Tank Closure without Tears

Question 1

What are the three points of the basic fire triangle? (NEIWPCC, p. 2)

Question 2

How many points of the fire triangle are necessary to support combustion? (NEIWPCC,
p. 2)

Question 3

Movement of which of the following causes static electricity: liquids, air or solids?
(NEIWPCC, p. 3)

Question 4

What must be eliminated prior to the use of heavy equipment for handling the tank?
(NEIWPCC, p.3)

Question 5

If static-producing movement can not be eliminated, how can the contractor provide a “safe” discharge of static electricity? (NEIWPCC, p. 3)

Question 6

How can electrostatic ignition hazards be reduced when removing product or residue from
the tank? (NEIWPCC, p. 3-4)

Question 7

Why should plastic (PVC) pick-up tubes be avoided on the stripping lines of vacuum
trucks? (NEIWPCC, p. 4)

Question 8

Where should the vacuum truck be in relation to the tank when removing liquid or residues
from a tank? Where should exhaust hoses be situated relative to the tank? (NEIWPCC,
p. 5)

Question 9

How does purging work? Which point of the fire triangle is dealt with in purging the
potentially explosive atmosphere in a tank? (NEIWPCC, p. 5)

Question 10

What is the flammable range of vapor given off by most petroleum products? (NEIWPCC
pp. 5-6)

Question 11

Below the lower explosive level (LEL) the mixture of fuel and vapor in a tank is too lean to
support combustion. What is the LEL for petroleum products? (NEIWPCC, p. 6)

Question 12

What is the goal of purging? (NEIWPCC, p. 6)

Question 13

How does inerting work? Which point of the fire triangle is dealt with in “inerting” the
atmosphere of a tank? (NEIWPCC, p. 6)

Question 14

What is the goal of inerting a tank? (NEIWPCC, p. 6)

Question 15

Why is it especially important to control sources of ignition when purging an underground
tank with air? (NEIWPCC, p. 6)

Question 16

Which method of purging with air pumps fresh air into the tank and which one draws
vapors out of the tank? (NEIWPCC, pp. 6-7)

Question 17

When purging a tank, one should NOT use .
(NEIWPCC, p. 7)

Question 18

Once a tank has been purged, is there any need to continue monitoring it for flammable
vapors? (NEIWPCC, p. 7)

Question 19

When testing with a Combustible Gas Indicator (CGI), a reading of 100 percent LEL
would indicate that what percent of gasoline vapors were present? (NEIWPCC, p. 8)

Question 20

What substances can foul or “poison” a CGI probe? (NEIWPCC, pp. 8-9)

Question 21

When inerting, how can carbon dioxide be generated? (NEIWPCC, p. 9)

Answer 21

crushing and distributing dry ice

Question 22

When inerting a tank with dry ice, how many pounds of dry ice should be used for every
1,000 gallons of tank capacity? (NEIWPCC, p. 9)

Answer 22

15-20 pounds per 1,000
gallons of tank capacity

Question 23

What are two ways to reduce the concentration of oxygen in a tank to a level that is
insufficient to support combustion? (NEIWPCC, p. 9)

Answer 23

Dry ice and nitrogen

Question 24

What readings on an oxygen meter indicate a non-combustible atmosphere in tanks that
have contained most petroleum products? What readings should you target for a more
conservative safety rule of thumb? (NEIWPCC, p. 11)

Answer 24

1-10%

Question 25

What percent oxygen by volume indicates a safe range for breathing? (NEIWPCC, p. 11)

Answer 25

19.5-21%

Question 26

Should a single point of the fire triangle be the focus of efforts to avoid fire and explosion during tank closure? (NEIWPCC, p. 12)

Answer 26

First, sources of ignition were removed or controlled so product could be pumped from the tank.

Question 27

Can a combustible gas indicator be used to monitor a tank which is being inerted? Why or why not? (NEIWPCC, p. 13)

Answer 27

KEEP TESTING for the flammable concentration of vapors both in and around the tank until the tank has been cleaned on- site, or loaded for transport to be cleaned off-site!

Question 28

What is the definition of “flashpoint”? (NEIWPCC, p. 13)

Answer 28

the lowest temperature at which the liquid product gives off sufficient vapors to support combustion (in the presence of enough oxygen and an ignition source).

Question 29

Why is it necessary to check the atmosphere in the tank before cleaning it when the tank has already been purged or inerted? (NEIWPCC, p. 14

Answer 29

To check if there’s any more vapors

Question 30

Why should tanks be cleaned regardless of whether they are to be removed or closed in place? (NEIWPCC, p. 14)

Answer 30

Cleaning the tank will decrease the amount of vapor regeneration.

Question 31

What are the primary safety factors to consider when deciding whether to clean a tank onsite or off-site? (NEIWPCC, p. 14)

Answer 31

The primary safety considerations have to do with physical surroundings, air flow and population in the area.

Question 32

When closing an UST in-place, what is used to fill the tank? (NEIWPCC, p. 15) UR

Answer 32

Cement slurry and sand

Question 33

Where is the most dangerous position in relation to a tank if it should explode? (NEIWPCC, p. 16)

Answer 33

The ends of the tank

Question 34

What is the procedure for sealing corrosion holes in a tank prior to transport? (NEIWPCC, p. 16)

Answer 34

Plugs

Question 35

When transporting an UST removed from a site, how large should the vent hole be on the top of the tank? (NEIWPCC, p. 16)

Answer 35

1/8 inch

Question 36

What are the elements of a safe removal checklist? (NEIWPCC, p. 17)

Answer 36

• Make sure that the equipment available is appropriate for the tank pull. • Sand well out of the way and behind stable objects until the tank has been lifted onto the ground and blocked, or onto the transport truck and secured. Cables and chains can snap and fly out in any direction. • Tanks should not be dragged at any time. • If a tank explodes, the weakest points of steel tanks are the ends, so stay away from them.