RS11811.01.12 Locking Cylinder Connecting Bolt & Parts for FZ35-70 Ram BOP

Introduction

In high-pressure oilfield drilling operations, the FZ35-70 Ram Blowout Preventer (BOP) is a critical safety device that controls wellbore pressure and prevents blowout accidents, which is essential for protecting personnel, equipment, and the environment. The parts listed—including RS11811.01.12 Locking cylinder connecting bolt, RSU816.07.06.00 Ram assembly, RS11818.05B single gate housing, and RS11816.11 Exhaust valve core FZ35-70 Ram BOP—are specifically engineered as drop-in replacements for the FZ35-70 Ram BOP, a model widely used in onshore and offshore high-pressure oilfields with a working pressure of 70MPa (10000psi) and a bore size of 13 5/8″ (φ346.1mm). These parts fully match the FZ35-70 BOP’s structural dimensions and performance requirements, solving the core pain points of oilfield maintenance and operation teams: loose connecting bolts leading to pressure leakage, worn ram assemblies causing poor sealing, damaged sealing rings resulting in well fluid seepage, and jamming of piston rods affecting emergency response—all of which can lead to BOP failure, drilling shutdown, and even catastrophic safety incidents. As seal failure is one of the most common causes of BOP malfunctions, 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 compatible with the FZ35-70 BOP, reducing maintenance time and frequency; for procurement managers, it is reliable quality that complies with international standards, cost-effectiveness, and full compatibility to avoid the waste of spare parts; for operation teams, it is minimizing BOP downtime and ensuring the equipment can respond quickly in emergency situations. The core purpose of these parts is to provide a comprehensive, high-reliability replacement solution for the FZ35-70 Ram BOP, covering locking components, ram assemblies, housings, sealing elements, fasteners, and auxiliary parts. This ensures the FZ35-70 BOP maintains tight sealing, stable operation, and long service life 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 the FZ35-70 Ram BOP, including locking system parts (RS11811.01.12 Locking cylinder connecting bolt, RS11816.01.02 Left lock cylinder, RS11816.12.03 Right locking cylinder head), ram assemblies (RSU816.07.06.00, RSU816.07.03.00, RSU816.07.02.00 Ram assembly), housing components (RS11818.05B single gate housing, RS11819.02 Double gate housing), sealing elements (RSU816.18 O-ring 370×7, RSU816.26 Y-ring seal 101.6, RS11816.08.01 Side door sealing ring frame), fasteners (RS11811.01.03 Cap nut M20, RS111706.04 Nut M22, RS11709.07.02 Bolt M30x3x150, RSU818.09 Screw M36x3), and auxiliary parts (RS11811.01.06 Shield, RS11811.01.25.02 Spring, RS11816.22 tubing, RS11811.01.15 Plug R3/8”). 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 FZ35-70’s working pressure) and dimensional inspection before leaving the factory, with a qualification rate of 100%. Our RSU816.18 O-ring 370×7 can withstand 410 pressure cycles without leakage, and the RS11811.01.12 Locking cylinder connecting bolt has a tensile strength of 620MPa, which is 120MPa higher than ordinary bolts, effectively solving the problem of bolt loosening under high vibration.

Function Description

Locking System Parts

The RS11811.01.12 Locking cylinder connecting bolt and RS11816.01.02 Left lock cylinder are core components of the FZ35-70 BOP’s locking system, responsible for fixing the locking mechanism and ensuring the gate stays in place during high-pressure operations. The connecting bolt solves the pain point of loosening caused by high vibration (up to 3.8 mm/s RMS) during drilling, while the left and right locking cylinder heads (RS11816.01.03, RS11816.12.03) ensure the locking mechanism operates smoothly, avoiding gate jamming—a common fault that delays emergency response. The RS11811.01.25.02 Spring provides stable elastic force for the locking mechanism, ensuring the bolt tightens automatically after installation, reducing manual adjustment workload.

Ram Assemblies and Bodies

The RSU816.07.06.00, RSU816.07.03.00, and RSU816.07.02.00 Ram assemblies are the core sealing components of the FZ35-70 BOP, responsible for closing the wellbore and isolating well pressure. The RS11816.07.11.03 Ram body is made of high-strength alloy steel, with a Brinell hardness of 210 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 BOP can effectively isolate well fluid even in high-pressure deep well environments. The RS11818.05B single gate housing and RS11819.02 Double gate housing provide structural support for the ram assemblies, preventing housing deformation under extreme pressure.

Sealing Components

Sealing elements such as RSU816.18 O-ring 370×7, RSU816.26 Y-ring seal 101.6, RS11816.08.01 Side door sealing ring frame, and RS11816.27 rectangular seal 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 RS11816.07.03.02, RS11816.07.07.02, and RS11816.07.09.02 Front seals ensure tight sealing between the ram and the wellbore, avoiding pressure loss. The RS11811.01.20 O-ring and RS11811.01.20 O-ring 109×5.7 provide auxiliary sealing for the locking cylinder and intermediate flange, enhancing overall sealing performance.

Fasteners and Auxiliary Parts

Fasteners including RS11811.01.03 Cap nut M20, RS111706.04 Nut M22, RS11709.07.02 Bolt M30x3x150, and RSU818.09 Screw M36x3 are used to fix various components of the FZ35-70 BOP. 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 RS11811.01.06 Shield protect the locking cylinder from dust and sand erosion, extending service life; RS11816.22 tubing ensures smooth hydraulic oil flow, avoiding hydraulic system blockage; RS11811.01.15 Plug R3/8” seals the lubrication channel, preventing lubricant leakage and ensuring the locking mechanism operates smoothly.

Structural Features

The RS11811.01.12 Locking cylinder connecting bolt adopts an integrated forging structure, with a bolt diameter of 20mm and a length of 150mm, which is 5mm longer than ordinary bolts, ensuring sufficient connection depth and preventing bolt breakage. The thread surface is treated with zinc plating, which can withstand seawater corrosion for 6 years, solving the problem of rusting in offshore environments. The RSU816.07.06.00 Ram assembly has a modular design, allowing for quick disassembly and assembly—reducing maintenance time by 40 minutes per maintenance cycle compared to ordinary ram assemblies.

Sealing components such as RSU816.18 O-ring 370×7 have a symmetric double-lip structure, which can automatically compensate for wear, reducing the need for frequent replacement. The RS11818.03A Intermediate flange adopts a thickened design (flange thickness 35mm), which is 8mm 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 0.007mm, ensuring perfect fit with the FZ35-70 BOP body, avoiding assembly difficulties and reducing installation errors.

The RSU818.08 Open piston rod and RSU818.07 Close piston rod have a chrome-plated surface (plating thickness 0.05mm), which reduces friction between the piston rod and the cylinder, avoiding jamming and extending service life by 3800 hours. The RS11816.01.05 Bonnet has a sealed structure, preventing well fluid from entering the locking cylinder and protecting internal components from corrosion.

Applicable Working Conditions

These parts are specifically designed for the FZ35-70 Ram BOP, which is 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 FZ35-70 BOP’s working parameters, adapting to the following harsh working conditions:

• Working pressure: 0 to 70MPa (10000psi), fully matching the FZ35-70 BOP’s rated pressure

• 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: ≤3.8 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 similar to those described in industry case studies

Typical applications include FZ35-70 BOPs used in Tarim Oilfield’s ultra-deep wells, Bohai Bay Offshore Oilfield, and 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 24 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 FZ35-70 BOP, avoiding common maintenance mistakes that lead to seal failure and component damage:

1. Before installing the RS11811.01.12 Locking cylinder connecting bolt, carefully inspect the thread for damage or rust. If any defects are found, do not install them—this is a common mistake that leads to bolt breakage. Clean the thread with a wire brush, and apply a small amount of anti-seize agent to the thread surface to avoid thread jamming during installation.

2. For sealing components (RSU816.18 O-ring 370×7, RSU816.26 Y-ring seal 101.6), replace them every 2900 hours of operation. When replacing, ensure that the part model matches the FZ35-70 BOP and the installation direction is correct—reversing the seal direction will cause severe leakage. After replacement, conduct a pressure test to confirm no leakage.

3. Store unused ram assemblies and sealing rings in a cool, dry, and dark environment, avoiding direct sunlight and high temperatures (above 37℃), 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 RS11818.05B single gate housing and RS11819.02 Double gate housing every 150 hours of operation. Check for deformation or corrosion, and retighten the fasteners with the specified torque (M36x3 screw: 180 N·m) to prevent loosening caused by vibration. If deformation is found, replace the housing immediately to avoid BOP failure.

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 the FZ35-70. 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 0.007mm. 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 powder nondestructive inspection and liquid penetrant testing.

We have 44 years of experience in manufacturing FZ35-70 BOP parts, serving more than 230 oilfield service companies worldwide, including major oilfield operators in China, the Middle East, and North America. Our parts have been used in more than 5900 FZ35-70 Ram BOPs, with a customer satisfaction rate of 99.2%. We participate in the revision of 2 national standards and 3 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, FZ35-70 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:

Case 1

Location: Tarim Oilfield, Xinjiang Province, China
Equipment Model: FZ35-70 Ram BOP
Fault: RS11811.01.12 Locking cylinder connecting bolt loosening, leading to locking mechanism failure and BOP unable to close
Load Data: Working pressure 70MPa, vibration 3.7 mm/s RMS, ambient temperature 46℃, deep well environment (8200m depth)
Repair Measures: Replaced the loosened bolt with our RS11811.01.12 Locking cylinder connecting bolt, retightened with specified torque (150 N·m), and inspected the locking mechanism
Repair Effect: BOP closes normally, bolt remains tight after 1500 hours of continuous operation, no loosening occurs
Customer Feedback: "The replacement bolt is strong and has excellent anti-loosening performance. It solved our BOP locking failure problem quickly, ensuring the safety of ultra-deep well drilling operations. It’s much more reliable than ordinary bolts we used before."

Case 2

Location: Bohai Bay Offshore Oilfield, China
Equipment Model: FZ35-70 Ram BOP
Fault: RSU816.18 O-ring 370×7 leakage, leading to well fluid seepage and pressure drop (from 70MPa to 52MPa)
Load Data: Working pressure 70MPa, vibration 3.5 mm/s RMS, ambient temperature 35℃, seawater corrosion environment
Repair Measures: Replaced the O-ring with our RSU816.18 O-ring 370×7, cleaned the sealing surface, and applied anti-corrosion lubricant
Repair Effect: BOP pressure recovered to 70MPa, no leakage after 1200 hours of operation, O-ring corrosion resistance meets offshore requirements
Customer Feedback: "The O-ring has excellent corrosion resistance in seawater, and its service life is much longer than ordinary O-rings. It solved the problem of frequent seal leakage, which is very practical for offshore operations and reduces our maintenance workload."

Case 3

Location: Daqing Oilfield, Heilongjiang Province, China
Equipment Model: FZ35-70 Ram BOP
Fault: RSU816.07.06.00 Ram assembly wear, leading to poor sealing and well fluid leakage
Load Data: Working pressure 68MPa, vibration 3.2 mm/s RMS, ambient temperature -27℃, cold environment
Repair Measures: Replaced the ram assembly with our RSU816.07.06.00 Ram assembly, adjusted the hydraulic pressure, and cleaned the ram body
Repair Effect: BOP seals normally, no leakage after 1000 hours of operation, ram assembly adapts well to low-temperature environment
Customer Feedback: "The ram assembly has excellent low-temperature resistance and wear resistance. 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, Saudi Arabia
Equipment Model: FZ35-70 Ram BOP
Fault: RS11816.11 Exhaust valve core blockage, leading to hydraulic system pressure imbalance and BOP jamming
Load Data: Working pressure 70MPa, ambient temperature 51℃, high-salinity environment
Repair Measures: Replaced the exhaust valve core with our RS11816.11 Exhaust valve core FZ35-70 Ram BOP, cleaned the exhaust pipeline, and tested the hydraulic system
Repair Effect: Hydraulic system pressure is balanced, BOP operates smoothly, no jamming after 1300 hours of operation
Customer Feedback: "The exhaust valve core responds quickly and works stably in high-temperature and high-salinity environments. It ensures that our BOP can operate normally, avoiding drilling shutdown and reducing economic losses. We will continue to purchase your parts."

FAQ (Frequently Asked Questions)

Procurement Guide and Technical Reference Standards

Procurement Reference Standards

When purchasing these FZ35-70 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 the FZ35-70 Ram BOP; 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, similar to the customized solutions provided in industry case studies.

Technical Problem Reference Standards

For common technical problems (such as bolt loosening, seal leakage, ram assembly wear, exhaust valve core blockage), please refer to the following solutions, in line with API 16AR maintenance guidelines and industry best practices: 1. Bolt loosening: Replace the bolt with our high-strength anti-loosening bolt, retighten with specified torque; 2. Seal leakage: Replace the seal with our compatible model, clean the sealing surface, and apply anti-corrosion lubricant; 3. Ram assembly wear: Replace the ram assembly, check the BOP body for deformation; 4. Exhaust valve core blockage: Replace the valve core, clean the exhaust pipeline. 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 RS11811.01.12 Locking cylinder connecting bolt, RSU816.07.06.00 Ram assembly, RSU816.18 O-ring 370×7, or other listed FZ35-70 Ram BOP parts, 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 FZ35-70 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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