Cleaning pipelines

The tapes are cold-applied, either by hand or by mechanically-operated equipment moving along the cleaned pipeline. 

Cleaning waterlines and fuel pipelines with pipe pigs has been an acceptable practice for many years. However, cleaning pipelines that conveyed explosives with a pipe pig is innovative, and proved to be very effective and economical. 

The use of solvents for cleaning pipelines and tanks, decomposing methane hydrate and similar non-routine cleaning is a good application for recoverers as is the supply and return of mixtures for testing the efficiency of distillation columns. 

FIGURE 5-2. High-Pressure jets for Cleaning Pipelines. 

While chemical cleaning solvents usually are applied by pumping solvents through process equipment or power boilers, several other methods of applying them have been used. These include foams, "vapor phase" solvents, and special methods for cleaning pipelines. Because of the literature available, only foam cleaning and pipeline cleaning procedures will be reviewed. 

Pipelines are cleaned and inspected using pigs . Pigs usually have a steel body fitted with rubber cups and brushes or scrapers to remove wax and rust deposits on the pipe wall, as the pig is pumped along the pipe. Sometimes spherical pigs are used for product separation or controlling liquid hold up. In field lines handling untreated crude may have to be insulated to prevent wax formation. 

All pipelines will be circulated clean and those that are buried, or on the seabed, left filled with water or cement. Surface piping will normally be cut up and removed. Flexible subsea pipelines may be reeled-in onto a lay barge and disposed of onshore. 

Fittings. Fittings connect pipes and provide for the attachment of equipment to change flow direction. They must be easily cleaned inside and out, have no exposed pipe threads, and, if of the detachable type, have an appropriate gasket. The fittings are constmcted of the same or similar materials as the pipeline and are installed on tubing. Standard shapes and sizes are specified by the 3A Standards Committee. 

A CIP system includes pipelines, interconnected with valves to direct fluid to appropriate locations, and the control circuit, which consists of interlines to control the valves that direct the cleaning solutions and water through the lines, and air lines which control and move the valves. A programmer controls the timing and the air flow to the valves on a set schedule. The 3A Standards for CIP components, equipment, and installation have been developed. A simple CIP system circuit is shown in Figure 11. 

Filtration and water-knockout systems are used to clean up the gas before it enters a compressor. Cooling systems are sometimes required to maintain compressor discharge temperatures below 54°C to avoid damage to the pipeline s protective coatings. Automated compressor stations are typically staffed by maintenance and repair personnel eight hours per day, five days per week. Other stations are staffed on a 24-hour basis because personnel must start, stop, and regulate compressors in response to orders from the dispatch office. 

Energy consumption for energy-using devices and systems is typically the same year after year, if heat exchanger surfaces, filters, pipelines, and other plant items are kept clean. 

It is almost impossible to completely clean pipes that have contained heavy oils or polymers. When demolishing old pipelines, there should be as many open ends as possible so that pressure cannot build up. And good access should be provided so that the burner or welder can escape readily if he or she needs to do so. 

The process involved in the incident is concerned with the separation of crude into three phases. The crude is pumped into a two stage separation process where it is divided into three phases oil, gas, and water. The water is cleaned up and dumped to drain. The remaining mixture of oil and gas is then pumped into the main oil line where it is metered and sent on for further processing. A simplified process diagram is shown in Figure 7.1. The case study described here is centered on a flange leak in one of the oil pipeline pumps (pump A) and its associated pressure relief valve piping. 

Ammonia is the precursor for many other chemicals such as nitric acid, hydrazine, acrylonitrile, and hexamethylenediamine. Ammonia, having three hydrogen atoms per molecule, may be viewed as an energy source. It has been proposed that anhydrous liquid ammonia may be used as a clean fuel for the automotive industry. Compared with hydrogen, anhydrous ammonia is more manageable. It is stored in iron or steel containers and could be transported commercially via pipeline, railroad tanker cars, and highway tanker trucks. The oxidation reaction could be represented as ... 

The interior of the pipelines through which the discharge air passes to the aftercooler or air receiver should be cleaned regularly so that a build-up of combustible oily carbon deposits is avoided. All the piping should slope downwards in the direction of airflow to a suitable drain point at the lowest point of the pipeline. 

Coal-tar enamels are claimed to have better adherence than the asphaltic enamels to clean metal, probably because of the presence of polar compounds, but little difference can be noted in practice under proper pipelining conditions. 

Armour wrapping In rocky ground it has always been considered good practice to pad the trench for a buried pipeline with clean sand. This procedure can be very expensive if the sand has to be hauled long distances, and an armour wrap has been developed to supplement the normal outer wrap to meet such conditions. 

Line Wrapping the technique of wrapping a pipeline over the pipeline trench applied only to welded steel pipelines. It is carried out by a linewrapping machine which travels along the pipe, cleaning it, priming it. 

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