Introduction: The three major determinants of hydraulic oil selection - variety, grade, and viscosity grade. According to statistics, most hydraulic system operation failures are caused by improper use and use of hydraulic oil. Selecting the correct hydraulic oil is a prerequisite for ensuring the normal operation of the hydraulic system.
Coupling
Tubing and casing couplings are the joining of two short length pipe, mainly used for the connection and repair of oil pipe and downhole tools
Tubing and couplings thread types : Non-upset thread(NU), External- upset thread(EU);
Casing and couplings thread types: Long-round thread(LC), Short-round thread(SC), buttress thread(BC)
Grade: K55,J55,N80-1,N80Q,L80-1,P110,etc.
Pup joint
Tubing and casing pup joints are machined according to the latest version of API SPEC 5CT. The steel grade includes J55,K55,N80-1,N80Q,L80-1,P110,etc. There are two types of thread widely used in tubing pup joint namely Non-upset thread(NU), External- upset thread(EU);
Casing and couplings thread types: Long-round thread(LC), Short-round thread(SC), buttress thread(BC).
Our testing and inspection method system is complete, using a whole set of thread instrument to inspect taper, pitch, tooth, height, tooth type,etc. The products have passed the identification of china petroleum pipeline. Quality supervision ,inspection and testing center and gained the unanimous praise from the customers.
Crossover
Crossover coupling any size ,length ,grade and weight is available on customer request.
Steel Grade,Steel Oil Casing Collar,Joint Oil Casing Collar,Pup Joint Oil Casing Collar Henan Dongfanglong Machine Manufacture Co., Ltd , https://www.eastlongmachine.com
So how do users choose hydraulic oil for the excavator?
The three major determinants of hydraulic oil selection - variety, grade, and viscosity grade.
General hydraulic equipment manufacturers will specify the type, grade, and viscosity grade of hydraulic oil used in the equipment system in the equipment manual or manual. The user should first select the hydraulic oil according to the manufacturer's recommendations. The operating conditions and the operating environment of the user's system may sometimes differ from those specified by the equipment manufacturer. In this case, the user needs to select the hydraulic oil.
Users need to follow the following principles when selecting hydraulic oil for themselves:
First, the type of hydraulic oil is determined based on the operating conditions of the system and the working environment. Second select the correct hydraulic oil viscosity level. Third, understand the performance of the selected hydraulic fluid. Under the premise of following these three principles, the right hydraulic oil can be selected according to the price of the product. 
What are the specific conditions for selecting the type of hydraulic oil?
1. Choose the type of hydraulic oil according to the working pressure and temperature of the hydraulic system;
2. Choose the type of hydraulic oil according to the working environment of the hydraulic system;
3 Select the type of hydraulic oil according to the special performance requirements.
After choosing the right type of hydraulic oil, it is also necessary to use hydraulic oil with a suitable viscosity level in order to make the hydraulic system work at its best. The user needs to select the hydraulic oil according to the ambient temperature. The higher the temperature, the lower the viscosity of the hydraulic oil. Therefore, high-pressure areas can use large-grade hydraulic oil (hydraulic oil number and proportional to the viscosity), and use low-grade hydraulic oil at low temperature.
In addition, although the high viscosity of the hydraulic oil is good for lubricity, it increases the resistance of the hydraulic system and increases pressure loss, resulting in increased power loss, increased oil temperature, unstable hydraulic operation, and noise. Excessive viscosity can also cause difficulty in sucking oil at low temperature start-up, and even cause interruption of oil supply during low temperature start-up to cause equipment failure. When the viscosity of the hydraulic system is too low, internal and external leakage of the hydraulic equipment will increase, causing the working pressure of the hydraulic system to be unstable, and the hydraulic working parts will not be located. In severe cases, the wear of the pump will increase.
Most of our excavators use L-HL hydraulic oil (ordinary hydraulic oil, China's current supply and demand of the largest hydraulic oil), the brand name is HL-32, HL-46, HL-68, brand L-HL-xx, L said Type of lubricant, H means hydraulic oil, L means rust-proof and oxidation-resistant, and number means the kinematic viscosity of the hydraulic oil (the greater the grade, the greater the viscosity).
In the end, the user needs to realize that the choice of hydraulic oil cannot blindly see the brand of hydraulic oil, and the important thing is the brand of hydraulic oil. In addition to selecting the correct hydraulic oil, it is also necessary to check regularly to ensure that the oil product, so as to extend the life of hydraulic components, ensure equipment safety, reduce the occurrence of failure.