Page 295 - Valve Selection Handbook

Table A-2.2 Section III Requirements (Continued)

PRESSURE RELIEF DEVICE OPERATING REQUIREMENTS
ALLOWABLE VESSEL
OVERPRESSURE SET PRESSURE TOLERANCE
(ABOVE MAWP OR VESSEL SPECIFIED WITH RESPECT TO SET REQUIRED
APPLICATION DESIGN PRESSURE) PRESSURE SETTINGS PRESSURE SLOWDOWN
SECTION III
(Continued) Pressure Relief Valve Pressure Relief Valve
Same as safety valve above Same as safety valve
NB (NB-7525 b) (NB-7524)
NC (NC-7525.2)
ND Same as safety relief valve above (ND-7524.2)
NE (NC-7523.3)
(ND-7523.3)
Power Operated
±1% of set pressure
(NB-7532b1) Power Operated
(NC-7533b1) Same as safety valve
(NB-7532 b2)
Same as safety valve above (NC-7533 b2)
(ND-7533b1) (ND-7533 b2)
Rupture Disc
±2% of burst pressure for
pressures up to 40 psi
(NB-7611)
(NC-7612)
(ND-7612)
±5% of burst pressure for
pressures above 40 psi
(NC-7612)
(ND-7612)
1 psi = 6.89 kPa
Table A-2.3 Section IV Requirements
PRESSURE RELIEF DEVICE OPERATING RE(QUIREMENTS
ALLOWABLE VESSEL
OVERPRESSURE SET PRESSURE TOLERANCE
(ABOVE MAWP OR VESSEL SPECIFIED WITH RESPECT TO SET REQUIRED
APPLICATION DESIGN PRESSURE) PRESSURE SETTINGS PRESSURE BLOWDOWN
SECTION IV
Steam Boiler 5psi(HG-400.1e) <l5psi(HG-401.1a) ±2psi(HG-401.1k) 2-4psi(HG-401.1e)
Hot Water Boiler 10% for a single valve One valve at or below MAWP ±3 psi up to and including 60 psi None specified
1 0% above highest set valve for Additional valves up to 6 psi above ±5% for pressures above 60 psi
multiple valves MAWP for pressures to and (HG-401.1k)
including 60 psi and up to 5% for
pressures exceeding 60 psi
(HG-400.2a)
1 psi = 6.89 kPa