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Unformatted text preview: Name = _______________________________ HW #2 CHE 461 Due Mon Apr 12, 2010 Read: Chapter 8 in SEM2 pgs 185-203 (if you have not done so already)
Chapter 9 in SEM2 pgs 206-228
1.(5) SEM2 - Ex 8.2 pg. 203
(a) Find the transfer function for Fig E8.2 (parallel constant and first-order transfer
function) in standard form.
(b) Compare your answers in part (a) with the first eqn. in Ex 8.1 (a lead-lag
transfer function) to obtain an equation for each: Kc, τD and α. in terms of
K1, K2 and τ1.
(c) Substitute the specific desired values of 3, 2 and 0.1 for Kc, τD and α
respectively into your equations for (b) and calculate the values of K1, K2
and τ1 that result in the desired transfer function form in the first equation
of Ex 8.1.
2.(3) SEM2 - Ex 8.5 do both (a) and (b) pg. 204: Control "action" is asking if the
controller should have:
Reverse "Action" (where Kc > 0)
or Direct "Action" (where Kc < 0).
3.(5) SEM2 - Ex 9.1 both parts a=expression and b=4 questions.
4.(3) SEM2 - Ex 9.2(part a only) pg. 228,229: Declare fail-close (F/C) or fail-open
(F/O) for the 5 valves.
5.(4) Control loop analysis problem on next page (show your work on that page) … Name = _______________________________
5.(4) The control system shown below is designed to maintain a desired internal pressure in the
tank shown ( Pgas = 60 psiG). Assume the pneumatic signals shown into and out of the controller
are in the range of 3-15 psig. For clarity here we use “psiG” for process gas pressure and “psig” for
pneumatic control system signals.
The direct-acting pressure transmitter, PT25, has an input range of 20 to 100 psiG for measured
values of Pgas and an output of 3 to 15 psig. The pneumatic controller, PC25, is a P controller.
Its bias value , p , is set at 9 psig for the desired set point (nominal steady state) of Pgas = 60 psiG.
(a) Determine the gain of the transmitter PT25: Km = (psig/psiG) If the pressure in the tank drops to 30 psiG, the valve (which is air-to-close, A-C) should be forced
to it’s “completely shut” condition by the controller.
(b) Determine the correct action of the controller and circle one choice:
(1) Reverse Action or (2) Direct Action (c) Calculate the required value for Kc for this specified behavior at low pressure. Kc = psig/psig Name = _______________________________ Figure E8.2 pg. 203 Physically realizable form of the PD transfer function
⎛ τ s +1 ⎞
from 8.1 for use in Exercise 8.2 Ga ( s ) = K c ⎜ D
⎝ ατ D s + 1 ⎠ Figure E8.5 pg. 204 Name = _______________________________
Figure E9.2 pg. 229 - do part (a) only where low T and low P in the flash vessel are the “safest”
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This note was uploaded on 04/17/2010 for the course CHE 213 taught by Professor Staff during the Winter '08 term at Oregon State.
- Winter '08