Marston NT/NR conventional discs are simple forward acting discs. They are manufactured from thin, precise foils, usually metallic, chosen to satisfy the individual process requirements. Since NT/NR discs generally fragment upon bursting, they are not recommended for the protection of Safety Relief Valves.
When subjected to vacuum conditions, many NT/NR discs will require a vacuum support.
These discs are suitable for all relieving phases. Operating ratios are dependent on materials, pressures, and temperatures. The Marston NT/NR disc type is generally suitable for operating ratios of up to 70% of minimum bursting pressure. However, it is possible, particularly at higher pressures, that the design may be capable of 90% operating ratios.
Operating Ratio: Up to 70% (typical)
Vacuum Duty: Generally Requires Support
Pressure Cycling Duties: Satisfactory
Leak Tightness (To Vent): <1 x 10-6 mbar.l.sec-1
Leak Tightness (To Atmosphere): <1 x 10-5 mbar.l.sec-1
KR Value: N/A
Marston is fully committed to an ongoing Total Quality Improvement programme. This was recognised with Marston audited and approved to design and manufacture bursting discs with its Quality Control procedure registered to the highest standard required by BS EN ISO 9001 Certification.
Quality is an integral part of all processes to provide customer satisfaction and confidence.
NT/NR bursting discs are manufactured and tested in accordance with the requirements of the relevant standard, including BS 2915, AD Merkblatt A1, ISPE SL, ASME VIII, ISO 6719, and EN ISO 4126.
All of the Marston standard disc designs have been approved for use in accordance with the requirements of the P.E.D., 97/23/EC.
NT/NR bursting discs can be manufactured from all commonly used disc materials, including Tantalum, Nickel alloys, and Stainless Steel. Fluorocarbon lining provides an excellent protection for corrosive duties.
Changes in temperature affect all bursting disc materials. Typically, as the temperature rises, the material strength reduces and the bursting pressure falls.