Method for coding safety valve models and explanations

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Methods for Designating Safety Valve Models and Explanations

I. Codes for Connection Types of Safety Valves
Connection type code: Internal thread – 1; Clamp connection – 7; External thread – 2; Clamp – 8; Flange connection – 4; Sleeve connection – 9; Welded connection – 6

II. Codes for Structural Types of Safety Valves
Spring-sealed with fins, full-opening type ------- 0
Spring-sealed, slightly opening type ------------------- 1
Spring-sealed, full-opening type ------------------- 2
Full-opening type with wrench ---------------------- 4
Unsealed, double-spring, slightly opening type------------- 3
Unsealed, full-opening type ---------------------- 8
Unsealed, slightly opening type ---------------------- 7
Pilot-operated type------------------------------- 9

III. Codes for Materials of the Valve Seat Sealing Surface
Copper alloy -------- T; Ammonia-resistant steel -------- D; Rubber -------- X; Boronized steel -------- P; Nylon plastic ----- N; Cemented carbide ----- Y; Alloy steel resistant to acids or stainless steel ------------------- H
Processing of the valve body itself --------------- W; Tin-based bearing alloy (Babbitt) ---------- B

IV. Codes for the Nominal Pressure of Safety Valves
The nominal pressure code is expressed in Arabic numerals, with the value being 10 times the nominal pressure in megapascals (MPa). When indicating the operating temperature and operating pressure, the operating pressure must be denoted by the symbol P, with the maximum temperature of the medium indicated in the lower right corner of this symbol; this value is the integer obtained by dividing the maximum temperature value by 10. For a valve with an operating temperature of 540°C and an operating pressure of 10 MPa, its code is P54100. V. Code for the material of the safety valve body: Gray cast iron ---------- H; Carbon steel ---------- C; Ductile iron ---------- Q; Chromium-molybdenum alloy steel ---- I; Chromium-nickel-titanium steel ------- P; Chromium-molybdenum-vanadium alloy steel ---- V. Note: This code is omitted for gray cast iron valve bodies with a PN of 1.6 MPa or less, and for carbon steel valve bodies with a PN of 2.5 MPa or more. For example: A42Y—16PA denotes a safety valve ； 4 indicates flange connection ； 2 indicates full opening of the spring ； Y indicates that the sealing surface material is cemented carbide ； 16 indicates a nominal pressure of 1.6 MPa ； P is stainless steel ； This safety valve is a spring-actuated, fully open safety valve. Additionally: 1. The main parameter of a safety valve is its discharge capacity, which is determined by the valve’s diameter and the opening height of the valve disc. Depending on this opening height, safety valves are classified into full-opening type and slightly-opening type. Full opening means that the opening height of the valve disc is 1/4 of the throat diameter of the valve seat. Slightly open type refers to a valve disc opening height of 1/40 to 1/20 of the valve seat throat diameter. General principle: 2. Incompressible media such as water generally use closed micro-tilt valves or safety relief valves. 3. Hot water boilers generally use an unsealed, wrench-operated slight-opening type. 4. Steam boilers or steam pipes generally use an unsealed, full-opening type with a wrench. 5. High-pressure feed water systems generally use closed slightly-open types, such as high-pressure feed water heaters and heat exchangers. 6. Class E steam boilers generally use gravity-type safety valves. 7. Compressible media such as gases generally use closed, full-opening safety valves, such as in gas storage tanks and gas pipelines. 2 For large-diameter, high-displacement, and high-pressure systems, pulse-type safety valves are generally used, such as in temperature and pressure reduction devices and power station boilers. 2. Tank cars, road tankers, and storage tanks used for transporting liquefied gas generally use internal safety valves. 2 Hydraulic safety valves are generally used on the top of oil tanks, and they need to be used in conjunction with breather valves. 2 Pilot-operated safety valves are generally used for underground drainage or gas pipelines. 2 A safety return valve is generally used on the liquid-phase return pipeline at the outlet of the tank pump at LPG stations. 2 Bellows safety valves are generally used for systems with large backpressure fluctuations, as well as for containers or piping systems that are toxic or flammable. 2 Systems that are under negative pressure or may develop negative pressure during operation generally use vacuum pressure relief valves. 2 Systems with a low freezing point of the medium generally use insulated jacketed safety valves.