OHE-Mast
Mast is erected on the foundation to hold the entire static and dynamic load of the OHE.
Mast are designed to suit different application and standardized accordingly. There are three major applications namely: Independent Structures, Portal and Two/Three Track Cantilever Structures.
Independent Structures
When structures hold OHE of one line including two/three cantilever assembly of the same elementary section. These structures are classified as RSJ (Rolled Steel Joists) and BFB (Broad Flange Beam).
- RSJ Mast: It is an I or H cross-section beam. The horizontal and vertical elements are called flanges and web respectively. Beam theory shows that I shaped section is very efficient for carrying both bending and shear loads in the plane of the web. Size used is 203x152mm. The mast is further classified into A, B, C, E &H depending upon drilling hole for supporting different type of OHE equipment.
- BFB Mast: The Horizontal and vertical dimensions are same in this design of mast. Sizes vary from 152x152mm to 400x400mm depending upon the load which the mast is required to carry. These masts are good for resisting bending moment but weak in arresting twisting moment. These masts are further classified into three category depending upon the drilling holes for mounting. Weight of 152x152mm size mast is 30.4kg./meter
- Fabricated Mast (K-series): These masts are fabricated by channels and flats welded in K design. The dimensions across the track is fixed as 300mm and varied along the track as K100 (23.12Kg/m) , K125 (29.56Kg/m) K150 (37.25Kg/m) K175 (42.65Kg/m) K200 (48.64Kg/m), K225 (56.10Kg/m) K250 (65.11Kg/m) where the suffix indicates the dimension and weight in Kg/meter. K100 is used for mounting auxiliary transformer and K125 de-standardized. Due to higher width they are unsuitable where minimum track center of 4.72 is available.
Independent structures having mechanical independence makes the best OHE design.
Portal Structures
- Portal structures are used to accommodate OHE of many lines (2 to 8 tracks) where it is not possible to erect independent mast due to restriction of track center.
- There are three types of portal namely N, O and R type.
- Clear span (distance between inner face) in N type- 10-20M (4 tracks), O type – 20-30M (upto 6 tracks), R type – 30-40M (upto 8 tracks). Portal of maximum M has recently been designed.
- Cantilever for the extreme tracks is provided on the uprights
- Cantilever on the middle tracks is provided on the drop arm suspended from the boom.
- Drop Arm
- Drop arms are classified as A (single cantilever on either or both side), B ( multiple cantilever on side) C (multiple cantilever on both side)
- Drop arms are fabricated from angles and are rod laced.
Two/three track Cantilever Structure (TTC)
This is an alternative where it is not possible to manage with mast as well as portal is difficult to erect or uneconomical.
This is generally used at turnouts and crossover, platform to provide adequate implantation (4.5m – distance between track center and inner face of mast). This can support OHE upto a distance of 10.5m from the upright. TTC is not used for supporting OHE of two main lines
TTC consists of Mast 12.21 m long 225x300mm Boom 5.0 long or 8.0m long Tie Road 20mm dia – 2 nos Drop arms : D type
Selection of Mast
General guidelines for use of different design of mast is as follows:
- Normal location and OHE on tangent Track : BFB Mast
- Normal Location on curves: RSJ Mast
- Structures with multiple OHE with anchorage: K150, 175
- Turn-out location with higher torsion stress: K200, 250
Implantation
This is the most important dimension measuring the horizontal distance of the inner face of the mast from the track center.
As per schedule of dimensions ( popularly called SOD in Railways) prescribed, there should not be any permanent structure at distance less then 2.16m from the track center. In view of this, implantation in initial stages of electrification was fixed at 2.36m and permitted upto 2.21 with some conditions.
With the introduction of 8 wheel BOX wagon, incidence of door opening during run and hitting the OHE were reported and thus minimum implantation increased to 2.5m.
With the introduction of mechanized ballast cleaning machine, and OHE foundation interfering with the showels, it was again revised to 2.8m. See Latest SOD
The mast grouting in foundation is 1.35 meters from the top of the foundation. The top of the foundation is kept 0.50 meters below the top of the rail. The measurement of rail=17.2cm, rubber pad =0.06cm, sleeper =21.0cm, normal ballast cushion =35.0cm in all the rail top is 73.80cm above ground. step distnce is taken 50cm than the top of the foundation above ground level is 23.80cm projected. but if the foundation isfully embeded in soil of ground a super block of 23.8cm is to be casted .
If cess level is less than 50 cm then we gives ED and adjust the embeded length 1.35 m. It is not necessary to make foundation, taking step distance 50 cm ,it changes as per site condition, if there is less cess level . Standard step distance is 48 cm and it can taken 50 to 40 cm also.
Sir. can anyone classify cess level and how it is measured?
It is right or not..pls confirm
What is the length of upright of R type special portal in OHE
R type portal length 10.66 mtr
YES
9.5m
What should be the minimum distance of any part of ROB or any structures from OHE horizontally and vertically?
There are three types of SOD applicable namely for 25 kV, 2×25 kV and 2×25 kV high rise OHE.
25 kV : 5870 mm
2x25kV : 6050 mm and at turnouts 6530 mm
High Rise OHE of WDFC : 8050 mm and at turnouts 8430 mm
Minimum Horizontal distance of 1600 mm on either side of the track center.
I would suggest to visit IR SOD 2004 for all related information The document is available on website.
10 mtr minimum
Weights in
/kgs and length in/ mtrs of N,O,R types of portal mast .
How to calculate reverse deflection of a mast?
I will reply you shortly
Reverse deflection should be 3mm for 1 mtr length.
It is in SOD or ACTM.
very useful
verygood knoweledge about the mast erection.
I am ohe engineer . Here the company is taking minimum implantation is 2.90 . Will u tell me minimum implantation of ohe as per latest sod
As per ACTM it is 2.5 mtr. but in practicaly see that in rail slowing by PWI very shortly it is destab. so precosanaly it is reshodul by local authorty.
Minimum implantation is 2.80 in latest SOD
What is the full form of SPS
Small parts of steel which Is used in OHE structure and PSI locations.
Small part of steel
What’s the full form of SPS in ohe erection.
SPS – Spare parts
What is the minimum implementation of DA
0lease tel me the implatation of
TTC. BFB R , O, &N type portels
for portals, ttc and the masts carrying more than one ohe the minimum implantation should be 3m from the track center.
The information is a ready reckoner.
N type portal exact weight in tons??
Mast reaction fundetion
Good evening sir, minimum implantation of mast changed from 2.5m to 2.8m for tangenet track —- can you share the letter please sir.
Very good Matters
TTK KA FULL FORM BATAY
Two/Three Track Cantilever with K-type
Long Super Mast Weight
Sir plz aap ke pass all material list ho to plz send me urgent ha single bracket and all material ke plz send me
What is the weight of N type,O type, & R type portal
Dear sir/Madam
Our company produces ductile Iron pipes and lighting pole. Recently we decide to produce Mast which is applicable to the railway electric line. Could you send us some requirements such as height and maximum working load which is needed for OHE mast? in other words, we need a specification or standard in this field, especially for the mast.
What is the permissible maximum implantation for portal upright mast ?
YES
Very informative Article. Would suggest to include the sketches also for a common man to understand.
C /10 type OHE MAST WEIGHT ?