Flange plunger valve quality appraisal

flange plunger valve is designed and manufactured to solve the defects of ordinary stop valves. The upper seal of ordinary stop valves uses root packing, which cannot eliminate leakage. The lower seal is made of a flat or angular seal (metal seal) between the valve disc and the valve body channel. The sealing surface causes leakage due to wear between metals and is difficult to maintain. The structural feature of the plunger valve is a stainless steel plunger and two upper and lower elastic sealing rings. and a metal partition frame. The sealing effect is achieved by the close cooperation between the plunger and the sealing ring. The plunger is inserted into the two sealing rings, and the sealing area is much larger than that of the ordinary stop valve. When the plunger valve is opened and closed, the plunger moves slowly in the sealing ring, and the contact surface is almost unworn. When closing, the plunger is inserted into the lower sealing ring to cut off the flow channel; when opening, although the plunger is separated from the lower sealing ring, it is still hidden in the upper sealing ring, maintaining isolation from the outside world and preventing leakage. The sealing ring is a technological product and a key part of the plunger valve. It is composed of polytetrafluoroethylene, graphite, high elastic glue, etc. It can still provide good sealing performance after millions of reciprocating motion tests. At the same time, the valve has the characteristics of small opening torque, large sealing area, wide application medium, high temperature adaptability, reliable sealing, long service life, and easy maintenance. Widely used in petroleum, chemical, electric power, pharmaceutical, food, textile, printing and dyeing, boiler, machinery and other industries.
In the case of flange plunger valve quality appraisal, Zhongke Testing can provide flange plunger valve quality appraisal services.

1. Material: The material of the flange should comply with relevant standards and requirements, such as mild steel, stainless steel, alloy steel, copper, aluminum, etc. When conducting quality appraisal, materials can be evaluated through chemical composition analysis, metallographic examination and other methods.
2. Dimensions and tolerances: The dimensions and tolerances of flanges should comply with relevant standards and requirements. When conducting quality appraisal, the quality can be evaluated by measuring the diameter, thickness, hole diameter and other dimensions of the flange with measuring tools, as well as the interface dimensions and tolerances of the pipes or equipment connected to the flange.
3. Surface quality: The surface of the flange should be smooth, flat, and free of defects such as cracks, pores, and slag inclusions. When conducting quality appraisal, the surface quality can be evaluated through visual inspection, touch inspection, magnifying glass inspection and other methods.
4. Sealing: The sealing of the flange is one of its key properties. During quality appraisal, water pressure test, air tightness test and other methods can be used to evaluate its sealing performance.
5. Labeling and packaging: Flanges should be labeled and packaged for easy management and use. When conducting quality appraisal, you can check whether the flange markings are clear and accurate, and whether the packaging meets the requirements, so as to evaluate its management and ease of use.

CB/T 4159-2011 Marine flange plunger valve
GB/T 43079.1-2023 Selection regulations for steel pipe flanges, gaskets and fasteners Part 1: PN series
GB/T 43079.2-2023 Selection regulations for steel pipe flanges, gaskets and fasteners Part 2: Class series
GB/T 7308.2-2021 Sliding bearings Thin-walled bearings with or without flange Part 2: Bearing wall thickness and flange thickness measurement
GB/Z 25756-2010 Vacuum technology Bakable flange Knife edge flange dimensions
GB/T 17185-2012 Steel flange pipe fitting
GB/T 34635-2017 Flange pipe joint
GB/T 4450-2008 Marine blind steel flange
GB/T 6070-2007 Vacuum technology Flange size
GB/T 15530.7-1995 Copper alloy flange cover
0GB/T 2032-2018 Marine flange fire hydrant
1GB/T 15530.2-1995 Copper alloy butt welding flange
2

A manufacturer purchased a flange plunger valve for steam pipes from a firm in the hardware market to regulate the steam pipes in the factory. However, a few months later, while an employee of the manufacturer was working normally, the bolt of the valve suddenly fell off, and steam pushed the valve gland open, causing steam to gush out. The employee was steamed to severe burns on the spot. As a result, the manufacturer found a firm that purchased flange plunger valves, but the other party ignored it and instead shifted the responsibility to the manufacturer. As a result, the manufacturer took the firm and the flange plunger valve manufacturer to court.
was entrusted by the court to conduct an appraisal and analysis on "whether there are quality problems" with the flange plunger valve involved in the case.
appraisal analysis results:
appraisal analysis expert group discussed the relevant information and on-site investigation of the flange plunger valve involved and conducted a comprehensive quality and technical analysis, and made the following suggestions and conclusions:
The tensile strength of this valve is far lower than the national standard. At the same time, the tightness between the center-mouth bolt and the thread is low and cannot achieve a tightening effect.
In summary, the valve was made of improper materials and had a large error in manufacturing accuracy. It was considered a substandard product, which was the main reason for the accident.