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|Troubleshooting the KENT / ABB / AMCO Water Meter|
The following relates only to oscillating piston flow meters, and specifically
to the AMCO C700 meter.
If meter damage occurs, it is almost always when the meter is new, or the piping is being modified and tape, pipe dope, rust, or chunks of product scale wash into the meter.
In the specific case of AMCO C700 water meters, or water meters utilizing plastic internals, the primary cause of damage is due to hot water or chemical attack.
The C700 working chamber is rated to 120oF, and will start deforming under its own weight at 132oF. The C700 uses polyacetal molded parts which cannot stand low pH fluids or most solvents. Other AWWA type water meters have similar problems because they use polycarbonates or polyacetals. These materials are totally different from PVC or CPVC.
The working chamber is easy to inspect for damage. Look on the inside walls, top and bottom of the working chamber for scratches or gouges. If you have a deep gouge, you will generally also have a matching gouge in the piston wall.
Scratches on the bottom of the working chamber - if you have light scratching in a oval shaped pattern, this comes from normal wear. In a new meter these scratches come from running a non-lubricating, low viscosity fluid, or by forcing air through the meter to see if it is turning. If the scratches are deep, or not uniformly distributed across the bottom of the chamber, you have had some hard foreign matter in there.
"Nose burn" - this is a deformity in the piston slot where it slides over the diaphragm plate. This is caused by somebody running compressed air through the meter for a prolonged period. The plastic piston heats and deforms under the frictionally generated heat.
Scratches on the side of the piston and working chamber wall. The gap between the chamber ID and the piston OD is typically .003 to .006 depending on meter size. The two never touch and scratches are always the result of foreign matter.
If the piston does not move easily in the working chamber -
On 1" and smaller AMCO C700 meters, you can assemble the working chamber with the piston and diaphragm plate and roll it slowly across the table. Gravity should keep the piston at the bottom.
On 1 1/2" and 2" AMCO C700 meters, you should be able to turn the piston easily with your finger tip.
If it doesn't turn easily, you have either foreign matter or a deformed piston or working chamber.
Broken or bent parts
Every now and then the moment arm (the bar driven by the piston pin) is bent, or the pin on the top of the piston has been snapped off. This occurs when a large piece of matter has jammed the piston and the fluid force has pushed the piston through the jam. The fluid force can be very large, at 100 PSI, a 2" piston will develop about 7500 lbs. of force, which is exerted sideways on the pin and moment arm. When this happens you can generally see a gouge or mark about 1/4 of the way around the chamber from the fluid entrance point.
Warranty - We very seldom have warranty claims on a ABB C700 meter. The meters are mass produced and sell in the thousands every week. The meters are optimized for clean, potable water service at under 120oF, and are warranted for such. Using them in other applications just because they are inexpensive, generally means that you are taking a chance.
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