PVC Corrosion Rack
Caltech Engineering Services manufacture corrosion test coupon racks to provide a convenient means of monitoring progress of corrosion in systems such as boilers, condensate lines, open re-circulating cooling water, closed circulating hot or chilled water systems, etc.
The corrosion test rack creates a side stream off the main system in which corrosion test coupons can be exposed to system water under controlled and reproducible conditions. The corrosion coupons can be periodically removed and either visually examined or returned to the laboratory for determination of weight loss, corrosion rate, and pitting severity.
PVC CORROSION RACK
The PVC Corrosion Rack is recommended for corrosion monitoring in low temperature systems such as open reticulating cooling water systems, chilled water process water systems, etc. The PVC Rack is constructed of l” threaded Sch. 80 PVC pipe. It is supplied with four 1” PVC mounting plugs and flow control valve. Two designs are available. These are constructed of blue or gray color. The other features transparent pipe sections for viewing the test coupons in place also can be supplied. We also manufacture carbon steel / stainless steel versions of corrosion test coupon racks. Please specify your need in ordering information.
FLOW VS VELOCITY CHART
Flow controller supplied with that rack should control velocities. Flow control valves shall be adjusted to control proper flow and velocities. In case of PVC rack velocity shall be 0.67 m/sec to 1.6 m/sec with flow rate of 5 gpm to 12 gpm.
CORROSION TESTRACK INSTALLATION
The corrosion test rack may be assembled for vertical mounting as shown in Figure l, or a horizontal position, Figure 2. Items shown in single line schematic are not furnished.
Attach the corrosion rack to a wall or column. DO NOT suspend it from the supply and return piping alone.
To avoid air binding, pipe the corrosion rack so that water will flow upward through it, and in such a way that it will remain full of water at all times and not backdrain when the main reticulating system shuts own.
Install gate or ball-type isolation valves of both sides of the rack.
DO NOT use this bypass loop for any other purpose such as chemical injection, or mounting of conductive or pH sensor.
For measurement of corrosion at points of highest temperature in the circulating systems, the water
supply to the corrosion rack should be from the exit of the heat exchanger (S). Average corrosion rate measurements may be obtained by supplying the corrosion rack with water from the main cooling tower riser, etc.
Return water may be piped to the re-circulating pump suction header, cooling tower basin, or other suitable point with sufficiently low pressure to insure flow through the rack.
Flow velocities should not be variable. Avid extremely high or low velocity condition. Suitable ow control valve is recommended to insure constant velocity.
For PVC test racks with transparent viewing sections, install the slotted pipe insulation over the transparent sections to avoid algae growth.
CORROSION TEST COUPON INSTALLATION
Keep the metal test coupon in the special treated envelope BEFORE AND AFTER exposure.
DO NOT leave fingerprints on the coupon. They will cause false corrosion readings.
Attach the coupon to the mounting stud using the special nut and bolt provided.
Corrosion coupons should always be installed so the water flows first over the plastic mounting rod and then over coupon. Water flowing directly onto the coupon may cause erosion-corrosion and lead to false weight loss measurements.
Use ONLY PTFE thread sealing tape on mounting plug threads. DO NOT pipe dope
The witness slot on the coupon-mounting plug should be parallel with the flat surface of the corrosion test coupon. Install the mounting plug in the tee and align the witness slot (and coupon) in the VERTICAL position in Figure l.
Note the date of installation on back of the white return envelope and seal envelope.
When removing, each test coupon should be carefully dismounted from the holder and immediately dried with a blastoff hot air or blotted with a re-insert the coupon in the treated brown envelope in which it was received.
Complete the back of the white coupon return envelope, insert the treated brown envelops with coupons inside, and return the envelope with the coupons to Caltech or laboratory.