Tag Archive for: supplier in china

Posts

Cryogenic valve principle |standard |illustration |selection

Principle of Cryogenic valve|Standard of Cryogenic valve|Selection of Cryogenic valve
The so-called cryogenic valve is a kind of altra-low temperature valve, as the name implies, is a valve suitable for working in cryogenic conditions. In the valve industry, valves that tend to -40°C are called cryogenic valves. Cryogenic valves are generally used in cryogenic systems such as liquid helium, liquid hydrogen, liquefied natural gas, and air separation. The medium used is liquid helium, liquid hydrogen, liquefied natural gas, liquid nitrogen, liquid oxygen and other cryogenic fluids. Under low temperature conditions, conventional metal hard seals and non-metal soft seals cannot meet the sealing requirements. In order to ensure that cryogenic valves can operate safely and reliably at low temperatures, there are some special considerations and requirements in the design and manufacture of cryogenic valves. see photo attached is a cryogenic triple offset butterfly valve.

triple offset valve parts-after-cryogenic process

triple offset valve parts-after-cryogenic process

Principle of ultra-low temperature valve: For valves used in ultra-low temperature conditions, the medium temperature is very low, and the metal materials will experience low temperature cold brittleness. The strength and hardness will be greatly improved, and the plasticity and toughness will be greatly reduced. This will directly affect the performance and safety of the valve. If an ordinary valve is used, the low temperature will freeze the packing in the valve stuffing box, and it will not be able to play a sealing role. In this way, the valve needs to be lengthened from the sealing seat on the bonnet to the bottom of the stuffing box. With sufficient isolation space and heat dissipation distance, the low-temperature medium in the valve body will not freeze the packing. As shown in the figure, the part marked with 175mm is the lengthened part.

In ultra-low temperature conditions, the valve stem and valve body can only adopt stuffing box or bellows structure. There are many restrictions on the use of bellows. Generally, the structure of the stuffing box seal is adopted. The stuffing box seal structure is simple to process and convenient to maintain. However, the sealing effect cannot be guaranteed under the condition of <-40℃, so the ultra-low temperature valves are all Keep the stuffing box as far away from the material as possible, and choose packing with low temperature characteristics.

Selection of ultra-low temperature valve:

Valve body: Ferritic stainless steel can be used when the temperature is higher than -100°C, austenitic stainless steel can be used when the temperature is lower than -100°C, copper alloy or aluminum alloy can be used for low-pressure and small-diameter valves. Stem: Made of austenitic stainless acid-resistant steel, it needs to be properly heat-treated to increase the tensile strength. At the same time, it must be hard chrome plated (coating thickness 0.04~0.06mm) or nitriding treatment to increase the surface hardness.

Gasket: When the working temperature is higher than -196℃ and the maximum low temperature working pressure is 3MPa, the asbestos rubber sheet made from long fiber can be used; when the working temperature is higher than -196℃ and the maximum low temperature working pressure is 5MPa, it can be used. Stainless steel spiral wound gasket with asbestos, stainless steel spiral wound gasket with PTFE, or stainless steel spiral wound gasket with expanded graphite.

Fasteners: when the temperature is higher than -100°C, the bolt material is Ni, Cr-Mo and other alloy steels, which need to be properly heat-treated to prevent thread bite; when the temperature is lower than -100°C, the bolt material can be austenitic Body stainless steel. The nut material is generally Mo steel or Ni steel, and the thread surface is coated with key disulfide.

Ultra-low temperature valve design standards:

1. Design: API6D, JB/T7749

2. Valve routine inspection and test: according to API598 standard.

3. Low temperature inspection and test of valve: According to JB/T7749.

4. Drive mode: manual, bevel gear drive and electric drive device.

5. Valve seat form: The valve seat adopts a welded structure, and the sealing surface is welded with cobalt-based hard alloy to ensure the sealing performance of the valve.

6. The ram adopts an elastic structure, and a pressure relief hole is designed at the pressure inlet end.

7. One-way sealing valve body is marked with flow direction mark.

8. The low-temperature ball valve, gate valve, and stop valve adopt a long neck structure to protect the packing.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Notes on selection and installation of butterfly valve

Product selection points of butterfly valves:
1. The main control parameter of the butterfly valve is the size.
2. The butterfly valve is a single-plate air valve. It has a simple structure, convenient processing, low cost, and easy operation, but the adjustment accuracy is poor. It

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

is only suitable for the occasion of switching or rough adjustment in the ventilation and air conditioning system.
3. It can be operated manually, electrically or by zipper, and can be fixed at any angle in the range of 90°.
4. Due to the single shaft and single valve plate, the bearing capacity is limited, and the service life of the valve is short under the condition of large pressure difference and large flow rate. The valve is divided into closed type and ordinary type, thermal insulation and non-thermal insulation.
5. The electric butterfly valve has only two-position control, and the electric actuator is the same as the multi-leaf valve.

Installation matters of butterfly valve:
The butterfly valve has a simple structure, small volume, light weight, and relatively few components. The key parts can form a butterfly valve. It is also very convenient to open. You only need to select the switch to ninety degrees. The butterfly valve The fluid control is very good, you can increase or decrease the flow at any time, the valve has a certain resistance when transporting any fluid, and the resistance of the butterfly valve mainly comes from its own, such as the thickness of the butterfly valve body, if you want to reduce the fluid The resistance only needs to reduce its thickness.
Elastic seals have the disadvantage of being limited by temperature.
Butterfly valves are also widely used. If they are used to control the flow rate, different types and sizes of valve bodies need to be selected, because butterfly valves are more suitable for valves with larger diameters when they are designed. Butterfly valves are not only widely used in general industries such as petroleum, gas, chemical, and water treatment, but also in cooling water systems of thermal power stations.

Tianjin Tanghai dongyang valve Co., Ltd. is one of the largest butterfly valve manufacturers in China, main products are butterfly valves, check valves. Product ranges: butterfly valve, lug type butterfly valve, wafer type butterfly valve, U-type butterfly valve, double flange butterfly valve, gate valves, check valves, globe valves, valve parts (Valve body, Valve disc, Valve shaft, Valve seat…)

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Related news /knowledge: Selection and application of eccentric butterfly valve; What is the material of the main parts of the butterfly valve?-(2); 

The advantages and disadvantages of butterfly valves

Advantages of butterfly valve:

1. Convenient opening and closing, labor saving, low fluid resistance, and can be operated frequently.

wafer type butterfly valve, NBR seat (11)

wafer type butterfly valve, NBR seat (11)

2. The structure is simple, the external dimensions are small, the structural length is short, the volume is small, and the weight is light. It is suitable for valves with large diameter.

3. Mud can be transported, and the least liquid is accumulated in the pipe mouth.

4. Under low pressure, a good seal can be achieved.

5. Good adjustment performance.

6. When fully opened, the effective flow area of the valve seat channel is large, and the fluid resistance is small.

7. The opening and closing torque is small, because the butterfly plates on both sides of the rotating shaft are basically the same under the action of the medium, and the direction of generating torque is opposite, so the opening and closing are more labor-saving.

8. The sealing surface material is generally rubber, plastic, so the low-pressure sealing performance is good.

9. Easy installation.

10. Flexible and labor-saving operation, you can choose manual, electric, pneumatic, hydraulic mode.

Disadvantages of butterfly valve:

1. The operating pressure and operating temperature range are small.

2. Poor sealing.

Butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type and lever type according to the structure.

According to the sealing form, it can be soft-sealed or hard-sealed. The soft seal type generally uses a rubber ring seal, and the hard seal type usually uses a metal ring seal.

According to the connection type, it can be divided into flange connection and wafer connection; according to the transmission mode, it can be divided into manual, gear transmission, pneumatic, hydraulic and electric.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

related news /knowledge: What is the material of the main parts of the butterfly valve?-(2); Characteristics and working principle of electric globe valve; Classification and advantages of gate valve