Continous and intermittent blowdown

Question 1

The type of blowdown system used on a boiler is usually a
function of
a) the type of internal water treatment used
b) the type of external water treatment used
c) the temperature at which the boiler operates
d) how long the boiler operates each day
e) water supply temperatures

Answer 1

b) the type of external water treatment used

Question 2

An external treatment method which minimizes blowdown is

a) sodium zeolite softening
b) deaeration
c) coagulators
d) demineralization
e) sludge conditioning

Answer 2

d) demineralization

Question 3

Blowdown guidelines can be found in

a) ASME Section VII
b) ASME Section VIII
c) CSA B51
d) CSA B52
e) applicable provincial Acts and Regulations

Answer 3

a) ASME Section VII

Question 4

A steam boiler is blown down in order to
a) clean the soot and carbon out of the firebox and tubes
b) lower the operating water level in the boiler
c) discharge sediment and scale forming matter from the boiler
d) test the rated relieving capacity of the safety valves fitted
to the boiler
e) locate the steam level

Answer 4

c) discharge sediment and scale forming matter from the boiler

Question 5

The continuous boiler water blowdown is used

a) in place of the main blowdown
b) in addition to the main blowdown
c) to adjust the drum water level
d) to introduce chemicals to the boiler
e) to control the bottom blowdown

Answer 5

b) in addition to the main blowdown

Question 6

If dissolved solids are not removed from boiler water the
result may be
a) overheating of convection zone tubes
b) foaming and carry-over
c) overheating of radiant zone tubes
d) steam which will be more saturated with latent heat
e) purer steam leaving the steam drum

Answer 6

b) foaming and carry-over

Question 7

Boiler water having the highest Total Dissolved Solids (TDS)
content is found
a) at the bottom of the mud drum
b) at the bottom of the steam drum
c) at the top of the steam drum
d) in the waterwall tubes
e) just below the waterline of the steam drum

Answer 7

e) just below the waterline of the steam drum

Question 8

A "rule of thumb" rate of continuous blowdown is
approximately
a) 10% of steaming rate
b) 5% of steaming rate
c) 15% of steaming rate
d) 1% of steaming rate
e) 3% of steaming rate

Answer 8

d) 1% of steaming rate

Question 9

According to the CSA B-51 code a blow-off tank is necessary to

a) prevent high temperature and pressure in the sewer
b) prevent blowing off too quickly
c) remove sludge from blow-off water
d) prevent overflowing the sewer
e) reduce the boiler water velocity

Answer 9

a) prevent high temperature and pressure in the sewer

Question 10

According to the Alberta Boilers Act Regulations, what fitting
is needed between the blow-off valve and the boiler if two boilers
use the same blow-off tank?
a) a non-return valve
b) a steam trap
c) a steam separator
d) an expansion joint
e) a check valve

Answer 10

e) a check valve

Question 11

A blow off tank is used to

a) lower the dissolved solids in the water
b) lower the pH of the water
c) prevent damage to the sewer
d) keep the condensate hot
e) to prevent sludge from entering the boiler

Answer 11

c) prevent damage to the sewer

Question 12

Boiler water having the greatest concentration of suspended
solids is found
a) just below the steam drum water line
b) in the bottom of the mud drum
c) at the bottom of the steam drum
d) in waterwall riser tubes
e) in convection zone downcomer tubes

Answer 12

b) in the bottom of the mud drum

Question 13

A blowdown tank will
a) have to be cleaned monthly to remove the collected sludge
b) not be classed as a pressure vessel since it is vented
c) lower the temperature and pressure of the incoming boiler
water
d) not have to have any specific capacity or volume
e) be allowed to accommodate only one boiler

Answer 13

c) lower the temperature and pressure of the incoming boiler

water

Question 14

Water leaving a blowdown tank and entering a sewer must not
exceed
a) 45 degrees C
b) 50 degrees C
c) 75 degrees C
d) 65 degrees C
e) 80 degrees C

Answer 14

d) 65 degrees C

Question 15

When two seatless valves are used for intermittent blowdown,
the operation sequence is
a) open the downstream valve first and close it last
b) open the upstream valve first and close it last
c) open the downstream valve first and close it first
d) open the upstream valve first and close it first
e) open the upstream valve last and close it last

Answer 15

a) open the downstream valve first and close it last

Question 16

The preferred arrangement of valves on a boiler blow-off line is
a) two quick-opening valves
b) a slow-opening valve closest to the boiler followed by a
quick-opening
c) a quick-opening valve closest to the boiler followed by a
slow-opening
d) one valve only (It must be a globe valve.)
e) a quick opening valve and a lift check valve

Answer 16

c) a quick-opening valve closest to the boiler followed by a

slow-opening

Question 17

A boiler blow down system is equipped with slow and fast opening

valves. The quick opening valve is placed
a) closest to the boiler and opened first
b) furthest from the boiler and opened first
c) closest to the boiler and opened last
d) furthest from the boiler and opened last
e) on the blow off tank

Answer 17

a) closest to the boiler and opened first

Question 18

The blow down system has two valves; they should be opened and
closed in the correct sequence to
a) carry out the blow down accurately
b) prevent excessive blow down
c) prevent a high level in the steam drum
d) prevent the boiler losing level
e) protect the valve closest to the boiler

Answer 18

e) protect the valve closest to the boiler

Question 19

The quick opening blow-off valve should be placed

a) at the second blowdown tank
b) second from the boiler
c) furthest from the boiler
d) between the boiler and the check valve
e) nearest to the boiler

Answer 19

e) nearest to the boiler