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Presentation
HDPE Liners(High Density Polyethylene)
and Tank Bottom Preparation
Prepared by: John Saji, Senior Project Inspector (Civil)
Wasea Bulkplant ProjectC
RRAPIU
Table of Contents
Introduction & Purpose
References
HDPE Raw Materials
Inspection Prior to installation
Installation
Testing and Inspection
Final Inspection
Lesson Learned
Conclusion
The HDPE (High Density Polyethylene) geomembrane is a
material which is widely used for the tank foundations. This
product is a high quality geomembrane to meet the
requirements of lining application and to protect the
environment from chemical contaminations.
It is an impervious vapor barrier which can be used as water proofing membrane for oil tank foundations to prevent the intrusion of oil contamination to the soil.
Introduction
Purpose
SAUDI ARAMCO STANDARDS SAES-A-114 – Excavation and Backfilling SAES-Q-001 – Criteria for Design and Const. of Concrete
Structures 32-SAMSS-005 - Manufacture of Atmospheric Tanks
INT’L STANDARDS API-650 – Welded Steel Tank for Oil Storage
SATIPs (SAUDI ARAMCO Typical Inspection Plan) SATIP-A-114-001 SATIP-Q-001-02 SATIP-HDPE-001- Installation of HDPE Liners
LESSON LEARNED
1. CRWR-088 – Tips on HDPE Installation
References
Two types of raw materials, natural resin and masterbatch of the concentrated carbon black along with the other additives, are used for the manufacturing of Geomembrane.
Natural resin is the main material of the product.
Masterbatch contains carbon black, stabilizer, anti-oxidant and UV absorber. These raw materials are mixed with the natural resin at an appropriate portion during the manufacturing.
HDPE Raw Materials
Visual inspection of goods at Store Yard: All materials reached at site yard, shall be inspected and
checked with the roll numbers, batch number and manufacturing time and date, together with the QA/QC certificate. Material handling and preservation to be controlled during storage.
Visual Inspection at Job Site: The HDPE membrane shall be checked against the mechanical
damages such as puncture, cuts, severe scratches etc., occurred in handling the materials.
Sub grade Visual Inspection: Before starting the installation of the membrane, the sub
grade must be thoroughly checked. Surface to be lined shall be smooth and free of all rocks,
stones, sticks, roots, sharp objects or debris of any kind. Surface to be lined should provide a firm, unyielding
foundation for the membrane with no sudden, sharp or abrupt change or break in grade.
Inspection Prior to Installation
The surface over which the liner is installed shall be free
from all debris, vegetation and sharp projections.
The surface shall be prepared and compacted with a
minimum of 98 % compaction.
The field density test, lines and levels are inspected.
Installation
The sump is made according to the drawing. The size , shape and slopes are to be checked. The position and slope of leak detection pipes are to be verified.
Leak Detection SumpRef. Drg. VA-384064 rev 001
The sump is filled by stone pebbles and the leak detection pipe mouth is covered by geotextile to prevent the sand in to pipe.
The liner should be cleaned, the over lap of each piece is in between 100 and 150 mm ,the number of joints shall be minimized.
Double wedge welding machine is a plastic welding machine. This should be calibrated, the welder shall be qualified. The machine shall be verified whether it is working or not on daily basis by sample welding. Before making field joints, all wrinkles shall be removed .Joining of surfaces shall use a hot double fusion welding and remaining by extrusion weld.
Used to repair large holes, tears and destructive locations All patches shall extend at least three inches beyond the edges of the defect and all corners of patches shall be rounded.Grinding and welding is used to repair section of extruded fillet seams.Spot welding or seaming is used to repair small tears, pinholes or other minor localized flaws.
Extrusion welding
Visual Inspection
Vacuum Testing
Spark Test
As welded seams are visible on the surface any suspected areas may easily be noted. Such areas, breaks or holes should be marked and repaired.
All field seams over their full length will be tested by
using
vacuum test unit or spark tester, where applicable. The
purpose of testing is to check the seams for leaks and to
ensure leak proof water tight containment sealing system.
In case of test failure, the failed portion of the seam shall
be
identified and marked for repairs. After repairing it is re-
tested until a passing result is obtained.
Testing and Inspection
Vacuum testing machine shall be calibrated. The technician should be familiar with it. If any damage or leak can be marked and rectified .
Prior to covering the membrane with sand, the membrane installed shall be checked thoroughly to be backfilled that day. This is the final inspection for the installation of the lining system. This final inspection is made to make sure there exists no damage or leak that was found, or caused after the previous repair is left un- repaired.
Final Inspection
Clean sweet sand of same grade for concreting with a compact fill of 150mm thick layers shall achieve dry density required by project specifications.
16
Top layer of sand-cement of 100 to 150 mm thick in which 3% of cement in terms of weight shall be compacted according to 32-SAMSS-005 Appx B.2.6- 1,2,3
Lesson Learned
Leak-Barrier Burned During Welding of Tank BottomFlexible membrane (High Density Poly Ethylene liner) was installed
as a leak-barrier to above-ground API 650 storage tank bottom. HDPE lining was extended onto upper horizontal surface of foundation with asphalt impregnated fiber board on top. During welding of tank bottom plate, there was heat transfer that led to burning of HDPE lining, in spite of a Bitumen impregnated board placed between lining and bottom plate.
CRWR-088 – Tips on HDPE Installation
Lesson Learned (cont’d)
Previous Design (Sect ion)
TANK BOTTOM PLATE
BITUMEN IMPREGNATED FIBER BOARD (12 mm)
CURRENT HDPE LINER EXTENDED ON UPPER SURFACE OF FDN
TANK RC FDN
Lesson Learned (cont’d)
Revised Design (Sect ion)
TANK BOTTOM PLATE
BITUMEN IMPREGNATED FIBER BOARD (12 mm)
HDPE LINER SHALL BE EXTENDING TO THE INTERNAL TOP EDGE OF THE RING FOUNDATION
TANK RC FDN
CONCLUSION
THANK YOU