Materials should be selected in accordance with the principle (1) should be implemented in the American Petroleum Institute standard API618 material requirements for the main components of the hydrogen compressor; (2) should be based on its operating conditions (gas pressure, exhaust temperature), compress medium composition ( In particular, the difference in the composition of hydrogen sulfide in the medium) is treated differently.

Other requirements for large and medium-sized hydrogen compressors for refinery hydrogenation units, whether oil-free lubrication, less oil lubrication, or oil lubrication, the average piston speed should be about 3 ~ 4m / s, should not be too high. If the average speed of the piston is designed to be too high, the resistance loss of the gas in the gas valve and the gas line will increase, the power consumption will increase, and the exhaust gas temperature will be too high, which seriously affects the economy of the compressor operation and the reliability of use. And has a direct impact on the wear of moving parts.

The special requirements for the mechanical properties of the materials are described in the structural design of the compressor.

Partial structural design and its characteristics Cross-head structure design and its characteristics The crosshead of the hydrogen press is made of ZG2302450, and the crosshead material is 42CrMo. The crosshead part is fastened by the crosshead body and screwed on the crosshead body. The two skateboards are formed. The working surface of the skateboard is cast with a bearing alloy (CnSnSb112b). The sliding plate is positioned in the longitudinal direction and the crosshead body by a gutter, and is fastened by a fastening screw with a certain tightening torque.

The structure of the crosshead member has the following structural features: (1) There are 3 brass adjusting washers with a thickness of 011mm between the crosshead body and the upper and lower sides of the slide plate. When installing, the crosshead should be slid according to the direction of rotation of the crankshaft. Remove the two spacers on the side without lateral force to realize the working gap between the crosshead and the slideway, and ensure that the axis line of the crosshead is consistent with the shaft axis of the slideway, so that the moving parts of the compressor run smoothly. This kind of structure has better processing technology and simple processing than other crosshead structures in China.

11 cross head shoe; 21 screw; 31 cross pin; 41 piston rod; 51 pressure body part hydraulic cross head structure (2) crosshead and piston rod connection using hydraulic connection structure. The hydraulic connection is to inject high-pressure oil into the inner cavity of the annular piston of the pressure body, forcibly extend the connection part of the piston rod (or the connecting rod bolt) in the elastic range, and the nut is pressed tightly with a small torque, and then the high pressure is released. Oil, this can avoid damage to the thread when the nut is tightened, so that the thread is evenly stressed.

The advantages of this new type of connection are: (1) simple installation and easy disassembly and assembly; (2) easy to find the center, no thread on the piston rod to avoid the breakage of the piston rod; (3) all the force parts are carried out The strength check is safe and reliable.

The structural design of the cylinder and its characteristics The cylinder design principle of the hydrogen compressor adopts the cast iron cylinder block and the forged cylinder cylinder according to the working pressure of the compression medium. When the working pressure is <4MPa, the cast iron cylinder block, the cylinder head and the cylinder seat are selected; when the working pressure is >4MPa, the forged cylinder block, the cylinder head and the cylinder block are usually selected.

Hydrogen Compressor Cylinder Structure Features (1) The general design cylinder is a cylindrical structure, and the air valve is radially arranged on the cylinder, and both are designed with air valve holes. The cylinder head, cylinder block and bonnet and cylinder seals are usually sealed with O-rings to prevent leakage of hydrogen. In high pressure or special media (such as H2S high), a rigid seal must be used. (2) The air cylinder is provided with air inlet and exhaust port; some have a liquid discharge port at the bottom of the cylinder diameter, which is convenient for discharging liquid in time to avoid liquid hammer. (3) The use of small air chamber cylinders helps to enhance the strength of the cylinder.

Cylinder liner design: cylinder liner material is generally low pressure (<4MPa). JT25247C alloy cast iron is used (the surface is nitrided, the hardened layer depth is 0117~0130mm, hardness ≥ HV380); medium pressure (<10MPa) is JT25247D alloy cast iron; high pressure ( ≥10MPa) 38CrMoAlA is selected. If the gas contains H2S<9%, the cylinder liner is NSTCr20; when H2S<4%, JT25247D is used. The cylinder liner and the cylinder block are statically matched.

The cast iron cylinder is a multi-walled cylindrical casting whose working volume, air passage and water passage are cast, and the water channel of the forged cylinder is machined.

1, 51 suction valve port, 2, 4 exhaust valve, 51 air inlet, 61 exhaust port, 71 water chamber; 81 cylinder cast iron cylinder structure piston component structure design and calculation 31311 structural design and material selection piston component by Piston, piston rod, piston ring, support ring, piston back cap and so on.

Material Selection (1) Pistons are usually made of castings or forgings. The material is selected according to the piston force: low-pressure grade (<4MPa) and HT200, HT250 and other cast iron parts; medium and high-pressure grade (<10MPa) selects 35 forged parts. If you consider the balance of reciprocating inertia between the stages, you can also choose aluminum alloy ZL401 and other materials.

(2) Oil-free lubrication or less oil lubrication The piston ring and support ring of the hydrogen pressure machine are made of materials filled with self-lubricating properties of tetrafluoroethylene.

(3) 42CrMo forgings are selected for the piston rod material. If the compressed medium is rich in hydrogen containing H2S components (3%~11%), the piston rod material is selected from 17-4PH forgings or a new process of amorphous hardening treatment on metal surface; The friction surface of the piston rod uses laser technology to spray new materials such as ceramic coating, which solves the problem of corrosion and wear of the piston rod parts of the medium and improves the service life of the wearing parts.

The piston and piston rod are tightened by a piston back cap, which is usually flanged into the piston recess after tightening. This method is prone to loosening and causing a vicious accident during driving. In order to avoid accidents, the piston rod and the piston can be tightened by electric heating and locking method.

The specific method is: processing a threaded hole at the top of the piston rod, placing the electric heating rod in the hole and heating it to heat the piston rod in the elastic range, and then rotating the piston nut by a predetermined angle with a small torque. (The angle is accurately calculated by the program). After the electric heater is removed and cooled to room temperature, the pre-tightening force can be evenly applied to the mating surface of the thread to ensure safe and long-term operation of the machine.

Conclusion The hydraulic coupling structure of the crosshead in the structural design of the hydrogen compressor introduced in this paper, the support ring of the piston component, the scraper ring structure, the packing sealing structure, etc. adopt advanced foreign technology. The product has good self-lubricating property, strong wear resistance and long service life.

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