REPLACE

Elaine Maruca,

The Pipe Line

Development

Company

(PLIDCO), USA,

explores why

pipelines may

need replacing

or repairing

and how these

procedures can

be approached.

Pipelines are the fastest, easiest and safest way of transporting liquids in large quantities across long distances. Operators of these pipelines have a responsibility to keep the lines in a good

working condition in order to prevent leaks. However, if there is a problem, operators also have a duty to fix it quickly and efficiently. While this may sound simple, there are many options for maintaining and repairing pipelines, and making the right choice is imperative.

OR REPAIR

What causes a pipeline to need repairing or replacing?There are many reasons why a pipeline needs to be repaired or a section of it replaced. These reasons can be broken down into five key categories: vandalism, corrosion (internal and external), nature (weather and temperature), material failure (gaskets and welds) and accidents (boat anchors and construction equipment). The above reasons can cause holes, cracks, thinning walls, dents, weak joints and, in the worst cases, a rupture. The question that then arises is: what is the best way to fix these problems?

Replace itIf the damaged area is large, then a section of the pipeline may need to be replaced. Rafi Haviv, Ashgar Tech Ltd., explained how a section of a 16 in. line was replaced using The Pipe Line Development Company’s (PLIDCO) Weld+Ends and Clamp+Rings. The pipeline was inspected by a smart pig, which suggested that a 900 m section was showing signs of heavy internal corrosion.

Haviv said: “The line was shut down, the corroded section was cut out and the new section of pipe was put into place. Weld+Ends were used to join the pipe and Clamp+Rings to handle the high hydrostatic and dynamic forces that would

occur in that specific application once flow resumed in the line.”

With the line back in operation, the Weld+Ends were welded to the line and the Clamp+Rings were removed, cleaned and put back in stock for future use.

PLIDCO’s Clamp+Rings can also handle thermal and external forces, which were not relevant in that case. Shutting down the line is usually the final choice as this causes large costs to be incurred while the pipe is down. However, sometimes this is the only safe choice.

Repair itExternal and internal corrosion can cause wall thinning on a pipeline. This defect can be repaired rather than the line being replaced on some occasions. Many products are available for this fix, including wraps and Sole+Mates, which are designed to reinforce non-leaking, weakened pipelines. Longitudinal butt welding is required for all applications and back-up strips are furnished. For pressure containing applications, the sleeve must be fully seal welded to the pipeline using circumferential fillet welds. Reinforcing the pipe before a leak occurs is, arguably, the best case scenario for the operator.

Leaks caused as a result of vandalism have, unfortunately, become a common occurrence. Bud Zanders, Chief Engineer at PLIDCO, explained: “Depending on working pressure and size, bullet holes in a pipeline can be quickly plugged with a PLIDCO Smith+Clamp.”

This fitting can be used for pit holes. The pilot pin directs the sealing cone into the hole and, after the force screw is tightened, the leak is stopped. A Weld+Cap can be welded over the clamp to make repairs permanent.

Illegal tapping is another form of vandalism that is currently causing losses of millions of dollars in operations across the world. The company’s Tap+Enclosures come in three variations, each used for different needs. These fittings have a domed section that fits over the illegal tap and can be welded onto the line while it is operating for a permanent repair. Fittings for this type of repair are custom made for each application.

Gaskets are weak spots on flanges and tend to leak over time. They can be fixed in two ways. One approach for repair is by using a Flange Repair+Ring. This is the method by which the 4 in. 300 Class flanges shown in Figure 2 were fixed on a rig in the Gulf of Mexico.

The product fits over the leaking flanges to create a seal around the circumference. Sealant is injected into the button-head fittings, which creates a complete seal around the existing flange studs and nuts. This fitting can also be kept in stock for immediate repair needs.

A Flange Repair Split+Sleeve is commonly used on flanges that are misaligned or have a leaking gasket, which was the case in Riohacha, Colombia (Figure 3). This offshore installation took seven hours from start to finish. Sealant is not needed on a Flange Repair Split+Sleeve as long as elastomer packing can be used. This sleeve seals on the pipe beyond the flange welds with the ability to cover a wide variety of flange types and classes.

Figure 1. A 16 in. PLIDCO Weld+End and Clamp+Rings.

Figure 2. A 4 in. 300 Class PLIDCO Flange Repair+Ring stopping a leak.

World Pipelines / REPRINTED FROM DECEMBER 2016

Weather cannot be controlled and, as a result, can cause storm damage to offshore lines. Riser pipelines on the ocean floor are prone to damage due to storms. One example of replacing these is with the Power+Grip connector. Using this connector means that welding is not required and there is minimal pipe end preparation. It has a double row of packing with a test port to prove seal integrity before pressurising the line. The connector accepts external loading and the seal and grip actuations work independently. This fitting grips the pipe and has less chance of being compromised during a storm.

Accidental damage can be caused by numerous factors. Pete Haburt, PLIDCO’s International Business Development Manager, gives an example: “A 48 in. line was hit by a ship’s anchor off the coast of Iraq, which caused deformation and a crack that leaked. It was repaired by a 48 in. PLIDCO Bellied Clamp+Sleeve.”

This fitting differs from the Split+Sleeve as it is designed to grip the outside wall of the pipe, which counteracts end-pull and axial stresses that are often encountered in offshore installations. It also does not require welding.

Welds tend to develop leaks from several types of anomalies. This is one of the most common causes of pipe leaks and can be repaired using the Split+Sleeve. These sleeves can be used to either temporarily or permanently repair both onshore or offshore leaks. The leak is stopped when the fitting is bolted on the line. For a permanent repair, the fitting can

be welded while the line is in service, which saves both time and money. There are several variations of the Split+Sleeve including tees, ells, crosses and fittings with bellies, all of which are based on the same general sealing principal.

Having repair fittings is the best case scenario. However, that is not always feasible. Therefore, knowing what product to use and who to contact is imperative.

Figure 3. A 24 in. 600 Class PLIDCO Flange Repair Split+Sleeve.

REPRINTED FROM DECEMBER 2016 / World Pipelines