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MPWT19-15307

Rotational Lining System and Use of High-Performance Thermoplastics Derek Lowth United Special Technical Services LLC Al-Harthy Complex Muscat-Sultanate of Oman Murali Adhyatmabhattar United Special Technical Services LLC Al Masoud Tower- Abu Dhabi UAE Emma Mitchell RMB Products Inc 1201 Rmb Ct, Fountain, CO 80817, United States ABSTRACT Protecting carbon steel oil and gas pipelines with thermoplastic liners is a proven and costeffective solution to prevent internal corrosion and abrasion. However, the industry is still facing considerable challenges when it comes to fittings and accessories such as elbows, tees, process equipment and complicated shapes. Rotational lining (aka rotolining) is a technology which bonds a single/multi layered uniform, vacuum resistant, seamless polymer layer to the interior of virtually any metallic structure, regardless of shape and complexity. Once cooled, the result is a monolithic corrosion and chemical resistant lining that conforms to complex shapes and virtually free of stresses. This system results in a high quality and fully thermoplastic lined system. Rotolining has been proven to provide long-term protection against corrosion and abrasion in various applications including saline water pipe systems, hydrocarbon service, mining and highly aggressive chemical service. This lining system can cover a wide range of fluid requirements, temperatures and applications using high-performance thermoplastics such as HDPE, PA-12, PVDF, ETFE and PFA. Rotolining is a cost-effective alternative to conventional solutions such as FBE, corrosion resistant alloy cladding or continuous chemical injection programs. In this paper, some of the insights of the rotational lining system and usage of different highperformance thermoplastics are shared. This includes some very challenging and internationally proven case studies, which substantially benefited the entire value chain as long-term solutions.

Key words:

Corrosion, rotolining, thermoplastics, high performance

INTRODUCTION Pipelines are lifelines in industries such as oil and gas. This infrastructure remains one of the most cost-effective means of transporting fluids across regions and continents. Over the years, numerous materials are being used as a material of construction for pipelines, from concrete, clay, and carbon steel to duplex and suppler fancy alloys. The consideration of the life cycle cost is an important factor for the overall success of the system. Carbon steel (CS) is the proven material of construction in oil and gas industries. Millions of kilometers of carbon steel pipeline have been in operation over many decades. The apparent capabilities of CS are its ability to operate at higher pressures and temperatures. However, like any other material CS does have problems in terms of integrity of the system, due to its inherent corrosion prone property. CORROSION & MITIGATION: Corrosion is single biggest concern in the oil and gas assets. As per NACE estimates the annual cost of total corrosion is more than 1 trillion USD. Along with extremely high cost, there is always the potential of a serious environmental problem due to oil leak and spillage. For this reason, it is necessary to adopt corrosion management techniques to protect pipelines and the surrounding environment. MITIGATION-PIPELINES Over the period the industry has adopted different practices to mitigate internal corrosion in pipelines. Typical solutions are: 1. 2. 3. 4. 5.

Corrosion allowance Continuous chemical injection along with CA Internal coatings (FBE, polymer lined) Cladding Corrosion resistant alloys

The selection of the appropriate technique is dependent on various factors such as fluid characteristics, operating pressure and temperature, as well as terrain of construction and operation. Out of the above, the most common are options are CS/corrosion allowance, chemical injection and coating.

Figure 1: Tight Lining Steps

The chart below shows approximate cost comparisons by one of the oil operators in the region.

Chart 1: Cost Comparison of various corrosion mitigation techniques for pipelines

Notes: 1) Life of CS flowline without any mitigation measures is 10 years. The pipeline needs complete replacement after 10 years. 2) Five leaks are assumed per flowline during life of 20 years. 3) One hydrotest took place during the 5th year and additional test during the 15th year of operation. 4) For HDPE liner, monitoring was required only during the first year of operation. As evident from the above analysis, carbon steel with HDPE liner (CS+HDPE) is the most technically, economically viable solution to mitigate internal corrosion in pipelines. This polyethylene polymer can be operated at an operational envelop up to 70°C for water and up to 50°C for hydrocarbon service. However, a thorough analysis needs to be done for each project based on fluid composition and other related factors. MITIGATION - FITTINGS: Fittings are one of the weakest links in the system. Various studies, including the one shown above, have demonstrated that pipes with internal polymer lining is the most economical when considering the life cycle cost. Current lining technologies are limited to elbows of 20 D maximum radius, which most depends of size of the pipe. Lining of elbows beyond 20D radius, tee sections and other complicated shapes is still a bottleneck for the system. All available

mechanisms are unable to provide complete corrosion protection to the fittings.

Figure 2: Elbow along with pipe.

ROTATIONAL LINING (ROTO-LINING) Rotational lining is a process which applies a seamless, fully bonded, thick polymer liner to the internal surface of a metallic substrate to protect against corrosion. These liners can be used to protect against corrosion from water service as well as more extreme services such as hydrochloric or sulphuric acids. A roto-lined liner will eliminate or reduce the failure modes of most other lining or coating methods. This is due to the strong bond, lack of space between the liner and substrate, lack of seams, mechanical bond with no adhesives, and thickness of the liner. PROCESS The rotational lining process, although it seems simple, requires knowledge of the appropriate resin shot weight, temperature, and time in the oven. The simplified steps of the rotational lining process are as follows: The first step of the process is to prepare the interior surface of the vessel by removing the old liner or other debris and blasting to white metal. Next, the vessel is mounted to a multi-axis rotational lining machine. Thermoplastic resin is placed inside the vessel and then the vessel is rotated inside of an oven. As the vessel rotates, the polymer becomes molten and forms an even layer across all internal surfaces. The rotation is slow, and gravity is used to spread the plastic material. Next, the vessel goes through a cooling process to set the liner in place, while continuing to rotate. This creates a seamless liner that is virtually free of any stresses. Flange faces are machined to provide a smooth sealing surface. The liner is bonded mechanically through the interaction with the rough blasted surface. Lastly, the liner is checked for quality. ADVANTAGES OF ROTATIONAL LINING The rotational lining process has many advantages and will eliminate or reduce the failure modes of all other lining and coating methods. One of the biggest advantages in this process is that complex parts are easily lined without needing access to internal surfaces. Because the

liner is seamless and mechanically bonded to the substrate, the need for failure-prone weld joints and adhesives reduces the risk of failure points and delamination of the liner. This also does not disturb the structural integrity of the part, which keeps the pressure rating consistent. Lastly, the liner is durable and can handle highly corrosive and abrasive production services. A variety of parts, including fittings, pressure vessels, pipes, dip tubes, scrubbers, fittings, pump casings, valve bodies can be lined using this process. CHALLENGES IN ROTATIONAL LINING The biggest challenge in the rotational lining process is that the part must fit inside the rotational lining oven in order to be lined. Liners must be installed in a manufacturing facility and cannot be installed in the field. The liner can only be installed on steel substrates, and complex internal components are difficult to line. Lastly, there are temperature constraints of the liner, due to the process being limited to plastics. QUALITY CONTROL There are several methods of quality control that can be used throughout the rotational lining process. When surface prepping the part, the substrate needs to be blasted to white metal maintaining a surface profile above 75 µm to allow the liner to mechanically bond to the metal substrate without risk of delamination. Materials used should have their properties tested to conform to international materials standards. After lining, a spark test and ultrasonic thickness test are performed to determine sufficient thickness and continuity of the liner. The liner thickness will vary up to 33% from the average liner thickness due to the nature of the application process. Therefore, the average thickness should be selected to ensure an acceptable minimum is achieved at all locations on the substrate. Additionally, a testing can be performed to test the mechanical bond strength of the liner. The bond strength should exceed the tensile strength of the material. HIGH PERFORMANCE POLYMERS Rotational lining can utilize many different high-performance polymers to meet the needs of specific applications. The materials below can be utilized to create a thick, fully bonded monolithic liner. Material

Characteristics

PFA (Perfluoroalkoxy alkanes) ETFE (Ethylene tetrafluoroethylene PVDF (polyvinylidene difluoride) Nylon 12 (Polyamiade) HDPE (High Density Polyethylene)

High purity and chemical resistance, operating temperature of 260°C/500°F to -268°C/-45°F. High chemical resistance and excellent bond strength in lining applications. Good chemical resistance, durable. Low moisture absorption, high impact resistance. High strength-to-density ratio, High chemical and abrasion resistance.

Table 1: High Performance Polymers Description

Maximum Service Temperature (°C)

260 150

PFA

127

ETFE

PVDF

104

PA-12

82 HDPE

Chart 1: Service Temperature of Polymers

CASE STUDIES REVISITING ROTOLINED FITTINGS IN SERVICE FOR 12 YEARS

Figure 3 : Rotolined Spools

A southeast Texas chemical plant installed 21 underground fittings that were rotationally lined with polyethylene. The fittings included 10” diameter spool pieces and 45° and 90° elbows. The service conditions of the fittings were a brine water service at ambient temperatures, which could reach 100°F in Texas summers. Rotolined polyethylene liners were chosen for this application because they are proven to last over twenty years in brine service. The liner is seamless, which eliminates failure prone weld joints. The liner is also mechanically bonded to the substrate, which eliminates the need for adhesives and reduces the risk of disbandment from the metal. The liner is thicker than most other alternative liners, with a thickness of up to 0.450”. Twelve years after the installation of these rotolined fittings, there was a maintenance shutdown at a chemical plant. Although no leaks or failures were reported while these parts were in use, managers at the plant decided to inspect the fittings to make sure that they were not close to failing. The rotolined fittings were shipped to RMB Products, who had originally lined the fittings for the chemical plant. The team at RMB inspected the fittings. During inspection, all liners were subjected to spark testing (NACE SP0274), ultrasonic thickness gauges, high-voltage electrostatic test (NACE SP0274), and visual inspection. The results of the inspection were as follows: Visual Inspection: All fittings appeared to be in good shape; internally there were no missing fragments, exposed metal or scratches. Spark Test: 14 of the 21 fittings (67%) passed the spark test after 15 years of use. Spark test failures were at the flange faces and looked to be caused by damage at install or decommissioning. Lining Thickness: All liners were still within the minimum allowable thickness requirement specified at the time of lining (above 0.221”). Additional Service Life: The liners’ service life was estimated to last another 3 - 5 years. This inspection showed the long-term durability of rotational lining in service. While the fittings would have lasted longer, the company selected to remove the liners and reinstall new liners with rotolined polyethylene. With the new liners, the company could delay another shut down for 20 years. ETFE ROTOLINED FITTINGS: During a chemical processing company inspection in 2017, 90 pieces of pipe were identified to be blistering and therefore needed replacement. These pipes were lined with a conventional fluoropolymer material (PTFE) and ranged from 3” diameter to 24” diameter. The chemical service that the pipe was exposed to was an Ethylene Dichloride Acid mixture in a VCM

plant reaching 250°F. The engineers planned to replace the pipe during the next two-week plant outage, which required meeting a tough schedule of 10 weeks for the replacements. If there was a delay in installation during that window of time, the chemical plant could lose hundreds of thousands of dollars for every day that it was shut down. Because of the tight deadline, all PTFE manufacturers that were contacted said they would not be able to deliver the lined pipe in time.

Figure 5: ETFE Lined Roto Fitting

Remembering that a 5-year old ETFE-lined tee looked brand new during the same inspection, the engineers decided to line the 90 pieces with ETFE-lined rotationally-lined pipe. At the end of the process, the ETFE-lined pipe was delivered on time and with a $100,000 savings compared to PTFE-lined fittings. This example clearly demonstrates value and benefits of rotationally lining with ETFE fittings in terms of o

Cost savings for the operator

o

Quickest delivery compared with conventional system

o

Most importantly, there is a longer lifespan of the ETFE liner, which was seen by the internal inspection at the chemical plant

ROTOLINED FITTINGS FOR HIGH PRESSURE SERVICE:

In 2013, a company that uses a produced water service was looking for solutions to protect barred tee steel pipe from corrosion. These barred tees were also exposed to negative and positive high pressure, which was needed to pump the produced water a long distance. Additionally, the project required ANSI 2500 pound flanges and each piece weighed 10,000 pounds. The total project consisted of 64 barred tees. The customer decided to use rotolined HDPE liners for the barred tees for many reasons.

Figure 6: Rotolined High Pressure Fitting

o

Many lining systems would not be able to handle this type of water pressure, because the negative pressure puts stress on the liner. However, the rotational lining process creates a liner that is mechanically bonded with the substrate, which does not reduce the pressure rating of the piping system.

o

The pieces were 10,000 pounds, which limits the type of liner installation process that can be used. Rotational lining machines have the capability of handling this size of part.

o

Rotational lining is efficient for lining complex geometries, including barred tees. No manual installation is required.

o

In rotational lining, the structural integrity of part is maintained, which keeps the pressure rating of the steel consistent. The part is also able to withstand negative and positive pressure because the liner is mechanically bonded to the substrate.

The fittings were lined with HDPE, including the bars. They were put into service with no issues and the customer ordered more rotationally lined pieces the next year.

ANTI-FOULING SOLUTION: Biofilm was an issue for a client who has produced water caissons in the Gulf of Mexico. This piping was an outlet for produced water back to the sea and was not under constant pressure. During low pressure service, barnacles (biofilm) would attach to the pipe and cause issues when flow was required again. Many solutions were tried, including coatings, FRP piping, and alloys but nothing worked.

The customer decided to use a rotationally lined homogenous blend of HDPE and antimicrobial powder for the 16 caissons. HDPE liner has proven to last over 20 years in brine water services by providing long-term protection against aqueous corrosion in saltwater

Figure 7: Rotolined Anti Fouling Solution

applications. Rotational lining creates a seamless, thick, vacuum-resistant liner that is fully bonded to the metal substrate. Creating a homogenous blend of HDPE and antimicrobial powder gives the added protection against localized biological attacks and biofouling build up on pipes. The project came in at budget and saved the customer $5 million on the caisson portion of the offshore project. The use of corrosion-resistant HDPE has increased operational life, reducing maintenance costs and long-term capital expense for the customer.

CONCLUSION Rotolining technology has rightly addressed the problems related to fittings, the weakest link in the system, including elbows and tee sections. and complicated shapes. Thermoplastic liners installed with the rotational lining process successfully protect fittings, vessels, and pipeline from corrosion. This technology also has flexibility of using a wide variety of thermoplastic materials such as HDPE, PA-12, and ETFE. The application of rotolined fittings is not limited to the oil and gas industry. It can also solve many corrosion-related problems in major industries like refineries, petrochemical, chemical and mining. ACKNOWLEDGEMENTS The authors would like to thank all value chain colleagues who helped to make this happen.

REFERENCES 1. Innovative Field Trial Results of Flangeless Grooved HDPE Liner Application in a Super Gigantic Field for Oil Flow line Internal Corrosion Management. Dr. Abby Kalio Amabipi et al 2. An Overview on The Deployment of HDPE Lining for Water Injection Systems In Saudi Aramco, Hassan S. Alsagour and Abdulaziz Y. Alasiri

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