CW Milestone – Part 8 - Tower Erection (And Recommended Torque Values)

Following must be ensured in installing different tower accessories:



Tower Erection In Progress



Lightening arrestor to be installed on legs adjacent to ones where BTS equipment is placed.

Antenna and dish mounts must be installed at heights and angles depicted in technical documents.

Fall arrest must be properly installed.

Rest platforms must be installed at the specified heights.

All the tower bolts must conform to the allowable torque limits.



Torque Wrenches



Ensure that torque wrench is being calibrated before use.

Torque test would be applied after finishing of tower erection by subcon in front of CW Engineer to ensure the tightening of tower nut & bolts up to the standards.

Tower Nut & Bolt Essentials

       It is to be ensures by a Civil Engineer by client or at least by major vendor to check the nuts and bolts supplied by tower manufacturer are of good quality and of high tensile strength. There are two possibilities for tower supplies. One is that tower is supplied by a company which manufacture its own tower. That is they have their in-house designers, set standards and manufacturing. Such supplies are more reliable and have good standards of quality. 2^nd scenario is that, which is becoming common now a days that a client or major vendor get their tower designed by a trusted designer, according to their own specific needs. And then they bid from local manufacturer for manufacturing of designed towers and come in agreement to those who have lowest rates. Later supply models need to be scrutinized carefully by occasional detailed quality audits, quality inspection of material before dispatch and at arrival on site.  

ISO grade 5.8 and 8.8 grades are normally recommended by designer. The number prior to the decimal point is approximately 1/100 of the nominal minimum tensile strength of the bolt in N/mm2 or MPa.The number following the first decimal point is more or less the ratio between the minimum yield stress and the minimum tensile strength, times ten. Grade 8.8 nuts and bolts are more durable and reliable.

Whatever the case is, it is highly recommended to use same grade of nuts for whole tower structure. Below are some common toque values used in tower telecom erections. Note: These values are just for a guide only if torque values recommended by designer or manufacturer are different then prefer those.

Bolt Dia.	ISO Grade	Minimum Torque		Recommended  Torque		ISO Grade	Recommended Torque
		(N-m)	(lb-ft)	(N-m)	(lb-ft)		(N-m)	(lb-ft)
M10	5.8	15	11.1	22	16.2	8.8	31	22.9
M12	5.8	40	29.5	55	40.6	8.8	54	39.8
M16	5.8	78	57.5	110	81.1	8.8	130	95.9
M20	5.8	120	88.5	170	125.4	8.8	255	188.1
M22	5.8	145	106.9	206	151.9	8.8
M24	5.8	150	110.6	200	147.5	8.8	440	324.5
M36						8.8	1550	1143.2

After tower erection, all the necessary tower accessories like cable ladder, lightening arrestor, fall arrest system, tower lights and mounts (both antenna & dish mounts) are installed as per technical documents.
Below are some more hotographs of tower erection in progress

CW Milestone – Part 7 - Boundary wall

Boundary wall is provided on a greenfield telecom site for safety purposes. Sometimes instead of boundary wall a steel fence can also be provided based upon agreement at the time of bidding or on a later stage. Steel fence will be discussed at a later stage. At some places it is more convenient to use concrete blocks. Same guidelines can be helpful with appropriate modifications.

Rough face of bricck boundary wall

A Typical boundary wall drawing on a telecom site

The backfilling of the compound would be done in layers up to the required level. Approved backfill material would be used to get the desired compaction.

Construction of boundary wall is then made on the edges of leased area. Any of the three options like, reinforced brickwork wall, pre-cast boundary wall and galvanized fence can be adopted. Barbed wire is then installed on the wall for security purposes using turn-buckles to tighten it. Meanwhile the gate (hot dip galvanized) is also installed on the entrance to site.

During the construction of reinforced brickwork boundary wall following points should be checked.

• A-Class bricks would be used.

• Alignment of area should be correct as per drawings.

• Brick Fog portion should be in the upward direction.

• Bricks should be properly soaked before application of mortar.

• Verticality should be checked after placement of every three layers of bricks.

• Ask mason to tie a string around the first stake and loop it around the rest of them until bricks are being laid to the last one, where the string is being tied off. This helps to keep the boundary wall straight and keeps the bricks at same level.