Piping interview and questions Part-2

Piping interview questions and answers -Part 1

Important stainless steel grades

Stainless Steel

Stainless Steel

Stainless steel is a group of heat and corrosion resistant steels. They have in general higher resistance to corrosion in some definite environment, as well as a higher resistance to scaling at high temperature.

Stainless Steel are iron-based alloys containing a minimum of 10.5% chromium with or without other alloying elements. Based on the alloy content and the micro structure,stainless steels are classified into three major categories viz, Austenitic, Ferritic, and Martensite.

Austenitic

This category of steel contains 16-26% Chromium and 6 to 22% Nickel. They are non magnetic in annealed condition and have excellent corrosion resistance. They are not hardenable by heat treatment.

However, they can develope high strength on cold working. They have excellent weldability, formability, hygiene factor and cryogenic properties. On cold working they exhibit different degrees of magnetism. They are identified in the AISI 300 series.

Ferritic

This category of stainless steel contains 10.5  to 30% Chromium without any Nickel. They are Ferro-magnetic in nature and generally not hardenable by any heat treatment. These steel posses good resistance to stress corrosion cracking and moderate weldability & formability.

They are identified in the AISI 400 series.

Martensitic

This group contains 11 to 14% Chromium without any Nickel but with a higher carbon content
compared to the  Austenitic and Ferritic stainless steels. They are Ferro-magnetic in nature and hardenable by heat treatment.

They possess moderate corrosion resistance and are identified in AISI 400 series.

HF-ERW pipes

HF-ERW pipes are made from hot rolled flat steel strip, formed into tubular shape and the longitudinal seam is welded by the application of mechanical squeezing of edges and heating the edges through High Frequency Electric Resistance applied by induction or conduction. The weld joint is achieved without addition of any filler metal.

Application Industry:

Oil and Gas Pipeline
Plumbing
Heating
Water Supply Systems
General purpose applications
Structural Pipe

FLANGES

Flanges

Codes to be refer for flanges are

B16.5 - dimensions and ratings of steel flanges NPS 24 and smaller

B16.47 series A - dimensions and ratings of steel flanges NPS 26 though NPS 60.

B16.47  series B used to mate existing equipment hole dimensions and PCD.

B16.36 - orifice Flange

Type of Flanges
Weld neck flange

Slip on Flange

Lap joint Flange

Socket weld Flange

Based on face of Flange classified as

Flat face  (FF)

Raised face (RF)

Ring Type Joint (RTJ)

Tong and Grove (T&G)