Corrosion services

Corrosion service Carbon dioxide (CO2) or hydrogen sulphide (H2S) in formation tluids will cause rapid corrosion of standard carbon steel and special steel may be required... 

With cobalt historically being approximately twice the cost of nickel, cobalt-base alloys for both high temperature and corrosion service tend to be much more expensive than competitive alloys. In some cases of severe service their performance iacrease is, however, commensurate with the cost iacrease and they are a cost-effective choice. For hardfaciag or wear apphcations, cobalt alloys typically compete with iron-base alloys and are at a significant cost disadvantage. 

Corrosivity. Corrosivity is an important factor in the economics of distillation. Corrosion rates increase rapidly with temperature, and in distillation the separation is made at boiling temperatures. The boiling temperatures may require distillation equipment of expensive materials of constmction however, some of these corrosion-resistant materials are difficult to fabricate. For some materials, eg, ceramics (qv), random packings may be specified, and this has been a classical appHcation of packings for highly corrosive services. On the other hand, the extensive surface areas of metal packings may make these more susceptible to corrosion than plates. Again, cost may be the final arbiter (see Corrosion and corrosion control). 

Casing Joint Gasket. A confined-type nonashestos gasket suitable for corrosive service shall he provided at the casing joint. 

Not understanding details of the corrosion service. Stating only the predominant acid without the other details (such as presence of chloride ion) is an example. The author explains how to use the acronym SPORTSFAN ... 

Typically, a corrosion allowance of 0.125 in. for non-corrosive service and 0.250 in. for corrosive service is added to the wall thickness calculated in Equations 12-1 to 12-4. 

Figure 2-5A. Lined-steel pipe and fittings for corrosive service. By permission. Performance Plastics Products.

There are many design features and styles of safety relief valves, such as flanged ends, screwed ends, valves fitted internally for corrosive service, high temperature service, cryogenic service/low temperatures, with bonnet or without, nozzle entrance or orifice entrance, and resistance to discharge piping strains on body. Yet most of these variations have little, if anything to do with the actual performance to relieve overpressure in a system/vessel. 

A rupture disk is a non-reclosing thin diaphragm (metal, plastic, carbon/graphite (non-metallic)) held between flanges and designed to burst at a predetermined internal pressure. Each bursting requires the installation of a new disk. It is used in corrosive service, toxic or leak-proof applications, and for required bursting pressures not easily accommodated by the conventional valve such as explosions. It is applicable to steam. 

For most process applications, the materia s of construction can be accommodated to fit both the corrosive-erosive and mechanical strength requirements. Manufacturers have established standard materials which will fit a large percentage of the applications, and often only a few parts need to be changed to adapt the valve to a corrosive service. Typical standard parts are (See Figures 7-3, 7-3A, and 7-4)... 

For corrosive service the wheel can be made of stainless or nonferrous alloys can be all plastic in some designs or may be covered with rubber, lead, or plastic. Rubber-covered fans are usually limited in wheel peripheral velocity to 12,000-15,000 ft/min, although some wheels with certain types of rubber can run higher. ... 

One of the most effective methods of preventing corrosion is the selection of the proper metal or alloy for a particular corrosive service. Once the conditions of service and environment have been determined that the equipment must withstand, there are several materials available commercially that can be selected to perform an effective service in a compatible environment. Some of the major problems arise from popular misconceptions for example, the use of stainless steel. Stainless steel is not stainless and is not the most corrosion-resistant material. Compatibility of material with service environment is therefore essential. For example, in a hydrogen sulfide environment, high-strength alloys (i.e., yield strength above 90,000 psi or Rc 20 to 22) should be avoided. In material selection some factors that are important to consider are material s physical and chemical properties, economics and availability. 

ASTM A 990-05 Standard Specification for Castings, Iron-Nickel-Chromium and Nickel Alloys, Specially Controlled for Pressure Retaining Parts for Corrosive Service [currently contains CW-2M (C-4C) and two others]. 

V e s s e I 0 Rupture Disc in Corrosive Service Or for Highly Toxic Materials where Spring Loaded Valve May Weep. 

Two Rupture Discs in Extremely Corrosive Service. The 1st May Periodically Need to be Replaced. 

With large holes (16 to 25 mm), these trays are some of the most fouling-resistant and corrosion-resistant devices in the industry. This defines their main application highly fouling services, slurries, and corrosive services. Dual-flow trays are also the least expensive and easiest to install and maintain. 

The best type of valve unit depends on the corrosive and fouling tendencies of the service, as some valve units tend to pop out of their seats in corrosive services, while others tend to stick to their seats in fouling services. 

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