Introduction
This guide is specifically crafted for FZ35-35 (single ram) and 2FZ35-35 (dual ram) Ram Blowout Preventers (BOPs), targeting drilling contractors, on-site maintenance technicians, and procurement specialists in oil and gas operations. Its core purpose is to act as a reliable dual-reference tool—providing precise parts compatibility guidance for procurement and practical troubleshooting solutions for on-site technical issues. Aligned with API Spec 16A (Wellhead and Christmas Tree Equipment) and GB standards (GB1235, GB290-64, etc.), this guide ensures that operations involving FZ35-35 series BOPs maintain high safety levels, minimize downtime, and optimize spare parts inventory. Whether for routine maintenance, emergency repairs, or parts replacement, the content integrates field-proven experience and authoritative technical insights to support the stable operation of these 35 MPa (5,075 psi) rated well control devices, which are critical for safeguarding wellbore integrity.
Product Overview
The FZ35-35 and 2FZ35-35 Ram BOPs are medium-pressure well control systems engineered for 35 MPa working pressure, widely used in onshore and shallow offshore drilling projects. The single-ram FZ35-35 offers cost-effective well control for standard operations, while the dual-ram 2FZ35-35 provides enhanced redundancy with two independent ram assemblies—ideal for high-risk wells where operational safety redundancy is a priority. Both models support an extensive range of pipe sizes (2 3/8” to 10 3/4”) via DFZ1310.01 series ram assemblies, including blind ram configurations for full wellbore closure. Key components include side door seal structures, ram shaft seal assemblies, secondary seal systems, and piston assemblies—all designed for interchangeability and durability under medium-pressure, corrosive drilling conditions. The unified part numbering for shared components (e.g., GB70 M12×65 retaining screws) simplifies inventory management and on-site replacement.
Functional Description
The FZ35-35 series BOPs deliver comprehensive well control functions through coordinated operation of specialized components, tailored to 35 MPa medium-pressure scenarios:
Multi-Size Ram Sealing: DFZ1310.01 series ram assemblies cover 19 pipe sizes (2 3/8” to 10 3/4”) and blind rams, each paired with dedicated ram blocks, rubber seals, and screws. The standardized retaining screws (GB70 M12×65) and holders (DFZ1310.01A-02) across all ram sizes simplify on-site maintenance and reduce spare parts variety.
Reliable Sealing Systems: Side door seals (2FZ3535-15) form a primary barrier against wellbore fluid leakage, while ram shaft seal assemblies (SKZF100 series Y-rings and backup rings) prevent hydraulic fluid loss. The secondary seal system (SFZ2835 series components) allows on-site grease injection (EM-09-1) without disassembling the BOP, enabling quick maintenance during operations.
Hydraulic Actuation & Locking: Piston assemblies (DFZ5414-14) drive ram movement via hydraulic pressure, with piston seals (DFZ5414-13) ensuring leak-proof actuation. Locking shaft seal assemblies (GB/T893.1 95 retainer rings, DFZ5414-25 W-rings) secure the ram position under pressure, preventing accidental movement.
Stable Hinge Operation: Hinge structures (with 2FZ3535.11 series pins, brackets, and GB290-64 needle bearings) enable safe, easy access to internal components for maintenance, even in harsh drilling environments.
Structural Features
The FZ35-35 series BOPs feature a modular, medium-pressure optimized design with structural characteristics that enhance reliability and maintainability:
Unified Component Standardization: Most non-size-specific components (retaining screws, holders, retracting screws) are shared across all ram assemblies, reducing inventory complexity and procurement costs. This standardization also ensures faster on-site part replacement during emergencies.
Robust Sealing Design: The ram shaft seal assembly integrates SKZF100.01 Y-rings and SKZF100.02 backup rings, which work together to resist medium-pressure hydraulic fluid and prevent seal extrusion. Side door seals (2FZ3535-15) are designed for easy installation and replacement, minimizing maintenance time.
Durable Mechanical & Hydraulic Parts: Piston assemblies, hydraulic cylinders (2FZ3535-04), and cylinder bolts (2FZ3535-07) follow GB standards, ensuring compatibility with common drilling rig hydraulic systems and long service life under cyclic loading.
Corrosion-Resistant Hinge System: Hinge pins, brackets, and bearings are made of corrosion-resistant materials, with multiple O-rings (GB1235 series) providing additional protection against drilling fluid and environmental corrosion.
User-Friendly Maintenance Access: Key wear components (wiper rings, O-rings, piston seals) are positioned for easy access, with clear part number labeling to help technicians quickly identify and replace faulty parts without specialized tools.
Applicable Operating Conditions
The FZ35-35 and 2FZ35-35 BOPs are optimized for 35 MPa medium-pressure drilling scenarios, with specific applicability to the following conditions:
Pressure & Temperature Range: Rated for 35 MPa working pressure and ambient temperatures ranging from -20°C to 120°C (-4°F to 248°F), compatible with water-based mud (WBM), oil-based mud (OBM), and synthetic-based mud (SBM).
Pipe Size Compatibility: Accommodates pipe sizes from 2 3/8” to 10 3/4” via dedicated DFZ1310.01 series ram assemblies, making it suitable for wells with multiple casing programs and varying pipe diameters.
Well Types: Ideal for onshore oil and gas wells, shallow offshore wells (platform and jack-up rigs), and well completion stages where medium-pressure well control is required. The dual-ram 2FZ35-35 is preferred for wells with moderate blowout risk due to unstable formation pressure.
Environmental Adaptability: Seals and metal components resist corrosion from drilling fluids, saltwater (offshore), and harsh atmospheric conditions, ensuring reliable performance in diverse operational environments.
Maintenance & Care Recommendations
Proactive maintenance is key to extending the service life and ensuring the reliability of FZ35-35 series BOPs. Below are practical, model-specific best practices aligned with API Spec 16A and GB standards:
Regular Inspection Schedules: Conduct weekly visual checks of side door seals, hydraulic connections, and ram shafts for leaks, corrosion, or wear. Perform quarterly disassembly inspections of piston assemblies, ram seals, and hinge structures—replace worn parts according to the one-year spare parts list.
Seal Maintenance: Replace side door seals (2FZ3535-15) every 6 months or if cracks, deformation, or leakage is detected. For ram shaft seals, inspect SKZF100.01 Y-rings and SKZF100.02 backup rings monthly; replace them every 80 operational cycles or 6 months, whichever comes first. Apply EM-09-1 secondary sealing grease every 3 months to keep the secondary seal system functional.
Ram Assembly Care: Clean ram blocks, rubber seals, and screws after each use to remove drilling fluid residue. Store spare ram assemblies in a dry, dust-free area to prevent rubber degradation. Always verify the pipe size matches the ram assembly part number (e.g., DFZ1310.01B-00 for 4 1/2” pipes) before installation.
Hydraulic & Piston Maintenance: Inspect piston seals (DFZ5414-13) and O-rings (95×3.1) monthly for damage. Replace hydraulic cylinder O-rings (250×5.7, 50×3.1) if leaks occur, and torque cylinder bolts (2FZ3535-07) to the specified torque after disassembly.
Hinge & Locking System Care: Lubricate hinge pins, brackets, and bearings monthly with anti-corrosion lubricant. Check locking shaft W-rings (DFZ5414-25) and wiper rings (DFZ5414-22) quarterly—replace worn parts to prevent structural loosening under pressure.
Part Numbers for Rams
Pipe Size | Pipe Ram Assembly Name(Qty) | |||||
Assembly (2) | Ram block(2) | Retaining Screw(4) | Holder(2) | Retracting screw (4) | Rubber(2) | |
5" | DFZ1310.01A-00 | DFZ1310.01A-03 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01A.01-00 |
4 1/2" | DFZ1310.01B-00 | DFZ1310.01B-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01B.01-00 |
3 1/2" | DFZ1310.01C-00 | DFZ1310.01C-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01C.01-00 |
7" | DFZ1310.01D-00 | DFZ1310.01D-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01D.01-00 |
blind | DFZ1310.01E-00 | DFZ1310.01E-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01E.01-00 |
9 5/8" | DFZ1310.01F-00 | DFZ1310.01F-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01F.01-00 |
2 7/8" | DFZ1310.01G-00 | DFZ1310.01G-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01G.01-00 |
5 1/2" | DFZ1310.01H-00 | DFZ1310.01H-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01H.01-00 |
2 3/8" | DFZ1310.01L-00 | DFZ1310.01L-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01L.01-00 |
10 3/4" | DFZ1310.01M-00 | DFZ1310.01M-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01M.01-00 |
4 3/4" | DFZ1310.01N-00 | DFZ1310.01N-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01N.01-00 |
5 3/4" | DFZ1310.01P-00 | DFZ1310.01P-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01P.01-00 |
4" | DFZ1310.01I-00 | DFZ1310.01I-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01I.01-00 |
7 5/8" | DFZ1310.01Q-00 | DFZ1310.01Q-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01Q.01-00 |
6 5/8" | DFZ1310.01R-00 | DFZ1310.01R-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01R.01-00 |
5 7/8" | DFZ1310.01S-00 | DFZ1310.01S-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01S.01-00 |
8 5/8" | DFZ1310.01T-00 | DFZ1310.01T-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01T.01-00 |
9 7/8" | DFZ1310.01U-00 | DFZ1310.01U-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01U.01-00 |
7 7/8 ― | DFZ1310.01V-00 | DFZ1310.01V-02 | GB70 M12×65 | DFZ1310.01A-02 | DFZ1310.01A-04 | DFZ1310.01V.01-00 |
Part list of Side Door Seal Structure
Description | Part No./Model |
Door Seal | 2FZ3535-15 |
Part list of Ram Shaft Seal Assembly
Description | Part No./Model |
Retainer ring | DFZ5414-33 |
Wiper ring 100 | Q/ZB336-77 |
Bushing | 2FZ5414B-07 |
O-ring | 105×3.1 |
Packing Bearing Ring | DFZ5414-31 |
O-ring | 120×3.1 |
Backup ring | SKZF100.02 |
Y-ring | SKZF100.01 |
Washer | DFZ5414-28 |
Secondary Seal System
Description | P/N |
Z1″ External hexagonal blocking | SFZ2835-38 |
Cock | SFZ2835-37 |
Secondary sealing grease | EM-09-1 |
Z1/2″ Internal hexagonal plug screw with hole | SFZ2835-40 |
Parts list of Locking Shaft Seal Assembly
Description | Part No./Model |
Retainer Ring | GB/T893.1 95 |
Thrust Shaft Sleeve | 2FZ3535-17A |
W-ring | DFZ5414-25 |
Back –up ring | DFZ5414-24 |
Wiper Seat Retainer | DFZ5414-23 |
Wiper Ring | DFZ5414-22 |
Parts list of Hinge structure
Description | Part No./Model |
Hinge Pin | 2FZ3535.11.01-08 |
O Ring | GB1235 70×3.1 |
O Ring | GB1235 55×3.1 |
Hinge Bracket | 2FZ3535.11-06 |
Hinge（one） | 2FZ3535.11.01-00 |
O Ring | GB1235 40×3.1 |
Hydraulic Connection | 2FZ3535.11-04 |
Spring | 2FZ3535.11-03 |
Left Hinge Bracket | 2FZ3535.11.02-00 |
Right Hinge Bracket | 2FZ3535.12.01-00 |
Hinge（two） | 2FZ3535.11.07-00 |
O Ring | GB1235 25×2.4 |
Pin | GB/T 120 B12×50 |
Screw | GB/T 70.1 M16×40 |
Screw | GB/T 70.1 M20×65 |
Pin | GB/T 120 B12×60 |
Screw | GB70 M16×45 |
O Ring | 30×3.1 |
O Ring | 35×3.1 |
Needle Bearing 941/30 | GB290-64 |
Washer, Adjust | 2FZ3535.11-05 |
Bearing 8107 | GB301-64 |
Parts list of Piston Assembly
Description | Part No./Model |
Piston | DFZ5414-14 |
Piston Seal | DFZ5414-13 |
O-ring | 95×3.1 |
Screw | GB71 M8×16 |
Locking nut | DFZ5414-44 |
Description | FZ18-70 Part No./Model |
Body | 1 |
Locating Pin | 2FZ3535-16 |
Ram Assembly | DFZ1310.01().00 |
Side Door Seal Structure | 2FZ3535-15 |
Left Door | 2FZ3535-02 |
O-ring | 250×5.7 |
Secondary Seal System | See 3.2.4 |
Door bolt | 2FZ3535-13 |
Hinge Assembly | See 3.2.7 |
O-ring | 50×3.1 |
Nozzle flange | SFZ2835-42 |
Screw | GB5782 M12×45 |
NPT 1" Plug | SFZ2835-41 |
Ram Shaft Seal Assembly | See 3.2.3 |
Ram shaft | 2FZ3535-05A |
Locking screw | 2FZ3535-10A |
Piston Assembly | See 3.2.8 |
Locking Shaft Seal Assembly | See 3.2.5 |
O-ring | 32×3.1 |
Hydraulic cylinder | 2FZ3535-04 |
Cylinder Bolt | 2FZ3535-07 |
Nut | DFZ5414-16 |
NPT 1/2" Plug | SFZ2835-39 |
Right Cylinder head | 2FZ3535-06A |
Left Cylinder head | 2FZ3535-18A |
Spare Parts list for one year for FZ35-35
Description | Part No./Model |
Door seal | 2FZ3535-15 |
O-ring | 250×5.7 |
Secondary sealing grease | EM-09-1 |
O-ring | 70×3.1 |
O-ring | 55×3.1 |
O-ring | 40×3.1 |
O-ring | 25×2.4 |
O-ring | 30×3.1 |
O-ring | 35×3.1 |
O-ring | 50×3.1 |
Wiper ring 100 | Q/ZB336-77 |
O-ring | 105×3.1 |
O-ring | 120×3.1 |
Y-ring | SKZF100.01 |
Back up ring | SKZF100.02 |
Piston Seal | DFZ5414-13 |
O-ring | 95×3.1 |
W-ring | DFZ5414-25 |
Back –up ring | DFZ5414-24 |
Wiper ring | DFZ5414-22 |
O-ring | 32×3.1 |
Field Fault Repair Cases
The following real-world cases offer practical troubleshooting tips for common faults in FZ35-35 series BOPs, helping technicians resolve issues quickly and reduce downtime:
Case 1: FZ35-35 Side Door Seal Leakage
Symptom: Wellbore fluid leakage at the side door during 35 MPa pressure testing. Root Cause: The side door seal (2FZ3535-15) was worn and contaminated with drilling fluid residue, compromising the sealing surface. Repair: Replaced the side door seal, cleaned the seal groove to remove residue, and reinstalled the door bolt (2FZ3535-13) with proper torque. A follow-up pressure test confirmed no leakage. Preventive Measure: Clean the side door seal area after each well operation and inspect the seal bi-weekly.
Case 2: 2FZ35-35 Ram Shaft Hydraulic Leakage
Symptom: Hydraulic fluid leakage around the ram shaft seal assembly. Root Cause: SKZF100.01 Y-rings were worn, and SKZF100.02 backup rings were deformed, leading to seal failure.Repair: Replaced the Y-rings and backup rings, cleaned the ram shaft to remove burrs, and inspected the bushing (2FZ5414B-07) for damage. Post-repair actuation was smooth with no leakage.Preventive Measure: Replace ram shaft seal components every 6 months, regardless of visual condition.
Case 3: FZ35-35 Ram Assembly Jamming
Symptom: DFZ1310.01C-00 ram assembly (3 1/2” pipe) jammed during actuation.Root Cause: Drilling fluid residue buildup between the ram block and holder, combined with loose retaining screws (GB70 M12×65). Repair: Disassembled the ram assembly, cleaned all components to remove residue, tightened the retaining screws to specification, and lubricated the ram block. The ram actuated smoothly after reassembly. Preventive Measure: Clean ram assemblies after each use and check screw tightness weekly.
Case 4: 2FZ35-35 Secondary Seal System Grease Injection Failure
Symptom: Unable to inject EM-09-1 grease into the secondary seal system. Root Cause: The cock (SFZ2835-37) was clogged with dried grease and debris. Repair: Disassembled the cock, cleaned it thoroughly to remove clogs, reinstalled the component, and injected fresh EM-09-1 grease. Grease flow was restored immediately. Preventive Measure: Clean the cock and injection channel quarterly to avoid debris buildup.
FAQ (Frequently Asked Questions)
Question | Answer |
Can ram assemblies of different sizes share holders and screws for FZ35-35 BOPs? | Yes, most non-size-specific components are shared. All DFZ1310.01 series ram assemblies use the same holder (DFZ1310.01A-02), retaining screws (GB70 M12×65), and retracting screws (DFZ1310.01A-04). Only the ram block, rubber seal, and assembly part number vary by pipe size—this simplifies inventory and on-site replacement. |
What is the difference between FZ35-35 and 2FZ35-35 in terms of parts and maintenance? | The core components (ram assemblies, seals, piston parts) are identical, but 2FZ35-35 has two independent ram systems, so you need double the quantity of ram assemblies, piston parts, and some seals for maintenance. The maintenance process is the same for both models—focus on doubling spare parts for dual-ram components in your inventory. |
Can I use other brands’ Y-rings instead of SKZF100.01 for the ram shaft seal assembly? | It’s not recommended. SKZF100.01 Y-rings are engineered to match the ram shaft dimensions and 35 MPa pressure rating of FZ35-35 series BOPs. Substituting with other brands may cause seal extrusion, leakage, or even BOP failure. Always use genuine SKZF100.01 Y-rings and matching SKZF100.02 backup rings. |
How to confirm if a spare part is compatible with FZ35-35 series BOPs? | Cross-check the part number with the model’s dedicated parts lists: ram assemblies use DFZ1310.01 series, side door seals are 2FZ3535-15, and piston parts use DFZ5414 series. Ensure parts comply with 35 MPa pressure rating and GB standards. Avoid substituting parts from other FZ models (e.g., FZ35-70) as dimensions may differ. |
Which spare parts are most critical to stock for emergency repairs? | Prioritize high-wear, quick-to-fail components: 2FZ3535-15 side door seals, SKZF100.01 Y-rings, SKZF100.02 backup rings, DFZ5414-13 piston seals, EM-09-1 secondary grease, and GB1235 series O-rings (70×3.1, 55×3.1, 250×5.7). Stock 2-4 sets of each for single-ram models and double for dual-ram 2FZ35-35. |
Procurement Guidance
The safety and reliability of FZ35-35 and 2FZ35-35 BOPs rely entirely on genuine, compatible parts. We supply a full range of authentic components tailored to these models, including DFZ1310.01 series ram assemblies (covering all pipe sizes), side door seals, ram shaft seal parts, piston assemblies, and hinge components—all manufactured to API Spec 16A and GB standards, with traceable material certificates and batch records.
Our parts ensure perfect fit and 35 MPa pressure resistance, matching the original equipment specifications of FZ35-35 series BOPs. For procurement, we recommend following the one-year spare parts list to balance inventory cost and emergency response capability. For dual-ram 2FZ35-35, double the quantity of key wear components to account for its two independent ram systems. Our team of well control experts provides free technical support for parts selection, helping you avoid compatibility issues and optimize inventory. Whether you need routine spares, emergency repair parts, or bulk orders for fleet maintenance, we deliver consistent quality that meets industry safety standards. Contact us today to discuss your specific requirements and secure reliable parts for your FZ35-35 series BOPs.
Conclusion
The FZ35-35 and 2FZ35-35 Ram BOPs are essential medium-pressure well control devices for oil and gas drilling, offering reliable performance through standardized components, robust sealing systems, and user-friendly maintenance design. This guide integrates technical insights, field-proven repair cases, and procurement best practices to support technicians and procurement professionals in maintaining operational continuity and safety.
By following model-specific maintenance schedules, using genuine compatible parts, and leveraging the FAQs and repair cases herein, you can maximize the service life of your FZ35-35 series BOPs and minimize downtime. Partnering with a trusted supplier for authentic parts ensures compliance with API and GB standards, safeguarding personnel, assets, and wellbore integrity in medium-pressure drilling environments. Invest in quality parts and proactive maintenance to keep your FZ35-35 series BOPs operating at peak performance.
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