INDEX

SR.

NO. TABLE OF CONTENTS

1 Rubber Gate seals

2 Manufactur ing processes

3 Shapes

4 Specif icat ions

5 Gate seal lengths

6 Joint ing of Gate seals

7 Storage & handl ing of Rubber Gate seals

8 Ordering of Rubber Gate seals

DRAWINGS :

9 Flat Type Rubber Seals

10 `P’ / `J ’ / Musical Note Type Rubber seals

11 Double Stem Type Rubber seals

12 Double Bulb Type Rubber seals

13 `L ’ / `Z’ Type Rubber seals

14 Corner Seals

15 Fluorocarbon Fi lm cladding

16 Rubber Seal c lamping

RUBBER GATESEALS

GENERAL

Rubber Gate seals are manufactured from specially formulated rubber compounds giving high abrasion resistance, flexibility and efficient sealing. The high flexibility of Rubber Gate seals results in overcoming inaccuracies due to allowable tolerances of construction, fabrication and erection of Gate / guide plates. The gate seal accommodates itself to the normal variations arising from thermal expansion / contraction, load deflections, etc., ensuring adequate and effective sealing.

Rubber Gate seals are manufactured for all applications in the widest range of types, shapes and sizes catering to the requirements of all Irrigation and Hydro-electric Projects.

TYPES

Plain Type

Brass / Stainless Steel Cladded

Abrasion Resistant Fluorocarbon ( PTFE / Teflon®) Cladded

PLAIN RUBBER SEALS

These are available in all standard shapes and sizes viz., Flat Type, `P /`J /Musical Note Type, Double Stem Type, Double Bulb Type, `L /`Z Type and special section seals.

METAL CLADDED RUBBER SEALS

Rubber Seals are metal cladded to reduce the friction during gate operation. Metal cladding also reduces and checks the tendency of rubber bulb to extrude in available spaces or gaps due to high water pressure during opening and closing of gate. The rigidity of metal cladding however, reduces the flexibility of the seal as compared to plain rubber seals or Fluorocarbon Film cladded rubber seals. Metal cladding may have center or edge slotting to reduce rigidity. Thickness of metal cladding normally provided is 1.5 mm to 3.0 mm. Metal cladded seals are manufactured in Brass, Bronze or Stainless Steel.

FLUOROCARBON FILM CLADDED RUBBER SEALS

Fluorocarbon Film Cladded Seals offer the advantage of extremely low coefficient of friction. The Fluorocarbon Film is moulded along with the rubber component of the gate seal making it an integral part of the seal. The Fluorocarbon Film does not project above the bulb surface since it is recessed into the rubber as it is with metal cladding. The high flexibility of specially formulated rubber compound of gate seal and the extremely low coefficient of friction of fluorocarbon film results in substantial reduction of frictional load, and thereby, hoists of reduced capacity can be used.

Fluorocarbon Film Cladded Rubber Gate Seals should never be bent or skewed during storage, transportation and erection. They should preferably be transported on wooden planks or by using similar methods to keep the cladding straight. Bending or skewing in not a method to test the bond strength.

Thickness of Fluorocarbon Film cladding normally provided is 0.75 mm to 2.0 mm; cladding angle being 900 to 1600.

In existing gates, where difficulty is encountered to operate the gate due to high frictional load, replacement with Fluorocarbon Film Cladded rubber seals will be advantageous.

RUBBER GATESEALS

MANUFACTURING PROCESS

Rubber Gate seals are manufactured by two manufacturing processes viz., extrusion and moulding.

EXTRUSION:

Extrusion is the cheapest method of manufacture of rubber gate seals. Expensive moulds are not required. However, close tolerances are difficult to maintain. Maintaining uniform cross section throughout the length of the gate seal is difficult to achieve thereby, non uniform pre-compression of the gate seals is observed. Cladded gate seals cannot be manufactured by this process.

MOULDING:

Rubber gate seals are manufactured in moulds whereby, a uniform cross section through out the length of the gate seal is attained. Close tolerances can be achieved by this process. There is better control over the quality and size of the gate seal.

RUBBER GATESEALS

SHAPES

Rubber Gate seals are available in the widest range of shapes. Since every Irrigation / Hydroelectric Project has its own design requirements, if the shape required does not fall in the existing range, gate seals of special sections as per the customer s specifications are also manufactured.

Flat Type - Rectangular - Half round at one end - Wedge Type

`P /`J /Musical Note Type* - Solid Bulb - Hollow Bulb

Double Stem Type* - Solid Bulb - Hollow Bulb

Double Bulb Type* - Solid Bulb - Hollow Bulb

`L /`Z Type Seals

Special Section Seals*

Corner Seals* - 2 Dimensional - 3 Dimensional

( * indicates with / without cladding)

RUBBER GATESEALS

GATESEAL SPECIFICATIONS

INDIAN STANDARDS

RUBBER:

Hardness : Shore `A

: 65 ± 5

Tensile Strength : N/mm2 : 14.5

Elongation at Break : % : 450

Water Absorption : % by wt. : < 10%

Oxygen Ageing : : > 80% of value of Tensile strength before ageing

RUBBER - METAL ADHESION TEST:

Tensile Strength : N/cm : 176

RUBBER - FLUOROCARBON FILM ADHESION TEST:

Tensile Strength : N/cm : 54

INTERNATIONAL STANDARDS

ASTM

RUBBER:

Hardness : Shore `A

: 65 ± 5

Tensile Strength : lb/in2 : 3000

Elongation at Break : % : 450 minimum

Water Absorption : % by wt. : < 5

Compression set : % : 30 maximum

Oxygen Ageing : % : > 80% of value of Tensile strength before ageing

FLUOROCARBON FILM:

Tensile Strength : psi : 2000

Elongation at Break : % : 250 minimum

RUBBER - METAL ADHESION TEST:

Tensile Strength : lb/inch width : 100

RUBBER - FLUOROCARBON FILM ADHESION TEST:

Tensile Strength : lb/inch width : 30

RUBBER GATESEALS

GATESEAL LENGTHS

Plain rubber gate seals are supplied in desired lengths. The essential criteria for deciding the length of such seals is the weight of the roll, ease in transportation and handling.

Metal cladded rubber seals should not be bent or skewed. Metal cladded rubber seals are supplied in maximum lengths of 5.0 meters. The limitation being with regard to the maximum lengths that can be accommodated in normal trucks.

Fluorocarbon Film cladded rubber seals cannot be bent or skewed as with metal cladded rubber seals. They are supplied in either:

a. Maximum straight lengths of 5.0 meters and parts thereof (refer Drg. # AI-24B). The total desired length of the gate seal can be made up of such lengths and jointed at site using any of the jointing methods (see `jointing of rubber gate seals ).

b. Fluorocarbon Film though having the lowest coefficient of friction, has its own limitation. It is a plastic material having limited modulus of elasticity. Thus, when a Fluorocarbon Film is stretched beyond its elastic limit, severe localized stress may occur, cannot regain its original dimension and leads to permanent deformation. This limitation is also applicable to Fluorocarbon Film Cladded Rubber Gate Seals whereby the Fluorocarbon Film and the bonding gets permanently damaged. In order to overcome this, the total Fluorocarbon cladding length is divided into smaller lengths with a `non-fluorocarbon portion of about ½ , comprising of rubber and matching the fluorocarbon film cross section (refer Drg. # AI-18).

When lowering / raising the gate, corner seals are subjected to maximum stress in the complete rubber seal assembly Corner seals should be single piece moulded type only.

RUBBER GATESEALS

JOINTING OF RUBBER GATESEALS

Plain rubber seals are easy to joint. However, with Fluorocarbon Film Cladded seals up to 5.0 meters, it is imperative to understand the problem associated with it.

Fluorocarbon Film is a non-stick material and jointed using specialized techniques at the factory. It is virtually not possible to bond the exposed Fluorocarbon Film section to Fluorocarbon Film at both ends of seal lengths at site (refer Fig. #1a, Drg. #24A). While attempting to bond such exposed sections, only the rubber section can be cemented with the fluorocarbon film section thickness unbonded. Leakages occur through such unbonded fluorocarbon film thickness sections of the seals under medium to high heads. The force exerted at such minute areas being high enough for fluorocarbon film bonding failure to occur over a period of time. The problem is overcome by providing a `non-fluorocarbon

length of apprx. ½ at the seal ends to attain a total rubber-rubber bond (refer Fig. #1b, Drg. #24A). There is no significant increase in the co-efficient of friction since the `non-fluorocarbon

length is negligible as compared to the total seal length. All Rubber-Rubber joints are stronger, reliable and can be easily executed at site. Additional extra length of rubber portion is provided for `Shop Trimming at site to achieve the exact desired total seal length.

Splicing and site jointing of rubber gate seals can be carried out by various methods:

Adhesive splice joint

Vulcanized splice joint

ADHESIVE SPLICE JOINT

Adhesive splice joint procedures are adopted at locations where vulcanized splicing is not possible.

All seals to be correctly punched cut to true length and fully fitted to the gate during shop assembly fusing the gate and clamp plate as templates. All seal joints to be butted up square with no visible gaps or steps in seal contact faces. On final site assembly, all seal joints are treated with a cyanoacrylate adhesive having maximum strength with longest open times.

VULCANISED SPLICE JOINT

Jointing of rubber seals at the gate fabricator s workshop or at site, vulcanized splice joints give the best results.

For making vulcanized splice joints, moulds, equipments, tools and rubber raw materials are required. The jointing is carried out in heated moulds with raw rubber compound used in-between. Best joint strengths (almost equal to the original seal) are achievable.

For cladded seal jointing at site, the procedure is the same. The cladding, however, will not be continuous at the joint. There will be a gap of about 6 to 12 mm between the cladding at the joint. The gap will however have rubber in between matching the cross section of the seal except for the shrinkage of the fresh rubber compound. The shrinkage however is very negligible and is accommodated during seal compression resulting in no leakage. Rubber gate seals cladded or plain should never be bent at the joints.

Vulcanising equipment complete with vulcanizing press, moulds, rubber compounds, splicing tools etc., are available.

RUBBER GATESEALS

SEAL ASSEMBLY

The fol lowing recommendat ions ensure even t ightening of seals and avoid over compression, and avoid leakage through the seal fasteners.

The rubber seal is provided with 12 mm Ø pins l imi t ing the seal compression in a staggered posi t ion f rom the axis of seal fasteners (refer Drg. # AI-06). The pin height is kept 0.5 mm less than the average seal th ickness.

Al ternat ively, nylon or brass ferrules may be used to l imit seal compression (refer Drg. # AI-12).

The fasteners of s tainless steel wi th counter-sunk head are preferred over the hex-head bol ts. Special bol ts of sel f locking type are preferred. For M-16 fasteners, hole in the rubber seal is kept 16 Ø, whereas holes in the structure and seal c lamps is kept 18 Ø.

Al l seals to be correct ly punched cut to t rue length and ful ly f i t ted to the gate dur ing shop assembly (using gate and clamp plate as template. Al l seal jo ints to be butted up square wi th no visual gaps or steps in the contact faces. I f adhesive jo inted, then adhesive should be appl ied to al l seal jo ints on f inal assembly; wi th al l seal bol t threads treated wi th thread sealant.

STORAGE & HANDLING OF GATESEALS

Rubber gate seals get affected when exposed to direct sunl ight, oxygen and ozone. Cont inuous contamination wi th oi l , petroleum products, acids and other detr imental chemicals also have del i r ious effect on rubber gate seals and i ts l i fe thus gets reduced. As such, rubber gate seals should be stored in a clean, cool and dark place. Seals should also be away from work areas to avoid physical & mechanical damage. Stor ing of seals one on top of the other should be avoided. I f space constraints area constraint and stocking one on tope of the other is unavoidable, care should be taken to ensure that the seals do not get physical ly distorted. Cladded Seals should be stored so as to avoid f requent handl ing and shif t ing.

Plain rubber seals are general ly transported in rol ls . Such seals when stored for considerable per iod should be kept in straight posit ion for at least 24 hours pr ior to use.

Cladded Seals should be l i f ted or transported for instal lat ion in such a way that i t is not curved or bent. I t is preferable to use a t imber plank support for c ladded seals whi le t ransport ing or handl ing in any way, extreme care should be taken so as not to damage the c ladding.

RUBBER GATESEALS

ORDERING RUBBER GATESEALS

The following information shall be provided while ordering gate seals:

Name of Project & location

Project authority & designation

Type of gate and overall size

Maximum head of water at the gate

Type & size of gate seal

Cladding (if required)

Corner Seals size and lengths

Length of each seal required and total number of seals

Detailed drawing (if available) otherwise seal part drawing

Whether required for new gate or for replacement

Informat ion g iven herein is based on our exper ience and is g iven in good fai th. However, no guarantee is impl ied nor any obl igat ions assumed by the recommendat ions or suggest ions g iven.

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