Composition, processing technology and common problems of mud pump cylinder liner

The mud pump is the "heart" of the oilfield drilling system, and the mud pump cylinder liner is an important and easily worn
part of the hydraulic end of the mud pump. Therefore, the life of the mud pump cylinder liner directly affects the life of the mud pump. Because the working surface of the cylinder liner
is in contact with the high temperature and high pressure gas, the piston ring reciprocates at high speed on its surface, which determines that
the cylinder liner should not only have sufficient strength and rigidity, but also must be resistant to high temperature, corrosion and wear. damage.

1.1 Composition and processing technology of mud pump cylinder liner:
inner sleeve: high chromium cast iron (generally containing 19%-22% chromium, American cylinder liner - generally containing 26%-28% chromium, or according to
customer requirements to add)
outer casing : Blank seamless steel pipe (45# steel), in which the outer jacket and inner jacket are assembled by hot-fitting (the outer
jacket is heated to expand, the inner jacket is cooled and contracted)
The processing technology of the cylinder liner is as follows:
Set
※Hot pressing/Hot forging (The induction coil is heated to about 1000 degrees)
Centrifugal casting
The latest process (patent of Lanzhou University): spraying (integrated, no inner sleeve), the material is Ni60, the WC
inner sleeve is manufactured by centrifugal casting, the raw material is scrap iron filings, high Ferrochrome. The centrifugal casting speed
is 1000r/min, and the medium frequency 750 furnace (1430C-1450C) is used for casting, and trace elements are tested before the furnace.
The instruments used in the assay are carbon-sulfur combined analyzer [C (hardness), Mn, Cr (default 18-23%)], and visible
spectrophotometer.

1.2 Common problems of cylinder liner
1. De-sleeve. GB is 4% random inspection, our company is 100% full inspection. The CDG-4000 cylinder liner fluorescent magnetic particle flaw detector
was used for non-destructive testing NDE. (UV lamp, fluorescent magnetic powder).
2. The disadvantage of centrifugal casting is the presence of blisters and cracks. After centrifugal casting, the blanks are put into a trolley-type resistance furnace for annealing treatment (200 pieces per furnace), heated to 980C, cooled with the furnace, and softened.

1.3 Cylinder liner quality plan: inner sleeve melting temperature 1430°C--1450°C chemical
inspection centrifugal casting speed 1000r/min ) 980°C for 5-6h with furnace cooling , quenching (hardness enhancement), 980°C for 30min air cooling , 200°C for 60min heat preservation, 100% Full inspection, pressure test after cooling for 24 hours.

1.4 Mechanical performance test of cylinder liner
Jacket: tensile test (tensile strength Rm, yield strength δs0.2MPa), expansion rate after fracture δ/A, section
expansion rate ψ, impact test (Xia's notch)
Inner jacket: metallographic structure analysis
Hardness HRC≥60 Calibration
of all measuring tools (Shaanxi Academy of Sciences, Xi'an Aerospace Metrology and Testing Institute)

1.5 The coating of the cylinder liner is
only a beautification function, but F2200HL (CNOOC) is used for offshore drilling and must be sprayed with anti-corrosion paint.

1.6 Classification
of cylinder liners Common types of mud pump cylinder liners are as follows: single metal cylinder liner, bimetallic cylinder liner, ceramic cylinder liner, and nickel-based alloy
cylinder liner.
1.6.1 Single-metal cylinder liner: After carburizing and high-frequency treatment, the single-metal cylinder liner can reach HRC58--62 in hardness. It
has the characteristics of high smoothness, wear resistance, corrosion resistance and long service life. For use in mild corrosive slurries
.
1.6.2 Bimetallic cylinder liner: Bimetallic cylinder liner is currently the most widely used and one of the hydraulic
end accessories of mud pumps with the largest consumption. The bimetallic cylinder liner combines the advantages of a hot forged high-wear outer jacket and a high-chromium wear-resistant and anti-corrosion inner jacket. The
outer jacket is formed by hot pressing of high-quality carbon steel
. The tensile strength of 900000psi, the hardness of the inner sleeve reaches HRC62 after heat treatment. It can withstand
the mud pressure of 7000psi, its inner surface is as smooth as a mirror, the inner hole size tolerance is strict, and the normal service life
can reach more than 800 hours.