• The membrane liner installation will be carried out in accordance with the installation plan. This plan will show the location of each membrane section- Field revisions to the installation plan may be required to liner installation.
  
  
• The plan is developed with three principle objectives:
  • Maximizing the installation speed
  • Minimizing the welding joints
  • Minimizing the waste of membrane
    
    
• The membrane sections are unrolled with approximately 13 cm overlap to adjacent membrane and are temporarily held down against the wind unrolling of the liner is usually carried out with available construction equipment, mechanical accessories or sometimes simply by hand.

A typical installation sequence for membrane lining is:

• The embankment surrounding the basin is inspected and covered with the membrane liner. This protects against erosion of embankments and shifting of sand or earth around the perimeter .
• The top edge of the membrane liner is temporarily secured in the anchor trench with small amounts of backfill .
• After the perimeter slopes are covered and welded, the bottom of the basin is covered and welder
• After the entire basin has been lined and inspected, the top edge of the membrane liner is permanently secured in the anchor trenches around the perimeter.

• Seam Layout
  In general, seams should be oriented parallel; to the line of minimum slope, i.e. oriented along, not across, the slope. In corners and odd shaped geometric locations, the number of seams should be minimized. No horizontal seam should be less than 5 ft (150 cm.) from the toe of the slope or areas of potential stress concentrations. On slopes of less than 10% (6:1), this rule shall not apply. When full roll lengths do not extend past the toe of slope, the panel ends cut at an angle greater than forty five degrees to minimize seam stress
  
  
• Field- Seaming methods
  Proper site welding ensures that the welded joints of sheet panels on site with a bond strength equal to that of the parent sheet. The method used must be capable of creating joints that will not be chemical- or physical-weak-points-in-the-famished-lining--system- under- varying site conditions.

There are two general categories of seaming methods:

1. Thermal fusion or melt bonding
2. Extrusion welding

In both cases, the final weld joint must be to withstand the same stresses as the liner itself with reasonable limits.

-Thermal fusion or melt bonding.

This process shall be used for seaming panels together and is not generally used for patching or detail work. There are two thermal fusion or melt bonding methods that can be used on all of the thermoplastic geomembranes.

• The hot wedge or hot shoe method.
• The hot air method.

• Hot wedge fusion welder as its-primary-method-for field-welding. (H.W) equipment shall be self-propelled devices and shall be equipped with functioning temperature and speed controllers and monitors to assure proper control by the welding technician- (H.W) Type shall be equipped pressure type seam testing.
  
  
• Hot wedge unit consists of an electrically heated resistance element 1.75 inch 4,40 CM) wide copper wedge, controlled by a programmable controller, with an audible off-temperature alarm & Variable speed drive unit which can operate between 0.1 and 16.0 feet/minute ( 0.30 to 5, meters/min)
  
  
• The copper dual wedge (split wedge) has two weld-contacts with machine out space, 0.05 inch (1.20cm) in the middle. This creates a double weld with an air space between the welds .
  
  
• As the heated wedge passes between the linear overlap ( 4 to 6 inches), it melts and seams the liners .
  
  
• Two pair of rollers ( 1.75 4.40c 0.5 inch ( 1.20 cm ) gap in the middle of each roller) press the heated liner together. Roller pressure is applied as the two liners converge at the tip of the wedge to form the final seam. Also provides propulsion for the machine ,
  
  
• The air space between the welds can be used to evaluate seam quality & continuity of the seam by pressurizing the space with air & monitoring any drop in pressure that may signify a leak in the seam.

The welding process consists of the following steps

• Assurance that the surfaces to be joined are clean. The liner surface is wieldable as manufactured, but may require cleaning after deployment over some sub grades.
• Adjust the overlap to accommodate the welding machine used. This is generally about 13 cm
• Adjust the welding machine for speed, temperature and membrane thickness on scrap liner prior to starting the weld.
• Complete the weld.
• Air pressure test to assure weld is leak free if a double track weld is used.
• Complete quality inspection and documentation.

Welding seam Geometry

The strength, water tightness and long-term behavior of a weld can be analyzed by the reduction of thickness in the weld area (Welding seam geometry). The welding seam geometry reflects within the permissible range (0.2 to 0.8mm) an optimum interaction of welding parameter temperature. Welding pressure and Speed Under changing ambient conditions (wind, moisture ext.) during the welding process.

Cross sectional diagram of an overlap weld

Hot air system

The hot air method make use of a device consisting of a resistance heater, blower, and temperature controls to blow hot air between two sheets to melt the opposing surfaces. Immediately following the melting of the surfaces, pressure is applied to the seamed area to bond the two sheets. As with the hot wedge method both single and dual seams can be produced. Hot air seaming devices are of two different types; the manual (hand-held type),the automatic (machine driven type).The approved process for field seaming is fusion - seaming(Hot wedge or hot air system). The fusion-seaming apparatus must be an automated vehicular mounted device which produces a double seam with an enclosed space. The fusion seaming apparatus shall be equipped with gauges giving the applicable temperatures.

Dual Seam Profile	Single Seam Profile

Typical Temperature Ranges For Hot Wedge And
Hot Air Seaming Do Thermoplastic Geomembrane.

• For day. Warm weather seaming conditions.
• For damp, cold weather seaming conditions.
• For textured or roughened HDPE or VLDPE sheet increase temperature about 40 C. Also, slower seaming rates and gathers pressures may be required.

Extrusion fillet seams

The hot wedge welding system is the primary seaming system for FML installation and extrusion welding system (extrusion fillet seaming) is utilized for repairs, Patching and detail work such as pipes and sumps and can also de used for seaming. The extrusion welding system produces a seam quality equal to the hot wedge weld and has the advantage that all welds are applied on top, and in irregular seam areas such as pipe boot. When tested in peel, the numerical values for weld strength of an extrusion weld will be slightly lower than for hot wedge welds. The lower value is the result of the weld bead on the top of the liner changing the geometry of the test and not an indication of an inferior weld quality.

Actual seaming process
Extrusion welding is presently used exclusively on HDPE and VLDPE geomembranes.  Aribbon of molten polymer is extruded over the edge of the two surfaces to be joined. The molten extrudate causes the surfaces of the sheets become hot and melt after which the entire mass cools and bonds together.
The technique is called extrudate is placed over the leading edge of the seam. Temperature and seaming rate both play important roles in obtaining an acceptable bond; too much melting weakens the geomembrane and too little melting results in inadequate extrudate flow across the seam interface and in poor seam strength.

The actual seaming process is as follow:

1. The geomembrane sheet to be joined must be properly positioned such that approximately 7.5 cm to 15.0 cm (3 to 6 inches) of overlap exits.
2. FML material to be extruded must have surface oxidation removed by lightly grinding the weld surface with 60 or 80 grit discs. The grinding is performed parallel to the seam and controlled such that grinding makes do not extend more than 0.25 inch outside the area of the weld bead. Grinding shall be completed in no more than one hour before seaming takes place so that oxidized surface are not recreated prior to placement of extruder and to prevent dirt from embedding itself in the patterned grooves 60 miles or thicker liners should have the edge of the top sheet beveled by grinding to approximately a 45 angle.
3. The FML material to be extrusion welded must be temporarily bonded to hold the material in place until the extrusion weld bead cools and attains full strength. This is normally accomplished by performing an automatic or hand air tack weld.
4. The extrusion welder should be purged of all degraded plastics prior to the start of seaming.
5. Extruder in the form of molten, highly viscous fluid is now deposited over the overlapped geomembrane. The center of the extruder must be located directly over the edge of the upper geomembrane. The extruder should cover the third grind marks on each side of the upper and lower geomembrane to within 0.6 cm (1/4 inch ) of the outside borders. The weld bead appearance is smooth and uniform.
6. The extruder thickness should be approximately equal to or greater than the specified sheet thickness measured from the top or crown of the extruder.
7. All extrusion welds should be non-destructively tested by the vacuum testing. Area which cannot be non-destructively tested should be capped.
8. Destructive test can be conducted when seam lengths are adequate.

Quality Control (Seam Testing)

Introduction
The seams should be tested to ensure good properties of the liner along the line of the seams. Some of the required tests are destructive while the others are non -destructive. These tests are crucial submitting the site to project manager.

• During Installation
  The quality control program during the installation stage consists of inspecting the membrane liner, laying and welding the liner, followed by comprehensive weld seam testing; testing of the installed membrane liner is continuously performed during production process with the test results provided for each roll of membrane.
  
  
• Laying and visual inspection
  
  1. Upon the delivery to the site, the rolls of the liner are matched with the approved manufacturing Quality Assurance documents.
  2. The rolls are then inspected visually for shipping damage.
  3. Each roll is placed in it predetermined position according to the installation layout plan.
  4. After the liner is unrolled. Its surface is subjected to thorough visual inspection for any possible damage which may have taken place during handling, storage, or laying.
     
     
• Site Seam testing
  The seam testing produces used will ensure the integrity of the lined area. Two types of the testing procedures cover individual machine performance the final weld quality obtained; pre-weld and post-weld testing.
  
  
• Pre-welding Simulation Testing Procedures:
  Each day prior to welding the liner. Welding tests on two pieces of the liner are carried out under the same conditions that exist for the liner to be welded. Test welds are essential in quality control of the welding process. The welding equipment, method and key welding parameters should be adjusted during this experimental welding. Tests will confirm the key welding parameters, e.g. welding speed and temperature. The resulting joint is subjected to an on-site tens meter test to determine behavior under tensile loading. This test ensures optimum machine settings for the conditions, as well as providing a strict operator control.
  
  
• Test Strips and Trial seams:
  Test strips and trial seams, also called qualifying seams, are an important aspect of field-seaming procedures, they are meant to serve as a pre qualifying experience for personnel, equipment, and procedures for making seams on the identical geomembrane material under the same climatic conditions as will be the actual field production seams the goal of these test stripe is to imitate all aspects of the actual production field-seaming activities intended to be performed in the immediately upcoming work session to determine equipment and operator proficiency, test stripe are typically made every four hours (for example, at the beginning of the work shift and after the lunch break), they are also made whenever personnel or equipment are changed and when climatic conditions reflect wide changes in geomembrane temperature or other conditions that could affect seam quality.
  
  
• Post - Welding test Procedures:
  One of the essential features of the installation quality control is that all site welds are tested for water tightness and mechanical strength after manufacture. This test procedure consists of two types of tests:
  • Nondestructive test for all weld joints for water tightness.
  • Destructive tests for random sample of weld joint for strength

• Air pressure testing.
• A Vacuum test unit.

The purpose of non-destructive tests is to check the continuity of the seams. It does not provide information on seam strength. Continuity testing shall be carried out as the seaming work progress, not at the completion of all field seaming. On seams that cannot be non- destructively tested by vacuum or air pressure methods due to physical constraints, i.e. a boot detail, the seam shall be tested using other approved method, e.g. (The Electric Wire Method)

1. Air pressure Testing
   
   The standard procedure for installations': is to test 100% of the seam length for leak. With the hot air welder, non-destructive testing is made more efficient by air pressure testing of the gap between the (dual) weld tracks the gap is pressurized by air injected through a needle inserted into the gap between weld tracks. Possible leaks are indicated by a loss of pressure over five minutes after the gap has been pressurized by a hand pump, and sealed by a valve. Very long sections of seam can be quickly tested for leaks, resulting in very efficient installation. Note that after a seam has passed a pressure test, pressure is released at the seam end opposite the pump / gauge assembly. This ensures that the seam is continues and has been 100% tested.

Equipment for testing double fusion seams shall be comprised of the following:

• An air pump (manual or motor driven) equipped with a pressure gauge capable of generating and sustaining a pressure between 25 and 30 psi and mounted on a cushion to protect the geomembrane.
• A manometer equipped with a sharp hollow needle or other approved pressure feed device.

The following procedures shall be followed by the installer:-

• Seal one end of the seam to be tested.
• Insert needle or other approved pressure feed device through the sealed end of the channel created by the double wedge fusion weld.
• Energized air pump to verify the unobstructed passage of air through the channel.



• Seal the other end of the channel.
• Energize the air pump to a pressure between 25 and 30 psi, and read pressure inserted into the air chamber of the seam. Allow the pressure to stabilize and if necessary, re-pressurize to between 25 and 30 psi and sustain it for approximately from ( 2 minutes to 5 minutes)
• If the loss of pressure exceeds 3 psi, or pressure does not stabilize , locate faulty area, repair and retest .
• Remove needle or other approved pressure feed device and seal

Pressure test specifications (for double fusion seam only)

•Procedure for air pressure Test Failure

Should the seam fail the air pressure test, the following procedure shall be followed :

1. While the seam air-channel is under pressure, traverse the length of the seam and listen for the leak

2. While the seam air-channel is under pressure, apply a soapy solution to the seam edge(do not trim excess material from edge of seam) and observe for bubbles formed by escaping air, OR;

3. Re-test the seam in progressively smaller increments, until the area of leakage is identified .

4. Repair the identified leak area by extrusion welding the excess material at the edge of the seam and then vacuum test

5. In areas where the air channel is closed and the integrity of the weld is not suspect, vacuum testing is acceptable .

Vacuum Box Testing

Where air pressure testing is not applicable, UG technicians use a vacuum chamber to test 100% of the seamed footage. This test also confirms that no leaks are present in seams .
To perform a vacuum test, a soup solution is sprayed on top of the seam . Then a rectangular flexi glass-faced vacuum chamber (Box) is placed over the seam and vacuum of approximately five psi applied when leak is encountered the soapy solution originally placed over the seam and passing through the in bonded zone .

The equipment shall be comprised of the following :

• A vacuum box assembly consisting of a rigid housing, a transparent viewing window, a soft rubber gasket attached to the bottom, port hole or valve assembly and a vacuum gauge .
• A steel vacuum tank and pump assembly equipped with a pressure controller and pipe connections .
• A rubber pressure/vacuum hose with fittings and connections .
• A plastic bucket and wide paint brush .
• A soapy solution .

The following procedures shall be followed by the installer :

• Excess overlap shall be trimmed away .
• Clean the window, gasket surfaces and check for leaks .
• Energize the vacuum pump and reduce the tank pressure to approximately - 5.0 psi .
• Wet a strip of geomembrane approximately 12 inches (length of box) with the soapy solution
• Place the box over the wetted area and compress .
• Close the bleed valve and open the vacuum valve
• Ensure that a leak tight seal is created .
• For a period of approximately 10 seconds, examine the geomembrane through the viewing window for presence of soap bubbles .
• If no bubbles appear after 15 sec. close the vacuum valve and open the bleed valve, move the box over the next adjoining area with a minimum 3 inches overlap and repeat process .
• All areas where soap bubbles appear shall be marked and repaired and then retested .

High Voltage (Spark Test)

Is an old technique used to detect pinholes in thermoplastic liners. The method uses a high voltage (15 to 30 kv) current, and any leakage to ground (through an unbounded area) will result in sparking. The method is not very sensitive to overlapped seams of the type generally used in liners and is used only rarely for this purpose. Today, the technique has been revived in a somewhat varied form.

The electric Wire method places a copper or stainless steel wire between the overlapped geomembrane regions and actually imbeds it into the completed seam. After seaming, a charged probe of about 20000 volts is connected to one end of the wire and slowly moved over the length of the seam. A seam defect between the probe and the embedded wire results in an audible alarm from the unit. The method is strongly advocated by some installation firms but results in the literature give conflicting opinions when compared to vacuum box testing.

A Peel Testing (in accordance with ASTMD413,D3083)

This test is the most sever test that a seam can be subjected to. The peel test is the greatest proof that a seam will have the strength to last the life of a flexible membrane liner (FML).

The mechanical procedures of the peel test are as follows:

• Seam Sample cut approximately one inch (25 mm) wide by approximately six inch (150 mm) long.
• Peel testing peels the top sheet back against the overlapped edge of the bottom sheet in order to observe how separation occurs. Only the inner weld track is peeled a part in this destructive test. The outer track\) directly at sheet edge is for the purpose of air pressure testing capabilities).
• Clamp bottom tabs into the testing machine (Filed Tens meter or lab Instrom) turn on machine and pull the seam (pull rate 2 inch/minute) a grip separation rate of two inches per minute at angle of 180 degree.
• The seam test specimen must not fail within the seamed region itself, that is, if a failure occurs it must be a sheet failure on either side of the means that as the weld is tested, the upper or lower sheet (film or liner) separates by tearing, as opposed to a separation between the top surface and bottom surface of the seam itself. A film Tear bond (FTB) test result means the seam is good a fully integrated weld.
• The magnitude of the force required for failure for seams tested in a peel mode. Failure forces of 50% to 70% of the minimum yield tensile strength of the parent material.
• The peel test indicates whether or not the sheets are continuously and homogeneously connected through the seam. It seams clear that the peel test is a great deal more critical that the shear test, the peel test is indeed the target test that should be focused upon.

• Film Tear Bond (FTB) id defined as failure of the sheets by tearing, instead of separating from the other sheet at the weld interface area(sheet fails before weld)

B Shear testing (in accordance mth ASTMD638, D3083)

Shear testing applies a tensile stress from the top sheet through the weld and into the bottom sheet. For seams tested in sheer mode, failure forces of 70% to 90% of the minimum yield tensile strength of the parent material.

In all cases the seams have lower strength than the parent material. It should be cautioned, however, that these results vary gradually with the type of geomembrane and of type of seam being evaluated.

Specification for Seam Strength
(Based on NSF 54 Standards)

• If there is a Failure in either Peel or Sheer Then Five total Coupons are tested.
• If more than one Coupon fails, then the Sample Fails. This is a Modifie
• ASTM method. The ASTM methods that are used are D 4437. D 413 and D 638 Which all can apply



Recommended Test Method Details For Geomembranes and Geomembrane seams in shear and peel
Type of Test	PVC	HDPE	VLDPE
Tensile test on sheet
ASTM test method-	...D 882.........	........D(638).......	...D638
Specimen shape......	...Strip..............	........Dumbel.....	...Dumbell
Specimen width (in)...	... (1, 00).............	......... (0, 25).......	...(0,25)
Specimen length (in).	... (6, 00)............	......... (4.50).......	...(1,45)
Gage length (in).........	... (2, 00).............	......... (1.30).......	...(1,30)
Strain rate (ipm)........	... (20)................	......... (2, 00).......	...(20)
Strength (psi) or (ib)....	...Force/(0,25 t)	....Force/(0,25 t)	...Force/(0,25 t)
Strain (in. /in.)..........	...Elong/ (1, 30)...	....Elong/ (1, 30).	...Elong/(1.30)
Modulus (psi)...........	...From Graph.	....From Graph...	...From Graph
Shear test on seams
ASTM test method......	.....D (3083).......	....D (4437)........	....D4437
Specimen Shape..........	.....Strip.........	. ...Strip............	.....Strip
Specimen width (in.)....	..... (1, 00)...........	.... (1, 00)............	.....(1.00) …
Specimen lengthens.)...	.....(6,00 + seam)	... (6, 00 + seam)...	...(6,00 + seam)
Gage lengthens.)..........	.....(4,00 + seam)	... (4, 00 + seam)...	(4,00 + seam)
Strain rate (ipm)..........	...... (20).............	... (2, 00).............	.... (20)..
Strength(psi),(ppi)or(Ib)	...Force/(1,00xt)	..Force/(1,00xt)	Force/(1,.00xt)
Peel test on seams
ASTM test method.......	...D (413)..........	D (4437)……..	...D4437
Specimen shape..........	...Strip..............	.....Strip............	....Strip
Specimen width (in.).....	... (1, 00)...........	.... (3, 00)...........	....(1.00)
Specimen length (in.).	... (4.00)...........	.... (4, 00)...........	....(4,00)
Gage Length(in.)	... (n/a)...............	.... (n/a)..............	....(n/a)
Strain rate (ipm).....,..	... (2, 00)............	..... (2, 00)..........	....(20)
Strength (psi),(ppi)......	Force /(1,00 x t)	Force/(1,00xt)	Force/(1,00xt)

Where: -

N/A = not applicable                                       ppi = pounds/linear inch width of specimen
psi   = pounds/square inch of specimen cross section;
Force = maximum force attained at specimen failure (yield or break)
t = geomembrane thickness                             imp = inches/minute;