Main objectives of project research

The MRC reciprocating compressor is the core key equipment for liquefied natural gas (LNG) plants with a circulation capacity of 300000 cubic meters per day or less. The main research objectives of this project are as follows:
The ratio of packing leakage to rated flow rate reaches 0.03% to 0.06%, which is 5-10 times higher than the industry's usual value of 0.3%;
The service life of the packing sealing ring is ≥ 12000h, which is twice as long as the industry's usual value of 6000h;
The service life of piston rings and support rings is ≥ 12000h, which is twice as long as the industry's usual value of 6000h;
The service life of the air valve is ≥ 12000h, which is twice as long as the industry's usual value of 6000h;

The main research content of this project is: the dynamic sealing low leakage mechanism of mixed refrigerant reciprocating compressor packing and the application of system level circulation without external leakage; Research and application of long-term operating life of vulnerable parts of high-speed heavy-duty compressors.

Technical key

• During the reciprocating motion of the compressor, the dynamic sealing mechanism of the packing with low leakage and the application of system level circulation without external leakage
• Evaluation of the impact of high-speed and heavy-duty operation on the service life of vulnerable parts such as valves, packing, piston rings, and corresponding structural parameter optimization methods;
• Select piston rings and packing materials based on the average speed of the piston and the lubrication conditions inside the cylinder and packing box. Select the number of piston rings and packing rings for sealing based on the sealing pressure difference and lubrication condition; Evaluate the lifespan of piston rings and packing rings based on the PV value of the seals, taking into account the material, average piston speed, and pressure difference.

The material used is E011 grade special polymer material, which has a lifespan 3 to 40 times longer than traditional conventional PTFE materials. Suitable for working in dry gas environments such as natural gas, hydrocarbons, ammonia, carbon dioxide, nitrogen, etc. Process and manufacture in a constant temperature workshop to ensure stable operation of the product under rated conditions.
The 34A zero state sealing ring breaks away from the conventional concept of packing design by gradually sealing and reducing pressure. A single set of zero state sealing rings is designed and controlled in terms of material and size, which can achieve a sealing effect of 50-100 kilograms per set, effectively controlling the leakage of the packing ring group while reducing the number of packing ring groups, reducing the load and frictional heat brought by the entire ring group design, improving the service life of the packing ring group, and facilitating standardized packing design.

Technical Challenges

The factors that affect the leakage of packing seals in reciprocating compressors include pressure, temperature, medium, piston rod diameter, roughness, levelness, roundness, assembly runout value, selection of sealing ring type, packing box processing and assembly, etc. As the packing wears down, the leakage will inevitably gradually increase.
In reciprocating piston compressors, piston rings and packing boxes are used to seal the gas inside the cylinder, which accelerates wear at high speeds and makes it difficult to dissipate frictional heat. This poses a serious challenge to the performance and service life of piston rings and packing boxes. In order to design a sealing element structure with efficient sealing effect, it is necessary to analyze and calculate the friction and wear characteristics of the sealing element, and quantitatively evaluate its wear failure and thermal failure.
The friction and wear problems caused by high speed can be reduced and wear can be slowed down through good lubrication in the design of the compressor and unit system; The problem of valve impact caused by high speed can be solved by reasonable design of valve lift and the use of PEEK plastic valve plates with good impact resistance; The problem of unbalanced inertia force and increased torque caused by high speed, due to the excellent balance characteristics of the symmetrical balance structure, is fundamentally guaranteed. In addition, the design ensures that the relative rotation and reciprocating motion mass of the two columns are as close as possible, thus avoiding potential severe vibration problems of the compressor in high-speed machines.
The service life of air valves, piston rings, and packing is guaranteed. The working frequency of these components is higher than that of low-speed machines, which poses a great challenge to their fatigue life.

Main parameters of the unit

Project performance objectives