Keep your pipeline project going

in-service pipelines the first time, every time. The area between the two plugging heads is depressurised through an internal bleed port, eliminating the need for extra taps or fittings to engage the bleed functionality. That means the ProStopp DS tool achieves double the sealing capability through a single fitting.

In addition, it includes a patented, hydraulically activated – or ‘energised’ – seal that compresses against the pipe’s inner wall, regardless of its shape or whether there are dents, gouges or irregular weld seams. The ProStopp DS also has a chip sweep function that removes excess cutter shavings that could interfere with the seal. What’s more, the seal can accommodate multiple wall thicknesses and can be used over and over again, reducing the need to replace consumable parts. All of which makes the ProStopp DS an ideal solution that’s gained strong market acceptance in just two short years.

For example, when TDW Partner Channel Onstream Pipeline Solutions (OPS) isolated a slightly oval 12 in. gas distribution pipeline near Antwerp, Belgium, it was one of the 300-plus times the technology has been put into action since 2020. “OPS invested in 12 in. ProStopp DS technology because it is universally applicable on 12 in. pipelines and is insensitive to ovality,” Danny Vreys, OPS General Manager, said. “The result was perfect, a 100% seal on the primary and secondary plugging heads.”

But it’s not just routine challenges that the tool is well suited for. As the operator of a gas distribution system in Florida, USA, recently learned, its flexibility also makes ProStopp DS technology appropriate for jobs that present extreme challenges. Including the isolation of a 10 in. pipe that had gotten out-of-round in a very unusual way.

In the thick of things TDW hot tapping and plugging (HT&P) technicians are always prepared for the unexpected. When they arrived at a Florida jobsite to isolate a 10 in. gas distribution pipe prior to rerouting, though, it was with the understanding there was nothing abnormal about the 0.375 in. thick pipe wall.

As soon as they cut the coupon to allow access into the pipe, a different story began to emerge.

Instead of being smooth and uniform as anticipated, the interior surface of the coupon was covered with a thick and rocky substance that appeared to have passages cut through it. The technicians reasoned that the rest of the pipe was in similar condition.

What could have created the black, pitch-like overlay?

Keelan Prewett, the TDW Application Engineer on the project, said the problem stemmed from what is usually a benign source: corrosion protection. “It appeared the pipeline had been treated with an asphalt/tar internal anticorrosion coating that had hardened and become uneven over time,” Prewett explained. While that was concerning enough, even more troubling was the fact that more than an inch of the coating had pooled along the bottom of the pipe, although the full extent of that issue wasn’t apparent at first. Together, the coating and gas buildup had made the pipe out-of-round for a reason like no other.

Well-equipped Although the unusual internal diameter surface condition would have taxed most static seal isolation equipment,

Figure 1. The interior surface of the coupon was covered with a thick and rocky substance that appeared to have passages cut through it.

Figure 2. More than an inch of coating had pooled and hardened at the base of the pipe interior, introducing ovality and making the isolation more challenging.

Figure 3. An internal anti-corrosion coating had hardened and become uneven over time.

HT&P technicians knew this was where the ProStopp DS tool had a distinct advantage: its energised seals could conform effectively to the uneven pipe wall.

Still, given the strange conditions, the crew consulted with TDW Services Application engineers about how to best ensure a successful isolation. The engineers advised following standard operating procedures and starting the isolation at standard hydraulic operating pressure, then incrementally elevating until it reached maximum hydraulic operating pressure, 172 bar (2500 psi). This would exert more force to compress the sealing elements against the pipeline’s rocky walls.

Insertion and chip sweeping operations were performed without issue. The technician energised the plugging heads, and the operator blew down the isolated section. However, after the blowdown was complete, the lower explosive limit (LEL) sensors indicated there was still a small amount of gas present downstream of the plugging heads.

A sneaky leak path Normally, any gas that escaped the isolation tool’s first seal would be safely bled off through a port – that’s the entire purpose of DBB technology. The fact that the LEL sensors were detecting gas suggested there was another leak path.

Without seeing exactly how deep the residue was at the bottom of the pipe, TDW engineers theorised the gas was traveling through the porous passages in the coating and getting between the coating and the internal diameter of the pipe. TDW detected the leak in two places: through the bleed port between the primary and secondary plugging heads and at the 2 in. Thread-O-Ring® fitting used for equalisation and blowdown of the isolated section of pipe.

With the isolation tool’s hydraulic pressure at its maximum level, TDW engineers recommended a customised – and somewhat unconventional – solution. The vapour barrier solution

The ProStopp DS is engineered so any product between the primary and secondary plugging head can be bled out through the tool, up through the control bar of the actuator away from the work area to the control box used to activate (or energise) the plugging heads. The control box is directly connected to each of the plugging heads on the isolation tool and to the area between the two plugging heads. Knowing that the technician had access to the area in between the plugging heads gave the TDW application engineer an idea; using a vapour barrier seal to reduce or eliminate hydrocarbon leakage would allow work to safely proceed as planned, without pipeline shutdown or risk of explosion or fire. To create the vapour barrier, TDW reverseengineered the system, which normally flows outward, to flow inward instead. Technicians plumbed a bank of nitrogen bottles into the bleed line through the hydraulic control box and started flowing the nitrogen back through the actuator, down the control bar and into the zone between the plugging heads. This way if there was a leak, it would be inert nitrogen, not hazardous natural gas.

Once the vapour barrier was in place between the plugging heads, the downstream LEL monitors detected no gas. Customer operations personnel determined the line to be safe and completed the rerouting activities.

The power of people There’s no question that quality equipment was key to solving this extraordinary challenge. But even the best tools can’t perform optimally unless they’re in the right hands – in this case, the hands of skilled TDW technicians, the people Ed Guidry, Senior Director, Intervention and Isolation Product Line, calls “the face of T.D. Williamson on the jobsite”. These are the guys, Guidry said, who “get in the truck, travel around with the equipment and, when it’s time to run the equipment, are basically in charge of everything.”

According to Guidry, it’s probably safe to say that TDW is home to the most experienced HT&P technician on the planet. And that’s not hyperbole – TDW technician Jackie York has 47 years on the job. “I’d bet no one has performed more hot tap isolations than he has,” Guidry said. And along the way, York, like every other HT&P technician, has been backed by a team of application engineers. They’re the behind-the-scenes professionals who provide technical support, including guidance when something comes up that’s out of normal – or out-ofround, like a pipe with hardened coating inside.

For this unique situation, the collaboration between experienced HT&P technicians and application engineers unlocked a bespoke solution. By combining ProStopp DS technology with a nitrogen vapour barrier, TDW crews performed a safe isolation while the pipeline remained in service. That level of execution is routine for TDW, even when the project demands are extraordinary.

Anne Knour, Market Communication Manager, TRACTO-TECHNIK, Germany, discusses the latest trenchless technologies and HDD assist and rescue methods for pipeline installation.

Figure 1. Directional Service South utilised a GRUNDORAM Taurus pneumatic pipe rammer by TRACTO to assist with the extraction of 360 m of 500 mm pipe.

renchless technology is primarily leveraged for the installation of underground utilities, creating the least amount of surface disruption possible, saving time, costs, and resources. In particular, pipe ramming and horizontal directional drilling (HDD) are favourable methods for implementing even highly complex and challenging pipeline construction projects. But when something goes wrong at an HDD jobsite and rapid action is needed, a pipe rammer is also the means of choice applying so called assist and rescue methods. This article describes the options for trenchless pipeline installation and illustrates the different HDD assist methods, including a practical example.

HDD technology for pipeline installation HDD is one of the most complex, but most versatile and flexible trenchless technologies. Nowadays HDD rigs are standard equipment for pipeline construction projects just like excavators, hoisting cranes, and other common auxiliary tools. This ever-advancing trenchless technology contributes a technical and economic edge as well as providing environmental and productivity advantages.

The main applications of HDD for pipeline projects are crossings underneath rivers and traffic ways (railways, highways, roads, runways, etc), flood protection dams, crossings below foundations of buildings or infrastructure objects, as well as longitudinal bores parallel to traffic and waterways, or in open terrain such as nature reserves. This flexibility is due to the HDD rig being ‘steerable’; the bore head contains a sonde to constantly monitor its position by means of a detection system, allowing the so-called pilot bore to follow any given path, and even to carry out directional corrections during drilling. Once the pilot bore has been established along the required bore path, the drill rods are retracted, and the bore channel is enlarged by an expansion head with the attached pipe pulled in at the same time.

There is a wide range of HDD rigs available on the market, ranging from Mini 1.5 t pit-launch machines

Figure 2. Installation of three pipes Ø 48 in. (1220 mm) each on the Isle of Sicily using a 450 t Maxi HDD rig PD 450/120 DZ by Prime Drilling as part of constructing the Trans-Mediterranean gas pipeline from Algeria via Italy to Holland. Figure 3. GRUNDORAM Apollo by TRACRO used to establish crossings underneath 45 traffic ways with DN 1220 steel pipes for the ‘Noord-Zuid’ gas pipeline running North to South in the Netherlands.

to Mega HDD rigs with a pullback force of 2500 - 6000 t. The principle of the directional drilling process remains the same, however high the pulling forces are. For installing pipelines with large diameters of 2000 mm and more over longer distances using HDD, 400 - 2500 Maxi rigs and Mega rigs are applied.

Ramming technology for pipeline installation The dynamic steel pipe ramming technique plays a significant role in expanding the worldwide pipeline infrastructure for the supply of resources such as oil and gas. Mainly, pneumatically driven pipe rammers are being used for the installation of pipelines beneath roads, railway embankments, and rivers. These machines, which provide impact forces up to 40000 J enable the underground installation of open steel pipes as casing or product pipes up to 4000 mm dia., over lengths up to 80 m, in soil classes 1 - 5 (partly even class 6 – easily soluble rock) without the need for jacking abutments. Pipe rammers are suitable for installing horizontally and helically welded pipes, seamless pipes and pipes with insulation protection without tearing up valuable surfaces. Pipe ramming can can be used for various applications in all kinds of soil types except for muddy areas, swamps and compact, non-displaceable soils.

The potential of dynamic impact energy for HDD projects Dynamic impact force is one of the most efficient methods of energy application in the construction trade. Other than static energy, dynamic impact power can move or loosen the soil or elements stuck in the ground. Thus, pipe rammers are not only used for underground pipeline construction, but also to free stuck drill rods or pipes, allowing them to be removed, relocated or mobilised subsequently. These HDD and rescue methods can help with a variety of onsite problems, as detailed in the following.

HDD assist and rescue methods Pipe rammers have been used in various ways on HDD projects for several decades. These HDD assist and rescue methods have been developed cooperatively between HDD contractors, engineers and trenchless equipment manufacturers. These developments have largely taken place in the USA, where HDD has long been used for largescale pipeline projects.

Pipe ramming specialist, Rick Melvin from US trenchless manufacturer TT Technologies explains: “Contractors have been using pipe rammers on HDD projects to help install pipe under challenging areas like waterways for a long time. Through the pullback assist methods, percussive force from a pipe rammer on the back end of a pipe string can help prevent hydrolock and ensure a smooth installation. Now when things don’t go as planned, a drill rod breaks or a segment of pipe needs to be removed, we can do those things as well, again using the percussive power of the pipe rammer to help remove or salvage those products from the ground.”

Considering the amount of money and time that is lost when a major pipeline installation project comes to an unexpected halt, it’s worth taking a closer look at the individual HDD assist and rescue methods, namely conductor barrel, pull back assist, bore salvage, drill rod recovery and the latest technology pipe extraction.

Conductor barrel: installation of casing pipes for HDD crossings The concept behind the conductor barrel is creating a clear pathway through poor soil conditions so that drilling

can begin in more favourable soil conditions. If drilling does not begin in soil that is conducive to drilling, the success of the entire project can be put in jeopardy. Loose, unsupported soils are prime candidates for this method.

During the conductor barrel process, casings are rammed into the ground, at a predetermined angle, until desirable soil conditions are encountered. The spoil is removed from the casing prior to the drilling operation.

Drilling starts within the casing in the favourable soil conditions. The conductor barrel pullback assist can also serve as a friction-free section during the pullback operation or prevent situations in unstable soils acting in a similar fashion to containment cells.

Pull back assist: overcoming hydrolock The pullback assist technique incorporates the use of both a pipe rammer and an HDD rig working in tandem to get a problematic product pipe installed. When drilling underwater or in loose flowing soil conditions, hydrolock can occur. This happens when the external pressure being put on the product pipe from ground water pressure, drilling fluid pressure and/or soil conditions exceeds the drill rig’s pullback capacity, or the product pipe’s tensile strength. The percussive action of a pipe rammer in this situation is used to help free the jammed pipe. The pullback assist technique has been successfully used on steel pipe, as well as HDPE. This method can be used as a safety measure in anticipation of hydrolock problems, or after the pipe has become jammed.

Bore salvage: rescuing/removing jammed product pipes This simple yet highly effective technique is used to remove jammed product pipes. During the bore salvage operation, the pipe rammer is attached to the end of the partially installed product pipe. The pipe rammer is attached to the product pipe so that it pulls the pipe from the ground. This can be accomplished through a fabricated sleeve. A winch or some form of pulling device is used to assist the rammer during operation. In many cases, the impact power of the pipe rammer is enough to free the jammed product pipe and allow it to be removed from the ground.

Drill rod recovery: loosening of jammed HDD drill rods The principal is the same during drill rod recovery, as it is during bore salvage, however, there are two possible tooling configurations. Depending on the situation, contractors can remove the drill rod from the ground or, if the rod is still attached to the drill rig, push on the rod while the drill rig pulls back.

Pipe extraction: replacing pipes already installed The impact force of the pipe rammer is combined with static pullback to extract an old or damaged product pipe. It is then replaced with a new pipe, allowing operators to save expensive pipe and bore again. To do so, a pipe rammer is attached to both ends of the pipe to be extracted. The percussive impact power of the rammer at one end helps free the pipe by pushing it, while the lead rammer at the other

Figure 4. Conductor barrel in practice: ramming of a casing through difficult soil conditions to gain a more favourable starting point for an HDD bore.

Figure 5. Pullback assist in progress with a pipe rammer helping to get a get a problematic product pipe installed.