RS11818.12 Locking Shaft Seat & Parts for FZ35-70/2FZ35-70/RS11818/RS11819 Ram BOP

Introduction

Ram Blowout Preventers (BOPs) are the cornerstone of well control safety in high-pressure oilfield drilling, and every component—from locking shaft seats and ram assemblies to sealing rings and fasteners—directly determines the equipment’s ability to isolate wellbore pressure and prevent catastrophic blowouts. The parts listed, including RS11818.12 locking shaft seat, RSU816.07 Ram assembly, RSU818.09 Screw 36 x 3, and RS11816.08 side door seal, are specifically engineered as drop-in replacements for four critical Ram BOP models: FZ35-70, 2FZ35-70, RS11818, and RS11819. These BOPs are widely used in onshore and offshore high-pressure oilfields, with a rated working pressure of 70MPa (10000psi) and a bore size of 13 5/8″ (φ346.1mm), playing a vital role in deep well, ultra-deep well, and high-salinity offshore drilling operations. Our parts fully match the structural dimensions and performance requirements of these BOP models, solving the core pain points of oilfield maintenance and operation teams: locking shaft seat wear leading to mechanism jamming, seal leakage causing well fluid seepage, ram assembly deformation resulting in poor pressure isolation, and fastener loosening triggering equipment failure—all of which can lead to costly drilling shutdowns, environmental damage, and even personnel safety risks. As side door seal damage and ram jamming are among the most common BOP faults, our high-quality replacement parts are designed to eliminate these risks and ensure uninterrupted well control operations.

Our target users include oilfield well control maintenance engineers, procurement managers of oilfield service companies, and BOP operation teams. For maintenance engineers, the key demand is parts that are easy to install, durable, and fully compatible with FZ35-70, 2FZ35-70, RS11818, and RS11819 BOPs, reducing maintenance time and minimizing downtime. For procurement managers, it is reliable quality that complies with international standards, cost-effectiveness, and a comprehensive product range to avoid the waste of spare parts and ensure timely supply. For operation teams, it is ensuring the BOP can respond quickly in emergency situations, maintaining tight sealing and stable operation under extreme pressure. The core purpose of these parts is to provide a one-stop, high-reliability replacement solution for the four target BOP models, covering locking mechanisms, ram assemblies, housings, sealing elements, fasteners, and auxiliary parts. This ensures the BOPs maintain optimal performance in harsh oilfield environments, reducing maintenance costs and operational risks, while meeting the strict safety requirements of high-pressure drilling operations.

Product Overview

The product portfolio covers all key components of FZ35-70, 2FZ35-70, RS11818, and RS11819 Ram BOPs, including locking system parts (RS11818.12 locking shaft seat, RS11816.12 Right hydraulic locking mechanism, RS11811.01.05 Wedge lock piston), ram assemblies (RS11816.07, RSU816.07.09.00, RSU816.07.05.00, RSU816.07.04.00, RSU816.07.01.00 Ram assembly), housing components (RS11818.05 single gate housing, RSU818.03 Left middle flange, RSU818.11 Right side door), sealing elements (RS11816.08 side door seal, RSU816.19 Piston seal, RSU816.20 Y-ring seal 76.2, RSU816.18 O-rings 370 x7), fasteners (RSU818.09 Screw 36 x 3, RS11148.02A Cap Nut M39X3, RS11811.01.02 Unlock cylinder connecting bolt), and auxiliary parts (RS11816.35 Support rod, RSU818.10 Ram Shaft, F9301.29 Z1″ plug, RSU816.13 oil line connector). All parts are manufactured in strict accordance with API Spec 16A (Fourth Edition) international standards and GB/T 20174-2019 national standards, and have passed API 16A Monogram certification and ISO 9001:2015 quality management system certification. Each part undergoes 100% static pressure testing (up to 105MPa, 1.5 times the rated working pressure) and dimensional inspection before leaving the factory, with a qualification rate of 100%. Our RSU816.18 O-rings 370 x7 can withstand 430 pressure cycles without leakage, and the RS11818.12 locking shaft seat has a wear resistance of 3800 working hours, which is 1200 hours longer than ordinary locking shaft seats, effectively solving the problem of premature wear under high vibration.

Function Description

Locking System Parts

The RS11818.12 locking shaft seat and RS11816.12 Right hydraulic locking mechanism are core components of the BOP’s locking system, responsible for fixing the ram shaft and ensuring the ram stays in place during high-pressure operations. The locking shaft seat solves the pain point of wear and jamming caused by high vibration (up to 3.9 mm/s RMS) during drilling, while the hydraulic locking mechanism ensures smooth locking and unlocking, avoiding delay in emergency response. The RS11811.01.05 Wedge lock piston provides stable locking force, ensuring the ram does not move under 70MPa working pressure, and the RS11811.01.02 Unlock cylinder connecting bolt fixes the unlock cylinder, preventing loosening and ensuring reliable operation of the unlocking mechanism.

Ram Assemblies and Bodies

The RSU816.07.01.00, RSU816.07.04.00, RSU816.07.05.00, and RSU816.07.09.00 Ram assemblies are the core sealing components of the BOPs, responsible for closing the wellbore and isolating well pressure. The RS11816.07.08.03, RS11816.07.09.03, and RS11816.07.05.03 Ram bodies are made of high-strength alloy steel, with a Brinell hardness of 220 HBW, which can withstand 70MPa working pressure without deformation. These ram assemblies solve the pain point of poor sealing caused by wear and tear, ensuring the BOPs can effectively isolate well fluid even in high-pressure deep well environments. The RS11818.05 single gate housing provides structural support for the ram assemblies, preventing housing deformation under extreme pressure.

Sealing Components

Sealing elements such as RS11816.08 side door seal, RSU816.19 Piston seal, RSU816.20 Y-ring seal 76.2, and RSU816.18 O-rings 370 x7 are critical for preventing well fluid leakage. Made of HNBR (hydrogenated nitrile rubber), these seals have excellent high-temperature resistance (-29℃ to 121℃) and corrosion resistance, solving the problem of seal aging and leakage in high-temperature, high-salinity offshore environments. The RS11816.07.01.01 Top seal, RS11816.07.04.02 Front seal, and RS11816.07.05.02 Front seal ensure tight sealing between the ram and the wellbore, avoiding pressure loss. The RS11816.27 Rectangular seal, RS11816.28 Rectangular Seal Gasket, and RS11816.08.02 Rectangular sealing ring for side door provide auxiliary sealing for the side door and intermediate flange, enhancing overall sealing performance.

Fasteners and Auxiliary Parts

Fasteners including RSU818.09 Screw 36 x 3, RS11148.02A Cap Nut M39X3, and RS11811.01.02 Unlock cylinder connecting bolt are used to fix various components of the BOPs. These fasteners are made of 10.9-grade high-strength steel, with anti-loosening thread design, which can withstand high vibration and pressure without loosening. Auxiliary parts such as RS11816.35 Support rod provides structural support for the ram shaft, preventing bending; RSU818.10 Ram Shaft transmits hydraulic force to drive the ram movement, ensuring smooth operation; F9301.29 Z1″ plug seals the lubrication channel, preventing lubricant leakage; RSU816.13 oil line connector ensures smooth hydraulic oil flow, avoiding hydraulic system blockage.

Structural Features

The RS11818.12 locking shaft seat adopts an integrated forging structure, with a diameter of 58mm and a thickness of 22mm, which is 4mm thicker than ordinary locking shaft seats, enhancing wear resistance and impact resistance. The surface is treated with carburizing and quenching, which increases the surface hardness to HRC 58, solving the problem of premature wear in high-friction environments. The RSU816.07.01.00 Ram assembly has a modular design, allowing for quick disassembly and assembly—reducing maintenance time by 45 minutes per maintenance cycle compared to ordinary ram assemblies.

Sealing components such as RSU816.18 O-rings 370 x7 have a symmetric double-lip structure, which can automatically compensate for wear, reducing the need for frequent replacement. The RSU818.03 Left middle flange and RSU818.06 Right middle flange adopt a thickened design (flange thickness 38mm), which is 10mm thicker than ordinary flanges, enhancing pressure resistance and avoiding deformation under 70MPa working pressure. All parts have precise dimensional accuracy, with a tolerance of less than 0.006mm, ensuring perfect fit with the FZ35-70, 2FZ35-70, RS11818, and RS11819 BOP bodies, avoiding assembly difficulties and reducing installation errors.

The RSU818.10 Ram Shaft has a chrome-plated surface (plating thickness 0.06mm), which reduces friction between the ram shaft and the cylinder, avoiding jamming and extending service life by 4200 hours. The RS11816.34 Master cylinder liner has a smooth inner surface (Ra ≤1.2μm), reducing wear of the piston seal and ensuring stable hydraulic pressure transmission.

Applicable Working Conditions

These parts are specifically designed for FZ35-70, 2FZ35-70, RS11818, and RS11819 Ram BOPs, which are widely used in high-pressure onshore and offshore oilfields, including deep wells, ultra-deep wells, and high-salinity offshore drilling platforms. They fully meet the API 16A T-20/250 temperature grade requirements and the BOPs’ working parameters, adapting to the following harsh working conditions:

• Working pressure: 0 to 70MPa (10000psi), fully matching the rated pressure of the target BOP models

• Temperature range: -29℃ to 121℃, adapting to extreme temperature changes in desert and offshore environments

• Medium compatibility: Resistant to well fluid, drilling mud, seawater, hydrogen sulfide, and high-salinity media

• Vibration range: ≤3.9 mm/s RMS, withstanding the vibration generated during high-speed drilling operations

• Environmental adaptability: Dust-proof, sand-proof, and corrosion-proof, suitable for desert, offshore, and high-humidity oilfield environments, including North Sea offshore drilling scenarios and Tarim Oilfield’s ultra-deep wells

Typical applications include FZ35-70 and 2FZ35-70 BOPs used in Tarim Oilfield’s ultra-deep wells, RS11818 BOPs in Bohai Bay Offshore Oilfield, and RS11819 BOPs in Middle East high-pressure oilfields, providing reliable replacement parts for these key well control equipment and ensuring smooth drilling operations.

Maintenance and Care Recommendations

Based on the on-site operation experience of our senior well control engineers with more than 25 years of experience, and referring to API 16AR maintenance guidelines, the following practical maintenance and care suggestions are provided to extend the service life of the parts and ensure the stable operation of the BOPs, avoiding common maintenance mistakes that lead to seal failure and component damage:

1. Before installing the RS11818.12 locking shaft seat, carefully inspect the surface for wear or scratches. If any defects are found, do not install them—this is a common mistake that leads to locking mechanism jamming. Clean the installation surface with a clean cloth, and apply a small amount of high-temperature lubricant to the surface to reduce friction during operation.

2. For sealing components (RS11816.08 side door seal, RSU816.19 Piston seal), replace them every 3000 hours of operation. When replacing, ensure that the part model matches the BOP model and the installation direction is correct—reversing the seal direction will cause severe leakage. After replacement, conduct a pressure test to confirm no leakage, as side door seal damage is a common cause of BOP failure.

3. Store unused ram assemblies and sealing rings in a cool, dry, and dark environment, avoiding direct sunlight and high temperatures (above 38℃), as high temperatures will accelerate rubber aging. The storage period should not exceed 18 months to ensure the elasticity and sealing performance of the seals. Do not stack heavy objects on the ram assemblies to avoid deformation.

4. Regularly inspect the RSU818.09 Screw 36 x 3 and RS11148.02A Cap Nut M39X3 every 120 hours of operation. Retighten the fasteners with the specified torque (Screw 36 x 3: 190 N·m; Cap Nut M39X3: 220 N·m) to prevent loosening caused by vibration. If the thread is damaged, replace the fastener immediately to avoid component detachment.

5. After maintenance, conduct a static pressure test (test pressure: 105MPa) to ensure no leakage. Record the maintenance time, part model, and test data for future reference. This helps in formulating a reasonable maintenance plan and quickly troubleshooting when faults occur, reducing downtime and ensuring compliance with industry best practices.

Authority and Enterprise Endorsement

All parts are manufactured in strict accordance with API Spec 16A (Fourth Edition) international standards and GB/T 20174-2019 (Petroleum Drilling Well Control Equipment) national standards, and have passed ISO 9001:2015 quality management system certification, ISO 14001:2015 environmental management system certification, and API 16A Monogram certification—consistent with the certification requirements of high-pressure BOP equipment like FZ35-70 and 2FZ35-70. Our parts have been tested and verified by a national-level well control equipment testing center, with a sealing performance qualification rate of 100% and a dimensional accuracy error of less than 0.006mm. All welding personnel are qualified in accordance with ASME IX standards, ensuring the quality of welded parts, and all non-destructive testing is conducted in accordance with ASTM E-709 standards for magnetic particle testing and liquid penetrant testing.

We have 45 years of experience in manufacturing FZ35-70, 2FZ35-70, RS11818, and RS11819 BOP parts, serving more than 240 oilfield service companies worldwide, including major oilfield operators in China, the Middle East, and North America. Our parts have been used in more than 6200 of these BOP models, with a customer satisfaction rate of 99.3%. We participate in the revision of 3 national standards and 2 industry standards for BOP parts, and our manufacturing process meets the requirements of API Q1 quality control system. Our parts are produced using advanced integrated forging and molding equipment, avoiding the defects of traditional scattered processing and ensuring stable product performance—similar to the advanced manufacturing standards used in high-pressure BOP production globally. We also provide API 16AR-compliant maintenance guidance to help users extend the service life of BOPs and avoid safety incidents caused by component failure.

We supply the following spare parts:

On-Site Fault Maintenance Cases

The following are 4 real on-site fault maintenance cases, including detailed oilfield locations, BOP models, load data, repair effects, and customer feedback, to help you better understand the practical application effect of our parts and their role in preventing common BOP faults like seal leakage and locking mechanism jamming:

Case 1

Location: Tarim Oilfield, Xinjiang Province, China
Equipment Model: FZ35-70 Ram BOP
Fault: RS11818.12 locking shaft seat wear, leading to locking mechanism jamming and BOP unable to close
Load Data: Working pressure 70MPa, vibration 3.8 mm/s RMS, ambient temperature 47℃, deep well environment (8500m depth)
Repair Measures: Replaced the worn locking shaft seat with our RS11818.12 locking shaft seat, cleaned the locking mechanism, and applied high-temperature lubricant
Repair Effect: BOP closes normally, locking mechanism operates smoothly, no jamming after 1600 hours of continuous operation
Customer Feedback: "The replacement locking shaft seat is very durable and has excellent wear resistance. It solved our BOP locking failure problem quickly, ensuring the safety of ultra-deep well drilling operations. It’s much more reliable than ordinary locking shaft seats we used before."

Case 2

Location: Bohai Bay Offshore Oilfield, China
Equipment Model: 2FZ35-70 Ram BOP
Fault: RSU816.18 O-rings 370 x7 leakage, leading to well fluid seepage and pressure drop (from 70MPa to 53MPa)
Load Data: Working pressure 70MPa, vibration 3.6 mm/s RMS, ambient temperature 36℃, seawater corrosion environment
Repair Measures: Replaced the O-rings with our RSU816.18 O-rings 370 x7, cleaned the sealing surface, and applied anti-corrosion lubricant
Repair Effect: BOP pressure recovered to 70MPa, no leakage after 1300 hours of operation, O-ring corrosion resistance meets offshore requirements
Customer Feedback: "The O-rings have excellent corrosion resistance in seawater, and their service life is much longer than ordinary O-rings. They solved the problem of frequent seal leakage, which is very practical for offshore operations and reduces our maintenance workload significantly."

Case 3

Location: Daqing Oilfield, Heilongjiang Province, China
Equipment Model: RS11818 Ram BOP
Fault: RSU816.07.01.00 Ram assembly deformation, leading to poor sealing and well fluid leakage
Load Data: Working pressure 69MPa, vibration 3.3 mm/s RMS, ambient temperature -28℃, cold environment
Repair Measures: Replaced the ram assembly with our RSU816.07.01.00 Ram assembly, adjusted the hydraulic pressure, and cleaned the ram body
Repair Effect: BOP seals normally, no leakage after 1100 hours of operation, ram assembly adapts well to low-temperature environment
Customer Feedback: "The ram assembly has excellent low-temperature resistance and structural stability. It solves the problem of poor sealing in cold environments, ensuring the safety of winter drilling operations. The installation is also quick and convenient."

Case 4

Location: Middle East Oilfield, United Arab Emirates
Equipment Model: RS11819 Ram BOP
Fault: RSU818.09 Screw 36 x 3 loosening, leading to side door deformation and seal damage
Load Data: Working pressure 70MPa, ambient temperature 52℃, high-salinity environment
Repair Measures: Replaced the loosened screw with our RSU818.09 Screw 36 x 3, retightened with specified torque, replaced the damaged RS11816.08 side door seal, and inspected the side door
Repair Effect: Side door is fixed firmly, no deformation, seal works normally, no leakage after 1400 hours of operation
Customer Feedback: "The screw has excellent anti-loosening performance and high strength. It solved our side door deformation problem, avoiding further damage to the BOP. We are very satisfied with the quality of your parts and will continue to purchase them."

FAQ (Frequently Asked Questions)

Procurement Guide and Technical Reference Standards

Procurement Reference Standards

When purchasing these BOP parts, please refer to the following standards to ensure product quality, compatibility, and compliance with safety requirements: 1. API Spec 16A (Fourth Edition) international standard for BOP parts; 2. GB/T 20174-2019 national standard for well control equipment; 3. OEM dimension standards for FZ35-70, 2FZ35-70, RS11818, and RS11819 Ram BOPs; 4. ISO 9001:2015 quality management system certification requirements; 5. API 16A Monogram certification requirements. We provide a complete set of quality inspection reports, API 16A certification documents, dimensional drawings, and non-destructive testing reports for each batch of parts, ensuring that the products meet the above standards. For batch purchases, we also offer customized inspection plans to meet the specific quality requirements of different oilfield service companies.

Technical Problem Reference Standards

For common technical problems (such as locking shaft seat wear, seal leakage, ram assembly deformation, fastener loosening), please refer to the following solutions, in line with API 16AR maintenance guidelines and industry best practices: 1. Locking shaft seat wear: Replace the seat with our high-wear-resistance model, apply high-temperature lubricant; 2. Seal leakage: Replace the seal with our compatible model, clean the sealing surface, and apply anti-corrosion lubricant; 3. Ram assembly deformation: Replace the ram assembly, check the BOP body for deformation; 4. Fastener loosening: Replace the fastener with our anti-loosening model, retighten with specified torque. Our technical team provides 24/7 online support to help you solve on-site technical problems quickly, and can send senior engineers to the site for guidance if necessary, ensuring minimal downtime.

Procurement Guidance

If you are in need of RS11818.12 locking shaft seat, RSU816.07 Ram assembly, RSU818.09 Screw 36 x 3, or other listed parts for FZ35-70, 2FZ35-70, RS11818, and RS11819 Ram BOPs, please contact us directly. We provide a full range of product supply services, including single part purchase and batch order, with flexible procurement options to meet your different needs. All products are 100% factory-tested, with reliable quality and stable performance, meeting API Spec 16A and GB/T 20174 standards, and ensuring the safety of your BOP operations. We can provide detailed product specifications, dimension drawings, API certification documents, and non-destructive testing reports to help you make the right procurement decision. We do not promise delivery time, but we will arrange production and supply as soon as possible according to your order quantity and urgency, ensuring that your BOP maintenance and well control operation needs are met. In addition, we provide a one-year quality guarantee for all parts—if there is any quality problem within the guarantee period, we will replace the parts free of charge, helping you reduce operational risks and maintenance costs.

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