Secondary Seals & Selected Floating Roof Issues. Secondary Seals & Selected Floating Roof Issues

Transcription

1 Secondary Seals & Selected Floating Roof Issues 2006 Storage Tank Conference September 27, 2006 Presentation by Larry C. Hiner Chicago Bridge & Iron Co S. Route 59 Plainfield, Illinois Phone: Secondary Seals & Selected Floating Roof Issues Why Use Secondary Seals Impact of Secondary Seals on Capacity New CBI Secondary Seal Developments Suggested Tank Parameters

2 Why Secondary Seals? 1. Environmental Protection emission reduction (clean air stds) 2. Safety reduced fire / deflagration possibilities 3. Reduced product loss Gallons/Year Emissions Impact (TANKS 4.0.9d) ' Dia Gasoline RVP 10 Houston, Texas Fitting Losses Seal Losses Tank Type EFRT EFRT EFRT IFRT IFRT Rim Seal Mech Shoe Prim Mech Shoe Prim Shoe Mtd Sec. Mech Shoe Prim Rim Mtd Sec. Mech Shoe Prim Shoe Mtd Sec. Mech Shoe Prim Rim Mtd Sec. Deck Fittings Uncontrolled Controlled Controlled Controlled Controlled

3 Impact Tank Capacity Tank 300ft diameter For every one inch of secondary seal height 1000 bbls of capacity is potentially lost. A conventional rim mounted secondary seal is replaced with a low profile seal, the high liquid level could increase 29 inches, or 29,000 bbl of product. DEVELOPMENT OF SECONDARY SEALS Pre 1940 s 1994 to present 1970 s to 1985 CBI 1000 VS 200

4 VS 200 SECONDARY SEAL Seal Tip Tank Shell Secondary Seal Primary Seal Fabric 24 to 31 Vertical Mount Shoe Rim Vapor Space Stainless Steel Hanger Stainless Steel Spring Shoe Lap Retainer Normal Product Level Floating Roof Top Deck Bottom Deck VS 300 Secondary Seal For 8 Rim Space Low Profile *6 vs for current designs 6 Rim mounted secondary (Sealing Force from Rim) Added force maintains tight gap on primary shoe Less vapor space Utilizes strength of SR 1S Continuous secondary seal material eliminates locations for leakage US Patent 6,354,488 B1 *Ultra Low Option can be 1 or 1 less

5 VS 300 Low Profile Secondary Seal New VS 400 with 12 Rim Space Compared to VS 200 Low Profile 6 vs for current seal designs Rim mounted secondary (Sealing Force from Rim) Added force to maintain tight gap on primary shoe Less vapor space Utilizes strength of SR 1A Continuous secondary seal material eliminates locations for leakage US Patent Pending

6 Suggested Tank Parameters New Construction 1. Rim Space Expansion to Design Increased Product Height 3. Corrosion Allowance/Protection Existing Tanks (general interest) 1. Inspection of Outer Rim 2. Proper Repairs 12 Rim Space Reduce Concerns Relating to Shell Out of Roundness 8 Rim Space will typically provide about +/ 4 tolerance for construction, settlement, and lateral loads 12 Rim Space will typically provide about +/ 7 tolerance and allows for easier inspection of rim and seal.

7 Product Design Height Specify design height to allow for future innovations and product flexibility Improved tank capacity due to seal innovations only available if the shell is designed for the increased tank height and the foundation allowable soil bearing is adequate. Corrosion Allowance/Protection Consider for New Construction: 1. A corrosion allowance or coating system on decks and outer rims 2. Using corrosion resistant materials such as duplex stainless steel

8 Existing Tanks Outer Rim Inspection The outer rim is subject to liquid vapor interface which can be highly corrosive. Repair of Decks Patches Deck Plates may not be advisable Rim Plate Corrosion Normal Floating Position

9 Rim Plate Corrosion Pontoon Submergence Rim Plate Corrosion Pontoon Rupture

10 Repair Patches on Floating Roof Decks Punctured Deck Design Case Compressive stress in pontoons is directly proportional to the deck weight Weld shrinkage adds to inward pull on the pontoons increasing compressive stress