Crude Oil Pipeline Valve Selection Guide

In the petrochemical industry, the selection of crude oil pipeline valves is of great importance. Valves are not only important components of the pipeline system but also key elements in ensuring the safe and efficient operation of the entire production process. With the continuous development of petrochemical technology and increasingly complex operating conditions, the requirements for valves are also becoming higher. This article will provide a detailed introduction to the factors that should be considered when selecting valves for crude oil pipelines, helping you make wise choices in practical applications.

Valves used in crude oil pipeline systems generally have no special requirements because crude oil is not a flammable or explosive medium, and the content of toxic components such as hydrogen sulfide is relatively low. In addition, the working pressure and operating temperature of the crude oil system pipelines are relatively low. Therefore, in general, the valves selected for crude oil pipeline systems should have reliability and economy. Common choices include gate valves and globe valves, and in special cases, ball valves can also be used.

Gate valves and globe valves are widely used in crude oil pipeline systems because of their simple structure, convenient operation, and good sealing performance. Gate valves are suitable for full-open or full-close occasions, providing good sealing performance while having smaller operating torque, making them suitable for large-diameter pipelines. Globe valves are suitable for occasions where flow regulation is required, and their sealing performance is also reliable, but the operating torque is relatively large, making them suitable for medium and small-diameter pipelines.

Although ball valves have better fluidity in viscous media, the manufacturing cost of large-diameter ball valves used at high temperatures is relatively high. Therefore, economic factors need to be comprehensively considered when selecting them. Under low-temperature conditions, if the viscosity of crude oil is high, ball valves can be considered as shut-off valves to avoid viscous media accumulating in the gate valve, which affects the opening and closing operation.

The atmospheric and vacuum distillation systems are important links in the petrochemical industry, and the selection of their valves needs to consider multiple factors, including the temperature, viscosity, and corrosiveness of the medium, as well as the valve diameter.

The medium in atmospheric and vacuum distillation systems has high temperature and high viscosity, and there are problems such as naphthenic acid erosion and corrosion. Therefore, wafer-type check valves should not be used, and flanged check valves should be given priority. In general, when the valve diameter is greater than or equal to DN50, a swing check valve should be selected; when the valve diameter is greater than or equal to DN400, a tilting disc swing check valve should be preferred; for DN40 and below, a lift check valve should be selected. The tilting disc swing check valve, due to the buffering effect of its auxiliary disc, can effectively alleviate the impact of large-diameter valve discs during opening and closing, thereby extending the service life of the valve.

Since most valves in atmospheric and vacuum distillation systems operate under medium and low pressure conditions, bolted bonnet connections can ensure the sealing of the medium. In addition, since most of the pipelines in this system operate under high-temperature conditions, the packing should be made of stainless steel combined with flexible graphite braided packing to avoid using other nonmetallic packing materials that are not resistant to high temperatures.

Considering that the pipe diameters of atmospheric and vacuum distillation units are relatively large, the operability of valves is also very important. The usual requirements are as follows: for gate valves, when Class ≤ 300 and DN ≥ 400, gear transmission mechanisms should be added; when Class = 600 and DN ≥ 350, gear transmission mechanisms should also be added. For butterfly valves, when the pressure level is any grade and DN ≥ 200, worm-gear mechanisms should be added. For ball valves, when the pressure level is any grade and DN ≥ 200, worm-gear mechanisms should be added. These transmission mechanisms can effectively reduce the labor intensity of operators and improve convenience and safety during operation.

The overhead pipeline gathers more hydrogen sulfide, hydrogen chloride, and other highly hazardous and corrosive media. Therefore, when selecting valves, it is necessary to consider not only corrosion resistance but also low fugitive emission performance.

The diameter of the overhead pipeline is relatively large, and some low-pressure pipeline valves can use butterfly valves instead of gate valves. Butterfly valves have the advantages of a simple structure, small size, light weight, and low pressure drop. They can effectively reduce valve weight, lessen the load on pipeline supports, and reduce valve structural dimensions, thereby lowering operating difficulty.

Since the vacuum of the vacuum distillation tower is established through the ejector on the overhead oil-gas pipeline, the pressure drop and tightness of the valve have a great impact on the establishment of the vacuum. Therefore, it is recommended to use ball valves and adopt low fugitive emission measures to maintain the required vacuum.

The medium at the bottom of the tower is viscous, but the temperature is high (240–395℃), the pump outlet pressure is also high (1.5–3.0MPa), and it is often accompanied by high-temperature sulfur corrosion and/or high-temperature naphthenic acid corrosion. Therefore, reliable shut-off valves such as gate valves and globe valves should be selected. When the design engineer determines that the material has high viscosity and is prone to deposition, ball valves can be considered. When the medium exhibits strong naphthenic acid corrosion, full-bore ball valves are recommended as shut-off valves to reduce valve flow velocity, decrease or avoid medium turbulence, and thereby slow down naphthenic acid corrosion.

The pressure and temperature of flare lines are relatively low, and the diameter is large. Therefore, gate valves and butterfly valves should be selected as the main shut-off valves for the corresponding main pipelines. The inlet and outlet valves of flare safety valves can be gate valves or butterfly valves depending on the diameter. The inlet and outlet shut-off valves should be lead-sealed open or locked open to ensure safety.

With the rapid development of petrochemical deep processing technology, the sources of crude oil are becoming increasingly diverse, and operating conditions are moving toward high temperature, high pressure, and strong corrosiveness. Therefore, the demand for valves resistant to high temperature, wear, hydrogen corrosion, hydrofluoric acid corrosion, and sulfur corrosion will further increase.

The problem of naphthenic acid corrosion in atmospheric and vacuum distillation units processing high-acid-value crude oil directly threatens the safe operation of the unit. Testing data show that the corrosion rate of naphthenic acid on carbon steel can reach up to 14 mm per year at certain temperatures. The most severe corrosion occurs at the atmospheric furnace outlet (350–355℃) and vacuum furnace outlet (405℃) high-temperature sections. To solve this problem, some Cr5Mo valves used in atmospheric furnace outlet pipelines have been replaced with ultra-low-carbon stainless steel valves due to severe corrosion.

The operating temperature of the catalyst pipelines in the catalytic cracking unit's reaction-regeneration system reaches above 650℃. To meet operational requirements, valve manufacturers have cooperated to develop high-temperature-resistant gate valves. Most of them have performed well, but some still fail to meet design requirements.

Butterfly valves, due to their simple structure, small size, light weight, low pressure drop, and good flow control characteristics, are increasingly welcomed by users. In particular, for large-diameter pipelines where gate valves are too heavy, butterfly valves are gradually replacing them. The valves on the main blower outlet pipelines of catalytic cracking units previously used ordinary gate valves, which caused difficulties in design, construction, and operation due to their large size, heavy weight, and long structural dimensions. In recent years, replacing gate valves with butterfly valves has achieved very good results. The currently used butterfly valves operate at temperatures above 200℃, with nominal diameters between DN450 and 1000. However, due to high requirements for manufacturing precision and quality, there are still many areas for improvement.

The selection of crude oil pipeline valves is a complex process that requires comprehensive consideration of various factors, including the nature of the medium, operating conditions, valve reliability, economy, and ease of maintenance. Through reasonable valve selection, not only can the safety and reliability of the pipeline system be improved, but operating costs can also be effectively reduced, and production efficiency enhanced. It is hoped that the introduction in this article can provide useful reference for you and help you make more scientific and reasonable decisions in actual work.

When selecting valves, it is recommended to communicate in depth with professional valve manufacturers and suppliers to understand the latest product information and technological developments, ensuring that the selected valves meet the needs of practical applications. At the same time, regular maintenance and inspection of valves, as well as timely detection and resolution of problems, are also important measures to ensure the long-term stable operation of the pipeline system.