Flow Control

Vanessa Triple Offset valves under Cryogenic testing.
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Due to the importance of valves at any petrochemicals plant, buyers should make sure all aspects are covered before making a final decision.

In an industry where the smallest leakages could cause a disaster, flow control plays a critical role in safeguarding plants from disaster and in maximising production of the different products. Key to this process is valves.

The first step in the production of petrochemical is cracking the feedstock, whether ethane or any other heavier feed like naphtha, into ethylene and propylene.

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This cracking process take place in a furnace, and it is called pyrolysis which is the thermal cracking of petroleum hydrocarbons with steam, also called steam cracking. “Valves in the furnace section play a critical role in maximising ethylene production and throughput,” says Ian Turner, general manager of IMTEX Controls.

“There are three critical control valve applications in the furnace area including dilution steam ratio control, feed gas control, and fuel gas control,” he explains.

Precise control of the steam dilution valve is necessary to maintain the proper steam ratio, which can greatly affect the efficiency of the furnace, while the feed gas control valve controls the flow of feedstock used in the ethylene plant.

Tight control of the valve is critical in the steam dilution valve so that the proper reaction ratio can be maintained within the furnace, and thus avoids wastage.

Fuel gas regulates the temperature of the furnace by controlling the fuel to the burners. “Due to the nature of the fuel, many plants use emissions control packing to limit the emissions of the fuel gas. This is for environmental concerns as well as general safety reasons,” says Turner.

“As with the other valves in the furnace area, due to location, the fuel gas valve may also see high ambient temperatures. Depending upon on the ambient temperatures for each particular application, special care may need to be taken in selecting the actuator and accessories,” Turner explains.