Leak Detection Technique

Leak detection techniques are based on either continuous or intermittent measurements of specific parameters. Intermittent leak detection methods are often able to detect smaller leak rates compared with continuous leak detection techniques.

 

Some continuous techniques can only detect transient pipeline conditions during the onset of a leak, and will not be able to identify the presence of a leak at a later time.

 

For some intermittent techniques fluid transportation through the pipeline needs to be interrupted. Using intermittent techniques, the detection time of a leak will be completely dependent on the frequency of inspection.

 

Techniques for detection of leaks in liquid lines offer better performance than those for gas pipelines, which in turn are better than those for two-phase pipelines.

 

The conflicting balance of sensitivity to leaks and false alarms will determine the sensitivity setting of the leak detection system. Large leaks can normally be detected more rapidly than small ones. To maintain the user’s confidence in the system, avoiding false alarms should have a higher priority than attempting to shorten the leak detection time or reducing the minimum detectable leak rate.

 

The performance of pipeline leak detection techniques is dependent on fluid type, operating pressure

including fluctuations, batch or continuous operation, pipeline length and size, metering accuracy, etc.

 

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Duplex Stainless Steel Fabrication and Welding

With the ever-increasing demand for duplex stainless steel process equipment fabricators have developed procedures for the welding and fabrication of these grades. A lot of data on these procedures as well as practical experiences have become available. When fabricating duplex stainless steels special attention should be paid to heat treatment and welding. Unsuitable heat treatment can result in precipitation of inter metallic phase and deterioration of toughness and corrosion resistance. Although most welding methods can be used to weld duplex steels, they require special procedures for the retention of properties after welding. Below you will find some general guidelines for welding duplex stainless steels

Introduction

It is assumed that the reader already has experience in welding of austenitic stainless steels such as Type 316L.This section addresses some to commonly discuss welding characteristics and procedures of the duplex stainless steels in terms of how they differ from austenitic stainless steels. Addressing each of these features is essential for the design of technically and economically effective welding procedures to be qualified. Differences between Duplex and Austenitic Stainless Steels Duplex stainless steels are typically twice as strong as common austenitic stainless steels. The thermal expansion of the duplex grades is intermediate to that of carbon steel and the austenitic stainless steels. The thermal conductivity of the duplex stainless steels is also intermediate to that of carbon steels and the austenitic stainless steels.

When there are problems with welding of austenitic stainless steels, those problems are most frequently associated with hot cracking of the weld metal itself. This hot cracking tendency is aggravated by fully or predominantly austenitic solidification, and by the combination of high thermal expansion and low thermal conductivity. For the more common austenitic stainless steels, hot cracking is minimized by adjusting the composition of the filler metal to provide significant ferrite content. For the more highly alloyed austenitic stainless steels where the use of a nickel-base filler metal is necessary, austenitic solidification is unavoidable. In these cases these problems must be managed by minimizing joint constraint and by low heat input, often requiring many passes to build up the weld.

Duplex stainless steels have good hot cracking resistance. Hot cracking of the duplex weld metal is seldom a concern. The problems most typical of duplex stainless steels are associated with the heat-affected zone (HAZ), not with the weld metal. The HAZ problems are not hot cracking but rather a loss of corrosion resistance and toughness, or of post weld cracking. To avoid these problems, the welding procedure should focus on minimizing total

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Controlled Investing and Casting Procedures

Untuk berhasil, ada teknik dan prosedur yang harus dilakukan untuk melakukan pengecoran suatu bahan baja/besi. Besi Cor atau istilah tekniknya Casting, harus benar dilakukan sesuai dengan prosedur yang tepat.

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