Problem Solving Article: CLEANING THE PIPES 

Fifth Article in a Series of Problem Solving Articles in an Industrial Setting

The pipes at the olive cannery where I worked would become clogged with a buildup of congealed olive oil. The pipes were flushed with a concentrated cleaning solution at the end of every day, but some oil would still collect on the walls of the white, food-grade, PVC pipes.

The solution in the past had been to completely remove the pipes and replace them with new pipes. I was determined to identify and place into use a solution not quite so drastic and expensive.

We hooked up a steam and water mixer that would put nearly boiling water into the pipes and would clean the pipes fairly rapidly. This worked very well on all the steel piping. All we had to do was add insertion points and cleanouts on the steel pipes and that problem was solved.

The PVC pipes were a different story. The high heat from the steam caused the PVC pipes to become soft and they would would sag or split open. The hot water could not be used in the PVC piping systems.

I recalled reading about the high-pressure systems used to clean the old oil and gasoline stains off driveways. I wondered if the same type high-pressure system could be used to clean pipes.

I checked in the Grainger catalog for high-pressure cleaning systems and there it was. A portable, electric, cold water pressure washer with a 3 Horse Power electric motor driving a pump with an output of 1500 PSI.

There were attachments for the cleaning head that sprayed out through the front and back. The 1500 PSI pressure on the head and the three back nozzles caused the head to spin and push itself through the pipe at the same time.

We had a 25 foot and a 40 foot section of pipe already removed for replacement when the pressure washer was delivered. After the unit was setup and ready to be tested, we turned it on and water sprayed everywhere. 

We turned it off and inserted it into one of the pipes. As we turned it on, the hose literally pulled itself into the pipe. Emulsified and chunks of olive oil spewed out the end of the pipe where the hose was inserted.

All we needed was a ground fault protected 120 VAC circuit and a hose outlet for drinking water. Each PVC pipe needed an insertion point and a cleanout point.

With the PVC, installing the insertion and cleanout points was considerably easier than on the steel piping.

The plant had it's own water wells, two, that had 75 HP electric motors driving the submerged pumps. The supply line from the main well was eight inch steel. We had a chlorine injection unit to sanitize the water before the water entered the plant.

Just outside the plant, four inch steel header header pipes teed off from the main, eight inch header. After entering the plant, the four inch steel headers stopped and four inch, sanitary grade, PVC pipes were used to distribute the plant water.

The plant normally ran canning operations for two eight hour shifts and then sanitized, cleaned up, and prepared for day shift start up the other eight hours. This cycle was usually for five days a week. 

Saturday and Sunday were normally off days. Maintenance work unable to be carried out while in operation were carried out on Saturdays and, if necessary, Sundays.

The big, 75 HP water well motor was turned off Saturday morning and not turned back on till Monday morning. Sometimes the person turning on the pump would fail to open several bleed off valves. 

The pump would start up at 480 VAC and send the water rushing up the pipe at a tremendous rate from 225 feet underground. The resulting water hammer of the water slamming into the smaller four inch and lesser piping could break the glued joints of the PVC piping. 

All mechanics and electricians were then dispatched to the various breaks with PVC solvent and glue to make repairs. This was costly and unnecessary as far as I was concerned.

There were several ways to solve this problem. One: install a pressure relief valve on the eight inch pipe; two: install water hammer relief chambers in the plant piping system; and three: install a soft start on the well electric motor to allow a slower startup of the motor driven pump thereby eliminating the water hammer and any possibility of problems.

The soft start would start the motor at a very slow speed and then ramp up to full speed over a preset period of time. This period of time would allow the water lines to fill up gradually and with a much reduced pressure.

I Looked up the correct size and ordered it. When the unit came in, I assigned an electrician to install it in the pump motor starter on the first Saturday.

The unit was installed and we set up the start rate and ramp time. Then we started the motor and no water hammer on the piping. The motor started and slowly came up to speed with no problems.

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Author: Larry Bush 
Profile: Electrician in industrial, construction, marine, and food industries for 47 years, with 22 of those years in management.
URL: http://www.reliability-consultant.com