OHE mast are structures that support to overhead part of OHE such as DA, Brackets & Wires. . These masts are generally made of steel and are strategically placed alongside of the railway tracks to carry the OHE parts (DA, bracket, super mast, catenary & contact wires) safely above the pantograph. OHE masts are designed while keeping in mind environmental conditions and smooth electrification.
Various types of Mast used in OHE.
| Mast used in OHE | ||||
| Sr. no | Types of Mast | Size | Length | Weight |
| 1 | Broad Flanged Beam (BFB) mast | 6”x6” (152×152) | 9.5 | 361.28 |
| 2 | Rolled Steel Joist (RSJ) mast | 8”x6”(203×152) | 9.5 | 507.2 |
| 3 | K-125 | 125×300 | 9.5 | 287.85 |
| 4 | K-150 | 150×300 | 9.5 | 262.71 |
| 5 | K-175 | 175×300 | 9.5 | 415.34 |
| 6 | K-200 | 200×300 | 9.5 | 473.76 |
| 7 | B-100 | 100×300 | 9.5 | 363.24 |
| 8 | B-125 | 125×300 | 9.5 | 308.46 |
| 9 | B-150 | 150×300 | 9.5 | 371.16 |
| 10 | B-175 | 175×300 | 9.5 | 423.79 |
| 11 | B-200 | 200×300 | 9.5 | 482.22 |
| 12 | B-225 | 225×300 | 9.5 | 584.25 |
| 13 | B-250 | 250×300 | 9.5 | 671.84 |
| 14 | T-150 | 150×300 | 9.3 | 355.07 |
| 15 | S-1 | 8”x6”(RSJ) | 11.4 | 608.646 |
| 16 | S-2 (Same as S-1) | 8”x6”(RSJ) | 11.4 | 608.646 |
| 17 | S-3 | (6″ X 6″ DBFB) | 11.4 | 870.96 |
| 18 | S-4 | (8″ X 6″ RSJ) | 8 00 | 427 12 |
| 19 | S-5 | (8″ X 6″ DRSJ) | 11.4 | 1271.44 |
| 20 | S-6 | (8″ X 6″ RSJ) | 12.4 | 662.03 |
| 21 | S-7 | (6″ X 6″ DBFB) | 12.4 | 947.36 |
| 22 | S-8 | (8″ X 6″ DRSJ) | 12.4 | 1382.97 |
| 23 | S-9 | (8″ X 6″ RSJ) | 9.4 | 501.86 |
| 24 | Dwarf Mast | 8″X6″ RSJ (Flat 15X50X6) | 3.85 | 205.62 |
| 25 | Dwarf Mast | 8″X6″ RSJ (Flat 15X50X6) | 4.35 | 232.31 |
| 26 | Dwarf Mast | 8″X6″ RSJ (Flat 15X50X6) | 4.75 | 253.67 |
| 27 | TTU | 250×300 | 10.135 | 707.85 |
| 28 | TTB-1 | 150X500 | 5.5 | 263.31 |
| 29 | TTB-2 | 150X500 | 8 | 362.82 |
| 30 | NU | 450X450 | 10.445 | 365.26 |
| 31 | OU | 550X550 | 10.535 | 584 95 |
| 32 | RU | 600X600 | 10.58 | 627.47 |
| 33 | BU or BFBU | 150X300 | 10.66 | 803.72 |
| 34 | GU | 250X400 | 10.8 | 1105.61 |
| OTHER STRUCTURES | ||||
| 1 | NE-1 | 5.38 | ||
| 2 | NE-2 | 5.88 | ||
| 3 | NB | 1.5,3.0,4.5,6.0,7.5,9 | ||
| 4 | #VALUE! | 10.548 | ||
| 5 | OE-2 | 11.048 | ||
| 6 | OB | 1.5,3.0,4.5,6.0,7.5,9 | ||
| 7 | RE-1 | 11.6 | ||
| 8 | RE-1 | 12.1 | ||
| 9 | RB | 7.5,9.0,10.5,12.0,13.0 | ||
Size of BFB mast is 152x 152 mm. This is suitable for Single OHE Cantilever/bracket. BFB mast have properties of resisting to bending moment, but these mast is weak in arresting twisting moment.
Size of RSJ mast is 203×152 mm (8″x 6″) and these are suitable for supporting Double OHE. This type of mast is suitable for resisting both bending moment and twisting moment. Weight of this mast is 507.2 kg.
TTC mast is mainly used in following conditions-
Where TC = track center , Minimum Imp value of DA for IR project is 2.20, for DFC project is 2.87.
When required track Centre (TC) is not available for single mast erection, then Portal may be used. One set portal consist of two upright & one one assembled boom. In assembled boom, two end pieces are joined with or without a Centre piece.
Mainly three types of portal are used in IR & DFCCIL projects.
1) N-type portal for clear spans of 10m – 20 m (4 tracks maximum)
2) 0-type portal for clear spans of 20 m -30 m ( 6 tracks maximum)
3) R-type portal for clear spans of 30 m -40 m ( 8 tracks maximum)
N-type portal are used for maximum 4 tracks & 20.4 meters maximum clear span. This is also capable for carrying anchors on uprights. This portal can with stand a maximum bending moment of 8000 kg-m at the base. Maximum 8 brackets can be used at N-type portal.
O-type portal are used for maximum 6 tracks & 30.50 meters maximum clear span. This is also capable for carrying anchors on uprights. This portal can with stand a maximum bending moment of 17000 kg-m at the base. Maximum 12 brackets can be used at O-type portal.
R-type portal are used for maximum 8 tracks & 36.0 meters maximum clear span. This is also capable for carrying anchors on uprights. This portal can with stand a maximum bending moment of 20000 kg-m at the base. Maximum 8 brackets can be used at R-type portal.
Three upright portal may be used in yard area with very complex track centers only, where the use of standard N,O & R type portals is not possible.
Drop Arm is a OHE structure , which is used for OHE wire holding through bracket. Implantation of DA are depend upon project requirement. Minimum implantation of DA should be 2.20 meters in IR project while 2.87 meters is acceptable in DFCCIL projects. Mainly three types of DA are used in OHE IR/DFCCIL projects.
1) 6”x6” BFB drop arm is acceptable for single Back to Back bracket .(DA-1)
2) 8”x6” RSJ drop arm is acceptable for multiple back to back brackets.(DA-2)
3) 6”x6” BFB cut DA are used at Cross over or Turnout locations.
All drawings of OHE such as CSD, LOP & symmetric diagrams are depend upon wind pressure zone. Generally three types of Wind pressure Zone are considered in OHE.
1) Heavy (red) wind pressure zone – 200 kgf/m2
2) Medium (yellow) wind pressure zone – 150 kgf/m2
3) Light (green) wind pressure zone – 100 kgf/m2