Specifications PLAS2FUEL 750 OIL SETTLING TANK - CODE ANALYSIS BASED
ON THE 2006 OREGON STATE FIRE CODE (OSFC)
INTRODUCTION
PIas2Fuel (P2F) is a producer of refined petroleum product from recycled plastics. P2F has commissioned and
constructed a vertical 750 gallon (nominal capacity) oil settling tank, which is an aboveground storage tank
(AST). The AST will be located in Tigard, OR.
At issue are the materials of construction, method of assembly and the design standard of this storage tank.
The tank was fabricated by U.S. Metal Works of Sandy, Oregon. The tank was constructed to engineering
standards but currently cannot be an approved tank in accordance with Oregon State Fire Code (OSFC)
Section 3404.2.7. Approved is defined in OSFC Section 202 as acceptable to the fire code official. Based on
the tank's orientation, volume, and the material it will store, the tank should have been listed as meeting the
requirements of Underwriters Laboratories (UL) 142, Steel Aboveground Storage Tanks for Flammable and
Combustible Liquids. The tank lacks a nameplate to indicate that it was constructed in accordance with good
engineering practices in accordance with National Fire Protection Association (NFPA) 30, Code for the
Storage of Flammable and Combustible Liquids, 2003 edition. UL 142 and NFPA 30 are adopted by
reference in the OSFC and have the force of law in the State of Oregon.
Scott Stookey was retained as the Technical Consultant for P2F. To better understand the tank's construction,
a schedule of the UL 142 tank construction elements or components and the applicable requirements was
developed. In this schedule, construction data about the P2F was added using the PWF Drawing PSF- OST -M-
10. The CAD drawing was produced by the tank fabricator. The schedule is a comparison of the tank
component or element requirement of UL 142 in comparison to the fabricated P2F tank.
RECOMMENDATIONS
1. Retain a Oregon licensed Professional Engineer to review the findings of the tank analysis and prepare
a letter stating that based on plan review, the 750 gallon AST complies with the construction
requirements of UL 142 and meets the requirements of NFPA 30, Section 21.4.2.1.1. This letter is
contingent on the modification of the tank in accordance with the recommendations, including
performing a structural analysis in accordance with the load requirement in UL 142 and verifying the
tank can withstand the required design loads in the Oregon State Building Code.
2. The tank columns require insulation to protect them from collapse in the event a pool fire occurs in
the containment dike. Insulate the tank columns because the tank is elevated 3- feet above grade
pursuant to OSFC Section 3404.2.9.1.3. The columns will be protected with an assembly meeting
ASTM E- 1529/UL 1709. The design XR301 from the UL Fire Resistance Product Directory complies
with the requirements in OSFC Section 3404.2.9.1.3.
3. Have the engineer of record witness the hydrostatic pressure test of the tank as required by UL 142 §
40.3.1.
4. Modify the storage tank by adding an emergency vent as indicated in the tank analysis.
5. Modify the storage tank by adding a normal vent as indicated in the tank analysis.
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Plas2Fuel 750 Gallon Oil Settling Tank
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ANALYSIS OF THE SETTLING TANK
Tank Element or Component UL 142 Requirement P2F Tank
Material of construction Tank shells and heads constructed of The P2F is constructed of ASTM A
stainless steel meets the Specification for 240 stainless steel.
Stainless and Heat - Resisting Chromium -
Nickel Steel Plate, Sheet and Strip,
ASTM A167; or Specification for Heat -
Resisting Chromium and Chromium -
Nickel Plate, Sheet and Strip for
Pressure Vessels, ASTM A240/A240M.
(UL 142, § 5.3)
Metal thickness Shell: minimum 0.086- inches The stainless steel sheet has a
Top and bottom head: minimum 0.086- thickness of 0.1875 inches.
inches (UL 142, Table 15.1)
Tank shell joint The design shall comply with UL 142, A full penetration weld was used in
Figure 6.1. the assembly of the tank shell.
The lap well shall be either a double
weld U, V, bevel or square groove butt
joint or a full penetration weld.
Tank bottom (bottom head) The design shall comply with UL 142, The weld was executed based on the
joint Figure 6.3. method illustrated in Figure 6.3,
The lap well shall be either a double Figure 5.
weld U, V, bevel or square groove butt
joint or a full penetration weld with full
penetration and complete fusion.
Tank roof joint The design shall comply with UL 142, The weld was executed based on the
Figure 6.4. method illustrated in Figure 6.4,
Figure 1.
3 -inch acid drain The pipe nipple connecting the Class 150 The weld was executed based on the
slip on flange has a minimum wall method specified in § 7.3. The weld
thickness of 0.216- inches. (UL 142, § was completed without
7.3) reinforcement plus an internal root
What is the method connecting the weld for a full penetration weld.
flange to the tank bottom? (UL 142, § This design exceeds the
7.4) requirements in § 7.3.
1 -inch emulsified crude The pipe nipple connect the Class 100 The selected nipple is Schedule 40,
nozzles flange has a minimum wall thickness of . with a wall thickness of 0.133
0.145 inches (UL 142, § 7.3) inches.
ASME /ANSI B31.3, Process
Piping, addresses deviations in
component material thicknesses.
The thickness of this pipe nipple is
8.3% less than that specified in UL
142, § 7.3.
All pressure and temperature ratings
for fittings like this are based on
straight seamless pipe. Except when
prohibited by ASME B31.3, Section
Plas2Fuel 750 Gallon Oil Settling Tank
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• Tank Element or Component UL 142 Requirement P2F Tank
302.2.2, the pipe wall thickness is
allowed provided the wall thickness
of the pipe nipple does not reduce
its pressure rating by more than
12.5 %. This is an atmospheric
storage tank, meaning the greatest
pressure on the fitting is the head
pressure of 750 gallons of synthetic
crude oil. Based on the density of
the liquid and the height of the tank,
measured from the flange to the top
of the tank, the total hydrostatic
pressure of a filled tank is about 2.5
PSIG.
Using the pipe thickness equation in
ASME B31.3, Section 304.1.2, the
8.3% reduction in the prescribed
metal thickness derates this nipple
by less than 0.02 %, which is within
the prescribed limit in Section
302.2.2 of the ASME standard.
Heater well A heater well shall have no joints in that Material is 0.1875 thick and was
portion located within the tank unless assembled with a fill penetration
such joints are continuously welded or weld.
brazed. The weld shall be a full fillet
weld. The thickness of the heater well
fitting shall equal the material thickness
of the tank shell (0.086- inches for the
P2F tank). (UL 142, § 37.1)
Roof manhole The wall thickness of the manhole wall The thickness of the P2F manhole
shall be minimum 0.250- inches. (UL wall is 0.375- inches.
142, Table 9.1) The thickness of the P2F manhole
The wall thickness of the manhole cover cover is 0.375- inches.
plate shall be minimum 0.250- inches. The roof manhole complies with
(UL 142, Table 9.1) Table 9.1 and Figure 9 -1.
The manhole insert is secured to the tank -
roof using a minimum 1/8 -inch
continuous fillet weld. (UL 142 Figure 9-
1)
Structural supports UL 142 requires a performance test of Recommend a structural analysis in
vertical and horizontal cylindrical and accordance with the referenced text
rectangular tank structural supports. UL or an equivalent scientific text in
142 requires the tank be completely conjunction with the requirements
filled with water and an evenly in the Oregon State Building Code.
distributed load equal to the weight of
the water filled tank is placed across the
top of the water filled tank on a line
parallel to longitudinal analysis. The tank
must withstand this load for 2 minutes.
(UL 142, § 44.2)
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Plas2Fuel 750 Gallon Oil Settling Tank
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• • Tank Element or Component UL 142 Requirement P2F Tank
As an alternate to the performance test,
UL allows a structural analysis using the
methodology in the Pressure Vessel
Design Handbook (Bednar). (UL 142, §
30.3.1)
Hydrostatic pressure test For a primary containment tank UL 142 Recommend a 25 PSIG hydrostatic
requires a hydrostatic pressure test in pressure test in accordance with UL
accordance with UL 142, § 40.3 to a 142, § 40.3.1
pressure of 25 PSIG.
Normal vent OSFC §3404.2.7.3 and UL 142 § 8.11 Based on the tank volume a
require the storage tank to be constructed minimum 1 '/4 - inch normal vent
with a normal vent to allow for opening is required.
equalization of the tank internal pressure
during product addition and withdrawal. Given the tank height a minimum
18 -inch 1 1/4 - inch pipe nipple is
required on top the tank and be
equipped with a UL listed
pressure /vacuum vent. (OSFC
§3404.2.7.3.3 and §3404.2.7.3.6).
Emergency vent OSFC §3404.2.7.4 and UL 142 § 8.4 Based on calculations of the tank
require the tank be equipped with an wetted area in accordance with
emergency vent. The tank is currently NFPA 30, the tank requires a
not equipped with an emergency vent. minimum 4 -inch emergency vent
with a flow rate of 84,200 standard
cubic feet with an opening pressure
< 2.5 PSIG.
It is suggested the tank be modified
by installing a 4 -inch female NPT
pipe nipple approximately 4 inches
in length and installing a 4 -inch
OPW Model 201-4080 emergency
vent. The vent has a rated exhaust
rate of 101,000 SFCH @a, 2.5 PSIG.
TANK COLUMNS
The tank is supported by four carbon steel columns attached to a tank shell support structure. Each column
has a nominal 8 -inch x 8 -inch (typical) footer plate with a hole for anchor bolting. Each of the four supports is
"L" shaped carbon steel measuring 6 -inch x 6 -inch x 3/8 -inch thick. The shop drawings do not indicate the
specification of the steel used in the manufacturing of these columns. Assuming that the steel meets ASTM
A36/A36M, Standard Specification for Carbon Structural Steel, each column has a density of 14.9
pounds /linear foot.
The shop drawing illustrates the tank being 36- inches above grade. OSFC Section 3404.2.9.1.3 requires the
structural supports of an aboveground storage that contains Class I, II or IIIA elevated more than 12 inches
above grade shall have a fire - resistance rating of not less than 2 hours in accordance with the fire exposure
criteria specified in ASTM E 1529. ASTM E -1529 Standard Test Methods for Determining Effects of Large
Hydrocarbon Pool Fires on Structural Members and Assemblies, is used to evaluate the fire - resistance of
protective assemblies which insulate and shield the columns for a hydrocarbon pool fire. These are extremely
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Plas2Fuel 750 Gallon Oil Settling Tank
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robust assemblies because they essentially must resist a 2,000 °F exposure for two hours, followed by an
impact resistance test from a fire hose stream nozzle.
Based on the column weights and dimensions, the columns should be protected using a UL listed assembly.
Using the UL Fire Resistance Product Directory, an assembly using Design XR301 is listed by UL as meeting UL
1709, which is equivalent to ASTM E -1529. The insulating calcium silicate board system is manufactured by
Industrial Insulation Group and is marketed as the Super Temp M series.
The reduce the required thickness of the calcium silicate board, each of the columns should be "boxed" to
create a tubular square using the same "L" shaped carbon steel measuring 6 -inch x 6 -inch x 3/8 -inch thick.
Welds should be full depth. Note that this change will require the footing plate to be modified so the 7/8 -inch
anchoring hole can be accessed by the installing contractor.