Case Study: Rolled And Welded Cylinders for Petroleum Tower & Columns

We contracted the cylinder processing of the tower project. The primary material is 316L stainless steel, with a total weight of more than 200 tons. This batch of products involves many parts specifications, drawings, and processes. And the production is more complex.

The metal fabrication process mainly includes cutting, bevelling, bending, plate rolling, welding, etc., all of which are strictly implemented in accordance with the quality requirements of the customer. It took three months to successfully complete the product processing. The cylinders are highly praised by the customer and lay a solid foundation for continued cooperation in the future.
Those rolled and welded cylinders are used for petroleum towers and columns.

Introduction of Towers and Columns

Towers are classified according to the type of “internals” in the tower, and according to the function performed by the tower.

• Towers may contain trays. If the tower contains trays, the vessel is called a tray tower, or synonymously a tray column.
• Towers may contain packing. If the tower contains a packing, the vessel is called a packed tower, or packed column.
• If the feed to the tower is a hydrocarbon mixture and the tower separates this mixture into two factions or streams, one stream containing the more volatile components of the feed and the other stream the less volatile components of the feed, the tower is called a fractionation tower. Other names for a fractionation tower are: fractionation column, fractionator, distillation tower and distillation column.
• If the feed to the tower is liquid, and the tower removes an undesirable gas which is dissolved in the feed, the tower is called a stripping tower. Other names for a stripping tower are stripping column and stripper.
• If the feed to the tower is a gas mixture containing one or more undesirable components which are removed within the tower by absorbing them with a suitable solvent, the tower is called an absorption tower. Other names for an absorption tower are: absorption column and absorber.
• If the feed to the tower is a gas or liquid mixture containing one or more undesirable components which are removed within the tower by adsorbing them onto solid catalyst pellets, the tower is called an adsorption tower. Other names for an adsorption tower are: adsorption column and adsorber.
• If the feed to the tower is a liquid mixture containing one or more undesirable components which are removed by absorbing them with another liquid, the tower is called an extraction tower or extraction column.

Towers are similar to vertical process vessels in that they are erected vertically and they are cylindrical in shape with heads at each end of the cylinder. Towers are, however, normally much taller then vertical process vessels. Typically the length to diameter ratio of a tower ranges from 3:1 to 20:1. Towers typically range in diameter from 3 to 20 FEET and in height from 20 to 150 FEET.

Tower/Column Applications

Towers are commonly used for the following purposes:

• Distillation
• Stripping
• Absorption
• Adsorption
• Extraction.

A description of these items follows.

• Distillation — Distillation is a process which separates a mixture of materials into two or more desired parts. The device which performs this operation may be called a distillation tower, distillation column or fractionator. The operation of a distillation column depends on the fact that different materials boil at different temperatures. For example, water boils at 212 DEG F and ethyl alcohol (the active ingredient in liquor) boils at 173 DEG F. Distillation is not a new concept. The material which boils at the lower temperature is called the light or more volatile component. The material with the higher boiling point is called the heavy or less volatile component. In the case of ethyl alcohol and water, we are dealing with a two component or binary mixture. This is not the usual case. More commonly, the feed to a distillation column is a multi-component mixture. For example, crude oil contains hundreds of different components. The purpose of distilling crude oil is to separate it into what are called fractions or cuts. Each fraction or cut is not a pure component, but a mixture of components which may be used as is or refined further. Crude distillation normally is used to produce these fractions: raw gasoline, raw kerosene, gas oil and reduced crude.
• Stripping — The process of extracting a material dissolved in a liquid phase and transferring it into a gas phase is called stripping or desorption. The stripping process is carried out in a device called a stripping tower or stripping column. The removal of ammonia from water is an example of the stripping process. Water with ammonia dissolved in it passes down the stripping tower. Air passing upward through the tower strips the ammonia from the water and the ammonia - air mixture exits from the top of the tower.
• Absorption — The process of transferring a material from the gas phase to the liquid phase is called absorption. The liquid into which the gaseous component dissolves is called the absorbent. The device in which the absorption process takes place is called an absorption tower, absorption column or absorber. The removal of carbon dioxide and hydrogen sulfide from the natural gas with deithanolamine (DEA) is an example of the absorption process. Natural gas, CO2 and H2S pass upward through the tower. DEA passing downwards absorbs the CO2 and H2S.
• Adsorption — The process of transferring a material from either the gas or liquid phase to the solid phase is called adsorption. The solid to which the liquid or gaseous component attached itself is called the adsorbent. The device in which the adsorption process takes place is usually called an adsorption tower, adsorption column or adsorber. If the purpose of the adsorber is to remove water, the term drying tower or dryer is often used.
• Extraction — The process of transferring material from one liquid phase to another immiscible liquid phase is called liquid - liquid extraction, solvent extraction or simply extraction. Immiscible liquids are liquids which do not dissolve in each other, or example, oil and water. If the two immiscible liquids are contacted countercurrently, the contacting device is called an extraction column, extraction tower or extractor.

more information about towers and columns, please visit Towers & Columns: Introduction, Application, Internals and Materials Explained.

What Do We Do For Towers/Columns with Our Metal Fabrication and Machining Services?

Key steel fabrication services that we perform for towers/columns companies, OEMs and equipment manufacturing firms include plate bending, mechanical engineering, manufacturing of wear-resistant components, ASME pressure vessel fabrication, heat exchanger construction, plate rolling, plate forming, metal forming, cold forming, hot forming, steel plate fabrication, welding, heat treating, plate cutting, and plate straightening. We have the capabilities, industry experience and specialized equipment needed to form, cut, machine, process and join most types of heavy steel, alloy steel or metal.

Openex provides turnkey services from machining, fabrication, blasting, painting, and delivery of internal trays of columns & towers for our customers. The fabrication process is carried out under strict adherence to international standards. Openex successfully manufactured and delivered one of the world’s largest single-piece process columns, the Propylene-Propane Splitter for a Propane Dehydrogenation Plant. Since then, Openex has manufactured and delivered many columns and towers of up to 13 m diameters with over 100 m length and weighing 1,000 T to many of its customers worldwide.

Openex’s strength is its ability to manufacture such large, heavy and long columns & towers to any international codes and standards. Openex’s unique capability is to perform PWHT of columns and towers with no restriction in size under one single firing which is a rare feat. Openex also offers its customers a one-stop center to include the installation of material trays and insulations if required.

Contact us at sales3@openex.com.cn or call us at +86 186 5928 0806 for more information about fabrication for towers & columns and to receive a free project quote today.