mkm0023's version from 2015-12-09 05:14

Ch 9

Question Answer
Spring Relief is?Adjustable spring tension offsets the inlet pressure
Conventional Spring ReliefValve opens based on P drop across valve seat

Flow proportional to differential pressure, depends on back pressure
Balances Bellows Spring ReliefBellows on the backside of the valve seat ensure that the pressure on that side is always atmospheric
Rupture disks (6 things)1. rupture at specified relief set pressure
2. calibrated sheet of metal
3. remain open after relief
4. flexing-premature fail
5. low cost
6. larger than spring operated
what does a scrubber do?treat toxic exit vapors before venting

Ch 10

Design of relief valves: overpressure, viscosity, and backpressure correction factors

Question Answer
backpressure correction term?Kb, accounts for Discharge at other maximum pressures
The viscosity correction Kv corrects for ?additional frictional losses resulting from flow of high-viscosity material through the valve
Kv - The required relief vent area becomes larger as the viscosity of the liquid? increases
How is the effect of discharge pressure compared to set pressure in the overpressure correction Kp?discharge pressure greater than the set pressure
As the specified overpressure becomes smaller, the correction value decreases, resulting in?larger relief area
Overpressures less than what percent should be avoided?10%
Liquid flow through spring-type reliefs is approximated as?flow through an orifice
For most vapor discharges through spring reliefs the flow is?critical
For liquid reliefs through rupture discs without significant lengths of downstream piping the flow is represented by?flow through a sharp-edged orifice
no corrections are suggested (like for spring-type)
Vapor flow through rupture discs are described similarly to?liquid flow but with the addition of correction factors
Calculation methods for the pilot-operated reliefs are similar to?those used for spring-operated reliefs
What happens to a rupture disc relief valve after the disc has ruptured?The valve does not close again, which may result in the discharge of all the process
Reliefs for fires external to process vessels; how are they sized?Sized based on the constant heat input rate, heat of vaporization of the liquid, volume of the vessel, etc.
Two-phase flow during fire relief can be prevented by providing?a suitable vapor space above the liquid in the vessel
The relationships for computing the heat added to a vessel are dependent on?the area of heat absorption
What is required in the process when installing a rupture disc?Material can get out, air in after rupture
Pieces can dislodge
Must be replaced
Need pressure gauge if put in before spring relief