Coupons may be used alone but they should be used in conjunction with other monitoring methods such as test nipples, hydrogen probes, galvanic probes, polarization instruments, resistance-type corrosion monitors, chemical analysis of process streams and nondestructive metal thickness measurements, caliper surveys, and corrosion failure records. Turn the ham m er nut 20 clockwise until the service valve is securely seated. Lessons learned: Uncontrolled movement of gangway. See 3. To back pressure the retriever, attach the fem ale quick connect to the retriever bleed valve 6A. These parts, while impressive, are probably dissimilar from many of the parts you currently produce or use. All Rights Reserved.
Note service, initial weights, exposure dates, exposure time, and location for each sample. Record such information on VCI Bag provided.
Each coupon is pre-weight before shipment, Ensure once again before exposure and during Pre-Exposure. Corrosion Coupons are highly used to monitor corrosion rates in any environment, which is critical when viewed in terms of the maintenance and repair costs associated with corrosion and material failure. Accurate monitoring of corrosion rates in any environment is critical when viewed in terms of the maintenance and repair costs associated with corrosion and material failure. Test coupons provide an inexpensive means of on-line monitoring that will allow you to effectively measure the corrosivity within your system.
By observing the mils-per-year corrosion rate of an exposed coupon, valuable information can be provided regarding the material's life expectancy. Metal Samples can make coupons in any size, shape, or material you need. Coupons can be stenciled with alloy and sequence numbers for proper identification.
Interval time may also depend on the process. Evaluating a 30 day coupon interval versus a 90 day will be of less use than a 90 to 90 where you can see if your system is stable or not.
What is the best location and position to be installed? A corrosion coupon is a sacrificial element that is inserted and held into the pipe flow. Corrosion coupons are installed to duplicate the corrosion rate Corrosion coupons should be located where corrosion is expected. Corrosion.
A coupon will have the most metal loss in the first 30 days and typically a lower loss rate in the last 60 days of a test. This is due to 30 days being too soon for a passivating layer to develop on the coupon. Pitting : Depressions on the metal surface from corrosion. Pits vary in size, depth, and density.
Pitting is typically caused by one of the following: low inhibitor levels, high chlorides, copper plating, pH variations, and under-deposit corrosion. Localized Corrosion : Caused from under-deposit corrosion.
Could be caused by a low flow rate through the rack or necessity for better deposit control. Copper Plating : Soluble copper attaches to non-copper alloy samples. Can cause severe galvanic corrosion and metal failure due to pitting. Operating Experience — Information is generated by the actual operation of equipment. The equipment itself is used as the corrosion coupon or corrosion test. Samples of pipe are taken for analysis of corrosion. Model Equipment — Model equipment can be installed in parallel with actual equipment or in a pilot plant.
All variables must be identical to the actual plant. Instrumental Test Methods — Electrical resistance and polarization scans are valuable, and can generate a continuous record of corrosion rate. Corrosion Monitoring, Corrosion Coupons, and Corrosion Coupon Racks Corrosion monitoring is intended to provide an accurate representation of how well metallurgies of a system are protected against corrosion and to alert facility operators and service companies if a change is necessary before too much damage takes place to the system.
General Corrosion Facts.
Corrosion can be expressed in mils per year MPY of metals degraded Corrosion produces by-products oxides that hurt systems through erosion, clogging, and fouling Corrosion oxides reduce system efficiency and increase energy costs by accumulating on heat transfer surfaces Corrosion can be reduced through proper system design, maintenance, and water treatment. Common Sources of System Corrosion. Dissolved oxygen Bacteria Electrolysis stray current Differential metal dielectric Differential cell Flow, temperature, and pressure can all influence corrosion.
Benefits of Corrosion Monitoring. Interpreting Corrosion Rates. What are corrosion coupons? How are corrosion coupons analyzed? Corrosion Coupon Test Intervals. Benefits of Corrosion Coupons.
The assembly can then be inserted or removed from the system using a special service valve and retrieval tool. These are available for all standard coupon configurations. Retrievable, retractable, and pipe plug style coupon holders cover the needs of most industries and applications. However, the requirement for special coupon holder designs is significant, and Metal Samples Corrosion Monitoring Systems has the facility to design and build coupon holders to any customer-supplied specification.
Line Items in Quote Request:. View PDF version. Introduction The simplest, and longest-established, method of estimating corrosion losses in plant and equipment is weight loss analysis. Coupon Preparation and Cleaning The choice of technique for initial preparation of the coupon surface, and for cleaning the coupon after use, is critical in obtaining useful data.
Coupon Position and Orientation Irrespective of the degree of care exercised in the surface preparation of coupons, many uncontrollable factors e. Figure 1. Preferred Flow Direction. Figure 2. Ladder Strip Coupon Holder. Figure 3.
Coupon Holders Specific design of coupon holders incorporates two basic factors: Number, style, and configuration of coupons System entry method. Fixed Pipe Plug Coupon Holders The simplest system entry design for coupon holders is the fixed or pipe plug coupon holder Figure 4. Figure 4. Fixed Pipe Plug Coupon Holder.
Retractable Coupon Holders A design that is commonly used in the refining and petrochemical industry is the retractable type coupon holder as shown in Figure 5. Figure 5. Retractable Coupon Holder.