API 2015: Requirements for Safe Entry and Cleaning of Petroleum Storage Tanks

Question 1

What type of information does this standard provide? To what types of tanks does it apply? (API 2015-18, Section 1.1)

Answer 1

This standard is applicable to stationary atmospheric and low-pressure (up to and including 15 psig) aboveground petroleum storage tanks used in all sectors of the petroleum and petrochemical industry, including: 
a)	crude oil and gas production, 
b)	refining, 
c)	petrochemicals, 
d)	pipelines and terminals, 
e)	bulk storage, 
f)	ethanol facilities. 
This standard provides requirements for safely planning, coordinating, and conducting tank entry and cleaning operations, from removal from service through return to service.

Question 2

What is “bonding”? (API 2015-18, Section 3.5)

Answer 2

The joining of metal parts to form an electrically conductive path that ensures electrical continuity and has the capacity to safely conduct any current likely to be generated.

Question 3

What is a “confined space?” (API 2015-18, Section 3.8, 3.8.3)

Answer 3

Confined Space: Any tank or space that meets all three of the following requirements:

a) is large enough and so configured that an employee can bodily enter and perform assigned work, and
b) has limited or restricted means for entry or exit NOTE Examples are tanks and vessels, storage bins, hoppers, and vaults that are spaces that may have limited means of entry or exit.
c) is not designed for or meant to be continuously occupied by employees.

Question 4

What is a “permit-required confined space”? (API 2015-18, Section 3.8, 3.8.3)

Answer 4

Permit-required Confined Space: A confined space that has all three of the confined space requirements and also has one or more of the following five characteristics.

a) Contains or has the potential to contain a hazardous atmosphere.
b) Contains a material with the potential to engulf an entrant.
c) Has an internal configuration such that an entrant could become trapped or asphyxiated by inwardly converging walls or by bottoms that slope downward, tapering to smaller cross-sections.
d) Contains any other recognized serious safety or health hazard.
e) Has a floating roof not properly prepared and secured in accordance with this standard. NOTE A tank’s floating roof not properly prepared and secured in accordance with this standard (liquid and gas free pontoons and/or compartments, open roof drain, and supports/restraints for vertical, horizontal, and rotational movement) is considered a permit required confined space, even if the tank is otherwise considered a non-confined space.

Question 5

Should a situation develop that is more hazardous than allowed by the confined space entry permit, what shall entrants do? (API 2015-18, Section 7.2.1)

Answer 5

Work shall stop and all entrants shall immediately vacate the tank until a qualified person has determined the cause of the change, conditions are evaluated and corrected, and the entry permit is reissued.

Question 6

What shall entrants require during entry into a confined space? (API 2015-18, Section 6.3.5.1)

Answer 6

Entry supervisors shall require that a qualified person test and monitor the atmosphere inside the tank after vapor and gas freeing and degassing and during ventilation to ensure that oxygen levels are satisfactory and flammable and toxic vapors are not present above acceptable or permissible levels.

Question 7

Must an entry permit be issued for a worker to enter an inert atmosphere for test purposes? (API 2015-18, Section 10.1.2)

Answer 7

Entry into tanks for the initial assessment of atmospheric and physical conditions shall be considered as permit required confined space entry until the results and evaluation of tank atmospheric testing demonstrate otherwise.

Question 8

What are the four requirements for personal protective equipment for workers entering a tank to clean it? (API 2015-18, Section 8.1.1)

Answer 8

1) potential hazards
2) atmospheric exposure
3) tank conditions
4) task, operation, or activity to be performed

Question 9

What three types of atmospheric tests (measurements) must be conducted before a tank is entered? In what order should these tests be performed? (API 2015-18, Section 6.3.1, 7.1.2)

Answer 9

1) oxygen content
2) flammable vapors
3) toxic exposures

Question 10

When vapor freeing (purging) a tank, where should measurements (tests) of vapor levels around the exterior of the tank be conducted? (API 2015-18, Section 6.3.4)

Answer 10

Tests shall be performed by a qualified person in the areas around the tank where vapors could collect.

Question 11

Prior to permitting vertical entry into a tank, how should the internal atmosphere be tested to assure that flammable and toxic vapors have not stratified in the tank? (API 2015-18, Section 6.3.5.5)

Answer 11

Prior to permitting vertical entry into a tank (entry from the top of the tank), a qualified person shall test the internal atmosphere at 4 ft (1.2 m) verticals intervals (from top to bottom) to ensure that flammable and toxic vapors have not stratified within the tank. This testing shall be done without entry, if possible.

Question 12

How long should the ventilation system be shut down before testing the interior of a tank that has been mechanically ventilated? (API 2015-18, Section 6.3.5.3)

Answer 12

Entry supervisors shall require that vapor and gas freeing, degassing, and ventilating equipment is shut down for at least 15 minutes prior to testing inside the tank (based on industry experience for 150 ft diameter tanks) to allow the atmosphere inside the tank to reach equilibrium conditions. Entry supervisors shall determine the time required for the atmosphere in larger size tanks to stabilize.

Question 13

What should a worker do if clothing becomes contaminated with tank sludge that contains toxic substances? (API 2015-18, Section 7.4.3.7)

Answer 13

Employers shall establish and implement procedures for decontamination and disposal of contaminated clothing and materials and provide workers with appropriate facilities for washing and changing clothes.

Question 14

What should be the level of flammable vapors in a tank where hot work is being done? (API 2015-18, Section 11.2.3.1)

Answer 14

During hot work, entry supervisors shall ensure that the flammable vapor-in-air atmosphere in the tank is not in excess of 0 % of the lower explosive (flammable) limit.

Question 15

Gasoline vapors are heavier than air. Because of this, how can gasoline vapors flow? How far can they travel? (API 2015-18, Section A.1.3.2.2)

Answer 15

They will flow from tanks, travel along the ground, and settle in low places. Flammable liquid vapors can travel considerable distances, reach remote ignition sources, and ignite. When removing covers from tanks that are rich with vapors, the vapors will pour from the manholes into the open air.

Question 16

Which two elements of the fire triangle are desirable to eliminate for safe work inside a tank? (API 2015-18, Section A.1.3.2.2, A.1.3.2.3)

Answer 16

Eliminating hydrocarbon liquids, vapors, and flammable gases (fuel)
Eliminating ignition sources

Question 17

How can flammable and toxic vapors be present in a tank, even after it has been thoroughly purged? (API 2015-18, Section A.1.5.2)

Answer 17

a) After a tank has been emptied and freed of vapor, flammable vapors may be emitted from any remaining product, sludge, or residue.
b) Flammable vapors may result from the inadvertent entry of liquid or vapor from outside sources, including, but not limited to, open connecting lines, leaks, and spills in the vicinity of the tank or vapors emitted from nearby tanks that are being filled with flammable liquids.
c) Flammable vapors may develop within a supposedly empty and clean tank from sources that were overlooked. The most common sources include, but are not limited to, sludge, scale, hollow roof supports, unsealed sections of foam chambers, pontoons, heating coils, leaking bottoms, sumps, columns, drain hoses, internal wooden structures, flotation devices, and other absorbent materials.
d) Exposure to the sun, use of heat tracing, steam or chemical cleaning, or hot work may heat sludge, residue, and rust to temperatures above ambient, thereby releasing vapors. Combustible liquids may also be heated to temperatures above their flash points, creating flammable vapors.
e) Flammable vapors may remain in areas of the tank due to stratification or channeling.
f) Flammable vapors may result from chemicals used to clean the tank and from solvents used in paints, coatings, and tank lining materials.
g) Flammable deposits including, but not limited to, hydrocarbon sludge, waxy deposits, residue, and oil-saturated rust and scale, may form on the underside of the tank roof, on walls, supports, and rafters, or on tank appurtenances. These deposits may be ignited by flames or heat that result from cutting, grinding, abrasive blasting, or welding operations on top of the roof, on the outside of the tank walls, or inside the tank. Whenever possible, such deposits should be removed and the area cleaned where work is to be done. If not removed, these deposits should be wetted down and kept wet in order to dissipate any heat buildup while hot work is being performed.

Question 18

To what two hazards might a person entering an oxygen-deficient atmosphere be exposed? (API 2015-18, Section A.1.2.4)

Answer 18

1) loss of reasoning ability

2) unconsciousness

Question 19

When calibrating an oxygen meter, to what level shall a qualified person adjust the meter in fresh air? (API 2015-18, Section E.2.3)

Answer 19

21%

Question 20

What is the reading on an oxygen analyzer that indicates the oxygen content is below the breathing range (oxygen deficient) and respiratory equipment must be worn? (API 2015-18, Section A.1.2.4)

Answer 20

19.5%

Question 21

What is the reading on an oxygen analyzer that indicates the oxygen content is so low that entry must not occur, even with respiratory equipment? (API 2015-18, Section A.1.2.4)

Answer 21

16%

Question 22

What percent oxygen constitutes an oxygen enriched atmosphere? (API 2015-18, Section 7.2.3.1)

Answer 22

23.5%

Question 23

What are four ways that toxic substances can enter the body? (API 2015-18, Section A.1.6.2)

Answer 23

1) inhalation
2) ingestion
3) skin and eye absorption
4) injection

Question 24

What compounds in petroleum hydrocarbons have been determined to have the potential to cause cancer? (API 2015-18, Section 7.4.5)

Answer 24

Aromatic compounds such as benzene

Question 25

What is its color of hydrogen sulfide? (API 2015-18, Section A.1.7)

Answer 25

Colorless

Question 26

What is its odor of hydrogen sulfide? (API 2015-18, Section A.1.7)

Answer 26

Foul, rotten-egg odor

Question 27

Is hydrogen sulfide heavier or lighter than air? (API 2015-18, Section A.1.7)

Answer 27

Heavier

Question 28

What tends to happen to hydrogen sulfide during the refining process? (API 2015-18, Section A.1.7)

Answer 28

It is eliminated

Question 29

At low concentrations, can hydrogen sulfide be detected by smell? (API 2015-18, Section A.1.7)

Answer 29

No

Question 30

At high concentrations, can hydrogen sulfide be detected by smell? Why or why not? (API 2015-18, Section A.1.7)

Answer 30

No, instantaneous exposure to slightly higher concentrations of the gas immediately paralyzes the sense of smell

Question 31

The atmosphere in any tank that contains sour crude stocks or sulfur-containing products should be considered __________.

Answer 31

Toxic

Question 32

By what routes of exposure can toxic lead alkyds enter the body? (API 2015-18, Section A.1.8.3)

Answer 32

All four routes (inhalation, ingestion, skin and eye absorption, and injection)

Question 33

When the potential exists for exposure to toxic and harmful dusts, the need for appropriate precautionary measures to mitigate and control exposure, and requirements for respiratory protection and protective clothing for entrants is determined and implemented by whom? (API 2015-18, Section A.1.9)

Answer 33

Engineering and an industrial hygienist

Question 34

Under what circumstances do most organic lead poisonings occur? (API 2015-18, Section A.1.8.3)

Answer 34

The greatest potential for organic lead poisonings during tank cleaning operations occurs when entrants inside a leaded-gasoline storage tank do not wear appropriate air-supplied or self-contained breathing equipment.

Question 35

What are the four steps that must be taken in order to properly isolate tanks or lines equipped with cathodic protection? (API 2015-18, Section 5.3.4)

Answer 35

1) Turn off the cathodic protection system.
2) Install a bond wire from the tank to the lines.
3) Disconnect and remove the valve or line.
4) Remove the bond wire only after the valve or line is disconnected.

Question 36

What makes a venturi-type eductor different from other types of blowers or educators? (API 2015-18, Section B.3.1.1)

Answer 36

It has no moving parts

Question 37

Vapors and gases released to the atmosphere shall be discharged at what height? (API 2015-18, Section B.2.2.1)

Answer 37

Regardless of whether an eductor is used to evacuate vapors and gases or an air blower is used to introduce fresh air, discharge the vapors to the atmosphere at a high elevation, preferably from or near the top of the tank roof and at least 3.7 m (12 ft) above the ground level, or discharge to a degassing system, where required.

Question 38

What are three factors to consider in the selection of an effective vapor freeing method for a tank? (API 2015-18, Section 5.5.3)

Answer 38

1) the nature of the vapors or gases involved;
2) degassing and emission control requirements;
3) the potential hazards of the vapor or gas; and
4) the area and the type, size, construction, and location of the tank

Question 39

What are four methods that may be used to vapor free a tank? (API 2015-18, Section 5.5.2)

Answer 39

1) vapor and gas freeing by the use of mechanical or natural ventilation;
2) displacing vapors and gas by purging the tank with inert gas, flue gas, or steam;
3) displacing the vapors or gas with water or fuel oil; and
4) degassing (where required) by the use of thermal oxidation, vapor recovery, carbon absorption, or other approved methods.

Question 40

Why is it important to avoid release of vapor near ground level during ventilation and cleaning operations? (API 2015-18, Section B.1.2)

Answer 40

Since some hydrocarbon vapors are heavier than air, discharging the vapors at the top of the tank or at a high elevation provides for quicker dispersion in the case where degassing is not required or used. This precaution prevents flammable vapor or gas from settling at ground level and flowing to an ignition source, being ignited, and flashing back into the tank.

Question 41

Requirements for electrical equipment to be used in and around tanks that have contained flammable liquids are contained in which publication? (API 2015-18, Section A.1.4.5)

Answer 41

NFPA 70 for Class I, Division 1, Group D, or Zone 1

Question 42

What are some components of external floating roof tanks? (API 2015-18, Section A.3.2)

Answer 42

a) decks,
b) pontoons,
c) shunts,
d) seals,
e) legs,
f) penetrations.

Question 43

When preparing a tank for entry, what is the next step to take after emptying the tank? (API 2015-18, Section C.2.4)

Answer 43

After all available nonrecoverable product, sludge, and residue have been removed from the tank through fixed connections, the remaining material may be removed from the outside of the tank through an open manhole, doorway, or door sheet opening without requiring entry. The door sheet may be opened using a water-cutting technique that minimizes heat, thus reducing the potential for ignition. The tank should be vapor-freed (degassed) and ventilated during these operations. Remove as much sludge and residue as possible from the tank prior to permitting workers to perform a tank entry. This may be accomplished using suction pumps, hose streams, solvent flooding and skimming, vacuum, and robotic mechanical cleaning devices, without requiring workers to enter the tank.

Question 44

What information must be recorded on the entry permit? Where must this permit be posted? (API 2015-18, Section 10.2)

Answer 44

1) Identification and specific location of the permit required confined space to be entered.
2) Purpose of the entry, work to be performed, issue date, time of issue, and the authorized duration of the entry permit.
3) Potential hazards of the permit required confined space to be entered and acceptable entry conditions.
4) Measures used to isolate the permit required and non-permit required confined spaces and to eliminate or control hazards before and during entry (and reentry, upon reissue of the permit) including, but not limited to, the following:
a) lockout and tag out;
b) blinding and blanking or blocking and bleeding; or
c) purging, vapor and gas freeing, inerting, flushing, degassing, and ventilating.
d) Conditions that shall require the permit to be canceled, work to stop, and entrants to leave the tank, including, but not limited to, the following:
e) approaching electrical storms, tornadoes, or other bad weather conditions;
f) emergencies occurring either inside or outside the tank;
g) flammable liquids receipt into a nearby tank with the potential to emit vapors into the tank cleaning work area;
h) hydrocarbon or toxic atmospheres within the tank at levels above those permitted for safe entry;
i) entry by an unauthorized person;
j) standing water, ice, or product on a floating roof deck or inside pontoons;
k) changed condition of a floating roof that could indicate instability not addressed by the method of securing the floating roof including:
l) bowing or buckling of roof legs;
m) missing or damaged roof leg pins or cables;
n) sagging of the floating roof deck;
o) removal of perimeter seals without securing the floating roof against translational;
p) broken or missing anti-rotation guide or pole; and
q) distorted or broken floating roof restraints.
5) Times and results of the atmospheric testing (initial, continuous and/or periodic) conducted, accompanied by the names or initials of the qualified persons conducting the testing.
6) Names of the designated attendants and entrants (and workers assigned to work around the outside of the tank) and the means of communication to be used by entrants and attendants to maintain contact with each other during the entry.
7) Designated emergency personnel available and the means of communication to use and the numbers to call for summoning such services, if designated qualified rescue personnel are not available at the work site.
8) Equipment to be used, including:
a) personal protective clothing and equipment and respiratory protection;
b) atmospheric testing equipment;
c) alarms and fire protection equipment;
d) vapor and gas freeing, degassing, ventilation, and air supply equipment;
e) tank cleaning materials and equipment;
f) product, sludge, and residue removal and disposal equipment;
g) emergency rescue equipment specific to the tank and the potential hazards;
h) non-destructive testing equipment;
i) vacuum trucks;
j) abrasive blasting and liner application equipment;
k) welding and cutting machines; and
l) generators.
9) Any other permits, including hot work and safe (cold) work permits or work authorizations issued to perform work in or around the tank during entry.
10) Other information to include on the permit in order to ensure entrant safety includes the following:
a) product information such as SDSs;
b) planned receipts into a nearby tank;
c) activities elsewhere in the facility which could affect the entry; and
d) a lockout/tagout (isolation) listing including names of persons controlling locks.
11) Required warnings, including, but not limited to, posted permits, signs and notices, barriers, and lockout/ tagout tags.
12) The means of protecting tank openings with temporary barriers or covers to prevent entrants from falling into openings and to keep foreign objects and unauthorized persons from entering the tank, both during operations and when operations are not in progress.
13) The individual, by name, currently designated to be the entry supervisor, with a space for the signature or initials of the entry supervisor who originally authorized entry and the entry supervisor(s) who may subsequently authorize reentry, if the permit was reissued.

Question 45

Where must the confined space entry permit be posted? (API 2015-18, Section 10.2)

Answer 45

A copy of the written permit shall be posted at the tank entry point or available at the tank cleaning work site.

Question 46

What are the three elements of the fire triangle, which are necessary for fire or explosion to occur? (API 2015-18, Section A.1.3.2)

Answer 46

1) Oxygen,
2) Fuel, and
3) Source of ignition

Question 47

Why is the elimination of ignition sources difficult? (API 2015-18, Section A.1.3.2.3)

Answer 47

Eliminating ignition sources may be difficult and less certain because ignition sources are sometimes difficult to recognize or may be remote from the tank cleaning area. Unlike oxygen, vapors, and gases, measuring and testing instruments cannot detect ignition sources.

Question 48

Why is it a mistake to believe that a tank where the gasoline vapor/air mixture is in the rich range is safe to enter? (API 2015-18, Section A.1.5.1)

Answer 48

The atmosphere in a tank that has just been emptied and opened is usually above the explosive (flammable) limit and is too rich to burn. However, as vapors are removed and the tank is ventilated, the original vapor-rich atmosphere will be diluted with air and the mixture will enter the explosive (flammable) range.

Question 49

What type of toxic effects are produced by irritants? (API 2015-18, Section A.1.6.2.1)

Answer 49

Irritants are substances that cause minor or transient (but possibly painful) injuries that heal without scars and produce no known aftereffects. Many petroleum hydrocarbons and polar solvents are irritants.

Question 50

What type of toxic effects are produced by “corrosives?” (API 2015-18, Section A.1.6.2.2)

Answer 50

Corrosives are substances that destroy tissue and leave permanent scars. Examples of corrosives include, but are not limited to, hydrofluoric acid, sulfuric acid, and caustics.

Question 51

What type of toxic effects are produced by “chronically toxic substances?” (API 2015-18, Section A.1.6.2.4)

Answer 51

Chronically toxic substances produce physiological impairment with long latency (for example, cancer), with gradual progression (for example, pulmonary obstructive disease), or that may produce harmful reproductive effects.

Question 52

A vacuum truck is to be used to remove sludge from a storage tank. (API 2015-18, Section A.1.4.3) Where should the truck be located?

Answer 52

Downwind of the tank

Question 53

A vacuum truck is to be used to remove sludge from a storage tank. (API 2015-18, Section A.1.4.3) Where should vacuum truck tank exhaust vapors be discharged?

Answer 53

Downwind of the truck

Question 54

A vacuum truck is to be used to remove sludge from a storage tank. (API 2015-18, Section A.1.4.3) What should be done to the suction and discharge hoses?

Answer 54

Electrically bond the vacuum truck suction and discharge hoses to both the truck and the tank.

Question 55

What type of lights should be avoided, if possible, when there is a potential of flammable vapors exceeding 10 percent of the lower flammable limit? (API 2015-18, Section A.1.4.5)

Answer 55

Artificial lighting (except approved low-voltage lighting and dry-cell flashlights) used in or around tanks during vapor and gas freeing, degassing, inspection, testing, or other activities can create a hazard where there is a potential for flammable vapors to exceed 10 percent of the LEL.

Question 56

What type of ventilation must be provided when entrants are working inside tanks? (API 2015-18, Section 10.5.1.2)

Answer 56

Forced ventilation