32 Samss 006
32 Samss 006
32 Samss 006
Contents
1 Scope ................................................................ 2
2 References........................................................ 3
3 Definitions ......................................................... 5
4 Materials ........................................................... 6
5 Design ............................................................... 8
6 Fabrication ...................................................... 13
7 Inspection, Examination and Testing .............. 15
8 Marking ........................................................... 20
9 Pressure and Vacuum-Relieving Devices ....... 21
10 Shell Attachments and Tank Appurtenances .. 21
11 Coatings and Painting ..................................... 22
12 Shipping Requirements ................................... 22
13 Disinfection ..................................................... 23
Revision Summary .................................................. 23
The following paragraph numbers refer to API STD 620, Twelfth Edition, October 2013,
Addendum 1, November 2014, which are part of this specification. The text in each paragraph
below is an addition or exception to or deletion of a requirement of API STD 620 as noted.
Paragraph numbers not appearing in API STD 620 are new paragraphs to be inserted in
numerical order.
1 Scope
1.1 General
1.1.2 This specification does not cover tanks designed in accordance with
Annex Q “Low-pressure Storage Tanks for Liquefied Gases at -325°F or
Warmer” and double wall tanks according to Annex R “Low-pressure
Storage Tanks Operating Between +40°F and -60°F” of API STD 620.
Additional requirements for such tanks shall be developed, if necessary, by
the Design Engineer. Such requirements shall be submitted to the Saudi
Aramco Engineer, as defined in this specification, prior to bidding with
sufficient time for review.
1.1.4.1 Any conflicts between this specification and other Saudi Aramco Materials
System Specifications (SAMSSs), Saudi Aramco Engineering Standards
(SAESs), Industry codes and standards, and Saudi Aramco Standard
Drawings (SASDs) and Forms shall be resolved in writing by the
Company or Buyer Representative through the Manager, Consulting
Services Department of Saudi Aramco, Dhahran.
1.1.4.2 Direct all requests to deviate from this specification in writing to the
Company or Buyer Representative, who shall follow internal company
procedure SAEP-302 and forward such requests to the Manager,
Consulting Services Department of Saudi Aramco, Dhahran.
1.2 Coverage
1.2.5 (Exception) Horizontal cylindrical tanks used for the storage of hydrocarbon
liquids within the scope of API STD 620, with design pressures in their gas
or vapor spaces not more than 103 kPa gauge (15 psig).
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Document Responsibility: Vessels Standards Committee 32-SAMSS-006
Issue Date: 26 June 2017
Next Planned Revison: 26 June 2020 Manufacture of Low Pressure Tanks
2 References
3 Definitions
3.6.1 The Tank Manufacturer shall prepare and submit for review a complete set
of assembly and shop drawings for the tank(s) being manufactured and in
accordance with Form SA-7918-1, Nonmaterial Requirements for Tanks
and Saudi Aramco Form SA-9580 “API STD 620 Storage Tanks Data
Sheet”.
3.6.2 Drawings and calculations which are approved by the Design Engineer
shall not relieve the Tank Manufacturer of the responsibility to comply
with the Code and this specification.
4 Materials
4.1 General
(Exception) All materials shall be clearly identified and provided with mill
test certificates. Materials shall be alloy-verified by the Tank Manufacturer
in accordance with SAES-A-206.
(Exception) Small parts shall be clearly identified and provided with mill
certificates.
4.2 Plates
4.2.1 General
4.2.1.1 Annular plate material for cylindrical, flat-bottom tanks shall be of the
same material specification, grade, and heat treatment, and meet the same
impact test requirements as the lowest shell course.
4.2.1.4 Rimmed or capped steels shall not be used for shell, bottom, and roof plates.
4.2.6 Plate used for the manufacture of tanks exposed to HIC environments shall
be manufactured from HIC resistant steels that meet the testing
requirements of 01-SAMSS-016. HIC resistant steel shall be procured from
Saudi Aramco approved manufacturers within a list available by the Saudi
Aramco Buyer, as defined in this specification.
4.6 Gaskets
5 Design
5.1 General
5.1.6.1 Information provided by the Design Engineer on the API STD 620 Storage
Tank Data Sheet and a completed Saudi Aramco Form SA-2696 shall be
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Document Responsibility: Vessels Standards Committee 32-SAMSS-006
Issue Date: 26 June 2017
Next Planned Revison: 26 June 2020 Manufacture of Low Pressure Tanks
5.4 Loads
e. (Exception) Roof live loads shall not be less than a concentrated load
of 225 kgs (500 lbs) over 0.4 m² (4.3 ft²).
h. (Exception) Tanks shall be designed for wind and earthquake loads
in accordance with ASCE 7-05 Wind Category Classification to be
used in the calculations of wind loads shall be Category III, and the
Seismic Hazard Exposure Group to be used in calculations of
earthquake loads shall be Group III.
l. Cool-down and cyclic operations, when specified by the Design
Engineer on the tank data sheet.
m. All applicable loads sustained by the tank during its erection, start-
up, or operation shall be considered as acting simultaneously,
including either wind or earthquake, whichever govern.
n. During hydrostatic test, wind pressure may be reduced to 40% of the
design wind pressure and shall be considered acting simultaneously
with the hydrostatic test load.
o. Associated piping systems loads.
Commentary:
5.9.4.6 (Exception) Only butt- welded annular bottom plates in accordance with
Paragraph R.3.5, of API STD 620, shall be provided under tank shell.
5.9.4.7 Bearing plates shall be provided under supports of all internal piping and
appurtenances. Bearing plates shall be 13 mm (½ in.) thick and twice the
diameter of tubular support members or twice the longest dimension of
prismatic support members, as applicable, and welded to the tank with
5 mm (3/16 in.) continuous welds.
5.11.5.1 A foundation drip ring shall be provided for flat-bottom tanks to prevent
the ingress of rainwater or condensation between the tank bottom and
foundation. The ring shall meet the following requirements:
1) Material shall be carbon steel, 3.2 mm (⅛ in.) thick.
2) Continuously seal welded to the edge of the tank annular plate.
All radial joints between the drip ring sections shall also be seal
welded.
3) Extend at least 75 mm (3 in.) beyond the outer periphery of the
concrete ring wall.
4) Turn down at its outer diameter at a 45 degree angle.
5) The top of the drip ring and a 75 mm (3 in.) height of the tank shell
shall be painted with a 10-12 mil thick epoxy coating in accordance
with SAES-H-001.
5.12 Design of Roof and Bottom Knuckle Regions and Compression-Ring Girders
5.12.5.9 Design of the compression ring and the roof-to-shell junction in insulated
tanks shall prevent infiltration of rainwater into the insulation.
5.14.9 The number, size, and orientations of nozzles and manways shall be as
specified on the tank data sheet and Saudi Aramco Form SA-2696.
A 610 mm (24 in.) minimum manway shall be provided at the top and
bottom of each non-cylindrical tank. For spheroid tanks, the bottom
manway shall be located above the supporting girder stiffeners.
The manway covers shall be hinged or provided with davits.
5.16.3.5 Thickness of reinforcing pads shall not exceed the thickness of the shell or
the roof plate to which they are attached.
5.19.1 General
5.19.1.1 Nozzle and manway necks shall be seamless or welded pipe, or rolled plate
with 100% radiography of the longitudinal seam.
5.19.1.4 (Exception) All nozzle and manway necks shall be attached to the shell or
roof by full penetration welds through the roof or shell wall. Backing rings,
if used, shall be removed. Tank openings and the associated opening
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Document Responsibility: Vessels Standards Committee 32-SAMSS-006
Issue Date: 26 June 2017
Next Planned Revison: 26 June 2020 Manufacture of Low Pressure Tanks
5.19.3.1 (Exception) All nozzle connections shall be flanged. Threaded and socket-
welded connections are prohibited.
5.19.3.4 Flange bolt holes shall straddle the normal horizontal and vertical centerlines.
5.22.1 Definitions
5.22.1.4 (Exception) Backing strips for single-welded butt joints, except for joints
in tank's sections placed directly on soil sub-grade, shall be removed after
the weld is completed.
5.22.1.5 (Exception) Lap-joints are permitted only to join bottom plates to each
other and to the annular plates in flat-bottom tanks.
5.22.1.7 Only butt joints shall be used to construct single-curvature shells (cylindrical
tank side walls) and double-curvature shells (spheres, spheroids, heads of
horizontal low-pressure tanks, etc.), roofs and double curvature bottoms.
5.22.1.8 Only bottom annular plates shall be used in cylindrical tanks and shall be
joined by full penetration butt welds.
5.26.6 (Exception) Exemption for radiography is not permitted for joints shown
in paragraph 7.16.1 of this specification.
5.28.1 Minimum thickness of shells and heads shall be 6.4 mm (¼ in.) including
corrosion allowance.
5.28.2 Tanks shall be supported on two saddles. The tank shall be fixed at one
saddle support and free to slide at the other saddle.
5.28.3 Locations of the fixed and sliding saddles, and dimensions from tank
centerline to underside of saddle base plate, and locations of fixed and
sliding saddles shall be according to the tank data sheet.
5.28.4 The shell shall be analyzed in accordance with the L. P. Zick Analysis
Method. Saddle supports and the tank shell shall be analyzed for operating
and hydrotest loads including any piping, wind or other external loads.
6 Fabrication
6.5.5.2 Reinforcing pads and all other external attachment pads shall have rounded
corners with a minimum of 50 mm (2 in.) radius.
6.5.5.3 Nozzles, manways and their reinforcement shall not be located within
50 mm (2 in.) of any weld seam. Where this requirement cannot be met,
100% radiography shall be performed on the encroached weld seam
according to API STD 650, paragraph 5.7.3.4.
6.5.5.4 All attachment welds to the tank shell, bottom, roof, and appurtenances
shall be continuously seal welded.
6.5.5.5 Lugs, clips, or any other components used to assist in erection may be
attached by welding, but all such attachments shall be removed and the
weld areas ground smooth and flush with the base metal and “PT” tested.
The removal of attachments by hammering is prohibited.
6.5.6 Foundation
6.5.6.4 Top fill layer 10-15 cm (4-6 in.) for tanks placed directly on soil sub-grade
shall be a mixture of sweet sand and 3% cement (33:1 ratio, i.e., 3%
cement). The material specifications and mixing requirements shall be as
follows:
1) The maximum permissible salts content is 0.1%. Sand shall be dried
to a free-moisture content of not more than 2.0% by weight of dry soil.
2) The dry sand must be screened through 6.4 mm (¼ in.) mesh
(maximum). Care must be taken in using clean mixing and handling
equipment to ensure mixture remains free from foreign matter.
3) The sand shall then be thoroughly mixed with cement in a 33:1 ratio
by weight in a concrete mixer. After laying the mixture it shall be
rolled a minimum six times by a 3 ton roller. Vibratory plate
tampers may be used in lieu of rollers for areas where a roller cannot
reach and/or cover.
6.10.5 The bottom side of the bottom plates shall be cleaned of all foreign matter
and grit-blast cleaned prior to being coated and placed in position for
welding. The topside surface of bottom plates, regardless whether internal
coating of the tank is required or not, shall be grit-blast cleaned prior to
welding. Surface preparation shall be according to APCS-3 or APCS-113,
as applicable.
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Document Responsibility: Vessels Standards Committee 32-SAMSS-006
Issue Date: 26 June 2017
Next Planned Revison: 26 June 2020 Manufacture of Low Pressure Tanks
7.0 General
7.0.2 Prior to final inspection and pressure testing, the inside and outside of the
tank shall be thoroughly cleaned of all slag, scale, dirt, grit, weld spatter,
paint, oil, etc.
7.3.1 The Saudi Aramco Inspector shall have free access to the work at all times.
7.3.2 All of the rights of Saudi Aramco and their designated representatives for
access, documentation, inspection, and rejection shall include any work
done by sub-contractors or sub-vendors.
7.6.1 Saudi Aramco shall have the right to inspect the fabrication at any stage
and to reject the use of any equipment, tools, construction material or
workmanship which does not conform to the specified requirements or
jeopardize safety of personnel, or impose hazard of damage to Saudi
Aramco property.
7.16.1 Butt-welds
b. Similar examination as in (a) above at the nozzle and manway with reinforced plate and the final surface of
the fillet welds attaching the reinforcing pad to vessel and nozzle/ manway, for weld joints without a
reinforcing plates.
2. The initial weld pass outside the shell shall be examined for its entire
length both visually and by the dye-penetrant method.
3. After completing all welds (inside and outside) and prior to hydrotest,
the inside fillet welds shall be examined for its entire length both visually
and by either dye-penetrant or wet-fluorescent
7.18.1 General
7.18.1.3 The Tank Manufacturer shall furnish all test materials and facilities,
including blinds, bolting, and gaskets.
7.18.1.4 The tank shall be completely drained and thoroughly dried immediately
after completion of the hydrostatic test.
7.18.1.5 The Tank Manufacturer's plan for disposal of hydrotest water shall be
evaluated against SAEP-327 by the engineering contractor.
7.18.2.7 Perform oil-penetrate leak test on the entire length of the first weld pass by
applying high flash point penetrant oil such as light diesel oil for a
minimum 4 hours (preferably overnight).
7.18.2.8 Perform oil-penetrate leak test on the entire length of the first completed
weld, before welding the second fillet weld, by applying high flash point
penetrant oil such as light diesel oil for a minimum 4 hours (preferably
overnight). Alternatively, apply a vacuum test at 35 kPa gauge (5 psig),
using a vacuum box fit to the shell-to-bottom junction.
7.18.2.9 The inside fillet welds of the shell-to-bottom joint in a cylindrical flat-
bottom tank shall be examined by either the dye-penetrant or wet-
fluorescent magnetic particle method before hydrotest.
7.18.2.10 Upon completion of welding of the tank bottom, all bottom joints
including bottom-to-shell joint shall be tested, before hydrotest, by using a
vacuum box fit for the joint geometry, with a soap solution, before any
surface coating is applied. Water or gas shall not be pumped underneath
the bottom to detect leaks.
7.18.2.11 Telltale holes in reinforcing plates shall not be plugged during the tank
hydrostatic test.
7.18.4.5 Hydrostatic test shall not produce a membrane stress in the bottom course
which will exceed 90% of the specified minimum yield strength.
7.18.11.2 Any differential settlement greater than 13 mm (½ in.) per 9 m (30 ft) of
circumference, or a uniform settlement in excess of 50 mm (2 in.) shall be
reported to the Saudi Aramco Engineer. Filling shall be stopped until
clearance to continue has been received.
8 Marking
8.0 General
8.0.2 Marking materials shall be free of lead, sulfur, zinc, cadmium, mercury,
chlorine, or any other halogens.
8.0.3 Tank number and content shall be painted in both Arabic and English at
90 degree intervals around the tank in accordance with SAES-B-067.
8.1 Nameplates
8.1.1.q All tanks with internal coatings shall have the Saudi Aramco's Approved
Coating System (APCS number) marked on the nameplate.
9.2.4 The Tank Manufacturer shall verify the set pressures and sizes of the
pressure and vacuum relief devices specified on the tank data sheet in
accordance with API STD 620 and API STD 2000.
10.1.1 Type and location of stairway shall be as specified on the tank data sheet
and Saudi Aramco Form SA-2696.
10.1.2 Stairs and platforms shall be fabricated of hot dipped galvanized open
grating. Checker-plate grating is not permitted.
10.1.5 Stairways on insulated tanks shall be provided with stringers on both sides.
10.2 Grounding
10.2.1 Tanks shall be provided with a grounding lug connection welded to the tank.
10.3.1 The Tank Manufacturer shall furnish and install firewater deluge system
piping and components, terminating at laterals at the base of the tank, in
accordance with the requirements of SAES-B-017.
11.2 Surfaces to be coated shall be cleaned and prepared prior to its coating in
accordance with the applicable coating and painting systems.
11.3 The soil side of all tank bottom including annular ring plates shall be
coated with APCS-3 or APCS-113A. APCS-3 shall be specified for tank
with maximum operation temperature of 70C, while APCS-113A shall be
specified for higher operation temperature up to 140C. Soil side of all
bottom plates (lap-welded) and annular ring plates (butt-welded) shall be
left uncoated approximately 50 mm wide. This will typically require
masking a strip along the underside of each end (edge) of each
bottom/annular ring plate approximately 50 mm wide.
11.4 In tanks placed directly on soil sub-grade and where internal coating is not
required, the following surfaces shall be coated according to the applicable
coating specifications.
11.4.1 In tanks where there is a potential of water accumulation, top side of the
bottom and the internal bottom portion of the shell in flat bottom tanks,
starting from the tank bottom up to minimum one foot above water line,
shall be coated according to the applicable coating specifications per
SAES-H-001.
11.4.2 Internal lower portion of the tank’s internal components from the lowest
point in the tank up to minimum one foot above water line.
11.6 The tank number and content shall be painted in both Arabic and English
at 90 degree intervals around the tank in accordance with SAES-B-067.
12 Shipping Requirements
12.1 Plates and tank material shall be loaded in manner that ensures delivery
without damage. Bolts, nuts, nipples, and other small parts shall be boxed
or put in kegs or bags for shipment.
12.2 All flange faces and other machined surfaces shall be greased and properly
protected for shipping.
13 Disinfection
13.1 All potable water storage tanks shall be disinfected in accordance with
AWWA C652.
Revision Summary
11 March 2014 Major revision.
26 June 2017 Major revision is made for consistency with the updated industry standards and for more
clarity. In addition;
1) Re-affirm its contents against company needs.
2) Benchmark against requirements of the latest edition of the pertinent API STD 620
“Design and Construction of Large, Welded, Low-Pressure Storage Tanks” that was
issued on November 2014.
Annex B – Use of Materials that are not identified with Listed Specifications
Annex R – Low Pressure Storage Tanks Operating Between +40F and -60F
R.2 Materials
R.2.1 General
R.2.1..2 Material for permanent structural attachments welded to the tank shell
shall be of the same nominal composition as the shell material.
R.5.6.8 All annular plate butt joints in cylindrical flat-bottom tanks shall be 100%
magnetic particle examined from the topside after completion of the root
pass and again after completion of the full weld.
R.8.1.1 Design of foundations shall consider thermal movement of the tank, the
insulation required for the bottom, the effects of foundation freezing and
possible frost heaving, and the anchorage required to resist uplift according
to API STD 620 and API STD 2510.