Questions regarding product selection and specifications for specific applications should be directed to BS&B Safety Systems, Inc. or BS&B Safety Systems Ltd.