Astec’s Dampier to Bunbury Natural Gas Pipeline (DBNGP) Stage 5B Expansion work included various loops between kilometre point 22.017 to kilometre point 1,237.220 of the pipeline. KT Pipelines operated two of the Trencor heavy duty machines for this section of work. The project required the T1360 trencher to work in harsh conditions, with temperatures up to 48 degrees, while digging through rock of varying hardness. A mechanic and operator were employed on a rotating roster to ensure that the work was completed on time.
In total, the Trencor T1360 machine worked for approximately 2,000 hours, supported with only routine maintenance and sustaining just one bearing failure throughout the gruelling work schedule.
The production rate of the trencher on the Stage 5B project peaked at just over 1 km per day, while KT’s other T1360 machine also successfully completed rock trenching projects on the Cape Preston Gas Pipeline and the Karratha Power Station Lateral.Article continues below…
KT Equipment Manager Matt Bennett said that the Trencor machine was deployed in these areas because other trenching machines and excavators had proven to be less effective.
“Cape Preston was a 450 mm lateral gas pipeline that travelled 13 km through hilly hard rock with restricted right-of-way and in close proximity to cultural heritage sites.
“The Karratha Power Station Lateral was a pipeline constructed in a road reserve within an urban area with high traffic volumes. Despite the size of the T1360, we managed to trench the pipeline with minimal disruption to road users,” Mr Bennett said.
“The reliability and serviceability of the machine’s Caterpillar engine and Allison automatic transmission were influencing factors in our choice of the T1360 for these projects. While we encountered some very hard rock, the equipment had the ability and stamina to cut through these obstacles.”
KT was initially asked to trench rock areas on one loop of the DBNGP expansion, digging a 1.1 m wide trench varying in depth from 1.9 to 2.4 m.
“After this work was completed successfully, Astec was retained to trench sections of another three loops. To date both T1360s have worked approximately 3,000 hours,” Mr Bennett said.
Design for high volume trenching
Astec Underground Trencor International Territory Manager Frank van der Hilst said a number of design features make the T1360 ideal for large trenching projects.
“For example, the chain-driven head shaft is fully enclosed in an oil bath for longer life. This design has been proven to deliver lower operating costs than hydraulic pumps and motors. A sealed and lubricated track drive also provides extended life and reduces maintenance costs.
“A processor based load control system rapidly regulates the trencher and track speeds to maintain performance and reduce engine stalls and machine wear, while the machine’s high volume hydraulic system operates tracks, conveyor, and boom lift to keep pumps and motors cooler, making them last longer and operate more efficiently,” said Mr van der Hilst.
In terms of safety protection, the location of the ISO rollover and crush test certified cab provides protection from trenching hazards, and from the conveyor and trencher boom.
Optional equipment includes a crumber shoe, road miner attachment, berm scrapers, automatic laser control for grade and steering, auxiliary truck loading conveyor, D-7 or D-8 Cat chain and an EarthPro digging chain.
Mechanical drive benefits
Chain trenchers generally use one of two types of power trains – hydrostatic or mechanical. In recent years, the hydrostatic drive has been the most common method of delivering power to moving parts. However, Astec said that this design has some disadvantages, including power loss due to heat, inherent inefficiencies with hydraulic pumps and motors, system complexity, high maintenance cost, and a short band of digging speeds.
The company said that the mechanical drive, on the other hand, offers a range of benefits. The most significant of these is increased torque, as more than 90 per cent of the engine horsepower can be delivered to the cutting tool for increased productivity. Astec said that the cutting tool tends to break out larger pieces of material due to the slow-moving digging tooth and the force delivered by the high torque.
The company said that mechanical drives also enable a broader range of chain speeds, and the transmission in the Trencor mechanical drive lets the operator choose a digging speed that matches the digging conditions.
According to Astec, the additional horsepower delivered by the system reduces fuel costs by getting more work done in the same amount of time, and the mechanical system is much less complex and easier to service. In most cases, a simple visual inspection can lead to the diagnosis of a problem.
System components are mostly off-the-shelf parts that can be replaced at a relatively low cost. There are also fewer moving parts to wear out or break and a mechanical drive system has been shown to better absorb the pounding shocks of trenching operations.