How to choose plunger pump and pump cylinder material

Plunger pump and pump tube material how to choose it?

From the point of view of the oil pump, the selection of the materials of the pump cylinder and the plunger and the surface treatment process become the decisive factors in determining the amount of corrosion wear of the tribological system. At present, the number of wells using rod pumps in domestic oil fields accounts for a large proportion, most of which are plunger-type pump, and conventional plunger pump has become one of the major oil extraction methods.

The wear, corrosion and scratch of the plunger pump and the plunger of the plunger pump are getting more and more serious. The average pump inspection period is getting shorter and shorter, and some even need to check the pump in less than 30 days, because most of the domestic oil fields have been Entering the period of high water cut development, coupled with high sand, high-temperature steam heavy oil mining, polymer mining and strong corrosive media environment and poor well conditions and other factors, seriously affecting the overall economic benefits of oil field development. Many organizations at home and abroad have invested a lot of power to study the failure reason and protective measures of the pump. One of the effective methods is to optimize the material and surface treatment process of the pump barrel and plunger.

The pump cylinder and plunger friction pair of the plunger pump and the surrounding working environment and conditions constitute a tribology system. Corrosion wear of the pump cylinder of the plunger pump and corrosive wear of the plunger are caused by the corrosion wear of this system. The sum of the amount is determined. The respective corrosion and wear of the pump barrel and the plunger are determined by the physical mechanical and chemical properties of the constituent materials, the mutual movement relations, the working environment and conditions and other factors.

The purpose of selecting and optimizing the plunger and plunger materials and surface treatment process of the plunger pump is to minimize the amount of corrosive wear of this tribological system. Due to the large number of influencing factors, there is still no theoretical guidance on the material selection and matching of the pump cylinder and the plunger. The most current work for R&D personnel is to select various pump cylinders and plunger materials and surface treatment processes, and then perform certain corrosion. An internal friction and wear test was conducted under wear conditions and the results of the tests were used to determine what pump plunger material should be selected under this test condition. Here are two test results:

The first result: the material of the cylinder of the plunger pump and the surface treatment process are electroless nickel-phosphorus alloy plating on the surface of 45 steel, chrome plating on the surface of 303 steel, and pressure nitriding of 4%-6% chrome steel; And the treatment process for the table is carbon steel chrome plating, carbon steel laser processing, naval brass chemical nickel-phosphorus alloy plating, monel alloy chrome plating and other four kinds. The above materials were paired and tested for wear resistance. The friction pair used in the test consisted of rings and blocks. The medium is clear water, the temperature is 60°C, and the viscosity is 0.000653 Pa/s. The tester is a MG-200 high speed high temperature friction and wear tester. The applied load is 1kN, and the total friction stroke of the test piece is 20km. Through the research on the paired wear resistance of different pump cylinders and plunger materials and surface treatment process, and according to the principle of plunger failure first, the optimal matching materials for the pump cylinder and piston friction pair are carbon steel chemistry respectively. Nickel-plated phosphor alloy and carbon steel chrome plated.

The second result: the cylinder material and surface treatment process of the plunger pump are chrome plating on the surface of carbon steel, nickel-phosphorus alloy electroless plating on the surface of carbon steel, and nitriding of 38CrMoAl; the plunger material and surface treatment process are chrome plating and carbon on the surface of carbon steel. Electroless nickel-phosphorus alloy plating on the surface of steel, carbon steel surface spray Ni-based alloy and 38CrMoAl nitriding, respectively paired into a pair of friction pairs. The test friction pair consists of a ring and a column. The test medium is oily sewage, which contains 5% of oil; mineral content in water: chloride ion 11000mg/1, carbon dioxide 25mg/1, calcium ion 25mg/1, bicarbonate ion 30mg/1, magnesium ion 13mg/1, total iron 8mg/1; Sand 0.4%; Temperature 60°C. The same domestic high-speed high-temperature friction wear tester MG-200 was used. Test load 100N, friction total stroke is about 6km. Comprehensive analysis of the test results, that the carbon steel spray plunger and the carbon steel chrome piston pump pump tube pairing is optimal, 38CrMoAI nitriding plunger and carbon steel chrome pumping cylinder paired second.

It can be seen from the above that the laboratory test results are obtained under the set conditions. If different test conditions are changed, the workload is huge. Even if the conditions vary, it is not necessarily consistent with the downhole condition of the oil field, so the experimental results are limited. Due to the difference in test conditions and the shape of the friction pair, there is no comparability between the individual test results.

With the development of material engineering and the emergence of new material surface treatment processes, many materials and surface treatment processes may be applied to the pump cylinder and plunger surface of the plunger pump, and the friction and wear test of a simple laboratory mating material is possible. Deciding whether or not the trade-offs are far from meeting the urgent requirements for improving the life of the pump cylinders and plungers of the oil pump, how to design the pump cylinder and the plunger pairing material based on the principles and techniques of materials science and other disciplines is an urgent problem to be solved.

It can be seen that the lack of matching between the pump cylinder and the plunger material of the plunger pump is determined through experiments, and the test has no theoretical guidance and thus the test workload is large. The materials selected for the test are only well-known existing materials, and it is difficult to propose other materials that may not have been used on the pump but may perform better.