Description
What are Corrosion Coupons?
Corrosion coupons are used by people to detect pipeline corrosion in the oil and gas industry. By using coupons people can better know the corrosion circumstance in pipelines. It can provide an effective result.
At first, they are intact without any corrosion. At that time, their initial weight should be record by people. Then they are usually put into the pipelines for 30, 60 or 90 days. They will expose in the pipelines and have reaction with impurities, such as, water, oil, rust and so on. After many days’ corrosion, coupons will loss some of their weights. And then through the weight difference, people can calculate the rate of corrosion in pipelines.
There are many types of them. Such as rectangle and circle. There is not that much difference between these two types. A pair of 3 inch strip coupons are generally recommended. They are common used.
There are many materials of corrosion coupons. MS 1018 is defaulted. Besides, we also provide other different materials to meet customers needs. For example, low carbon steel coupon, stainless steel coupon, DSS F51 coupon and so on. If you want to test the corrosion of the pipe, you must use coupons of the same material.
Matters Need Attention:
It is important to notice the position where to put corrosion coupons. Because the height of impurities in pipelines are different. Water is usually at the bottom. Oil is usually on the water. And gas is usually on the top. According to different impurities, coupons can choosed different heights. People usually install them on the top, middle and bottom parts of the pipe. The distance are generally equally divided.
Besides, the amount of them is important too. There are many uncontrollable factors that cause corrosion of the coupons. As a result, it is better to test various locations in the pipelines for corrosion. And remember do not take out them too early or too late. Because it will influence the accuracy of corrosion test. Typically, corrosion coupons should be set in a direction parallel to the process flow. Besides, it should monitor both of the 6 O’clock and the 12 O’clock positions. Corrosion coupons can be put in high, middle and low position. This can provide a good representation of the flow of substances in the pipe. It is especially important for pipelines with stratified flow or pipelines which have deposits at the bottom.
What Causes Corrosion in Pipelines?
Oil and gas pipes are very easy to be corroded because of internal and external factors. The reaction to some chemicals and oxygen in the air will cause pipe corrosion. The resulting compounds will attach to the surface of the oil pipeline. Oil and gas pipelines are usually buried under the ground. It is a very humid environment that is suitable for microorganism growing. The corrosion situation is intensifying, thus causing damage to the pipeline. Chemical reaction is the main factor of the corrosion of the oil pipeline. Because of the particularity of the working environment of the oil pipeline itself, the corrosion of the pipeline caused by chemical factors is difficult to avoid.
Besides chemical factor, corrosion can also happen due to biological factors. Soil contains a lot of fungi. These fungi also have a corrosion effect on the pipeline. They corrode pipes directly from the external corrosion. Under normal circumstances, the bacteria exist in groups. Therefore, local corrosion appears. In addition, the corrosion speed of the pipeline caused by biological factors is very fast. And the corrosion is very serious.
How to Calculate Corrosion Rate?
Through the corrosion rate, people can accurately estimate the situation in pipelines. Then how to calculate it? There is a formula following to calculate weightlessness coupon corrosion rate:
22300×loss weight(g)
Corrosion rate(mpy)=------------------------------------------------------------------------------------------
Metal density (g/cm 3)×coupon area (square inches)×time (days)
Here, the “loss weight” refers to the corrosion weight. It equals to initial weight minus the weight after cleaning. “Metal density” refers to metal or alloy density. “Coupon area” refers to the area that coupon surface exposed to corrosive medium. And “time” refers to the days from installation to removal.
Recommendation of Coupons:
If you want a recommend about coupons(with valve). We usually recommend a removable corrosion coupon with valve. There are two connection way of corrosion coupons. First is Welding connection. Second is Flange connection. This kind of coupon is suitable to both of these two ways. It can be removed by disassembly tools. The price of a single product is higher than that of other products of the same grade. However, because the price of disassembly tools is high, it is suitable for customers without disassembly tools. Compared with other corrosion coupons that need special disassembly tools, this one is more cost-effective.
If you want more recommendations, connect here. We will always provide the best choice for you.
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