interoffice memorandum
to: TRainees - chemical plant design.
from: Flavio
subject: steam system - deaerator malfunction
date: 09/08/99 - assignment due august 16, 1999 at 9:05 on the classroom´s desk
cc: training program file
This is an individual assignment
In the early part of our course we will learn about different kinds of flow charts and diagrams. This exercise will help you understand the level of detail needed to address a given operational problem.
The situation is as follows: Big Jim, a Sugar Refinery Superintendent, has trouble with cavitation of the high-pressure boiler feedwater charge pump. The pump is fed from a boiler feedwater (BFW) tank-deaerator which collects condensate from the vapor lines, and makes-up for liquid losses via a soft-water feed which reaches the BFW in the tank via a four plate deaerator. Heating steam is injected to keep the BFW temperature on target. Non-condensible gases vent to the atmosphere.
The symptoms of the cavitation are as follows:
1. An operator working at the main boiler would open the boiler´s blow-down valve - about 10% of the total lime-softened feedwater is drained.
2. This draws increased water flow from the BFW tank. The flow of softwater increases.
3. Suddenly, the flow of softened water would increase exponentially. The level control valve would rapidly open. Yet, the level in the deaerator would slowly continue to fall until the pump lost suction and cavitated.
You are hereby requested to report: a) why is the boiler blow-down valve opened?, what happens if it remains closed, thus avoiding the described problem?; and, b) what is happening in the BFW tank-deaerator?. How would you fix it?:
For P2000 you can buy the set of field observations made by the engineer who solved the problem. For P500 you can buy the Input - Output Diagram , For P100 you can buy the Generic Block Flow Process Diagram, For P1500 the BFD, P2000 for the PFD, and P2500 for the relevant P&ID. Successful solution will earn you P5000 in addition to your grade. Remember, this is an individual assignment. The diagrams can be acquired on Wednesday, August 11.
Yours truly,
Flavio Marín Flores
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