Page 229 - Valve Selection Handbook

216 Valve Selection Handbook

Maximum marked burst pressure. The marked burst pressure at the top
end of the manufacturing range.
Minimum marked burst pressure. The marked burst pressure at the bot-
tom end of the manufacturing range.
1
Burst tolerance: The maximum variation in burst pressure from the
marked burst pressure.
Manufacturing range. 2 A range of pressures within which the average
burst pressure of test discs must fall to be acceptable for a particular
application, as agreed between the customer and manufacturer.
3
Performance tolerance. A range of burst pressures comprising manu-
facturing range and burst tolerance at the specified temperature.
Operating ratio. The ratio of the maximum operating pressure to a mini-
mum burst pressure
Damage ratio. The ratio of the burst pressure of the damaged rupture
disc to the burst pressure of the undamaged rupture disc.
Reversal ratio. The ratio of the burst pressure of the reversed installed
rupture disc to the burst pressure of the correctly installed rupture disc.
Lot. A quantity of rupture discs made as a single group of the same type,
size, and limits of burst pressure and coincident temperature that is man-
ufactured from material of the same identity and properties.

Deflagration. Burning that takes place at a flame speed below the veloci-
ty of sound in the medium.

Detonation. Propagation of a combustion zone at a velocity that is
greater than the speed of sound in the unreacted medium.

Explosion. The bursting or rupture of an enclosure or a container due to
the development of internal pressure from a deflagration.

Application of Rupture Discs

Rupture discs do not reclose after bursting. The decision to install rup-
ture discs may therefore have important economical consequences. How-

1
ASME Code (1992) Sect. VIII, Div. 1, UG 127 (a)(l)(a)
2
ASME Code (1992) Sect. VIII, Div. 1, UG 127 (a)(l)(a)
3
ISO Standard 6718 and European Draft Standards EN 1286-2 and 6