Aboveground Tank Fabrication Standards Fabrication Standards.pdfRectangular tanks Requires performance testing to prove design at 15 psi Manufacturing air test at 3 psi 18 Performance

ABOVEGROUND TANK FABRICATION STANDARDS

UL-142, UL-2085, UCL-S601

KEY PURCHASING DECISIONS

Fuel to be Stored & Quantity

Tank Construction Specification

Underground or Aboveground

Tank Diameter and Length

Compartments

Fitting and Manway Requirements

Fabricator Proximity to Installation/Delivery

KEY PURCHASING DECISIONS

Regulatory Needs

Fire Code Compliance

Tank Geometry Vertical, Horizontal

Cylindrical, Rectangular

Determine type of Secondary Containment

Fire Protection Ratings

Support Design

STEEL SPECIFICATIONS

UL and STI standards specify steel requirements ASTM A 1011

ASTM A 36

Carbon Equivalency <0.53

Steel is purchased by fabricator in plate form or in coil form from steel mills or steel service centers

STEEL SPECIFICATION

Steel mills carefully control composition of steel

Carbon is added to iron to form steel. Addition of alloy and chemicals and the process in which it the steel is made gives the steel its desired properties.

STEEL SPECIFICATION

Carbon is kept below 0.3%. Higher carbon content adds strength but reduces weldability and formability.

Addition of manganese and silicon provide added strength.

Tank buyers depend upon the strength and ductility of steel

DESIRABLE PROPERTIES OF STEEL

Yield Strength

Tensile Strength

Flexural Strength

Ductility

Hardness

Resistance to Impact

Formed into any Shape and Size

UNDERWRITERS LABORATORIES

UL 142 “Steel Aboveground Tanks for Flammable and Combustible Liquids”

UL 2085 “Protected Aboveground Tanks for Flammable and Combustible Liquids”

Atmospheric Tank -0.5 to 1 psig

Single wall

Double wall

Steel Diked Tanks Open or Closed Top

Carbon or stainless steel

Stationary use only

UL 142ISBN 1-55989-385-0

Steel Aboveground Tanks forFlammable and CombustibleLiquids

UNDERWRITERS LABORATORIESUL 142

Capacities up to 75,000 gallons

Specifies steel thicknesses Primary tank

Secondary tank

Shells and heads

UL 142 STEEL THICKNESS

TANK HEADS

A machine will cold form the flange

The radius of the flange must be 2 times the thickness

The flange will be welded to the tank shell.

DOUBLE-WALL CONSTRUCTION

After the primary tank is built and tested, the outer wall is fabricated atop the primary tank.

The second wall is placed intimately atop the primary tank wall.

“A complete evaluation conducted on a limited quantity of representative tanks. These tests are intended to verify compliance with all applicable performance requirements in a standard.”

Support design test 2 times weight of another full tank

Ladder design test 1000 lb. static load at center of

longest rung

“A limited evaluation conducted on each tank prior to shipping. These tests are intended to verify compliance with production requirements in a standard, such as leakage.”

Air pressure test

Hydrostatic test

Performance Tests Production Tests

STI AST TECHNOLOGIES (UL 142)

UNDERWRITERS LABORATORIESUL 142

Horizontal Cylindrical Steel thickness specified, including shell and heads Optional support design requires testing or

calculations Diameters to 12 feet Air test at 5 psi

UNDERWRITERS LABORATORIESUL 142

Vertical cylindrical Steel thickness specified

Manufacturing air test at 1 ½ to 2 ½ psi

Dished or conical roof required

UL 142

Rectangular tanks Requires performance testing to

prove design at 15 psi

Manufacturing air test at 3 psi

18 Performance

18.1 Hydrostatic strength test

18.1.1 The tank shall be tested to demonstrate that the strength of the assembly and the welded joints are in accordance with these requirements.

18.1.2 The tank shall not rupture or leak when subjected to the Hydrostatic Strength Test, Section 40.

18.2 Top load test

18.2.1 After being subjected to the Top Load Test, Section 41, the tank shall then be subjected to the Leakage Test, Section 39, and shall not leak.

UL 142 SUPPORTS

Maximum height of 12 inches

Must withstand 2 times the weight of a full tank

Design using calculations approved by UL

Design using Performance Test

UL 142 LABEL

Will have one of these statements: Aboveground Tank for Flammable Liquids

Aboveground Tank for Flammable Liquids on Supports

Secondary Containment Aboveground Tank for Flammable Liquids

Open Top Diked Aboveground Tank for Flammable Liquids

Open Top Diked Secondary Containment Aboveground Tank for Flammable Liquids

Closed Top Diked Aboveground Tank for Flammable Liquids

Closed Top Diked Secondary Containment Aboveground Tank for Flammable Liquids

UL Serial No._________

“Protected Tank”

“Integral” Secondary containment Part of the construction of

the tank, monitorable

Insulation

Reduce heat in a fire

Protection from physical damage

UL 2085ISBN 0-7629-0238-8

Protected Aboveground Tanks forFlammable and CombustibleLiquids

2 Hour

2000 Degree

Furnace

VEHICLE IMPACT RESISTANCE

BALLISTICS RESISTANCE

150 grain M-2 ball ammunition

Muzzle velocity of 2700 feet per second

.30 caliber rifle

Distance of 100 feet

UL 2085 TANK CONSTRUCTION

Refer to UL 142 Steel thickness

Welding

Support design

Vents

Emergency vents

Must have provisions for monitoring interstitial space

FIREGUARD®

INSULATION IS PUMPED INTO SPACE BETWEEN PRIMARY AND SECONDARY

CLOSE-UP OF INSULATION

UL 2085 LABEL

GENERATOR BASE TANK

UL LISTED GENERATOR BASE TANK

UL LISTED GENERATOR BASE TANK TESTING

QUALITY CONTROL

Tank fabricators perform elaborate quality assurance to verify compliance with construction standards and customer specifications.

A visual inspection of the weld is always performed by multiple parties.

PRODUCTION TIGHTNESS PERFORMANCE TEST

All atmospheric tanks are tested with air pressure.

Horizontal cylindrical tanks are tested at 5 psi.

Vertical tanks at 3 psi.

Rectangular tanks are tested at a pressure based on its UL performance test, normally 3 -5 psi.

LOCATING PINHOLES

All welds are further tested during the pressure test with a soapsuds solution.

If the weld has a pinhole, air will escape at the pinhole and a bubble is easily seen

Welds must be repaired and proven tight.

PRODUCTION INTERSTICE TIGHTNESS PERFORMANCE TEST

Upon completion of production testing of the interstice with positive air pressure and soap testing the welds of the secondary containment, all air is released.

Then a vacuum is pulled within the interstice and monitored by the fabricator for tightness over time.

PREPARING THE TANK FOR DELIVERY

After ancillary equipment installed, coatings applied, etc. the tank is made ready for shipment.

Fabricators apply a vacuum into the interstice of secondary containment tanks

INTERSTITIAL VACUUM

After the vacuum is applied, the tank is held in storage until it is made ready for delivery

The vacuum remains on the tank during storage, delivery, and during much of the installation.

An easy view of the vacuum gauge to verify retention of the vacuum assures that both walls remain tight.

DOUBLE WALL VACUUM MONITORED TANKS – ULC-S601

Vacuum monitored tanks are constructed to maintain a Vacuum for their lifespan.

Vacuum is pulled to 24 inHg

Corrosion between tank wall is highly reduced due to the lack of atmosphere.

The Vacuum has an insulating factor, which helps to reduce tank condensation.

Vacuum monitored tanks can be equipped with a transducer allowing hookup with any monitoring systems.

Regular tank tank inspections can be as easy as viewing the Vacuum Gauge.

DOUBLE WALL VACUUM MONITORED TANKS – ULC-S601