Fire Door / Fire Wall / Fire Sealant / Fire Rated Equipment’s Guideline

Fire Door / Fire Wall / Fire Sealant / Fire Rated Equipment’s
Code	Clause No	Area	Descriptions
NBC-2016	2.24	Fire Tower Wall / Fire Tower Door	Fire Tower An enclosed shaft having protected area of 120 min Fire resistance rating comprising protected lobby, staircase and Fireman lift, connected directly to exit discharge or through exit passageway with 120 min Fire resistant wall at the level of exit discharge to exit discharge. The Fire fighting shaft shall be equipped with 120 min Fire doors.
NBC-2016	5.1.1(g)	Fire Fighting Shaft (Fire Hose Cabinet) Door	Hydrants for firefighting and hose reels shall be located in the lobby in firefighting shaft. Those hydrants planned to be provided near fire exit staircase on the floor shall be within 5 m from exit door in exit access. Such hydrant cabinet may finish with doors to meet interior finishes with requirement of glass panel to provide visibility to the installations inside and inscribed with the word: FIRE HOSE CABINET of letter size 75 mm in height and 12 mm in width. Such door of the fire hose cabinet need not be fire resistant rated. The location of such cabinets shall be shown on floor plan and duly displayed in the landing of the respective fire exit staircase.
NBC-2016	3.4.5.4	Electrical Shaft Door	The inspection door for electrical shafts/ducts shall be not less than 120 min Fire resistance.
Model Building-Bye-laws-2016	7.14.d	Electrical Shaft Door	The inspection panel doors and any other opening in the shaft shall be provided with airtight Fire doors having Fire resistance of not less then 1 hour.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.2	Electrical Shafts Door	Electrical Shafts shall have not less than 2 hours Fire resistance
Model Building-Bye-laws-2016	7.13.a	Service Shafts Door	Service duct shall be enclosed by walls and door, if any, of 2 hours Fire rating. If ducts are larger than 10 sq m. the floor should seal them, but provide suitable opening for the pipes to pass through, with the gaps sealed.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.2	Service Shafts Door	Services Shafts other than Electrical Shaft, the Fire resistance shall be not less than 1 hour.
NBC-2016	3.4.5.4	Plumbing Shaft Door (Inside the Building)	For plumbing shafts in the core of the building, with shaft door opening inside the building, the shafts shall have inspection doors having Fire resistance rating not less than 30 min
NBC-2016	3.4.5.4	Plumbing Shaft Door (Outside the Building)	For plumbing shafts doors which open in wet areas or in naturally ventilated areas or on external wall of the building, the shafts may not require doors having any specified Fire rating.
NBC-2016	3.4.5.4	Service Shafts Sealing	Service ducts and shafts Openings in walls or floors which are necessary to be provided to allow passages of all building services like cables, electrical wirings, telephone cables, plumbing pipes, etc, shall be protected by enclosure in the form of ducts/shafts having a Fire resistance not less than 120 min.
Central Electricity Authority	38.2	Service Shafts Sealing	No other service pipes shall be taken along the ducts provided for laying power cables. All ducts provided for power cables and other services shall be provided with Fire-barrier at each floor crossing
NBC-2016	3.4.5.4	Electrical Cable Sealing	The space between the electrical cables/conduits and the walls/slabs shall be filled in by a Fire stop material having Fire resistance rating of not less than 120 min. This shall exclude requirement of Fire stop sealing for low voltage services shaft.
NBC-2016	3.4.6.1	Electrical Shaft Sealing	The electric distribution cables/wiring shall be laid in a separate shaft. The shaft shall be sealed at every floor with Fire stop materials having the same Fire resistance as that of the floor.
IS	IS 3034	Electrical Cable Entry Sealing	All cable entries in the switch gear room shall be effectively sealed by use of Fire stops.
Model Building-Bye-laws-2016	7.14.a	Electrical Shaft Sealing	The electric distribution cables/wiring shall be laid in a separate duct shall be sealed at every floor with non-combustible material having the same Fire resistance as that of the duct.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.11	Electrical Services Shaft Sealing	The electric distribution cable/wiring shall be laid in a separate duct. The duct shall be sealed at every floor with non-combustible materials having the same Fire resistance as that of the duct.
NBC-2016	3.4.6.3	Meter Room Door	Meter rooms on upper floors shall not open into staircase enclosures and should be ventilated directly to open air outside or in electrical room of 120 min Fire resistant walls.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.11	Electrical Services Room Door	The doors provided for the Service Room shall have Fire resistance of not less than 2 hours
Model Building-Bye-laws-2016	7.14.f	Electrical Service Room Door	An independent and well-ventilated service room shall be provided on the ground floor with direct access from outside or from the corridor for the purpose of termination of electrical supply from the licenses service and alternative supply cables. The doors provided for the service room shall have Fire resistance of not less than 1 hour
NBC-2016	3.4.6.3	Substation / Transformers Room Door	An independent, ventilated or air conditioned MV panel room shall be provided on the ground level or first basement. This room shall be provided with access from outside (or through exit passageway accessible from outside). The MV panel room shall be provided with Fire resistant walls and doors of Fire resistance of not less than 120 min.
NBC-2016	3.4.6.3.2	Dry type Substation Door	Transformers located inside a building shall be of dry type and all substation/switch room walls, ceiling, floor, opening including doors shall have a Fire resistance rating of 120 min. Access to the substation shall be provided from the nearest Fire exit/exit staircase for the purpose of electrical isolation.
Model Building-Bye-laws-2016	7.19.37	Sub Station Door	Exits from basement electric substation shall have self-closing Fire smoke check doors of 2-hours Fire rating near entry to ramp
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.23	Outside Sub-Stations Door	The outside walls, ceiling and floor including doors and windows to the sub-station area shall be of 2 hours Fire rating.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.23	Inside Sub-Stations door	Oil Filled Equipment at Basement: A sub-station or a switch-station with oil- filled equipment must not be located in the building. When housed inside the building, The transformer shall be of premises by walls/doors/cut outs having Fire Resistance rating of 4 hours.
IEC	IEC 61936-1	Electrical Room / Sub Switching Room Door	Doors shall have a Fire resistance of at least 60 minutes. The doors of switchgear cubicles or bays should close in the direction of escape. Doors which open to the outside are adequate if they are of Fire-retardant material and construction. Ventilation openings necessary for the operation of the transformers are permitted. When designing the openings, the possible escape of hot gases shall be considered.
NEC	110.31	Electrical Room Door	Each doorway leading into a vault from the building interior shall be provided with a tight-fitting door that has a minimum Fire rating of 3 hours. Doors shall be equipped with locks, and doors shall be kept locked, with access allowed only to qualified persons. Personnel doors shall swing out and be equipped with panic bars, pressure plates, or other devices that are normally latched but that open under simple pressure.
NEC	110.31	Electrical Room Wall & Roof	The walls and roof shall be constructed of a minimum Fire rating of 3 hours. For the purpose of this section, studs and wallboard construction shall not be permitted.
NBC-2016	3.4.6.3.1	Oil filled substation Fire Barrier Wall	Substation equipment (exceeding oil capacity of 2000 litre) in utility building shall have Fire rated baffle walls of 240 min rating constructed between such equipment, raised to at least 600 mm above the height of the equipment (including height of oil conservators) and exceeding 300 mm on each side of the equipment.
NBC-2016	3.4.6.3	Electrical Panel Fire Protection	Electrical MV main distribution panel and lift panels shall be provided with CO2 /inert gas flooding system for all panel compartments with a cylinder located beside the panel
NFPA	NFPA 850	Outdoor Sub Station Fire Barrier Wall	OUTDOOR: Oil-insulated outdoor type transformer containing 1890 liters or more of oil. It is strongly recommended that any  is separated from nearby structures by a 2-hour–rated Firewall
NFPA	NFPA 850	Indoor Sub Station Fire Barrier Wall	INDOOR : oil-insulated transformer. In case however, an oil-insulated transformer is installed indoors, then if its oil content exceeds 379 Liters, then it should be separated from nearby areas by a Fire barrier of 3-hour Fire resistance rating.
NFPA	NFPA 850	Indoor Sub Station Fire Barrier Wall	INDOOR: oil-insulated transformer. In case an automatic Fire extinguishment system is installed, then it is allowed that the Fire resistance rating of the Fire barrier is reduced to 1 hour.
Central Electricity Authority	46.2.10.b	Transformer Room Wall	the direct access to the transformer room be provided from outside and the surrounding walls of 4-hours fire withstand rating be provided as per relevant standards
Central Electricity Authority	46.2.10.c	Transformer Room Door	the entrances to the transformer room be provided with fire resistant doors of 2- hour fire rating and the door shall always be kept closed and a notice of this effect be affixed on outer side of the door.
NBC-2016	3.4.6.3.1	Transformer Fire Protection (Water Spray )	All transformers where capacity exceeds 10 MVA shall be protected by high velocity water spray systems or nitrogen injection system
NBC-2016	3.4.6.4	Disel Generator Room Door	Standby supply Diesel generator set(s)shall not be installed at any floor other than ground/first basement. If the same are installed indoors, proper ventilation and exhaust shall be planned. The DG set room shall be separated by 120 min Fire resistance rated walls and doors.
NBC-2016	3.4.12	Fire Command Centre (FCC) Door	Fire command center shall be constructed with 120 min rating walls with a Fire door.
NBC-2016	5.1.2.2.(c)	Fire Fighting Pump house Door	Pump house shall be separated by Fire walls all around and doors shall be protected by Fire doors of 120 min rating.
NBC-2016	5.1.2.2.(b)	Fire Fighting Pump house	Pump house shall be installed not lower than the second basement. When installed in the basement, staircase with direct accessibility (or through enclosed passageway with 120 min Fire rating) from the ground, shall be provided. Access to the pump room shall not require to negotiate through other occupancies within the basement.
NBC-2016	3.4.9.2.1.(a)	Boiler Room Wall	The boilers shall be installed in a Fire resisting room of 180 min Fire resistance rating.
NBC-2016	3.4.9.2.1.(b)	Boiler Room Door	Entry to this room shall be provided with a composite door of 120 min Fire resistance rating.
NBC-2016	3.4.9.2.1.(c)	Mechanical ventilation system for Boiler rooms	The boiler room shall be provided with its dedicated natural or mechanical ventilation system. Mechanical ventilation system for the boiler room would be accepted with 120 min Fire resistance rating ductwork, if it has interface with other mechanical areas. Ventilation system should not be allowed to be routed through electrical room area or through exit corridor/exits
NBC-2016	3.4.8.1	Air conditioning and mechanical ventilation Room Wall	Wherever batteries are provided, the same shall be segregated by 120 min Fire rated construction. Ventilation to the room shall be provided as per manufacturer instructions.
NBC-2016	3.4.8.2.2	Air conditioning Shafts or ducts Sealing	Shafts or ducts, if penetrating multiple floors, shall be of masonry construction with Fire damper in connecting ductwork or shall have Fire rated ductwork with Fire dampers at floor crossing. Alternatively, the duct and equipment may be installed in room having walls, doors and Fire damper in duct exiting/entering the room of 120 min Fire resistance rating. Such shafts and ducts shall have all passive Fire control meeting 120 min Fire resistance rating requirement to meet the objective of isolation of the floor from spread of Fire to upper and lower floors through shaft/duct work.
NBC-2016	3.4.8.3.3	Air conditioning ducts Crossing on Wall Sealing	Wherever the ducts pass through Fire walls or floors, the opening around the ducts shall be sealed with materials having Fire resistance rating of the compartment. Such duct shall also be provided with Fire dampers at all Fire walls and floors unless such ducts are required to perform for Fire safety operation; and in such case Fire damper may be avoided at Fire wall and floor while integrity of the duct shall be maintained with 120 min Fire resistance rating to allow the emergency operations for Fire safety requirements
NBC-2016	3.4.8.3.4	Air conditioning ducts work within Fire Compartment	The ducting within compartment would require minimum Fire resistance rating of 30 min. Such ducting material in substantial gauge shall be in accordance with good practice. If such duct crosses adjacent compartment/floor and not having Fire dampers in such compartment/floor, it would require Fire resistance duct work rating of 120 min. The requirements of support of the duct shall meet its functional time requirement as above.
Model Building-Bye-laws-2016	7.16.1.c	Air Conditioning Duct Sealing	Wherever the ducts pass through Fire walls or floor, the opening around the ducts should be sealed with Fire resisting material of same rating as of walls / floors.
NBC-2016	3.4.8.4.1	Fire or Fire/smoke dampers	The dampers shall be evaluated to be located in supply air ducts, fresh air and return air ducts/ passages at the following points: (a) At the Fire separation wall, (b) Where ducts/passages enter the vertical shaft, (c) Where the ducts pass through floors, and d) At the inlet of supply air duct and the return air duct of each compartment on every floor.
NBC-2016	4.6.1	Smoke Exhaust Fan	The smoke exhaust fans in the mechanical ventilation system shall be Fire rated, that is, 250°C for 120 min
NBC-2016	4.6.2	Supply Air & Exhaust Air	All supply air and exhaust air fans on respective levels shall be installed in Fire resisting room of 120 min.
NBC-2016	4.6.2	Smoke Exhaust Fan	The smoke exhaust fans in the mechanical ventilation system shall be Fire rated, that is, 250°C for 120 min.
NBC-2016	4.6.2	Jet Fans	The smoke ventilation of the basement car parking areas. Jet Fans shall be Fire rated, that is, 250°C for 120 min.
NBC-2016	3.4.10.2	Glass facade	All gaps between floor-slabs and facade assembly shall be sealed at all levels by approved Fire resistant sealant material of equal Fire rating as that of floor slab to prevent Fire and smoke propagation from one floor to another
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.33	Glass facades	Glass facade for high rise building shall be of 1 hour Fire resistance.
NBC-2016	3.4.5.6	Floor’s Vertical opening Sealing	Every vertical opening between the floors of a building shall be suitably enclosed or protected, as necessary, to provide the following: Reasonable safety to the occupants while using the means of egress by preventing spread of Fire, smoke, or fumes through vertical openings from floor to floor to allow occupants to complete their use of the means of egress.
NBC-2016	4.8	Hazardous Areas (Gaseous, Oil Storage Yard ) Wall	Machinery, transformers or other service equipment subject to possible explosion shall not be located directly under or adjacent to exits. All such rooms shall be effectively cut-off from other parts of the building and shall be provided with adequate vents to the outside air. All rooms or areas of high hazard in additions to those hereinbefore mentioned, shall be segregated or shall be protected with Fire resistant walls having Fire rating of 120 min as Fire, explosion or smoke therefrom is likely to interfere with safe egress from the building.
NBC-2016	3.4.5.5	Refuse chutes Wall	If any provided in a building, shall have opening at least 1 meter above roof level for venting purpose and they shall have an enclosure wall of non-combustible material with Fire resistance of not less than 120 min.
NBC-2016	3.4.5.5	Refuse chutes Door	Refuse chutes inspection panel and doors shall be tight fitting with 60 min Fire resistance. Sprinkler protection system shall be provided for the refuse chutes. Refuse chutes shall be at least 6 meter away from exits.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.2	Refuse Cute Door	Refuse chutes shall have opening at least 1 m above roof level for venting purpose and they shall have an enclosure wall of non-combustible material with Fire resistance of not less than 2 hours. Inspection panel and doors shall be tight fitting with 1 hour Fire resistance.
NBC-2016	6.1.1.3 Subdivision A-4	Residential Buildings (Group A) Staircase Door	In case of high rise apartments, of the minimum exits as specified, the naturally ventilated exit staircases may not require the provision of Fire door. However, Fire door shall be provided for all other staircases and pressurized staircases. Panic bars shall be provided in the Fire exits. Panic  bars  shall  be  located  at  a  height between 865 mm and 1220 mm from the floor level.
NBC-2016	6.1.2.(d)	Residential Buildings (Group A) Storage Door	Stores, engineering workshops, areas of high hazard, etc used for storage of substantial amount of flammable liquids shall be of 120 min Fire resistance rating wall. Such areas shall be provided with Fire doors, to be kept closed and shall be posted with a sign on each side of the door in 25 mm high block letters stating FIRE DOOR  KEEP CLOSED.
NBC-2016	6.3	Institutional Buildings (Group C)	All compartments shall be divided with self closing (door closers) Fire doors with electromagnetic hold open. A coordinator shall be provided to sequence the closing of double leaf in case of emergency.
NBC-2016	6.3.g.6	Hospitals All Rooms Door	Operation  theatres,  delivery  rooms, Intensive care units, recovery rooms, etc, that  containing  patients  lacking  self-preservation in case of emergencies shall be  Fire/smoke  separated  (120  min minimum rating) from all the adjoining areas.
NBC-2016	6.3.g.12	Hospitals Corridor Exit Door	Exit access corridors from a compartment to another compartment shall be divided at the compartment intersection by a Fire door of 120 min Fire rating in the Fire compartment wall.
NBC-2016	6.3.g.13	Hospitals Laboratory Door	Rooms designated for laboratory and the like shall not exceed 100 m2 in area and if  additional  space  is  required,  Fire separation of 120 min shall be provided
NBC-2016	4.6.1	Corridors Exist Door in Hospital	Exit access corridors of guest rooms and indoor patient department/areas having patients lacking self-preservation and for sleeping accommodations such as apartments, custodial, penal and mental institutions, etc, shall be provided with 60 min Fire resistant wall and 20 min self-closing Fire doors along with all Fire stop sealing of penetrations.
NBC-2016	7.1.1.(c)	Lift Wall	Buildings of Height 15 m and Above: Walls of the lift bank well enclosure for a lift or group of lifts shall have a Fire rating of 120 min.
Model Building-Bye-laws-2016	7.10.1.a	Lift Wall	Walls of lift enclosures shall have a Fire rating of 120 min.
NBC-2016	7.1.1.(d)	Lift Landing doors	Buildings of Height 15 m and Above: Lift landing doors shall be imperforate. Collapsible doors shall not be permitted. Lift landing doors provided in the lift enclosure shall have a minimum Fire resistance rating of 60 min.
Model Building-Bye-laws-2016	7.10.1.c	Lift Landing doors	Landing door in lift enclosures shall have a Fire resistance of not less than 1 hour.
Model Building-Bye-laws-2016	7.10.1.e	Lift Car Door	Lift car door shall have a Fire resistance rating of 1 hour.
NBC-2016	6.1.1	Lift Well Enclosure Wall	Totally enclosed Lift Well shall be 120 min Fire-resistant.
Model Building-Bye-laws-2016	7.10.1.h	Lift Lobby Exit / Lift Enclosure Door	Exit from the lift lobby, if located in the core of the building, shall be through a self-closing Fire smoke check door of 1 hour Fire resistance.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.5	Lift Lobby / Staircase Exit Door	Fire doors with 2-hour Fire resistance shall be provided at appropriate places along the escape route and particularly at the entrance to lift lobby and stairwell where a funnel or flue effect may be created, inducing an upward spread of Fire and smoke.
NBC-2016	4.2.7	Non Ventilated Area’s Exit Door	For non-naturally ventilated areas, Fire doors with120 min Fire resistance rating shall be provided and particularly at the entrance to lift lobby and stair well where a ‘funnel or flue effect’ may be created, inducing an upward spread of Fire, to prevent spread of Fire and smoke.
NBC-2016	4.2.19	Direct  Basement Exit Door	Where basement is used for car parking and also there is direct approach from any occupancy above to the basement, door openings leading to the basement shall need to be protected with Fire doors with 120 min Fire rating, except for exit discharge doors from the basements.
NBC-2016	4.4.2.4.3.2	Internal staircases Door	Internal stairs shall be constructed of non-combustible materials throughout, and shall have Fire resistant rating of minimum 120 min.
NBC-2016	4.4.2.4.3.4	External staircases Door	The external stairs shall be constructed of non-combustible materials, and any doorway leading to it shall have minimum 120 min Fire resistance.
NBC-2016	4.4.2.5 (g)	Pressurized Staircase Wall	Wherever pressurized staircase is to be connected to unpressurized area, the two areas shall be segregated by 120 min Fire resistant wall.
NBC-2016	4.6.1	Exist Passage way Door	All exit passage way (from exit to exit discharge) shall be pressurized or naturally ventilated. The mechanical pressurization system shall be automatic in action with manual controls in addition. All such exit passageway shall be maintained with integrity for safe means of egress and evacuation. Doors provided in such exit passageway shall be Fire rated doors of 120 min rating.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.8	Internal /Additional Staircases Door	Around Lift Shaft: A staircase shall not be provided around a lift shaft unless provided with Fire stop door of 1 hour rating at every floor level and no other openings in the inside walls
Gujarat Fire Prevention and Life Safety Regulations, 2023	17 /18/19	Staircase Door	Buildings of Height more than 15 meters up to 70 meters: If the lifts and staircase from higher floors go directly to the basement then this area shall be protected by 1 hour Fire resistance construction including Fire doors subject to opinion and requirement of local Fire authority in specially designed building have to be considered and observed.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.5.3	External Stairs Door	The external stairs shall be constructed of non- combustible materials and any doorway leading to it shall have the required Fire resistance.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.5.4	Horizontal Exit Door	A horizontal exit shall be equipped with at least one Fire/smoke door of minimum 2-hour Fire resistance of self-closing type. Further, it should have direct connectivity to the Fire escape staircase for evacuation. horizontal exits shall be open able at all times from both side
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.28	Enclosed type Basement Staircase Door	The staircase of basements shall be of enclosed type having Fire resistance of not less than 2 hours and shall be situated at the periphery of the basement to be entered at ground level only from the open air and in such position that smoke from any Fire in the basement shall not obstruct any exit serving the ground and upper storey of the building.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.28	Enclosed type Basement Lift Lobby Door	Enclosed type Basement Lift lobby provided with Fire resisting self-closing doors of one hour resistance. If the travel distance exceeds the desired level, additional staircases shall be provided at proper places. The basement shall not open in to the staircase or lift well directly. If so then it has to be protected by 2 hours Fire resistant self-closing doors.
NBC-2016	4.4.2.4.1 (f)	Fire Certificate for Fire Door	All Fire rated doors and assembly shall be provided with certificate and labels prominently indicating the manufacturer identification, door details covering door type, serial/batch number, month and year of manufacture, Fire resistance rating, etc. The doors and assembly shall be certified with all prescribed hardware such as hinges, locks, panic bars, door closer, and door viewers.

Vibration Damper in Transmission Line

Vibration Damper in Transmission Line:

• Wind-induced vibration of overhead conductors is common worldwide and can cause conductor fatigue Near a hardware attachment.
• As the need for transmission of communication signals increase, many Optical Ground Wires(OPWG) are replacing traditional ground wires.
• In the last twenty years All Aluminum Alloy Conductors (AAAC) have been a popular choice for overhead conductors due to advantages in both electrical and mechanical characteristics. Unfortunately AAAC is known to be prone to Aeolian vibration.
• Vibration dampers are widely used to control Aeolian vibration of the conductors and earth wires including Optical Ground Wires (OPGW).
• In recent years, AAAC conductor has been a popular choice for transmission lines due to its high electrical carrying capacity and high mechanical tension to mass ratio. The high tension to mass ratio allows AAAC conductors to be strung at a higher tension and longer spans than traditional ACSR (Aluminum Conductor Steel Reinforced) conductors.
• Unfortunately the self-damping of conductor decreases as tension increases. The wind power into the conductor increases with span length. Hence AAAC conductors are likely to experience more severe vibration than ACSR.

What is Aeolian Vibration?

• Wind-induced vibration or Aeolian vibration of transmission line conductors is a common phenomenon under smooth wind conditions. The cause of vibration is that the vortexes shed alternatively from the top and bottom of the conductor at the leeward side of the conductor.
• The vortex shedding action creates an alternating pressure imbalance, inducing the conductor to move up and down at right angles to the direction of airflow.
• The conductor vibration results in cyclic bending of the conductor near hardware attachments, such as suspension clamps and consequently causes conductor fatigue and strand breakage.
• When a “smooth” stream of air passes across a cylindrical shape, such as a conductor or OHSW, vortices (eddies) are formed on the back side. These vortices alternate from the top and bottom surfaces, and create alternating pressures that tend to produce movement at right angles to the direction of the air flow. This is the mechanism that causes Aeolian vibration.
• The term “smooth” was used in the above description because unsmooth air (i.e., air with turbulence) will not generate the vortices and associated pressures. The degree of turbulence in the wind is affected both by the terrain over which it passes and the wind velocity itself.
• It is for these reasons that Aeolian vibration is generally produced by wind velocities below 15 miles per hour (MPH). Winds higher than 15 MPH usually contain a considerable amount of turbulence, except for special cases such as open bodies of water or canyons where the effect of the terrain is minimal.
• The frequency at which the vortices alternate from the top to bottom surfaces of conductors and shield wires can be closely approximated by the following relationship that is based on the Strouhal Number [2].
• Vortex Frequency (Hertz) = 3.26 V / d
• Where: V is the wind velocity component normal to the conductor or OHSW in miles per hour
• d is the conductor or OHSW diameter in inches
• 3.26 is an empirical aerodynamic constant.
• One thing that is clear from the above equation is that the frequency at which the vortices alternate is inversely proportional to the diameter of the conductor or OHSW.
• The self damping characteristics of a conductor or OHSW are basically related to the freedom of movement or “looseness” between the individual strands or layers of the overall construction.
• In standard conductors the freedom of movement (self damping) will be reduced as the tension is increased. It is for this reason that vibration activity is most severe in the coldest months of the year when the tensions are the highest.
• Aeolian vibrations mostly occur at steady wind velocities from 1 to 7 m/s. With increasing wind turbulence the wind power input to the conductor will decrease. The intensity to induce vibrations depends on several parameters such as type of conductors and clamps, tension, span length, topography in the surrounding, height and direction of the line as well as the frequency of occurrence of the vibration induced wind streams.
• Hence the smaller the conductor, the higher the frequency ranges of vibration of the conductor. The vibration damper should meet the requirement of frequency or wind velocity range and also have mechanical impedance closely matched to that of the conductor. The vibration dampers also need to be installed at suitable positions to ensure effectiveness across the frequency range.

Effect of Aeolian Vibration:

• It should be understood that the existence of Aeolian vibration on a transmission or distribution line doesn’t necessarily constitute a problem. However, if the magnitude of the vibration is high enough, damage in the form of abrasion or fatigue failures will generally occur over a period of time.
• Abrasion is the wearing away of the surface of a conductor or OHSW and is generally associated with loose connections between the conductor or OHSW and attachment hardware or other conductor fittings.
• Abrasion damage can occur within the span itself at spacers Fatigue failures are the direct result of bending a material back and forth a sufficient amount over a sufficient number of cycles.
• In the case of a conductor or OHSW being subjected to Aeolian vibration, the maximum bending stresses occur at locations where the conductor or OHSW is being restrained from movement. Such restraint can occur in the span at the edge of clamps of spacers, spacer dampers and Stock bridge type dampers.
• However, the level of restraint, and therefore the level of bending stresses, is generally highest at the supporting structures.                                       
• When the bending stresses in a conductor or OHSW due to Aeolian vibration exceed the endurance limit, fatigue failures will occur.
• In a circular cross-section, such as a conductor or OHSW, the bending stress is zero at the center and increases to the maximum at the top and bottom surfaces (assuming the bending is about the horizontal axis). This means that the strands in the outer layer will be subjected to the highest level of bending stress and will logically be the first to fail in fatigue.

working of Vibration Damper

• When the damper is placed on a vibrating conductor, movement of the weights will produce bending of the steel strand. The bending of the strand causes the individual wires of the strand to rub together, thus dissipating energy. The size and shape of the weights and the overall geometry of the damper influence the amount of energy that will be dissipated for specific vibration frequencies.
• Since, as presented earlier, a span of tensioned conductor will vibrate at a number of different resonant frequencies under the influence of a range of wind velocities, an effective damper design must have the proper response over the range of frequencies expected for a specific conductor and span parameters.

(1) VORTX/ Stock bridge Type:

• Some dampers, such as the VORTX Damper utilize two different weights and an asymmetric placement on the strand to provide the broadest effective frequency range possible.

• The “Stockbridge” type vibration damper is commonly used to control vibration of overhead conductors and OPGW. The vibration damper has a length of steel messenger cable. Two metallic weights are attached to the ends of the messenger cable. The centre clamp, which is attached to the messenger cable, is used to install the vibration damper onto the overhead conductor.
• Placement programs, such as those developed by PLP for the VORTX Damper, take into account span and terrain conditions, suspension types, conductor self-damping, and other factors to provide a specific location in the span where the damper or dampers will be most effective.
• The asymmetrical vibration damper is multi resonance system with inherent damping. The vibration energy is dissipated through inter-strand friction of the messenger cable around the resonance frequencies of the vibration damper. By increasing the number of resonances of the damper using asymmetrical design and increasing the damping capacity of the messenger cable the vibration damper is effective in reducing vibration over a wide frequency or wind velocity range.

(2) Spiral Vibration Damper:

• For smaller diameter conductors (< 0.75”), overhead shield wires, and optical ground wires (OPGW), a different type of damper is available that is generally more effective than a Stockbridge type damper.

• The Spiral Vibration Damper (Figure 15) has been used successfully for over 35 years to control Aeolian vibration on these smaller sizes of conductors and wires.
• The Spiral Vibration Damper is an “impact” type damper made of a rugged non-metallic material that has a tight helix on one end that grips the conductor or wire. The remaining helixes have an inner diameter that is larger than the conductor or wire, such that they impact during Aeolian vibration activity. The impact pulses from the damper disrupt and negate the motion produced by the wind.

References:

1. Sarah Chao Sun. Dulhunty Power (Aust.). Australia
2. Joe Yung. Dulhunty Yangzhou Line Fittings, Canada.