api.620.2002

APPENDIX M-RECOMMENDED SCOPE OF THE MANUFACTURER'S REPORT

M.1 General want to have a record of these repairs or changes attached to
the manufacturer's report.
This appendix does not set down rigid rules for the prepa-
ration of the manufacturer's report. The extent ofthe informa- M.4 Tank Certification
tion contained in the report-with the accompanying
supplementary sketches, graphs of tests, and possibly special A certificate shall be supplied for each tank. This practice
items required by the purchaser, as shown on purchase is intended to simplify keeping the records of future inspec-
orders-cannot possibly be listed here (see 7.13). tion in separate files for convenience. When a group of tanks
is being constructed on one order and in one general location
M.2 Shop Stress Relief some specific form of reporting other than a manufacturer's
report may be preferred by both parties. It would seem desir-
When parts of the stmcture are shop assemblies, which are able that the details on each contract be settled when the pur-
stress relieved as called for in 5.25 and 6.18, the plans shall chase order is placed; if they are not covered in the proposal,
indicate this in the customary general notes. then they shall be given as information in the inquiry.

M.3 Field Repairs or Changes M.5 Tank Certificate Wording

When more than minor repairs or changes and/or additions The suggested format and wording for a certificate is as
are made to the structure in the field for any reason, it is follows:
assumed that both the manufacturer and the purchaser will

WE CERTIFY that the design, materials, constmction and workmanship on this low-pressure tank conforms to the
requirements ofAPI Std 620, Design and Constroction (4Large, Welded, Low-Pressure Storage Tanh.

Date,_ _ _ _ _ 20_ Signed _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ by _ _ _ _ _ __

I have inspected the tank described in this manufacturer's report dated , and state that to the best of my

knowledge, the manufacturer has constructed this tank in accordance with the applicable sections of API Std 620.

The tank was inspected and subjected to a test of Ibf/in.2 gauge.

Date,_ _ _ _ _ 20_ Signed _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ by _ _ _ _ __

M-1



APPENDIX N-INSTALLATION OF PRESSURE-RELIEVING DEVICES

N.1 General be fitted with an open drain to prevent water or other liquids
from lodging in the discharge side of the valves.
Pressure-relieving devices shall be installed so that they are
readily accessible for inspection and removable for repairs. N.4.2 Discharge pipes shall be supported so that no undue
The practices suggested in API RP 520, Part II, for the instal- stress is placed on the valve body. Open discharges shall be
lation of ASME approved safety relief valves shall generally placed and oriented so that the outflow is directed away from
apply, with due consideration given to the difference in pres- the tank and will not create a hazard over walkways, stair-
sure ranges. ways, or operating platfonns.

N.2 Location N.5 Security Against Damage

If the relieving devices for gases are not located on the The assemblies of relieving devices shall be secured
roof, they shall be installed on the piping connected to the against damage in service, the effects of stonns, or mishan-
vapor space, if any, as close to the tank as is practicable; if the dling. Access ladders and platfonns that meet plant safety
relieving devices are vented to atmosphere, they shall be at a rules are suggested.
sufficient height to prevent chance ignition (see API Std
2000). N.6 Vacuum-Relieving Devices

N.3 Size of Tank Opening A vacuum-relieving device, when used, shall be as direct
in inflow as possible with no pockets where moistllre can
The opening from the tank leading to the relieving device collect, and it shall have no piping except a weather hood
shall have a size at least as large as the inlet nominal pipe size ahead of the inlet. An adequate vacmUll-air inlet shall also
of the relieving device. be provided.

N.4 Discharge Pipes N.7 Stop Valves

N.4.1 When a discharge pipe is used on the outlet side of Stop valves, if used between the relieving devices and the
such relieving devices, its area shall be not less than the area tank to help service these devices, shall be locked or sealed
of the valve outlet, or if a single pipe provides for discharge open, and an authorized person shall be present if this condi-
from several relief devices, its area shall be not less than the tion is changed. If the tank is in use, the authorized person
aggregate area of the valve outlets. The discharge pipe shall shall remain there tmtil the locked or sealed-open position of
the affected relieving devices is restored.

N-1



APPENDIX O-SUGGESTED PRACTICE REGARDING INSTALLATION OF
LOW-PRESSURE STORAGE TANKS

0.1 Introduction 0.5 Drainage

The practices recommended in this appendix are intended All tanks in which water might accLUnulate lUlder the
for general guidance only. They are not essentially a part of hydrocarbon contents shall be provided with adequate drains
the construction mles for low-pressure storage tanks because that are suitably protected from freezing.
in most instances SOlUld engineering principles for safe and
efficient operation will dictate the proper procedure for each 0.6 Fireproofing
installation.
0.6.1 Although general fire prevention and fire protection
0.2 Marking measures are expected to be fully covered by other safety
codes, tanks constnlcted according to these niles, which may
When the owner or operator provides an additional plate to be subject to fire exposure resulting from any cause, shall
show the current operating pressure range in a tank, the plate have their supports suitably fireproofed.
shall be securely attached, preferably near the manufacturer's
nameplate (showing the markings required by these niles). 0.6.2 Special consideration shall be given to provisions for
Such markings shall not be covered by the additional plate. ample drainage facilities for accidental spills or leakage of
flammable contents from such tanks or adjacent piping and
0.3 Access other equipment if the contents may become ignited.

All openings and accessories for tanks constnlcted accord- 0.6.3 Subject to special considerations in isolated loca-
ing to this standard shall be installed so that any periodic tions, tanks in which flammable liquid products are stored at
inspections required can be readily made. temperatures well above their average boiling point shall be
suitably fireproofed or otherwise protected.
0.4 Corrosion

When a tank bottom rests directly on the grOlUld, a survey
shall be made to establish the need for cathodic protection.

0-1









































Q-16 API STANDARD 620

0.8.4.2 During water filling, the elevations of at least four Q.9 Testing the Outer Tank of a Double-
equidistant points at the bottom of the tank shell and on top of Wall Refrigerated Tank
the ringwall or slab shall be checked. Differential settlement,
or unii()rm settlement of substantial magnitude, requires an 0.9.1 GENERAL
immediate stop to water filling. Any further fLlling with water
will depend on an evaluation of the measured settlement. The tightness test shall be made before insulation is
installed. Where the pneumatic pressure described in Q.8.5
0.8.4.3 The tank shall be filled with water to the design acts against the outer tank, the testing requirements of Q.8.5
liquid level unless height is limited as noted in Q.8.1. will result in a check ofthe outer tank, and the procedure out-
lined in Q.9.2.1 through Q.9.2.5 may be omitted.
0.8.4.4 Atler the tank is filled with water and before the
pneumatic pressure is applied, anchorage, if provided, shall 0.9.2 TEST PROCEDURE
be tightened against the hold-down brackets.
0.9.2.1 The inner tank shall be opened to the atmosphere,
0.8.4.5 All welds in the shell, including the comer weld and a suiIlcient amount of water shall be added to the inner
between the shell and the bottom, shall be visually checked tank to balance the upward pressure against the inner tank
for tightness. bottom produced by the pneun1atic test of the outer tank; as
an alternative, the pressure between the inner and outer tanks
0.8.5 PNEUMATIC PRESSURE can be equalized.

0.8.5.1 An air pressure equal to 1.25 times the pressure for 0.9.2.2 Air pressure shall be applied to the space enclosed
which the vapor space is designed shall be applied to the by the outer tank equal to at least the design gas pressure but
not exceeding a pressure that would overstress either the
enclosed space above the water level. rn the case of a double- inner or outer tank.

wall tank with an open-top inner tank, where the air pressure 0.9.2.3 While the test pressure is being held, all welded
acts against the outer tank and the inner tank is thus not seams and connections in the outer shell and roof shall be
stressed by the air pressure, the inner tank may be emptied of thoroughly inspected with a solution (ilm unless they were
water belore the pneumatic pressure test begins. previously checked with a vacuum box.

0.8.5.2 The test pressure shall be held for 1 hour. 0.9.2.4 The air pressure shall be released.

0.8.5.3 The air pressure shall be reduced until the design 0.9.2.5 Pressure relief and vacuum relief valves shall be
pressure is reached. checked by applying the design gas pressure to the outer tank,
followed by evacuation of the outer space to the vacuum set-
0.8.5.4 Above the water level, all welded joints, all welds ting of the relief valve.
arOlmd openings, and all piping joints against which the
pneumatic pressure is acting shall be checked with a solution Q.10 Foundations
1ilm. A visual inspection may be substituted for the solution-
film inspection if the welded joint has previously been 0.10.1 GENERAL
checked with a vacuum box. The solution-film inspection
shall still be made, above the water level, on all welds around Appendix C describes the factors involved in obtaining
openings, all piping joints, and the compression ring welds, adequate foundations for tanks that operate at atmospheric
including the attachment to the roof and shell. temperature. The foundations for refrigerated tanks are com-
plicated because of the thermal movement of the tank, the
0.8.5.5 The opening pressure or vacuun1 of the pressure insulation required tor the bottom, the effects of foundation
relief <md vacuum relief valves shall be checked by pumping freezing and possible frost heaving, and the anchorage
air above the water level and releasing the pressure and then required to resi st uplift.
partially withdrawing water from the tank.
The services of a qualified foundation engineer are essen-
0.8.5.6 Aller the tank has been emptied of water and is at tial. Experience with tanks in the area may provide sufficient
atmospheric pressure, the anchorage, if provided, shall be data, but nomlally a thorough investigation, including soil
rechecked for tightness against the hold-down brackets. tests, would be required for proper design of the foundation.

0.8.5.7 Air pressure, equal to the design pressure, shall be 0.10.2 BEARING ON FOUNDATIONS
applied to the empty tank, and the anchorage, ifprovided, and
the foundation shall be checked for uplift. Foundations shall preferably be designed to resist the load
exerted by the tank and its contents when the tank is filled
0.8.5.8 All welded seams in the bottom and the comer with water to the design liquid level. Foundations shall be
weld, between the shell and bottom, shall be inspected by designed at least for the maximum operating conditions
means of a solution film and vacuum box test similar to that
described in Q.8.2.1 and Q.8.2.2.