EMT Retractable Corrosion Coupons


The EMT-RCC Retractable Corrosion Coupon comes with a retrieval tool that makes it possible to take the coupon apart for pipelines under pressure



Corrosion coupons can be used to test the corrosion rate in different industries, such as the oil and gas industry and the water industry. The EMT-RCC Retractable Corrosion Coupons come with a retrieval tool that makes it possible to take the coupon apart for pipelines under pressure. The designed pressure is below 10 MPa.  During operation, the implantation depth of the corrosion coupon can be adjusted to accommodate the pipeline’s diameter and wall thickness. The standard system is available in various lengths—24, 30, 36, 42, and 48 inches (to meet customer needs)—making it suitable for pipes of different diameters. The EMT Retractable Corrosion Coupons comprise a corrosion coupon, a ball valve, and an adjustable safety clamp kit. It is recommended to use the safety closure when the pipeline pressure drops below 1500 psi and the temperature falls below 500 °F.

Retractable Corrosion Coupon

Understanding the Test Results: Take the Water System as An Example

The corrosion rate of a coupon is determined by the amount of metal lost over a specified period. To determine metal loss, the coupons are meticulously weighed and reported before and after. Corrosive “pitting” is also quantified by measuring the area of the pitted surface.

Location, exposure length, pH, water temperature, coupon design or placement, flow velocity, and current water treatments are all factors that influence the corrosion rate.

Following the evaluation, the technician will compute the rate in mils per year. Each metal or alloy has a different allowable corrosion rate.

Stainless Steel

Evaporative Water SystemsClosed Water Systems
Acceptable<0.1 MPY<0.1 MPY
Unacceptable>0.1 MPY>0.1 MPY

Copper and Copper Alloys

Evaporative Water SystemsClosed Water Systems
Pretty Good<0.1 MPY≤0.1 MPY
Very Good0.1-0.25 MPY0.1-0.15 MPY
Good0.25-0.35 MPY0.15-0.20 MPY
Fair0.35-0.5 MPY0.2-0.3 MPY
Poor0.5-1.0 MPY0.3-0.5 MPY
Unacceptable>1.0 MPY≥0.5 MPY

Low Carbon Steel

Evaporative Water SystemsClosed Water Systems
Pretty Good≤1.0 MPY≤0.2 MPY
Very Good1.0-3.0 MPY0.2-0.3 MPY
Good3.0-5.0 MPY0.3-0.5 MPY
Fair5.0-8.0 MPY0.5-0.8 MPY
Poor8.0-10.0 MPY0.8-1.0 MPY
Unacceptable>10 MPY≥1.0 MPY


Evaporative Water SystemsClosed Water Systems
Acceptable<0.2 MPY<0.2 MPY
Marginal0.2-0.25 MPY0.2-0.25 MPY
Unacceptable>0.25 MPY>0.25 MPY


Components of EMT Retractable Corrosion Coupons

Safety Clamp AssemblyThis part guarantees that the system is securely attached to the pipeline. It is intended to withstand the system’s high pressure and temperature conditions.
Lock NutThe lock nut is critical in locking the system and preventing it from loosening due to pipeline vibration or pressure variations.
Sealing NutThe sealing nut, in conjunction with the lock nut, forms a secure and tight seal, preventing pipeline leakage.
Connection PipeThis is the system piece that links the corrosion coupon to the pipeline. It is built to endure the same pressure and temperature levels as the pipeline.
Full Bore Ball ValveThe flow of the pipeline media is controlled by this valve. It can either fully halt or allow full flow, which is critical for system maintenance and operation.
Welded BaseThe welded base serves as the coupon system’s foundation, providing a robust and sturdy platform for the other components.
Coupon Mounting RodThis rod secures the corrosion coupon and is adjustable to fit various pipeline diameters and wall thicknesses.
Adjustment NutThe adjustment nut allows the corrosion coupon to be precisely positioned within the pipeline. This is essential for acquiring precise corrosion data.
Upper Safety ClampThis clamp attaches the system’s upper portion and works in tandem with the bottom safety clamp to guarantee the system is securely fastened to the pipeline.
Locking NutThe locking nut adds an extra layer of protection to the system by ensuring that the coupon position modifications remain fixed throughout the operation.
Lower Safety ClampThis clamp secures the lower portion of the system, collaborating with the higher safety clamp to provide a tight and secure connection to the pipeline.

Retractable Corrosion Coupons

Reinstallation of EMT-RCC Retractable Corrosion Coupons

When the corrosion coupon replacement is completed or reinstalled after the inspection, proceed with the reinstallation of the coupon device. Proceed with the reinstallation of the coupon device when the corrosion coupon replacement is completed or reinstalled following the inspection work.

(1) Check to see if the adjustment rod is in position.

The distance between the two safety clamps should be measured and adjusted (L2 = 515525mm). If it does not fit this condition, its range should be adjusted. (Note: During the adjustment procedure, keep the lower safety clamp stationary and only adjust the upper safety clamp.)

(2) Replace the sealing compound.

Clear the residual sealing material from the branch pipe threads and the sealing nut, then wrap the new sealing material around the threads.

(3) Connect the coupon device.

Align the coupon device with the branch pipe threads, hand-tighten it until it doesn’t move, and then tighten the sealing nut with a wrench.

(4) Turn on the valve.

Check for leaks at the branch pipe connection and any threaded connections after opening the valve. Close the valve if there is a leak, then deal with the leaking seal (change the sealing material or replace parts, maintain, and reinstall). If there is still a leak, repeat this process until no leakage exists.

(5) Return the upper safety clamp to its original position.

Adjust the lower adjustment nut of the upper safety clamp to the lowest position as soon as it affects the upper adjustment nut’s adjustment. To the original installation record distance L, adjust the distance between the upper safety clamp and the surface of the welded base; see step 4 of the initial installation. When tightening the nuts, one person can alternately tighten the two nuts, or two persons can tighten the two nuts simultaneously, striving to keep the upper safety clamp perpendicular to the coupon support rod to avoid excessive tilt.

(6) Snap the Coupon Support Rod into place.

After adjusting the upper safety clamp, verify the direction of the coupon support rod and turn it such that the indicator surface points in the direction of the pipeline medium flow. Tighten the upper and lower adjustment nuts of the upper safety clamp, and inspect and tighten the lower safety clamp’s lock nut. The installation is finished.

The reinstallation process is now complete.


The EMT-RCC Retractable Corrosion Coupon provides a critical tool for assessing corrosion rates in various industries, including the oil, gas, and water sectors. The retractable design, adjustable implantation depth, and various lengths make it a versatile solution for pipes of different diameters and wall thicknesses. This system, comprising a corrosion coupon, a ball valve, and an adjustable safety clamp kit, offers a practical, safe, and efficient method for corrosion analysis under different pipeline conditions.

Understanding the test results, such as the degree of metal loss and pitting, is crucial for maintaining the integrity of these systems. Factors like location, exposure length, pH, water temperature, coupon design or placement, flow velocity, and current water treatments significantly influence the corrosion rate. With the EMT-RCC Retractable Corrosion Coupon, industries can monitor and manage corrosion effectively, ensuring the long-term operational efficiency and sustainability of their pipeline systems.



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