GRAB SHIP UNLOADER - GSU

GSU- Grab Ship Unloader , of all the different equipment's i worked till now , this is my favorite one . Because this is a combination of many equipment's and there is a lot of scope for learning in this equipment. Everyday is a new day and some or the other thing always used to surprise me. Have to say hatsoff to the team that developed or invented this type of machinery. I  had worked in  GSU's of two makes , one is ZPMC and the other is TRF . ZPMC is of Chinese make and TRF is Indian i.e TATA's product , but have to admit that the Chinese equipment i.e ZPMC GSU is top notch , maintenance friendly and operation effective. There wont be any difficult in maintenance even if there is no previous maintenance history .

ZPMC Grab Ship Unloader

GSU is a machinery which runs on electric power. The bottom portion of the machinery is called gantry and the entire crane that is the structure rests on the four legs , each leg consists of six bogies and each bogie consists of one drive wheel and one driven wheel or non drive wheel . The wheels are catridge wheels and are rail mounted. The span between each rail is 20 m . The drives are having thruster brakes which acts as primary braking system and there are hydraulic brakes on the wheels which acts as emergency brakes . The hydraulic power required is supplied by the power pack situated on both sides of the gantry.

The next level of the crane is the discharge section. The cargo from the hopper is discharged through a feeder belt which is a variable one . The speed can be varied with respect to the discharge quantity or the TPH (Tonnage per Hour ) needed. The belt sway can be adjusted by manually operated hydraulic pump which pumps oil to the hydraulic cylinder's provided on both sides of the tail pulley of the feeder belt . This also acts as the take up of the feeder belt . In the same level of the crane there can also be a transfer conveyor depending upon the requirement of the  port , if the main conveyor carrying the cargo to the yard conveyor is situated outside of the crane  i.e the cane is actually custom made , if the conveyor system is below the crane the feeder belt directly discharges the material or else it discharges material on to the transfer conveyor which in turn discharges material on to the main conveyor . This is like a series operation , one after the other .

Feeder Belt are from Side view

The crane is like a multistoried building , as previously said the feeder belt is in the first floor. In the second floor we are at the hopper section. the hopper is provided with two wind walls which acts as a protection from wind and also these wind walls are provided with nozzles for dust suppression system. Every company operating bulk material should adhere to ISO 14001:2015 environmental policy, where in it states that the air cannot be polluted with the dust which is emitting from the operation. these wind walls can be lowered and up with respect to hydraulic cylinders provided for two wind walls. There is this spill plate for providing protection from contamination of sea water during the operation. The spill plate can also be lowered and taken up with hydraulic cylinders provided underneath the spill plate. This all hydraulic cylinders described at various location at this level are operated with a hydraulic power pack provided on the same floor. As previously we talked that the crane runs with electrical power , so in the same floor two cable reel drums are provided one for the electrical cable and the other for water cable , while the crane travels from one position to other  the electrical or water  cable winds or unwinds accordingly to the position.

Grab Unloading the coal in Hopper

The third floor is a cantilever beam called as boom , in this the trolley is operated . The main trolley consists of four wheels mounted on the rail . The main trolley is a robust structure used for displacement of the grab for operation. Unlike the container crane this trolley is not operated by winch and also the operator cabin is not attached to trolley, the trolley is operated only through the hoist and open close ropes provided for grab operation. For providing tension to the trolley auxiliary ropes and auxiliary trolleys are provided on both sides of the main trolley i.e sea side and land side . For providing tension two hydraulic cylinders along with sheaves are provided on the back reach of the beam. Another hydraulic power pack is situated at the back reach to provide hydraulic power to the cylinders. In the same floor the reeving system is located , reeving system is nothing but the sheaves for the operation of ropes.

Main trolley

The top floor which is the last floor of the crane , consists of the heart and brain of the crane. The machinery house consists of drive house and E house. the E house consists of the PLC system and all the drives required for the running of the crane . The drive house consists of Four rope drums with four ropes reeved along the crane from boom to back reach , two planetary gear boxes and 5 electrical AC motors, four for each drum operation and one for trolley operation. For trolley operation all the drums have to be rotated in sync , so a cardan shaft runs along the two gearboxes which can be disconnected for maintenance purpose , if at all single winch or drum have to be rotated.  The braking system consists of thruster brakes , two thrusters for each motor brake drum and an additionally emergency breaking system which is hydraulically operated will be there for drums. Similarly for hoisting and lowering of boom , winch drum for boom also located for which an electrical motor and hydraulic brakes are present same as the main ropes. All the hydraulic equipment's will be power sourced by the power pack provided in the machine room . for personal to come from ground floor to top , an elevator is present and for maintenance activities electric over head transport crane is present in machinery house.