Automation - Instrumentation (Set 1) | Multiple Choice Questions

1. Why do most temperature control valves in diesel engine closed freshwater cooling systems vary the flow of jacket water through the cooler instead of through the engine?

Changing the rate of flow in the jackets could cause localized hot spots.

Emergency hand control would not be possible if water flow through the jackets were controlled.

Excessive cooling would take place in the heat exchangers at high loads.

Excessive cavitation erosion would take place in the coolers.

2. Which of the following statements is true concerning pressure limit switches and pressostats installed on auxiliary boilers?

They are bimetallic elements sensing temperature differentials corresponding to pressure changes.

They consist of a bellows assembly, linked with a snap action switch, through a pressure adjusting mechanism.

They automatically relieve excessive steam pressure by acting as a pilot to the safety valve.

They automatically restart the burner sequence via the high water level signal

3. If the combustion control system of an automatically fired auxiliary boiler fails to relight the burner after a normal shutdown, you should check for a/an _____________.

low steam pressure

high voltage on the ignition electrode

open air damper

faulty photocell detector

4. A sudden flame failure in an operating auxiliary boiler, equipped with an automatic combustion control system and burning light fuel, could be attributed to a ____________.

dead or malfunctioning step up transformer

faulty ignition cable connector

loose connection on the photocell

rapid fuel viscosity increase

5. In an automatically fired auxiliary boiler, restarting from the normal shutdown cycle in response to steam demand, is initiated by a/an .

modulating pressostat, sensing both steam pressure and temperature

pyrostat measuring decreased steam temperature

pressostat measuring only the steam pressure

electrode sensing water level

6. In a diesel engine cooling system, the high temperature alarm contact maker will be activated on excessively highwater discharge temperature from the .

raw water pump discharge

expansion tank outlet

cooling water heat exchanger outlet

engine jacket water outlet

7. Ignition failure in an automatically controlled auxiliary boiler can be caused by ______________.

carbon deposits on the electrode

excessive fuel oil temperature

excessive return oil pressure

brickwork failure

8. The flame safeguard controls of a large automatically fired auxiliary boiler, may consist of a ______________.

stack switch

pyrostat

photoelectric cell

thermistor

9. Ignition failure in an automatically controlled auxiliary boiler could be caused by ______________.

carbon deposits on the flame scanner

high fuel oil temperature

low fuel oil viscosity

high steam pressure

10. Ignition failure in an auxiliary boiler can be caused by ____________.

carbon deposits on electrodes

a jammed open oil solenoid

excess fuel pressure at the nozzle

an excessively long purge cycle