Rubber Gate Seals - · PDF fileGENERAL Rubber Gate seals are manufactured from specially...
Transcript of Rubber Gate Seals - · PDF fileGENERAL Rubber Gate seals are manufactured from specially...
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.
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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.
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)
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GATESEAL SPECIFICATIONS
AS PER INDIAN STANDARDS IS: 11855:1986
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
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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.
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.
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 `nonfluorocarbon 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.
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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.
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Flat Type Rubber Seals
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TYPE F1 / F2 / F3 / F4
TYPE F1
A
A
DC
A
B
c
B
B
TYPE F1 / F2 / F3 / F4
TYPE F1 / F2 / F3 / F4
A
A
c
BD
c
BD
A
B
TYPE F1 / F2 / F3 / F4
A
c
BD
T Y P E F 1
A
B
c
TYPE F1 / F2 / F3 / F4