What does valve degreasing mean?

Is this degreasing process carried out before valve assembly, or after the assembly is complete?

All of these steps need to be carried out; generally, carbon tetrachloride is used for degreasing, but its use has been prohibited. There are other degreasing agents available, and one can refer to the HG standards for more information.

The valve is disassembled, degreased using carbon tetrachloride, then reassembled, with the valve position adjusted!

1. Cleaning steps: The components of the valve must undergo the following treatments before assembly: 1) Depending on the processing requirements, some components need to be polished, with no machining burrs or similar defects on their surfaces； 2) All components are degreased ； 3) Perform acid washing and passivation after degreasing (the cleaning agent contains no phosphorus) ； 4) After pickling and passivation, rinse thoroughly with pure water to ensure no residues of chemicals remain (this step is omitted for carbon steel components) ； 5) Wipe each component individually with non-woven fabric to ensure no fibers or similar residues remain on its surface, or dry it using clean nitrogen gas ； 6) Wipe each component with non-woven fabric or precision filter paper dipped in analytically pure alcohol until no dirty stains remain. 2. Assembly requirement: The cleaned components must be stored in a sealed condition for installation. The requirements for the installation process are as follows: 1) The installation workshop must be kept clean, or a temporary clean area must be created (for example, using newly purchased striped fabric or plastic film), to prevent dust from entering during the installation process. 2) Assembly workers must wear clean cotton work clothes, cotton caps to keep their hair covered, clean shoes, and plastic gloves (degreased). 3) The tools used for assembly must be degreased and cleaned before use to ensure cleanliness. 3. Other requirements: 1) The assembled valves must be purged with nitrogen for at least 1 minute. 2) The airtightness test must be conducted using pure nitrogen. 3) After passing the airtightness test, encapsulation is carried out by sealing it with a clean polyethylene cap; the polyethylene cap should be soaked in an organic solvent before use and then wiped clean. 4) Then seal it with a vacuum bag. 5) Final packing. 6) Measures should be taken during transportation to ensure that the enclosure remains unbroken. 4. Acceptance requirements: Trichloroethylene and carbon tetrachloride are currently used primarily for degreasing; carbon tetrachloride is likely to be cheaper, but it can no longer be used.

Refer to HG 20202-2014 Code for Construction and Acceptance of Degreasing Projects

The grease inside the valve must be removed completely, and then relevant tools are used to check whether it meets the requirements. For valves that use oxidizing gases, the seals need to be thoroughly degreased to avoid future problems. There are solvent-based degreasers such as carbon tetrachloride and trichloroethylene, but they are highly toxic; in some areas, a permit is required to purchase them. Other options are environmentally friendly water-based degreasers, such as Blue Gold Degreaser; they are non-toxic and cause little environmental impact. When using them, they should be diluted with softened water or deionized water before being used for wiping or soaking for cleaning.

Generally, only the oxygen valve needs to be degreased; as for those special cases, I’m not sure either

1. Cleaning steps: The components of the valve must undergo the following treatments before assembly: 1) Depending on the processing requirements, some components need to be polished, with no machining burrs or similar defects on their surfaces； 2) All components are degreased ； 3) Perform acid washing and passivation after degreasing (the cleaning agent contains no phosphorus) ； 4) After pickling and passivation, rinse thoroughly with pure water to ensure no residues of chemicals remain (this step is omitted for carbon steel components) ； 5) Wipe each component individually with non-woven fabric to ensure no fibers or similar residues remain on its surface, or dry it using clean nitrogen gas ； 6) Wipe each component with non-woven fabric or precision filter paper dipped in analytically pure alcohol until no dirty stains remain. 2. Assembly requirement: The cleaned components must be stored in a sealed condition for installation. The requirements for the installation process are as follows: 1) The installation workshop must be kept clean, or a temporary clean area must be created (for example, using newly purchased striped fabric or plastic film), to prevent dust from entering during the installation process. 2) Assembly workers must wear clean cotton work clothes, cotton caps to keep their hair covered, clean shoes, and plastic gloves (degreased). 3) The tools used for assembly must be degreased and cleaned before use to ensure cleanliness. 3. Other requirements: 1) The assembled valves must be purged with nitrogen for at least 1 minute. 2) The airtightness test must be conducted using pure nitrogen. 3) After passing the airtightness test, encapsulation is carried out by sealing it with a clean polyethylene cap; the polyethylene cap should be soaked in an organic solvent before use and then wiped clean. 4) Then seal it with a vacuum bag. 5) Final packing. 6) Measures should be taken during transportation to ensure that the enclosure remains unbroken. 4. Acceptance requirements: Trichloroethylene and carbon tetrachloride are currently used primarily for degreasing; carbon tetrachloride is likely to be cheaper, but it can no longer be used.