Preparation Of Pipes, Tubes, And Fittings Before Installation In A Hydraulic System

General Requirements
When installing the various iron and steel pipes, tubes, and fittings of a hydraulic system, it is necessary that they be absolutely clean, free from scale, and all kinds of foreign matter. To attain this end, the following steps should be taken:

– Tubing, pipes and fittings should be brushed with boiler tube wire brush or cleaned with commercial pipe cleaning apparatus. The inside edge of tubing and pipe should be reamed after cutting to remove burrs. Also remove burrs from outside edge.

– Short pieces of pipe and tubing and steel fittings should be sandblasted to remove rust and scale. Sandblasting is a sure and efficient method for short straight pieces and fittings. Sandblasting should not be used however, if there is the slightest possibility that particles of sand will remain in blind holes or pockets in the work after flushing.

– In the case of longer pieces of pipe or short pieces bent to complex shapes where is is not practical to sandblast, the parts should be pickled in a suitable solution until all rust and scale is removed. Preparation for pickling requires thorough degreasing in a recommended vapor degreasing solvent.

– Neutralize pickling solution.

– Rinse parts and prepare for storage.

– Tubing must not be welded, brazed, or silver soldered after assembly as proper cleaning is impossible in such cases. It must be accurately bent and fitted so that it will not be necessary to spring it into place.

– If flange connections are used, flanges must fit squarely on the mounting faces and be secured with screws of the correct length. Screws or stud-nuts must be drawn up evenly to avoid distortion in the valve or pump body.

– Be sure that all openings into the hydraulic system are properly covered to keep out dirt and metal slivers when work such as drilling, tapping, welding, or brazing is being done on or near the unit.

– Threaded fittings should be inspected to prevent metal slivers from the threads getting into the hydraulic system.

– Before filling the system with hydraulic oil, be sure that the hydraulic fluid is as specified and that it is clean. DO NOT use cloth strainers or fluid that has been stored in contaminated containers.

– Use at least a No. 120 mesh screen when filling the reservoir. Use of a Vickers clean cart, porta filtering and transfer unit, is recommended. Operate the system for a short time to eliminate air in the lines. Add hydraulic fluid if necessary.

– Safety precautions. Dangerous chemicals are used in the cleaning and pickling operations to be described. They should be kept only in the proper containers and handled with extreme care.

Pickling Process
– Thoroughly degrease parts in degreaser, using a recommended vapor degreasing solvent.

– Tank No. 1 Solution. Use a commercially available derusting compound in solution as recommended by the manufacturer. The solution should not be used at a temperature exceeding that recommended by the manufacturer, otherwise the inhibitor will evaporate and leave a straight acid solution. The length of time the part will be immersed in this solution will depend upon the temperature of the solution and the amount of rust or scale which must be removed. The operator must use good judgement on this point.

– After pickling, rinse parts in cold running water and immerse in tank No. 2. The solution in this tank should be a neutralizer mixed with water in a proportion recommended by the manufacturer. This solution should be used at recommended temperatures and the parts should remain immersed in the solution for the period of time recommended by the manufacturer.

– Rinse parts in hot water

– Place in tank No. 3. The solution in this tank should contain antirust compounds as recommended by the manufacturer. Usually the parts being treated should be left to dry with antirust solution remaining on them. If pieces are stored for any period of time, ends of the pipes should be plugged to prevent the entrance of foreign matter. Do not use rags or waste as they will deposit lint on the inside of the tube or pipe. Immediately before using pipes, tubes and fittings should be thoroughly flushed with suitable degreasing solution.