Variable Orifice Valves

Improved Safety and Reliability of Flue Gas Systems with Variable Orifice Valves.

In today’s modern refineries, the need to achieve pressure control is available by the use of variable orifice valves in lieu of conventional orifice chambers. The disadvantage of fixed orifices is that pressure control and/or sound attenuation is achieved only at a constant flow rate. However, since refineries operating conditions are seldom uniform and therefore experience variable internal flow rates and pressure fluctuations, a variable orifice design is highly advantageous to accomplish optimum results.

variable orifice valve rendering
variable-orifice-valve
variable orifice valve diagram
TapcoEnpro’s Approach
  • Provide a valve system to replace the orifice chamber that provides reliability to the flue gas system regardless of the process flowing conditions.
  • Provide a valve system to increase safety to the overall operability of the FCCU
  • Provide a flue gas valve system to control the velocities to eliminate sonic velocities which is a major cause of equipment failure and erosion issues
  • Provide a valve that will control the flue gas pressure reduction process in all flowing process conditions to maintain constant Delta P across the equipment
Three Valve System (DDFG plus 2 VOV)
Inlet Pressure, psig 30 30 30 30 35 35 35 35 40 40 40 40
Temperature ºF 1450 1400 1350 1300 1450 1400 1350 1300 1450 1400 1350 1300
Flowing Velocity, fps 1600 1579 1558 1536 1690 1667 1645 1622 1768 1745 1721 1697
Sonic Velocity, fps 2056 2029 2001 1974 2056 2029 2001 1974 2056 2029 2001 1974
1st DP, psi 13.162 13.162 13.162 13.162 15.582 15.582 15.582 15.582 18.619 18.619 18.619 18.619
2nd DP, psi 9.286 9.286 9.286 9.286 10.796 10.796 10.796 10.796 12.281 12.281 12.281 12.281
3rd DP, psi 7.552 7.552 7.552 7.552 7.352 7.352 7.352 7.352 8.1 8.1 8.1 8.1
variable-orifice-valve-diagram-3

The variable orifice valve will adjust it’s flapper (disc) to close more so that the flow through the outer fixed orifice plate holes will remain constant. The delta p through the outer fixed holes will remain constant therefore the velocities through these holes will remain below sonic conditions