Jun 1, 2006 12:00 PM
CAUSTIC costs rose by as much as 25% over the past year. Inadequate pump maintenance means higher operating costs for a wash rack. Regular testing and maintenance are needed to ensure safe and long life for hoses. Boilers that are out of compliance with the latest federal Clean Air Act requirements can bring stiff fines for wash racks.
These were some of the key points made by speakers addressing technology issues at the National Tank Truck Carriers annual Tank Cleaning Seminar April 3 and 4 in Las Vegas, Nevada. Technology speakers included Brad Holmes, Hibrett Puratex; Bart Smith, Valley Equipment Company Inc; Kip Hart, Hart Industries Inc; and Joe Brown, The WCM Group Inc.
Holmes addressed the increase in caustic cost, pointing out that other cleaning chemicals also are more expensive. Dibasic ester, the main ingredient in resin cleaning solutions, is 31% more expensive. The cost of diLimamine has increased by 80%.
Good cleaning solution management starts with an understanding of chemical properties. Holmes pointed out that when oils and fats (fatty acids) are cleaned out with caustic, especially at high temperatures, soap is made. The oil or fat is “saponified,” making it water-soluble. The caustic reacts with the fatty acid and becomes soap.
To avoid losing too much caustic when cleaning fatty acids, wash rack workers must remove as much product residue as possible before the tank cleaning begins. Holmes recommended using a strong detergent for an initial wash. Caustic should be used in a second wash just to remove built-up product from the tank wall.
While caustic is an important part of the cleaning process for chemical tanks, Holmes reminded the audience that it is a corrosive product that must be handled properly. Workers also must be trained and have adequate protection.
“Back in my tank cleaning days, we drilled it into our staff to never store caustic and sulfuric acid in the same area,” he said. “They were never to put bleach and detergent in the same place.
“Working with caustic taught me to keep household vinegar on hand. When you feel the burn of caustic on your skin, pour the vinegar directly on the affected area. Because vinegar is a weak acid, it neutralizes the caustic in a heartbeat.
“Always keep a bag of soda ash available when you have acids on site. When treating a spill, sprinkle the soda ash like snow and not big clumps. When the spill area stops bubbling, you know the problem is neutralized.”
Addressing tank-cleaning pumps, Smith said the first step is to understand what types of pumps are being used in the facility. For instance, is it an end suction or center discharge pump? Is it a self-priming pump?
Wash rack workers also need to know the names of the parts that apply to the specific pumps used at the wash rack. For instance, some pumps have reverse vane impellers and others have open-vane impellers. Does the pump have packing or mechanical seals? Staffers must be able to read the data plates to determine pump size and other details.
Pumps need regular maintenance. “Don't just forget about it, once the pump is installed and started up,” Smith said. “Every wash rack needs a pump maintenance program. “This includes monitoring, record keeping, and stocking spare parts.”
Wash rack hoses need regular inspection and testing, as well as maintenance, according to Hart. Hoses need to be tested whenever a fitting is removed and reattached or rebanded. Hoses must be tested in compliance with federal regulations.
Hart stressed the importance of testing a hose whenever safety concerns are raised. Testing should be done if there is concern that over pressurization, pressure spikes, or over heating occurred. Hoses should be checked if there are signs of kinking or excessive abrading. Testing is needed anytime an inspection turns up signs of a potential problem.
Fittings should be checked for cracks or flaws, pitting or corrosion, distortion, broken or missing cam arms, and worn or cracked gaskets. The locking mechanism must function properly.
Band clamps should be inspected for tightness and correct placement. If the wrong band is used or if it is installed incorrectly, the hose and coupling could separate resulting in injured workers and damage to the wash rack.
During the testing, hoses should be checked for static electricity conductivity. This should be done at least annually or in conjunction with a hydrostatic pressure test.
Only hydrostatic pressure testing should be used for hoses. “Never test a hose with compressed gas or air,” Hart said. “This can be extremely hazardous. Don't stand at either end of the hose during testing, because the hose end could fail.”
Hoses should be tagged after testing, and the details should be recorded. Tag information should include date of the retest and test pressure.
Hart also offered some hose-handling tips. Hoses not in use in the wash rack should be stored on a solid support in a cool, dry area. They should be kept away from sunlight, electric motors, welding equipment, or any other source of ozone.
When customers' product hoses are cleaned, they shouldn't be left to soak in caustic and other solutions for too long. The hose interior never should be cleaned out with a pressure wand or steam lance. The hose liner will be sliced to pieces.
Wash rack boilers are getting more attention from government agencies that regulate emissions of nitrogen oxides (Nox), according to Brown. Wash racks are under greater pressure to install low-Nox boilers.
“You can reduce Nox from a boiler in a number of ways,” Brown said. “This can include low excess air firing, off-stoichiometric combustion, flue-gas recirculation, gas reburning, reduced air preheat, water or steam injection, and selective catalytic reduction.
“Low excess air firing typically reduces Nox by 10%. Flue gas recirculation cuts it by 75%. Selective catalytic reduction will lower Nox by 90%. Flue gas recirculation is the most effective Nox reduction method for industrial boilers with inputs below 100 MMBtu/hr.”
Boilers must be correctly sized to the operation. Computerized controls are available that help to improve boiler efficiency. The key is to keep the air/fuel mixture at the optimum level.
Boilers need daily maintenance to be kept in top shape. Wash rack staffers must blow down the boiler every day, and they need to check for solids in the water. In addition, the water must be treated to keep out minerals and other contaminants. Scale and sludge will significantly reduce thermal efficiency.
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