Can welded hydraulic cylinders be used in high or low temperature environments?

In modern industrial equipment, hydraulic systems are widely used in various types of mechanical power transmission, and hydraulic cylinders are crucial actuators in these systems. With the increasing complexity of the application environment of engineering equipment, welded hydraulic cylinders are frequently used in extreme climatic conditions, such as high temperature conditions (metallurgy, steel, foundry industry) or low temperature environments (Arctic, cold chain, cold storage, oil drilling, etc.). So, can welded hydraulic cylinders operate stably in high or low temperature environments? This article will provide detailed answers from the perspectives of structural characteristics, material selection, sealing technology, design optimization, etc.

1. What is a welded hydraulic cylinder?

A welded hydraulic cylinder is a hydraulic actuator that uses welding to connect the cylinder body to key components such as the cylinder bottom and cylinder head. Compared with traditional tie rod hydraulic cylinders, welded hydraulic cylinders have the advantages of small size, compact structure, high strength, and good sealing performance. They are widely used in engineering machinery, agricultural machinery, mining equipment, industrial automation and other fields.

Due to its compact structure and high manufacturing flexibility, welded hydraulic cylinders are very suitable for use in harsh or special environments, including high and low temperature scenarios.

2. Can welded hydraulic cylinders be used in high-temperature environments?

2.1 Effect of high temperature on hydraulic cylinder

High-temperature environment (generally ≥70°C or even over 150°C) will bring the following challenges to the operation of hydraulic cylinder:

Hydraulic oil viscosity decreases, lubrication performance weakens;

Seals age faster, easily deform and fail;

The risk of stress deformation at welding parts increases;

Coatings and surface protective materials are easy to peel off;

Material thermal expansion leads to changes in fit clearance.

2.2 High temperature adaptation design of welded hydraulic cylinder

In order to make welded hydraulic cylinders adapt to high temperature conditions, the design needs to be optimized from the following aspects:

Material selection

Under high temperature conditions, ordinary carbon steel and low alloy steel are prone to fatigue cracking due to thermal stress. Therefore, materials with good thermal stability and creep resistance should be selected, such as:

High temperature alloy steel (such as 15CrMo, 12Cr1MoV, etc.)

Piston rod materials treated with hard chrome or ceramic coatings

Seal selection

The sealing system is the key weakness of welded hydraulic cylinders in high temperature environments. Traditional nitrile rubber (NBR) is prone to aging at high temperatures and needs to be replaced by:

Fluororubber (FKM): temperature resistance up to +200°C;

Polytetrafluoroethylene (PTFE): temperature resistance up to +260°C, suitable for harsh conditions;

Silicone rubber (MVQ): suitable for short-term high temperature conditions.

Lubrication and hydraulic oil selection

High temperature will affect the viscosity and lubrication performance of hydraulic oil. High-temperature hydraulic oil with high viscosity index, good thermal stability and strong anti-oxidation performance should be selected, such as:

HV hydraulic oil

Synthetic ester-based hydraulic oil

And the oil cooling system can be properly configured to maintain the system temperature within a reasonable range.

Welding process optimization

For high temperature environments, low-stress welding processes are required for welding parts, and heat treatment is performed after welding to eliminate internal stress, improve structural stability, and avoid weld cracking caused by temperature differences.

3. Is the welded hydraulic cylinder suitable for low-temperature environments?

3.1 Effect of low temperature on hydraulic cylinders

Low temperature environment (e.g. below -20°C, extreme temperature can reach -50°C or even lower) will also cause the following problems to welded hydraulic cylinders:

The material becomes brittle and prone to cracking;

The viscosity of the hydraulic oil increases and the fluidity is poor;

The seal loses its elasticity and is prone to leakage;

The starting resistance increases and the response becomes slower;

The cold brittleness of the weld is obvious.

3.2 Low temperature adaptation design of welded hydraulic cylinder

Special steel for low temperature

For low temperature brittleness, steel with good low temperature impact toughness should be selected, such as:

16MnDR (applicable to -40°C)

09MnNiD (applicable to -60°C)

Austenitic stainless steel (such as 304L, 316L, with better low temperature performance)

Low temperature sealing technology

For seals, rubber or plastic materials suitable for low temperature conditions need to be selected, such as:

Special low temperature formula of nitrile rubber (NBR) (-40°C)

Hydrogenated nitrile (HNBR)

Polyurethane (TPU): has good resilience, suitable for temperatures below -40°C

In ultra-low temperature occasions, metal skeleton auxiliary sealing structure can also be selected to improve cold resistance.

Hydraulic oil configuration

Low freezing point hydraulic oil needs to be used at low temperatures, such as:

L-HV low-temperature hydraulic oil

Synthetic hydraulic oil, freezing point can reach below -50°C

The oil tank should be equipped with a heating device to ensure that the oil temperature is not lower than the working critical point during the initial startup.

Cold-resistant treatment of welds

Low-hydrogen electrodes are used during welding, and slow cooling or stress relief annealing is performed after welding to prevent low-temperature brittle cracking caused by residual stress in welding. Important weld parts should also be non-destructively tested by X-ray flaw detection to ensure reliability.

4. Typical industry application cases

4.1 High-temperature working condition application cases

In the automatic loading system of furnace materials in a large steel plant, a welded structure hydraulic cylinder is used to replace the traditional cylinder body. By using a high-temperature alloy cylinder and a fluororubber sealing ring, it can achieve continuous operation of 3000 hours at nearly 200°C without failure, which improves the reliability of the equipment.

4.2 Low-temperature working condition application cases

In the winter inspection vehicle project of the Central Asian natural gas pipeline, the welded hydraulic cylinder is made of 09MnNiD material and uses a special low-temperature sealing system. It has successfully passed the -45°C environmental test, ensuring the stable operation of the equipment in winter.

In summary, welding hydraulic cylinders can operate stably in high or low temperature environments, provided that the following key aspects are done according to the actual application environment:

Precise material selection: ensure that the cylinder body and key components have heat or cold resistance;

Scientific design: control thermal expansion, gap changes and stress release;

High-quality seals: use targeted sealing materials;

Hydraulic oil adaptation: select suitable oil according to temperature;

Reliable process: use adaptive welding and heat treatment processes.

Equipment operating in harsh environments has extremely high requirements for the stability and reliability of the hydraulic system. Welding hydraulic cylinders have been widely verified in many fields due to their structural advantages and adaptability. Choosing professional manufacturers to customize suitable high and low temperature hydraulic cylinder solutions will escort the efficient operation of corporate equipment.

If you need to customize welding hydraulic cylinders suitable for high or low temperature environments, please feel free to contact us. We have a professional technical team and support non-standard customization services. We can tailor high-performance welding hydraulic cylinder solutions according to your specific application environment, temperature conditions, installation methods and working pressure requirements.

http://www.toringcylinder.com
Ningbo Toring Machinery Manufacturing Co., Ltd.