เคยสงสัยหรือไม่ว่าตัวย่อเช่น DN, PN, ½, การชั่ง, and CWP letters on a valve mean? Curious about the markings on a valve body and what other letters might appear? Let’s dive in and explore.
The markings on a valve typically represent crucial information such as its size, pressure and temperature ratings, material composition, brand, flow direction, and certifications. These details are vital in proper selection, installation, and operation, ensuring the valve is used safely and correctly.
1. Valve Size Marking:“DN” และ “½” Fraction or Letters on Valve
The valve size is its most fundamental parameter, indicating the nominal bore of the pipe it fits. It is typically marked in one of two ways:
- DN (Diameter Nominal): The nominal diameter, a metric unit (in millimeters) used in international (กอ.รมน) and European/Chinese (EN/GB) standards. ตัวอย่างเช่น, DN50 means the valve is for a pipe with a 50 mm nominal diameter.
- กรมอุทยานฯ (Nominal Pipe Size): An imperial unit (in inches) used in American standards (ASME/ANSI). ตัวอย่างเช่น, 4″ or NPS 4 indicates the valve is for a 4-inch pipe. Sometimes, only the number, such as 4, is cast on the body.
2. Valve Pressure Rating Marking: “PN” and Numbers on Valve
The pressure rating indicates the maximum working pressure a valve can safely withstand at a given temperature and is critical for selection.
- ISO/EN/GB Standards: Uses “Nominal Pressure” (PN), where the unit is bar. The PN value represents the pressure rating at room temperature. Examples: PN16, PN40.
- asme/Ansi มาตรฐาน: Uses a “ระดับ” ระบบ, written as CLASS, CL, LB, or #. Examples include CLASS 150, 300#, or 150 LB. This represents a pressure-temperature curve, not a constant pressure value.
- General Purpose Ratings:
- การชั่ง (น้ำ, Oil, Gas): Indicates the pressure rating in psi for water, น้ำมัน, and gas service at ambient temperatures. Example: 600 การชั่ง.
- CWP (Cold Working Pressure): The modern equivalent of WOG, also indicating the maximum allowable pressure at ambient temperature. Example: 1000 CWP.
3. Valve Material Marking:
The material code is one of the most important markings, specifying the material of the main pressure-containing parts like the body and bonnet.
- Cast Carbon Steel: WCB is the most common grade.
- Cast Stainless Steel: CF8(equivalent to 304 SS), CF8M(316 SS), CF3(304L), CF3M(316L).
- Cast Alloy Steel: WC6, WC9(chrome-moly steel for high-temperature service).
- Forged Materials: A105(carbon steel), A182 F316(stainless steel).
- นำฟรี: “LF” means lead-free material, including brass and bronze.
4. Valve Media Marking:
The specific service medium (e.g., “Sulfuric Acid”) is generally not marked. Suitability for a medium is determined by the valve’sวัสดุ. อย่างไรก็ตาม, for certain special services, specific markings are used:
- การชั่ง: suitable for normal Water Oil Gas medium
- S: Steam medium
- G: Gas medium
5. Valve Brand Marking:
This refers to the manufacturer’s trademark, logo, or name abbreviation, used to identify the producer. ตัวอย่างเช่น, “กทม” or a unique symbol.
6. Valve Flow Direction Marking:
For unidirectional valves like globe valves, check valves, and angle valves, a clear arrow symbol(→) must be cast or stamped on the body. This arrow indicates the correct direction of media flow. Incorrect installation can lead to malfunction or damage.
7. Valve Certifications Marking:
These markings indicate that the valve complies with specific regional or industry regulations and standards.
- ซีอี: Abbreviation for “Conformité Européenne,” indicating compliance with EU safety, health, and environmental protection standards, required for market access in Europe.
- API: The American Petroleum Institute monogram is commonly found on valves used in the oil and gas industry.
- ซีเอสเอ: Canadian Standards Association, a certification required to sell equipment in Canada.
- UL: Underwriters Laboratories, certification is a safety certification provided by Underwriters Laboratories, a global safety science company. It signifies that a product, component, or system has been tested and meets specific safety standards.
Find Top-Quality Valves at กทม.
