How to clean the hydraulic oil tank of an HDD drilling rig?
Sep 19, 2025| I. Preparation
1. Draining the Old Oil
Completely drain the hydraulic oil from the tank to prevent residual oil from contaminating the new oil.
2. Safety Precautions
Wear protective gloves and goggles, and ensure the work area is well ventilated.
II. Cleaning Method
1. Blow-down (Recommended)
Leave 1/3 of the oil (diesel or gasoline) in the tank. Insert a compressed air hose (196-294 kPa) to agitate the oil and flush the inner wall.
Repeat 2-3 times until the oil is drained and clear.
2. Chemical Cleaning
Use a 20% sulfuric acid/hydrochloric acid solution for pickling, neutralize with baking soda, rinse with warm water, and dry.
Strictly avoid using corrosive solvents or steam cleaning (they may damage seals).
III. Key Steps
1. Inner Wall Treatment
Vibrate the tank to remove impurities. Wipe away any deposits with a clean cloth. Check the interior surface for particles and rust. Apply rust-proof oil if necessary.
2. System Flushing
After filling with new oil, start the system, circulate and flush the oil lines, and replace the filter element.
IV. Acceptance Criteria
1. Pressure Test
After cleaning, perform a 15 MPa pressure test for 5 minutes with no leakage.
2. Oil Testing
The contamination level of the new oil must be below NAS level 8, and the oil temperature must be stable between 35-55°C.
V. Precautions
Prevent sand and scale from entering the oil lines throughout the cleaning process.
Do not mix different brands of hydraulic oil (e.g., ISO VG 46 and VG 68).
The recommended cleaning interval is every 2000 hours or once a year.
