Bangladesh launching gantry project-HZQ50/150 bridge girder launcher

How to Install and Dismantle HZQ50-150 Bridge Girder Launching Gantry

FAQ 七 02, 2012 No Comments

(1) Installation and test run

Launching gantry in the worksite

The bridge girder launcher is of heavy bridge construction equipment, to ensure its normal work, it is necessary to operate the machine in accordance with operation instruction manual and current related rules.

● Install the bridge girder launcher

A. Personnel and equipment

a. personnel: 8-10

As a large-sized special equipment for constructing a bridge, only with clear, definite division of labor and uniform command, only with full-time operator, full-time electrician, full-time safety inspector, the bridge girder launcher can work normally. To ensure construction safety, there must have strict construction organization and measures. The basic personnel conditions are as follows:

One commander: be acquainted with bridge structure and basic requirement of hoisting work. Firstly learn more about bridge structure, assembly program, operating method and instruction manual, then he must have certain organization ability, be familiar with command signal and have a strong sense of responsibility

One electrician: could read the circuit diagram of bridge girder launcher and connect the wire according to drawing, be capable of rapidly clearing trouble in work. The one with strong responsibility, skilled operation experience, quick response can handle and be in charge of operating the machine.

One hydraulic worker: know well basic knowledge of hydraulic system and master skills of use and maintenance, be capable of correct operation and trouble-shooting.

Two lifting workers: have lifting work experience many years, with strong sense of responsibility and certain mechanics knowledge, be familiar with operating regulation and safety code of lifting worker, be responsible and serious

Six helpers:  have certain knowledge, strong, can bear hard work and be keen to learn professional knowledge.

b. Equipment:   crane with lifting capacity > 20t   1 set

Φ19.5 steel wire rope 8m           4 ropes

Sleeper                             some sleepers

Electric welder                      1 set

Oxygen, acetylene                     1 set

Steel hammer (12 pounds, 8 pounds)     1 piece for each

Wrench, pincher                         several pieces

Gradienter                             1 set

B. Measuring, positioning and field engineering:

Usually, the bridge girder launcher is installed on roadbed at bridgehead. The assembly site requires certain working surface, the min size of worksite is 95m×10m, the roadbed should have enough bearing capacity to satisfy the demands of installing bridge girder launcher and carrying girders: the site can has a longitudinal gradient but should be smooth and flat, the longitudinal gradient should less than 3%; measure the position of operation centre line of the bridge girder launcher, front support leg, middle support leg and rear support leg.


C. Install the bridge girder launcher

Installation order: measure and position—install two main girders in a balanced and symmetrical position (with temporary support)—assemble front connection frame, rear connection frame and temporary inclined strut—install front, middle, rear support leg and rear bracket—install trolley—install hydraulic system—install electrical system—preliminary operation check and commissioning.

As installing the main girder, there should be at least 3 temporary supports.

Launching gantry in the worksite

a. install left main girder and right main girder

Use temporary support to assemble left and right main girders, control centre distance between two main girders (add temporary connecting rod according to practical situation), after installing the main girder, put power distribution cabinet and control cabinet into main girder (near to middle support leg)

b. Install front, rear connection frame and temporary inclined strut;

c. Install middle, rear support legs and rear bracket.

As installing the middle support leg first time, put it at the position of abutment, adjust its height according to the height of precast girder and the gradient of bridge, then transversely connect support legs of two sides together.

Install rear support leg and rear bracket according to the position shown in the drawing.

d. Lift and install trolleys

Use big crane to lift trolley assembled, then install it on the main girder; or use small crane to lift the structure of trolley to install them steps by steps

e. Install electrical system

1. Connect circuit according to circuit diagram;

2. Outfit steel wire rope, hang the cable on the relative pulley, make wire shelving without block, reach the scheduled position of trolley;

3. Connect the ground wire, ensure the rail in connection with ground;

f. Installation and commissioning of hydraulic system and attentions

The whole set hydraulic system has been installed before leaving factory and has a test run with load, installation steps on the worksite are as follows:

1. Install hydraulic pump station and jack in position;

2. Remove caps at two ends of high pressure hoses, firstly blow off using compressed air, then clean inner parts with oil;

3. Check whether seal ring at hose connection is complete, there should be one white block circle (inner part), one O type ring (outside);

4. Both ends are respectively connected with pump station and hydraulic cylinder, and fix it with U type card

g. Lay rails of the bridge girder launcher (suggest P43 or P43 rails above)

1. Lateral sliding rail layout

It is unnecessary to lay longitudinal sliding rail for the bridge girder launcher, it is needed to lay lateral sliding rails for front and middle support legs, sleeper layout should be stable and reliable, use spike to fix outside rail on the sleeper, inside use spikes to buckle symmetrically with edges of two rails; cushion block is used between rail connections, outside is connected by rail splint and long bolt.

2. Lay trolley rail on the bridge girder launcher

Rails are directly fixed on the main longitudinal girder, rail connections are connected firmly by rail splint, set up limit switch and rail stop iron at both ends of rail.

Rail layout above demands smooth rail joint, correct rail distance, solid support. Distance and size should be strictly controlled to be paralleled between two lateral rails (front, middle support legs) (see table below)

Table 5-1        Rail Layout Requirements



New layout

In service


rail top height difference at same section ≤25mm ≤40mm


track gauge difference of the bridge girder launcher ±5mm ±6mm


rail longitudinal gradient ≤3‰ ≤3.6‰


Rail straightness(in 2 meters distance) ≤1mm ≤1.5mm


Height and lateral deviation at rail joints ≤1mm ≤1mm


Interval at rail joints (20℃,rail length 12.5m) ≤2mm


h. Install front support of the bridge girder launcher

After installing main longitudinal girder, middle support leg and other support legs, connection frame and temporary inclined strut, put front support leg at position of abutment under main longitudinal girder in accordance with the height of front support leg.

i. Set up the steel wire rope of winch: the setting of steel wire rope between winch and movable pulley is as follows:


●Test run of the bridge girder launcher

After finishing installing the bridge girder launcher, make a comprehensive check:

A. Check whether connection parts are tight

B. Check whether electric connection is right and whether limit switch is reliable

C. Check whether each part for hydraulic system has a oil leakage phenomenon and a good lifting function

D. Check whether the mechanical and structural parts work well

E. Check whether rotating parts have a good lubrication

F. Check whether oil level in oil tank can meet the demand and start a test run of hydraulic system:

  1. Infuse 32# (old brand 20#) hydraulic oil to oil tank through pouring orifice
  2. Do not mix together hydraulic oil with different mark and different category, according to the weather, the hydraulic oil brand can be changed. Filter hydraulic oil once half a year, replace it every two years
  3. Infuse certain oil to pump through oil drainage orifice of oil pump on fuel tank cap
  4. Completely loosen relief valve and plug in, start oil pump, run with empty load for 5-10 minutes to check whether oil pump rotation direction is correct, monitor whether oil pump is noisy
  5. Turn hand-operated direction valve and screw properly relief valve to make hydraulic cylinder begin to start, then keep cylinder stretch out and draw back 4-5 times in whole trip to remove air in the system, because the normal phenomenon is: after finishing installing the bridge girder launcher first time, air in hydraulic cylinder may sometimes make cylinder not move or move slowly, while the oil pump has run a long time. It should be avoided to adjust direction valve repeatedly. (that can not remove the air in the hydraulic cylinder)
  6. When control hand-operated direction valve to change direction, the force can not be too fast and too sudden. When change positive movement to counter movement, stop for a minute in the central place to avoid hydraulic shocks
  7. Above examination and adjustment are confirmed to be normal, do test run as follows:

    girder carrier for the launching gantry

1. Move two lifting trolleys to rear part of the bridge girder launcher, take back front auxiliary support leg, measure the height of front part of launching nose and deflection of bridge girder launcher, see whether they can meet the demand of crossing front pier caps.

2. If it meets the demand, adjust front support leg in position, adjust each mechanism to work well, do lifting weight test. The lifting weight is restricted in regulated range to allow lifting trolley to repeatedly lift objects 2-3 times. Method: lift objects–stop–lower–draw back—stop, keep this process for many times

After finishing test with empty load and full load above mentioned, check whether all machines, institutions, hydraulic and electrical parts work well, put the bridge girder launcher in use after confirming its safety and reliability.

(2)Dismantle the bridge girder launcher

When last one piece of precast girder is installed, begin to disassemble the bridge girder launcher.


  1. Cylinders in front support, rear support and auxiliary support jacks to lift the whole machine to rise up 250-300mm
  2. Lay sleepers to 2m high near to middle support and rear support
  3. Take back cylinders in support legs, put them on transporter
  4. Lift two trolleys separately by using a 30t crane, put them on transporter
  5. Disassemble front support leg, middle support leg, rear support leg, auxiliary support leg, front connection frame and rear connection frame
  6. Remove connection pins from rear parts to front parts, carry away segmental girders, disassembly is finished.
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