Methods for Cleaning Electric Butterfly Valves

There are various methods for cleaning electric butterfly valves, and it is important to understand each of them. Electric butterfly valves are suitable for installation in pipelines for heating, gas supply, and water supply; power plant heating systems typically utilize triple-offset, metal-seated (hard-seal) butterfly valves. Following installation, the pipeline system requires purging. Three common purging methods are used: water flushing, air purging, and steam purging.

The specific requirements for these three methods are as follows:
1. Clean water must be used for flushing pipelines. When flushing austenitic stainless steel pipelines, the chloride ion content in the water must not exceed 25 ppm (25 × 10⁻⁶).
2. A high flow rate should be used during flushing, with a flow velocity of no less than 1.5 m/s.
3. Discharge water must be directed into a reliable drainage well or trench. The cross-sectional area of ​​the discharge pipe must be at least 60% of that of the pipe being flushed. Negative pressure must not be allowed to form during drainage.
4. All drainage branch pipes must be flushed.
5. Water flushing should be performed continuously; the process is considered complete when the color and transparency of the water at the outlet visually match those at the inlet.
6. If the pipeline is not put into immediate operation after passing the water flush test, the water must be drained completely, and the pipeline must be dried promptly.

Air Purging

1. Air purging should utilize the large compressors of the production unit; alternatively, large vessels within the unit may be used to store air for intermittent purging. The purging pressure must not exceed the design pressure of the vessels and piping, and the flow velocity should not be less than 20 m/s.

2. When purging oil-free piping, the air must be free of oil.

3. During air purging, once the exhaust appears free of smoke and dust to the naked eye, a wooden target plate covered with white cloth or painted white should be placed at the exhaust outlet for inspection; the purging is considered acceptable if no rust, dust, moisture, or other debris is found on the target plate within a 5-minute period.

Steam Purging

1. Temporary piping installed for steam purging must meet the technical requirements for steam piping, and the installation quality must comply with the provisions of this specification.

2. Steam piping should be purged using a high flow rate of steam, with a velocity of not less than 30 m/s.

3. Prior to steam purging, the piping must be warmed up and drained of condensate in a timely manner, and thermal displacement of the piping must be checked.

4. Steam purging should be conducted in a cyclic manner following the sequence of heating, cooling, and reheating. A method of purging one line at a time in rotation is recommended.

5. For steam piping leading to steam turbines or as specified in the design documents, target plates must be inspected after steam purging. In the absence of specific design requirements, the quality must comply with the prescribed standards.