In the last article, we discussed the application scope, types, and development of valves. Today, let's study the requirements for valve installation and acceptance.
1. Valve assembly requirements:
Cleaned valve parts must be kept sealed for installation.
The requirements for the valve installation process are as follows:
(1) The valve installation workshop must be kept clean, or a temporary clean area should be built, such as using newly purchased color strips or plastic films to prevent dust from entering during the installation process.
(2) Valve assemblers must wear clean cotton work clothes, cotton caps on their heads, no hair leakage, clean shoes on their feet, plastic gloves on their hands, and degreased.
(3) The tools for valve assembly must be degreased and cleaned before assembly to ensure cleanliness.
2. Valve acceptance requirements:
Valve acceptance must follow HG 20202-2000 "Degreasing Engineering Construction and Acceptance Specifications". Before assembly, each component is wiped with clean precision filter paper, and the dead corners of the components are selected. If the filter paper does not change color, it is qualified.
3. Valve specification requirements:
(1) The model of the valve should indicate the requirements of the national standard number. If it is an enterprise standard, the relevant description of the model should be indicated.
(2) The working pressure of the valve is required to be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can withstand should be greater than the actual working pressure of the pipeline.
(3) The valve manufacturing standard should indicate the national standard number based on it. If it is the enterprise standard, the enterprise document should be attached to the purchase contract.
4. Valve performance testing requirements:
(1) When a valve is manufactured in batches of a certain specification, an official agency should be entrusted to carry out the following performance tests: ①the opening and closing torque of the valve under industrial pressure conditions; ②the detection of the flow resistance coefficient of the valve under the condition of pipeline water delivery.
(2) The valve should be tested as follows before leaving the factory: ①When the valve is open, the valve body should be subjected to an internal pressure test that is twice the working pressure value of the valve; ②When the valve is closed, both sides are subject to 11 times the working pressure of the valve. Pressure value, no leakage; but metal-sealed butterfly valve, leakage value is not greater than the relevant requirements.
5. Valve sealing requirements:
The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent the leakage of the medium, which is the most important technical performance index of the valve. There are three sealing parts of the valve: the contact between the opening and closing parts and the two sealing surfaces of the valve seat; the cooperation between the packing and the valve stem and the stuffing box; the connection between the valve body and the valve cover. The leakage in the former part is called internal leakage, which is commonly referred to as lax closure, which will affect the ability of the valve to cut off the medium.
For shut-off valves, internal leakage is not allowed. The leakage in the latter two places is called external leakage, that is, the medium leaks from the inside of the valve to the outside of the valve. External leakage will cause material loss, pollute the environment, and even cause accidents in severe cases. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
6. Other valve requirements:
(1) The assembled valve is purged with nitrogen for at least 1 minute.
(2) The air tightness test must be performed with pure nitrogen.
(3) Encapsulate after passing the air tightness test, and seal with a clean polyethylene cap. The polyethylene cap should be soaked in organic solvent and wiped clean before use.
(4) Then seal it with a vacuum bag.
(5) Final packing.
(6) Measures should be taken to ensure that the package is not damaged during transportation.
You must pay attention to these details in the installation and acceptance of the valve.
The valves and components produced by PARFECT STEEL are of high quality, and a professional after-sales team guarantees you a worry-free shopping.
