OPI 350D Mud Pump

 

Meta Title: OPI 350D Mud Pump | Forged Steel Triple-Cylinder Pump | API 7K Wear Parts

Meta Description: Discover the expert-engineered design of the OPI 350D three-cylinder mud pump. Its advanced materials, forging techniques, and API 7K-certified wear parts ensure maximum durability and lower total cost of ownership in high-pressure drilling operations.

 

 

This table provides a concise summary for users who need to quickly access top technical data, clarifying the pump's operating level and core capabilities.

parameter	specifications
Pump type	Three-cylinder single-acting piston/plunger pump
Maximum input power	350 HP
Maximum stroke length	8 inches (203.2 mm)
cylinder diameter	5 inches (127 mm)
Hydraulic end	Steel hydraulic end
Main applications	Well repair, cementing, acidizing, drilling (land and sea)

 

 

Crankshaft-the cornerstone of forging strength

 

The crankshaft serves as the pump's core component. The OPI 350D pump features a monolithic crankshaft forged from high-strength alloy steel (4340 or 35CrMo).

After forging, the crankshaft also needs to undergo multi-stage heat treatment, nitriding hardening and micro polishing of the shaft neck and other finishing processes.

Precision gears-the guarantee of efficient power transmission

 

The OPI 350D features a **double helical gear (herringbone gear) design**. Unlike straight gears, this herringbone structure ensures multiple teeth engage simultaneously, delivering smooth, continuous, and progressive power transmission while significantly reducing operational noise and vibration.

Bearings, Frame, and Lubrication System-Designed for Long-Term Performance

 

The power side uses high quality roller bearings, including spherical roller bearings for the pinion shaft and straight roller bearings for the spindle.

The power side rack is made of welded steel structure and subjected to stress relief heat treatment after welding.

A complete lubrication system combining compulsion and splashing ensures that all moving parts, including bearings and crosshead guides, are protected by a continuous, clean and cool oil film, thus maximizing their service life.

 

 

High strength forged alloy steel module

The hydraulic end module is forged from high-quality high-strength alloy steels including 35CrMo, 40CrMnMo, and 4135.

Advanced valve and seat assembly: the guardian of pressure

 

The valve body and seat are forged from high-quality alloy steel (20CrNiMo / AISI 8620) and undergo carburizing and quenching heat treatment. This process diffuses carbon atoms into the surface layer of low-carbon alloy steel at high temperatures. The subsequent quenching process hardens this carbon-rich surface to HRC>60 while preserving the core's original toughness and ductility. This dual-engineered composite material combines extreme surface hardness to withstand intense erosion from high-speed, solid-containing drilling fluids, with a resilient core absorbing the massive impact forces generated by thousands of valve closures per hour, effectively preventing brittle fracture. This innovative composite structure forms the core technology enabling the valve assembly's ultra-long service life.

 

 

High-performance cylinder liner-comparative analysis

High chromium bimetallic cylinder liner

Manufacturing Process: The outer shell is constructed from high-strength forged steel (AISI 1045) to ensure structural integrity. The inner sleeve, made of high-chromium cast iron (>27%), is formed through centrifugal casting to achieve a dense and uniform microstructure. After heat treatment, the inner sleeve reaches a hardness of HRC 62-69 and is press-fitted into the outer shell with an interference fit.

Performance: Provides an excellent service life of more than 800 hours under standard drilling conditions.

Zirconia ceramic cylinder liner

 

Manufacturing process: Ultra-pure zirconia ceramic powder is used to form by isostatic pressing, sintered at high temperature to achieve maximum density, and finally assembled into a forged steel shell.

technological superiority ：

Outstanding performance: Zirconia ceramic has higher hardness (HRC>92), better impact toughness and finer surface finish (4-8 RMS), far higher than super chromium steel.

Chain benefits: This ultra-hard, ultra-smooth surface greatly reduces the friction between the cylinder liner and the piston. This brings a series of chain advantages:(1) the piston life is significantly extended (according to the data up to 5 times);

(2) Reduced heat generation, thereby lowering the load on the cylinder liner spray system; (3) The service life of the cylinder liner itself is greatly increased, usually more than 4000 hours.

Table 2.1: Comparison of cylinder liner material properties

This comparison table allows customers to easily weigh the cost-effectiveness of different options based on their specific needs.

characteristic	High chromium bimetallic cylinder liner	Zirconia ceramic cylinder liner
sheathing material	Forged steel (AISI 1045)	Forged steel (AISI 1045)
Inner lining material	High chromium cast iron (Cr>27%)	Zirconia ceramic (ZrO2)
fabrication process	Centrifugal casting inner sleeve with hot pressing fit	Isostatic forming, high-temperature sintering
Hardness of inner wall (HRC)	62-69	>92
maximum working pressure	7500 PSI	7500 PSI
Typical service life	~800+ hours	4,000+ hours

 

Durable piston for various drilling fluids

Design Core: Our pistons are made of high-strength forged steel (40Cr or 45# steel) to ensure maximum structural integrity.

stock option ：

Adhesive polyurethane piston: A premium choice for oil-based and synthetic-based drilling fluids. Its specially engineered polyurethane formulation delivers exceptional chemical resistance, wear resistance, and extrusion resistance under high pressure.

Adhesive nitrile rubber piston: A robust and cost-effective choice, particularly suitable for water-based slurry. The specially formulated rubber offers excellent sealing performance and heat resistance.

Piston rod and sealing assembly

Piston rod: Crafted from premium forged alloy steel (e.g., 40Cr) and treated with surface finishes (e.g., chrome-plated or zinc-plated) to ensure high tensile strength and exceptional corrosion and wear resistance.

Seals and gaskets: We provide a full range of high-performance gaskets and seals to ensure absolute integrity of all hydraulic end connections (including valve cover, cylinder head and cylinder liner seals).

 

 

This table is a basic tool for the drilling engineer to match the pump performance to the well team hydraulic parameter requirements, and clearly shows the relationship between cylinder liner size, pressure, and displacement.

Cylinder liner size (inches)	Maximum pressure (PSI)	Flow rate at rated stroke (GPM)
6	1027	661
5 ½	1222	555
5	1479	459
4 ½	1710	397
4	2169	313
3 ½	2816	240

The data is based on performance under a specific charge.

Table 3.2: Detailed Description of Wear Parts Materials and Processes

 

This table directly responds to customer needs for detailed materials and process information, and serves as both a technical specification and a quick reference guide for procurement.

component	Material Options	Key manufacturing processes	Core Specifications/Advantages
Hydraulic end module	4135/35CrMo/40CrMnMo alloy steel	Forging, heat treatment (quenching and tempering), non-destructive testing	Complies with API 7K standard, high strength, fatigue resistant, high pressure resistant
crank axle	4340/35CrMo Forging alloy steel	Overall forging, multi-stage heat treatment, nitriding, dynamic balancing	Continuous grain flow, high tensile strength and toughness, wear resistance
gear wheel	4340 Forging alloy steel	Double helical (Herringbone) machining and heat treatment	Complies with AGMA standards, smooth transmission, low noise, long service life
Valve body/seat	20CrNiMo (AISI 8620) alloy steel	Forging, carburizing and quenching	Hardness>HRC 60, core tough, erosion resistant, impact resistant
cylinder sleeve	High chromium bimetallic / zirconia ceramic	Centrifugal casting / isostatic pressing	Wear-resistant/super wear-resistant, corrosion-resistant, service life 800+/4000+ hours
plunger	Forged steel piston hub + polyurethane/nitrile rubber	Bonding process	Wear and chemical corrosion resistant, suitable for different slurry systems
piston rod	40Cr forged alloy steel	Forged, surface chrome/galvanized	High tensile strength, corrosion resistance, wear resistance

 

 

application area

The OPI 350D three-cylinder pump, with its outstanding design and robust performance, is the ideal choice for a range of high-pressure operations, including:

Oil and gas well repair operations

Cementing and acidizing operations

Drilling from shallow to middle depth in land and sea

Our OEM Commitment

As the Original Equipment Manufacturer (OEM) of OPI 350D, we provide robust safeguards for every component of the product. Our commitment extends beyond sales to include comprehensive technical support, rapid spare parts supply, and professional after-sales service. Through rigorous control over the entire design, material, and manufacturing process, we ensure that each OPI 350D pump and its components deliver the high reliability and superior performance required for your operations. We not only meet industry standards like API 7K, but also build upon them to create the most durable and cost-effective slurry pump products in the industry.

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