Corrosion monitoring
Corrosion monitoring is the use of a corrosion meter or set of methods[1] and equipment to provide offline or online information about corrosion rate expressed in mpy (mill per year)[2]. - for better care and to take or improve preventive measures to combat and protect against corrosion.
Corrosion protection or corrosion monitoring
Various methods are used to prevent and protect against corrosion, such as cathodic protection, selection and injection of chemicals or other ways to prevent corrosion. However, in order to see the results of these methods and how effective these measures are, corrosion monitoring should be done and, if necessary, corrosion protection methods should be modified or optimized based on the results obtained from corrosion monitoring. In many industries, preventive measures are used to protect against corrosion, but obviously without knowing the results of these measures, protection is a chance, that is, either full protection will not be done or in case of excessive protection, it will waste capital and resources.
The difference between corrosion inspection and corrosion monitoring
There may be a general misconception between the term corrosion inspection and corrosion monitoring, but inspection means frequent checkpoints to check for changes or deviations from predicted results, while corrosion monitoring is a continuous check to control and act quickly against change. In inspection, the purpose is to evaluate or estimate the corrosion time in order to replace or correct the corrosion, while in corrosion monitoring, the purpose is to take care of the change in order to prevent corrosion and to improve the ways of prevention.[3]
Online corrosion monitoring methods
Online corrosion monitoring is mostly done using the following methods:[4]
Use of weight loss coupons
Corrosion coupons are made in different shapes and sizes, the most common of which are as follows: These coupons are often made of a tube or container that is to be monitored for corrosion.
- Strip coupon
- Ladder strip coupon
- Flush disc Coupon
- Multi disc coupon[5]
Use of electrical resistance (ER) corrosion probes
Electric resistance corrosion probes are used in different types for different applications of online corrosion monitoring. The corrosion rate of these probes can be measured online or transferred to the control system by using corrosion handheld or fixed data loggers or by corrosion transmitters. The general type of ER probes element are as below:
- Flush type
- cylindrical
- Spiral loop
ER probes can be provided by adapter in order to connect to data logger or transmitters. The length of probes is depend to mounting and monitoring position.
Use of linear polar resistance probes
This method is mostly used for corrosion monitoring in water industry.
Use of hydrogen probes
Hydrogen probes are used to monitor the penetration of hydrogen into steels, which can cause brittleness, porosity or decarbonization.[6]
Using a sand probe
These probes are mostly used to monitor corrosion caused by erosion or wear.
Use a biological probe or bio-probe
Biological probe or bio-probes are used to collect samples for microbiological analysis. Microorganisms can accelerate the corrosion process, so monitoring the corrosion caused by them is effective in timely notification and preventive measures.
Main equipment of corrosion monitoring system
In addition to probes, the main below items are used in corrosion monitoring:[7]
Access fittings
The access fittings - such as flanged, flare-weld, etc.- are used for connection and access to coupons and probes. The general size of A/F is 2" which is called 2" system. But for small pipe sizes, 1" system can be used.
Coupon holder
Coupon holders are used to fix corrosion coupons inside a pipe or tank and attaches itself to a solid plug or hollow plug. They are usually made from stainless steel 316/316L or Monel and inconel or other corrosion resistant materials.[8]
Service valve
Service valve is used to block fluid while replacing corrosion coupons or probes despite fluid flow.
Retriever for retrieval without process interruption
retriever is used to insert and retrieve coupons and probes without interrupting the process.[9] They can be provided in hydraulic and mechanical types.
References
- ^ Corrosion Monitoring in Oil and Gas Production Maarten J.J. Simon Thomas; Sieger Terpstra Paper presented at the CORROSION 2003, San Diego, California, March 2003. Paper Number: NACE-03431 Published: March 16 2003
- ^ https://www.merusonline.com/mpy-mils-per-year/
- ^ http://www.jmcampbell.com/tip-of-the-month/2009/06/corrosion-monitoring-and-inspection-%E2%80%93-is-there-a-difference/
- ^ http://www.jmcampbell.com/tip-of-the-month/2009/06/corrosion-monitoring-and-inspection-%E2%80%93-is-there-a-difference/
- ^ http://www.rcslgroup.com/Global/RCSL/Technical/Tn010296.pdf
- ^ http://www.caproco.com/indexflash.htm
- ^ https://www.cosasco.com/products/all
- ^ https://petroparda.com/hc-coupon-probes-holders
- ^ https://www.alspi.com/retrieval.htm