Valve material& packing material

Yes, every valve requires packing to keep the stem and bonnet tight!

The specific device of the packing test consists of a packing seal test bench and a test part for the characteristics of the packing wood body. The packing seal test bench is used to simulate a valve that uses packing as the valve stem seal, and has the function of detecting leakage at the valve packing. During the test, the valve stem is in a horizontal position. Considering the different orientation of the valve stem when the valve is actually used, it is considered that the position of the valve stem can be changed at any time during the test process, which will not interfere with the test results of the valve. In addition, the test device shall be equipped with a driving device to simulate the lifting or rotating movement of the valve stem, and the driving device shall ensure that no lateral loads and transverse stresses are applied to the valve stem. The unit shall be equipped with thermocouples and temperature monitors to ensure that the temperature stability of the stuffing box and fluid piping is provided and continuously monitored throughout the thermal cycle to avoid interfering with the results of the valve seal packing performance test. The device used for leak measurement shall be a certified ionizing flame steam analyzer to effectively collect and record the data obtained from the test.

The filler material test is a measurement of filler weight loss, density, leachables analysis, and lubricant content. The sample filler tested should be randomly selected to effectively perform reliable testing of the product produced by the manufacturer. In order to avoid the influence of temperature changes during the test results, it is of great significance to ensure the continuous reasonable and stable temperature conditions throughout the test process. The filler weight loss test is tested separately for lamellar graphite (flexible graphite) and braided graphite depending on the contact environment and action, and the lubricant content test includes the measurement of the content of PTFE and wet lubricant. Special element or component testing requirements can be set according to the different requirements of different working conditions for the elements of filler components.

Commonly used valve materials are:

cast iron

Cast iron is subdivided into four categories: gray cast iron, malleable cast iron, ductile iron, and nickel cast iron. This article mainly introduces the two main cast iron materials made by BAND valves: gray cast iron and ductile iron.

Gray cast iron is cast iron with flake graphite, because the fracture is dark gray when broken, so it is called gray cast iron. Gray cast iron is the most widely used cast iron, and its output accounts for more than 80% of the total output of cast iron. The casting performance, cutting performance and wear resistance of gray cast iron are very good. Its disadvantage is that its strength, plasticity and toughness are lower than other cast irons.

Grey cast iron is used as the material of butterfly valve, which is usually suitable for weak acid and weak alkali media such as water and air, but not suitable for pipelines with perhydrochloric acid and nitric acid media.

Ductile iron is a high-strength cast iron material with very high strength, toughness and wear resistance, and its comprehensive performance is close to that of steel. At present, the application range of ductile iron is second only to gray cast iron. We often say “replace steel with iron”, which refers to ductile iron.

Ductile iron is used as the material of the butterfly valve, which has certain corrosion resistance and performance is much higher than that of the butterfly valve made of gray cast iron. The applicable medium includes steam, general gas and oil.

The second category: cast steel

Cast steel is a cast iron alloy, which is a general term for iron-based alloys used to produce castings that do not undergo eutectic transformation during solidification. The advantages of cast steel are greater design flexibility and variability, increased overall structural strength and a wide range of weight variations. Using cast steel as the butterfly valve material, the performance is better than that of cast iron but not as good as stainless steel. Butterfly valve made of cast steel is suitable for steam, non-corrosive gas, oil, etc.

The third category: stainless steel

Stainless steel refers to steel that is resistant to weak corrosive media such as air, steam, and water, and chemically corrosive media such as acid, alkali, and salt, also known as stainless acid-resistant steel. Generally, the butterfly valve made of stainless steel has the best performance and can be used in more severe working conditions. It is used in some ultra-high temperature, ultra-low temperature and strong acid-base corrosive medium pipelines. Wear-resistant and long-lasting.

For example, what material is WCB/LCB/LCC/WC6/WC in the valve?

W, Wrought, casting;

C-Carbon steel;

A, B, C indicate the strength value of steel grade from low to high

WCA, WCB, WCC represent carbon steel, ABC represents the strength level, and WCB is commonly used. The pipe material corresponding to WCB should be A106B, and the corresponding forging material should be A105.

WC6 is a casting of alloy steel, the corresponding pipe material is about A355 P11, and the forging is A182 F11;

In addition, there is WC9, high temperature resistant alloy steel, corresponding to about A355 P22, and forgings corresponding to A182 F22.

WC Weldable Castings

LCB/LCC (ASTM A352) Low Temperature Carbon Steel

ITCS is impact toughness carbon steel; Impact Test C=Carbon S=Steel (A350)

Split body split type, side entry side loading (referring to the actuator) corresponds to the TOP entry top loading type

Carbon steel castings and forgings material table commonly used in valves

Low temperature steel casting material grade and applicable temperature

Comparison table of commonly used ASTM materials for valves and castings (ASME B16.5)

Note: 1) The material of the forged valve body is dense, not easy to be defective, the structure size is not limited by the mold, and the pressure bearing performance is reliable. It is mostly used in the manufacture of high pressure, oxygen conditions, small diameter or other small batch valves. Forgings are selected under high temperature, high pressure or low temperature or special media; castings are generally only suitable for medium and low pressure, and are mostly used in the mass production of standardized formed valves.

2) The difference between material A351 CF3M and A182 F316L: The material corresponding to the two standards is 316 stainless steel. CF3M stands for casting and is often used as a valve material. The corresponding forged steel code is A182 F316L. ASTM A216 WCB is a casting, and its forging is A105; the casting of SS304 is A351-CF8, and its forging is A182-F304.

Choose the right valve material

Valve selection: selection of medium and valve material

WCB

carbon steel

ASTM A216

Non-corrosive applications including water, oil and gas,

Temperature range: -30°C to +425°C

LCB

Low temperature carbon steel

ASTM A352

Low temperature applications, temperatures as low as -46°C

Can not be used in occasions where the temperature is higher than +340℃

LC3

3.5% nickel steel

ASTM A352

Low temperature applications, temperatures as low as -101°C

Can not be used in occasions where the temperature is higher than +340℃

WC6

1.25% chromium 0.5% molybdenum steel

ASTM A217

Non-corrosive applications including water, oil and gas,

Temperature range: -30°C to +593°C

WC9

2.25 chrome

ASTM A217

Non-corrosive applications including water, oil grade WC9 and gas,

Temperature range: -30°C to +593°C

C5

5% chromium 0.5% molybdenum

ASTM A217

mildly corrosive or aggressive applications and non-corrosive applications,

Temperature range: -30°C to +649°C

C12

9% Chromium 1% Molybdenum

ASTM A217

mildly corrosive or aggressive applications and non-corrosive applications,

Temperature range: -30°C to +649°C

CA6NM(4)

12% chrome steel

ASTM A487

corrosive applications,

Temperature range: -30°C to +482°C

CA15(4)

12% chrome

ASTM A217

corrosive applications,

Temperature range up to +704°C

CF8M 3

16 stainless steel

ASTM A351

Corrosive or ultra-low temperature or high temperature non-corrosive applications,

Temperature range: -268°C to +649°C,

If the temperature is above +425℃, the carbon content should be specified as 0.04% and above

CF8C

347 Stainless Steel

ASTM A351

Mainly used in high temperature, corrosive applications,

Temperature range: -268°C to +649°C,

If the temperature is above +540℃, the carbon content should be specified as 0.04% and above

CF8

304 stainless steel

ASTM A351

Corrosive or ultra-low temperature or high temperature non-corrosive applications,

Temperature range: -268°C to +649°C

If the temperature is above +425℃, the carbon content should be specified as 0.04% and above

CF3

304L stainless steel

ASTM A351

Corrosive or non-corrosive applications,

Temperature range up to +425°C

CF3M

316L stainless steel

ASTM A351

Corrosive or non-corrosive applications,

Temperature range up to +454°C

CN7M

alloy steel

ASTM A351

Has good resistance to hot sulfuric acid corrosion,

Temperature up to +425°C

M35-1

Monel

ASTM A494

Weldable grade. Has very good resistance to all common organic acids and salt water

corrosion properties. Also highly resistant to corrosion by most alkaline solutions

performance at temperatures up to +400°C

N7M

Hastelloy B

ASTM A494

Especially suitable for processing hydrofluoric acid of various concentrations and temperatures.

Has good resistance to sulfuric acid and phosphoric acid corrosion, temperature

Up to +649℃

CW6M

Hastelloy C

ASTM A494

It has good corrosion resistance in strong oxidizing environment. at high temperature

Has good properties, formic acid (formic acid), phosphoric acid, sulfurous acid

and sulfuric acid have high corrosion resistance, temperature up to +649 ℃

CY40

Inconel

ASTM A494

Performs well in high temperature applications. For strong corrosive fluids

Has good corrosion resistance.

1. Gray cast iron: Gray cast iron is suitable for water, steam, air, gas and oil with nominal pressure PN≤1.0MPa and temperature of -10℃～200℃. The commonly used grades of gray cast iron are: HT200, HT250, HT300, HT350.

2. Malleable cast iron: suitable for water, steam, air and oil medium with nominal pressure PN≤2.5MPa and temperature of -30~300℃. Commonly used grades are: KTH300-06, KTH330-08, KTH350-10.

3. Ductile iron: suitable for media such as water, steam, air and oil with PN≤4.0MPa and temperature of -30~350℃. Commonly used grades are: QT400-15, QT450-10, QT500-7.

In view of the current domestic technological level, each factory is uneven, and it is often difficult for users to test. According to experience, it is recommended that PN≤2.5MPa, the valve should still be made of steel for safety.

4. Acid-resistant high-silicon ductile iron: suitable for corrosive media with nominal pressure PN≤0.25MPa and temperature lower than 120℃.

5. Carbon steel: suitable for media such as water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure PN≤32.0MPa and temperature of -30～425℃. Commonly used grades are WC1, WCB, ZG25 and high-quality steel 20, 25, 30 and low-alloy structural steel 16Mn.

6. Copper alloy: suitable for water, seawater, oxygen, air, oil and other media with PN≤2.5MPa, as well as steam media with temperature of -40 ~ 250 °C, the commonly used grades are ZGnSn10Zn2 (tin bronze), H62, Hpb59-1 (brass), QAZ19-2, QA19-4 (aluminum bronze).

7. High temperature copper: suitable for steam and petroleum products with nominal pressure PN≤17.0MPA and temperature≤570℃. Commonly used grades are ZGCr5Mo, 1Cr5M0.ZG20CrMoV, ZG15Gr1Mo1V, 12CrMoV, WC6, WC9 and other grades. The specific selection must be in accordance with the valve pressure and temperature specifications.

Eight, low temperature steel: suitable for nominal pressure PN≤6.4Mpa, temperature ≥-196 ℃ ethylene, propylene, liquid natural gas, liquid nitrogen and other media, commonly used brands) are ZG1Cr18Ni9, 0Cr18Ni9, 1Cr18Ni9Ti, ZG0Cr18Ni9

Nine, stainless acid-resistant steel: suitable for nominal pressure PN≤6.4Mpa, temperature ≤200 ℃ nitric acid, acetic acid and other media, commonly used grades are ZG0Cr18Ni9Ti, ZG0Cr18Ni10 <nitric acid resistance>, ZG0Cr18Ni12Mo2Ti, ZG1Cr18Ni12Mo2Ti <acid and urea resistance>