Saturday, January 10, 2015

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.

ISO/ANSI Basic Symbols For Fluid Power Equipment And Systems



 

 

  

Note
Additional symbols are shown in Vickers Circuitool booklet available for a nominal charge. Ask for circuitool template kit 352.

Color Code For Fluid Power Schematic Drawings
Function Color
Intensified Pressure . . Black
Supply . . . . . . . . . . . . . . Red
Charging Pressure . . . Intermittent Red
Reduced Pressure . . . . Intermittent Red
Pilot Pressure . . . . . . . . Intermittent Red
Metered Flow . . . . . . . . Yellow
Exhaust . . . . . . . . . . . . . Blue
Intake . . . . . . . . . . . . . . . Green
Drain . . . . . . . . . . . . . . . Green
Inactive . . . . . . . . . . . . . Blank

Definition Of Functions
Function Definition
Intensified Pressure - Pressure in excess of supply pressure which is induced by a booster or intensifier.
Supply Pressure - Power-actuating fluid.
Charging Pressure - Pump-inlet pressure that is higher than atmospheric pressure.
Reduced Pressure - Auxiliary pressure which is lower than supply pressure.
Pilot Pressure - Control-actuating pressure.
Metered Flow - Fluid at controlled flow rate, other than pump delivery.
Exhaust - Return of power and control fluid to reservoir.
Intake -Sub-atmospheric pressure, usually on intake side of pump.
Drain - Return of leakage fluid to reservoir.
Inactive -Fluid which is within the circuit, but which does not serve a functional purpose during the phase being represented.
 

Oil Flow Velocity In Tubing

Figures in the chart are USgpm flow capacities of tubing, and were calculated from the formula: GPM = V x A / .3208, in which V = velocity of flow in feet per second, and A is inside square inch area of tube.


Pump Test Procedure For Evaluation Of Antiwear Fluids For Mobile Systems

Test Pump
35VQ25A-11*20 (Cartridge Kit P/N 413421)

Test Conditions
Speed: 2350-2400 rpm
Outlet Pressure: 205-210 bar gage, (2975-3025 psig)
Inlet Pressure: 0-.15 bar gage, (0-2 psig) with flooded inlet
Inlet Temperature: 90-96degC (195-205degF)

Operating Mode
Steady-state pressure at above rated conditions for 50 hours. Terminate test if flow degradation exceeds 7.5 L/min (2 gpm) prior to the completion of the 50-hour test. Such terminations are not considered to be failures since this flow degradation can be due to causes other than excessive wear, such as erosion on the side plates resulting from insufficient inlet pressure.

Initial Fluid Condition
Water Content: .075% maximum Contamination Level: ISO Code 18/16/14 or better particle count. Alternatively, 30 mg/liter maximum gravimetric contamination (using filter membrane of 0.8 micrometer porosity).

Pump Break-In Procedure
1. Increase pump speed to test level and apply 70 bar gage (1000 psig) outlet pressure. When inlet temperature of approximately 50degC (125degF) is achieved, maintain it for elapsed time of 1/2 hour at pressure.

2. Increase pressure to 140 bar gage (2000 psig). When inlet temperature of approximately 80degC (175degF) is achieved, maintain it for elapsed time of 1/2 hour at pressure.

3. Increase pressure to 205-210 bar gage (2975-3025 psig). When temperature stabilizes at 90-96degC (195-205degF), record operating parameters, including flow. Terminate test if flow is below 136 L/min (36 gpm) after five hours of operation. With production tolerances, low flow sometimes occurs while pumping light fluids. This condition tends to increase the wear rate.

Test Duration
Continue operation of the unit for 50 hours total (including break-in time), periodically monitoring operation parameters.

Number Of Cartridges
Evaluation requires a minimum of three pump cartridges. The fluid should not be changed during the total 150-hour test period.

Accept/Reject Guidelines
1. Total weight loss of all vanes from individual cartridge tested should be less than 15 mg (not including intravanes).

2. Weight loss of ring from individual cartridge tested should be less than 75 mg.

3. Regardless of weight loss measurements, the pump parts, especially the rings, should not have evidence of unusual wear or stress in contact areas. There may be instances when unsatisfactory performance is indicated even though the weight loss is low; for example, galling or excessive burning would not show as excessive weight loss but would be unacceptable.

When any one cartridge out of three fails for any reason, two more cartridges should be tested. In this case, four of the five tested cartridges must meet the above accept/reject guidelines. This procedure is offered only as a fluid screening method. Successful completion of this test does not constitute endorsement or approval of fluids by Vickers.

Test Circuit


Description of Components
1. Reservoir (50 gallons minimum; elevated above pump centerline to provide gravity feed)
2. Temperature gage or thermocouple
3. Inlet pressure gage
4. Pump: 35VQ25A-11*20 (cartridge kit P/N 413421)
5. Electric motor (125 HP)
6. Outlet pressure gage
7. Pressure relief valve
8. Filter (10 micrometer nominal)
9. Cooler
10. Flow meter

Oil Viscosity Recommendations


Crankcase Oils


Hydraulic System
Operating Temperature
Range1
SAE Viscosity
Designation
–23degC to 54degC
(–10degF to 130degF)
5W, 5W-20,
5W-30
–18degC to 83degC
(0degF to 180degF)
10W

–18degC to 99degC
(0degF to 210degF)

10W-30,
10W-40

10degC to 99degC
(50degF to 210degF)

20-20W






Antiwear Hydraulic Oils



Hydraulic System
Operating Temperature
Range1
ISO Viscosity
Grade

–21degC to 60degC
(–5degF to 140degF)
22

–15degC to 77degC
(5degF to 170degF)
32

–9degC to 88degC
(15degF to 190degF)
46

–1degC to 99degC
(30degF to 210degF)
68



 1 Temperatures shown are cold (ambient) start-up to maximum operating. During cold start-up, avoid high-speed operation of hydraulic components until the system is warmed up to provide adequate lubrication.