Cast iron parts are metal products cast from molten iron. The material is mostly gray cast iron alloy with a carbon content of 2.5% to 4%. They are mainly used in handicrafts (such as ornaments, bells and tripods) and industrial fields (such as automotive parts, electrical hardware, valves). Its casting processes include sand casting, shell casting, die casting and centrifugal casting, etc. Among them, sand casting has become the mainstream due to its low cost and strong adaptability, while centrifugal casting can reduce porosity defects.

The quality of cast iron parts is divided into three dimensions: appearance, internal quality and service performance. Defects include pores, cracks, slag inclusions, etc. They are often repaired by argon arc welding or cold welding. Surface treatment can be carried out through an automated polishing process to remove oxide scale and burrs, enhancing brightness and rust resistance. The price is influenced by factors such as the complexity of the process, annual demand and transportation costs [1]. In 2012, among the regional output in China, Hebei Province had the highest proportion (19.18%), followed by Jiangsu and Henan. The output of Shanxi, Chongqing and other places showed a downward trend.

The quality of cast iron parts has a significant impact on the performance of mechanical products. For instance, the wear resistance and dimensional stability of machine tool castings directly affect the precision retention life of the machine tool. The accuracy of the dimensions, profiles and surface roughness of the impellers, casings and inner cavities of hydraulic components of various types of pumps directly affect the working efficiency, energy consumption and the development of cavitation of pumps and hydraulic systems. The strength and resistance to sudden cooling and heating of cast copper parts such as the cylinder block, cylinder head, cylinder liner, piston rings and exhaust pipe of internal combustion engines directly affect the working life of the engine.

More than 20 senior engineers from our technical department provide one stop services including product design, cost calculation, production process, inspection, issued part solution.

We have currently obtained over 15 patents in the fields of valves and castings.

All our product are customized &OEM,parts are totally made according to customer’s 3D drawing or sample.

Customer’s drawing and designs are kept as confidential !

Safety valve

1.Structural features:

It is composed of main components such as the valve body, valve stem, valve disc, valve seat, adjusting screw, and spring. It is divided into three types: lever type, spring type and pilot-operated type.

2. Working principle:

The lever-type safety valve is a subtype of direct-acting safety valve. It uses the lever principle to apply the torque generated by the heavy hammer to the valve disc. When the system pressure exceeds the set value, the valve disc opens to relieve pressure. This type of safety valve features a simple structure and precise adjustment. It is suitable for industrial scenarios with high working temperatures but low pressures, such as steam boilers and fixed pressure vessels. Its working principle is based on mechanical balance. The opening pressure can be adjusted by changing the position or mass of the counterweight, but it has limitations such as being bulky and prone to leakage due to vibration.

Spring-loaded safety valve Spring-loaded safety valves use the preload of the spring to balance the pressure of the fluid inside the equipment. When the fluid pressure inside the equipment exceeds the pressure of the safety valve spring, the valve disc is pushed open to release air and relieve pressure. When the fluid pressure inside the equipment drops below the compression force of the spring, the safety valve automatically closes. By adjusting the tightness of the spring through the adjusting screw, different preload setting values can be obtained. Meet the different pressure value requirements of the allowable working pressure for different equipment. Spring-loaded safety valves are classified into fully enclosed, semi-enclosed and open types based on different usage conditions. According to the different opening heights of the valve disc, it is further divided into fully lift type and slightly lift type. The fully lift type and fully enclosed type are mostly adopted in gas transmission stations.

Pilot-operated safety valve: Composed of a main valve and an auxiliary valve. The medium pressure and spring pressure are simultaneously applied to the main valve disc. When overpressure occurs, the auxiliary valve disc opens first, causing the main valve to open. It is mainly used in large-diameter and high-pressure applications.

Cast iron parts are iron-carbon alloys with a carbon content greater than 2.1%. They have excellent castability and machinability and are widely used in components such as automotive engines and gearboxes. The characteristics of cast iron parts include good wear resistance, shock absorption and low price. Common cast iron parts structures include engine blocks, crankshafts, etc., which have good mechanical properties and wear resistance.

Gray cast iron is the most widely used type of cast iron, with its output accounting for over 80% of all types of cast iron. For parts with low mechanical performance requirements but complex shapes, such as machine tool beds, cylinder blocks, cylinder heads, and transmission cases in automobiles, gray cast iron can be used for manufacturing.

Malleable cast iron is suitable for manufacturing some thin-section parts with complex shapes and high requirements for strength and toughness, such as rear axle housings, wheel hubs, brake pedals, and leaf spring brackets on automobiles.

In automobiles, heat-resistant cast iron can be used to manufacture intake and exhaust valve seats as well as exhaust pipe sealing rings, etc. The cylinder liners and piston rings of automobiles are generally made of wear-resistant alloy cast iron, with high-phosphorus series alloy cast iron being the main type. Piston rings are generally made of high-phosphorus wear-resistant cast iron containing tungsten, chromium and manganese, while the piston rings of the CA1093 engine are made of niobium-containing alloy cast iron with better wear resistance. The cylinder liner of EQ1092 is cast from high-phosphorus cast iron. High-strength alloy cast iron can be used to manufacture diesel engine crankshafts, connecting rods and main bearing covers, etc.

Check valve

Check valves, also known as single-flow valves or one-way valves, belong to the category of non-return valve components. They are used to restrict the unidirectional flow of air and prevent backflow. There are two types: lift type and swing type. The check valves of our company are swing check valves. Its structural features and working principle are as follows:

Structural features: It is composed of a valve body, valve cover, valve disc, sealing ring, rocker, etc.

2. Working principle: Fluid is introduced into the valve from the lower end. When the thrust generated by the pressure difference between the fluid before and after the valve is greater than the weight of the valve disc, the fluid pushes the valve disc open, causing the valve disc to rotate along the rocker, allowing the fluid to pass through. When the fluid flows back, the pressure at the outlet end is greater than that at the inlet end. Under the action of gravity and pressure difference, the valve disc moves in the opposite direction along the rocker, preventing the fluid from flowing back.

3. Precautions

When installing this valve, it is essential to pay attention to the inlet and outlet directions to ensure that the flow direction of the valve disc is consistent with that of the fluid.

4. Common Faults and Their Handling

(1) Repair and installation of valve disc detachment; (2) Check and replace the sealing ring if the seal is not tight

Electric Ball Valve

Electric ball valves are used to control the cut-off of air flow and are generally not suitable for regulation. Therefore, their state should be fully open or fully closed. Ball valves are installed in the inlet and outlet stations, pigging device receiving and dispatching devices, and some bypass processes for crossing stations. Ball valves have good reliability in terms of valve seats, automatic pressure relief, fire prevention, sealing design and material selection. The connection method is flange butt type, and the actuator is an electric actuator.

1. Common Faults and Their Handling

(1) The oil cup is leaking

A. The oil cup is leaking at the threaded part of the oil cup

B. Grease leakage at the mouth of the oil cup; Replace the oil cup

(2) If the handwheel is too tight, turn the valve lead screw

(3) Internal leakage drainage; Repair the sphere

2. Daily maintenance: Cleaning, turning the wheel, draining, adding lubricating oil, and greasing

(4) Ball Valve:

1.The structure of a ball valve: A ball valve is mainly composed of a valve body, a ball, a sealing ring, a valve stem and a driving device.

2. Features of ball valves:

(1) Low flow resistance;

(2) Simple structure and small volume;

(3) Good sealing performance;

(4) Easy to operate and quick to open and close;

(5) Easy to maintain;

(6) At high temperatures, the opening and closing torque is large and the sealing performance is poor.

3. Application scope of ball valves:

Nominal pressure PN1.6-32.0Mpa;

Nominal diameter: DN10-700mm;

Working temperature t≤200℃

4. Precautions

Ball valves are generally used in situations where rapid opening and closing are required or low resistance is needed. They can be applied to media such as water and gasoline, and are also suitable for pipelines containing slurry and viscous liquids. Ball valves can also be used in high-pressure pipelines and pipelines with low pressure drops.

(2) Since throttling may cause damage to the sealing parts or the ball, ball valves are generally not used for throttling. Full-channel ball valves are not suitable for regulating flow.

5. Common Faults and Their Handling

(1) The oil cup is leaking

A. Leakage at the oil cup thread – Tighten the oil cup

B. Oil cup mouth leakage – Grease injection; Replace the oil cup

(2) The handwheel is too tight – turn the valve lead screw. Reduce the pressure difference before and after the valve; Check the transmission worm gear

(3) Internal leakage – Replace the sealing valve seat and repair the ball

6. Daily maintenance: Cleaning, turning the wheel, adding lubricating oil, and greasing

(2) Stop valves and throttle valves:

Structural features of stop valves and throttle valves:

It is mainly composed of the valve body, valve cover, valve stem, valve disc and handwheel, etc.

Advantages and disadvantages of stop valves

Advantages: Good sealing performance, with low friction on the sealing surface

The phenomenon is not serious, maintenance is relatively convenient, and the opening height is high

The degree is small and the flow rate can be appropriately adjusted.

Disadvantages: High resistance to medium flow and long structural length

It is relatively large, with a greater opening and closing force.

2. Precautions

1) Stop valves are not suitable for regulating the pressure or flow of the medium. Throttle valves should be selected for parts that frequently need to adjust pressure or flow rate.

2) Straight-through and direct-flow stop valves and throttle valves can be installed on pipes that intersect horizontally or vertically. Angle stop valves and throttle valves need to be installed on pipes that intersect vertically. During installation, it is necessary to ensure that the indication direction of the valve body is consistent with the flow direction of the medium.

3) When the fluid flows upward through the valve seat, the tightness is affected when there is sediment on the valve seat. Therefore, it is generally not suitable for fluids with suspended solids.

3. Faults and Handling

(1) If the packing is exposed, replace the tight cover or stop the gas supply

(2) If the handwheel is too tight, loosen the cover or replace the packing

(3) Clean and repair the sealing surface for internal leakage

4. Daily maintenance: Cleaning, turning the wheel, and adding lubricating oil

Connection method

Flange connection

This is the most commonly used connection form in valves. According to the shape of the mating surface, it can be further classified into the following types:

1. Smooth type: Used for valves with low pressure. It is relatively convenient to process.

2. Concave-convex type: It has a relatively high working pressure and can use medium-hard gaskets

3. Tenon and groove type: It can use gaskets with relatively large plastic deformation and is widely used in corrosive media, providing a good sealing effect.

4. Trapezoidal groove type: It uses an elliptical metal ring as a gasket and is suitable for valves with a working pressure of ≥64 kilograms per square centimeter or high-temperature valves.

5. Lens type: The gasket is in the shape of a lens and made of metal. It is used for high-pressure valves with a working pressure of ≥100 kilograms per square centimeter or high-temperature valves.

6. O-ring type: This is a relatively new form of flange connection. It has developed along with the emergence of various rubber O-rings and is an effective sealing connection form.

Wafer connection

A connection form in which the valve and the two ends of the pipe are directly clamped together with bolts.

Butt welding connection

A connection method that is directly welded to the pipe.

Threaded connection

This is a simple connection method, often used for small valves. It can be divided into two situations:

1. Direct sealing: The internal and external threads directly serve the sealing function. To ensure that there is no leakage at the connection points, lead oil, hemp thread and polytetrafluoroethylene raw material tape are often used for filling. Among them, polytetrafluoroethylene raw material tape is being used more and more widely. This material has excellent corrosion resistance and an outstanding sealing effect. It is convenient to use and store. When disassembling, it can be completely removed because it is a non-sticky film, which is much superior to lead oil and hemp thread.

2. Indirect sealing: The force from tightening the threads is transmitted to the gasket between the two planes, allowing the gasket to perform a sealing function.

Cleaning steps

The components of the valve must undergo the following process treatment before assembly:

1. According to the processing requirements, some components need to be polished, and the surface must not have any processing burrs, etc.

2. All components undergo degreasing treatment.

3. After degreasing is completed, acid washing and passivation are carried out. The cleaning agent does not contain phosphorus.

4. After pickling and purification, rinse thoroughly with pure water to ensure no chemical residue remains. This step is omitted for carbon steel components.

5. Dry each component one by one with non-woven fabric, ensuring no lint or other impurities remain on the surface of the component, or blow dry them with clean nitrogen.

6. Use non-woven fabric or precision filter paper dipped in analytical pure alcohol to wipe each component one by one until there is no dirt or color.

Daily maintenance

1. Attention should be paid to the storage environment of valves. They should be stored in a dry and well-ventilated indoor area, and both ends of the passage should be blocked.

2. Valves should be inspected regularly, and the dirt on them should be removed. Anti-rust oil should be applied to their surfaces.

3. After the installation and application of the valves, regular maintenance should be carried out to ensure their normal operation.

4. Check whether the sealing surface of the valve is worn and carry out maintenance or replacement as the situation requires.

5. Check the wear of the trapezoidal thread of the valve stem and the valve stem nut, whether the packing is outdated or ineffective, etc., and make necessary replacements.

6. The sealing performance of the valve should be tested to ensure its performance.

7. The valves in operation should be in good condition, with all bolts on the flanges and brackets complete, the threads undamaged and no loosening.

8. If the handwheel is lost, it should be replaced in time and cannot be replaced by an adjustable wrench.

9. The packing gland must not be skewed or have no pre-tightening clearance.

10. If the valve is used in a harsh environment and is prone to contamination by rain, snow, dust, sand and other contaminants, a protective cover should be installed on the valve stem.

11. The scale on the valve should be kept complete, accurate and clear. The lead seal and cap of the valve.

12. The insulation jacket should be free from depressions and cracks.

13. For valves in operation, avoid knocking on them or supporting heavy objects, etc.