Pipelayers

A pipelayer, commonly called a sideboom, is a crawler tractor fitted with a boom mounted on one side and a counterweight on the other. It is designed to lift, carry and lower heavy pipe sections into trenches during pipeline construction. Working in groups along the right of way, several pipelayers can pick up a long welded string of pipe and lower it gradually into the trench, a task that no other single machine can do as efficiently.

Pipelayers are highly specialised. They are found mainly on oil, gas, water and slurry pipeline projects, although they are also used for some heavy lifting jobs where rough terrain rules out conventional cranes. Their crawler undercarriage gives them the traction and stability to work on uneven, soft and sloping ground, often far from paved roads. On a typical cross-country pipeline, a fleet of pipelayers moves along the right of way with the welding and coating crews, stringing joints, holding pipe for welding and finally lowering the finished string into the trench before backfilling.

Brief History of Pipelayers

The first pipelayers appeared in the 1920s and 1930s, when the growth of oil and gas pipelines in the United States created the need for machines able to handle long, heavy steel pipe across open country. Several manufacturers developed sideboom attachments for existing crawler tractors, with the boom on the left side, counterweights on the right and winch drums powered by the tractor’s power take-off. Trackson was one of the best-known makers of such attachments for Caterpillar tractors.

In 1955 Caterpillar introduced the 583C, based on the D8 tractor and generally regarded as the first purpose-built pipelayer, with a frame and undercarriage designed for sideboom work. Other tractor manufacturers, including International Harvester, Allis-Chalmers and later Komatsu and Liebherr, offered pipelayers in the following decades. Hydraulic winches replaced mechanical drums, and hydrostatic drive, better cabs and electronic load monitoring arrived on later generations. Since the 2000s, excavator-based pipelayers and conversion kits for hydraulic excavators have joined the traditional tractor-based sideboom in the market.

How a Pipelayer Works

A pipelayer combines a crawler tractor with a lifting system designed for side loads.

Base machine. A crawler tractor, often derived from a dozer, with a reinforced frame and a longer or wider undercarriage for stability. The operator’s seat is usually positioned to give a good view of the boom and the trench.
Boom. A lattice or box-section boom is pinned to the side of the tractor. It can be raised and lowered to change the reach and the lifting capacity.
Winches. Two hydraulic winches control the boom and the hook: one sets the boom angle, the other raises and lowers the load.
Counterweight. Mounted on the opposite side of the boom, it balances the load. On many machines it can be extended outwards hydraulically to increase stability when lifting.
Load monitoring. Modern pipelayers have load moment indicators that show the operator how close the machine is to its tipping limit.
Tipping capacity. The size of a pipelayer is expressed as its maximum lifting capacity at a short overhang, a rating that falls quickly as the load moves further from the tracks.

Types of Pipelayers

Tractor-Based Sideboom Pipelayers

The traditional design, built on a crawler tractor. They are available from small machines for water and distribution lines to very large units for large diameter transmission pipelines.

Excavator-Based Pipelayers

Pipelayers built on a hydraulic excavator undercarriage and upper structure, with a boom and winch arrangement adapted for pipe lifting. Some can rotate, which helps on narrow right of ways.

Excavator Conversion Kits

Kits that turn a standard excavator into a sideboom for a project, then allow it to return to normal digging work.

Electric and Hybrid Pipelayers

Recent designs with electric winch drives or electric drive trains, developed to reduce fuel use and improve control.

Size Classes

Class	Typical lifting capacity	Typical use
Small	about 10 to 30 t	Water, gas distribution, small pipelines
Medium	about 30 to 70 t	Medium diameter transmission pipelines
Large	about 70 to 100 t	Large diameter pipelines
Very large	over 100 t	Very large pipelines, special lifts

Figures are indicative.

Attachments and Lifting Gear

A pipelayer is only as useful as the gear hanging from its hook. Pipe is usually lifted with wide nylon or rubber-lined slings, belts or roller cradles that support it without damaging the coating. Roller cradles allow the pipe string to slide through them while the machines move along the trench, which is useful when lowering in long sections. Spreader bars and pipe hooks are used for handling individual joints, and vacuum lifting devices, which grip the pipe with a suction pad, are increasingly used for joints and bends. Pipelayers also support the pipe while it is fed through bending machines on the right of way. The rated capacity of the lifting gear must match or exceed the load, and it should be inspected regularly for wear and damage.

Main Manufacturers

Caterpillar, with a long history in the segment and current models such as the PL87.
Komatsu, with tractor-based pipelayers built on its dozer platforms.
Liebherr, with hydrostatic pipelayers in its RL range.
Volvo Construction Equipment, which has offered pipelayer conversion kits for its excavators.
Maats, a Dutch pipeline equipment specialist that sells, rents and customises pipelayers.

Main Uses of Pipelayers

Lowering welded pipe strings into the trench on oil and gas pipelines.
Moving and placing pipe joints along the right of way.
Holding pipe in position for welding and coating.
Installing water, slurry and district heating pipelines.
Handling pipe at river crossings and horizontal directional drilling sites.
Occasional heavy lifts in rough terrain where cranes are impractical.

Planning a Lowering-In Operation

Size the spread. The number and class of pipelayers depends on the pipe diameter, wall thickness, coating and the length of string to be lowered.
Check the lift plan. Each machine should work within its load chart, with a margin for dynamic loads, slopes and ground conditions.
Prepare the ground. The working side of the right of way must be firm and level enough for the machines to travel along the trench.
Coordinate the team. Lowering-in requires close communication between operators and a single person giving signals.
Protect the coating. Use cradles or padded slings designed to avoid damage to the pipe coating during lifting.

Safety

Pipelayers can tip over sideways if the load moves too far from the tracks, if the ground under the tracks gives way at the edge of a trench, or if the machine travels on a slope with a raised load. Operators must follow the load chart, keep the counterweight extended when required, and keep the load low while travelling. Workers should stay out of the area under the boom and load and away from the trench edge when pipe is being lowered. Overhead power lines are a serious hazard when the boom is raised. Load moment indicators, cameras and proper training reduce risk, and several machines working on the same string must follow a coordinated lift plan.

Trends and Technology

Load moment indicators with visual and audible warnings are now standard on many models. Some manufacturers offer electric winch systems, hydrostatic drives and improved operator stations with better visibility. Excavator-based designs have grown as contractors look for more versatile machines. Telematics, remote diagnostics and wireless systems that link several pipelayers are being introduced to support coordinated lifts on large projects.

Key Terms

Sideboom: the common name for a pipelayer, from its side-mounted boom.
Right of way: the corridor of land cleared for pipeline construction.
Lowering-in: the process of placing the welded pipe string into the trench.
Load moment indicator: a system that shows how close the machine is to its tipping limit.
Overhang: the horizontal distance from the track edge to the load hook.
Counterweight: the weight opposite the boom that balances the load.

Frequently Asked Questions

Why do pipelayers have the boom on the side? A side boom allows the machine to travel along the trench while holding the pipe over it, which is how pipe strings are lowered in.

How is a pipelayer’s capacity rated? Capacity is usually expressed as a tipping load at a short overhang. Actual working loads are lower and fall with distance.

Can an excavator be used as a pipelayer? Excavators handle pipe on many projects, and some are purpose-built or converted for sideboom work. Traditional sidebooms are still preferred for large diameter lowering-in.

Is a pipelayer the same as a crane? No. A pipelayer lifts loads to one side only, close to the tracks, and is designed to travel with the load. A crane usually rotates, reaches much higher and is set up in one position before lifting. Rules on certification and inspection may still treat pipelayers as lifting equipment.

Why do pipelayers work in groups? A long welded pipe string is too heavy and too flexible for one machine. Several pipelayers share the load and control the pipe’s curvature as it is lowered.