Manufacturing Design Range (MDR) can be a confusing concept and is often the source of errors in the specification and re-ordering of rupture disks. Attention needs to be taken to fully understand MDR.
ASME UG-127(a)(1) defines MDR as “the range of pressure within which the marked burst pressure must fall to be acceptable for a particular requirement as agreed upon between the rupture disk manufacturer and the user or his agent”. The MDR simplifies the manufacturing and testing process and accordingly provides an economic benefit to the user. All rupture disk manufacturers publish their standard MDR for each disk style in either a table or as a percentage of the specified rupture pressure.
ZOOK’s own Simplifying the Selection, Sizing and Troubleshooting Rupture Disks webinar, best describes MDR in the common context of rupture disk selection and burst pressure specification:
It's important that the MDR be considered during the selection process to ensure that the stamped burst pressure is not greater than the MAWP of the pressure vessel.
Don’t re-order a rupture disk, solely based on the marked burst pressure on the disk tag. Always specify the original lot number when re-ordering replacement disks. This will guarantee the disk will be manufactured to the original specification.