Recessed Side-Shell Mounted Towing Bitt | Steel Plate Fabricated Type B for Large Ship Towing (ISO 13798)

Recessed Side-Shell Mounted Towing Bitt | Steel Plate Fabricated Type B for Large Ship Towing (ISO 13798)

Product Overview

The ISO 13798 Type B recessed ship towing bitt is a steel plate fabricated towing and mooring fitting installed in a recess of the vessel side shell. It provides a lower line-attachment position when high freeboard or an elevated mooring deck limits access to deck fittings. Selection should consider SWL, towline lead, shell opening, local reinforcement, and class or flag requirements.

ISO 13798 covers nominal sizes 200, 250, 400A, and 400B; Type A uses steel pipe and Type B uses steel plate. The supplied Type B data cover SWL values of 294–1,177 kN, reference rope diameters of 30–60 mm, and calculated weights of 16.1–96.1 kg. Material, welds, load direction, marking, drainage, and certificate scope remain project-specific.

Quick Specifications

• Product type: Recessed ship towing bitt → lower side-shell line point for high-freeboard vessels.
• Standard and type: ISO 13798:2020 Type B → steel plate fabricated; Type A is the steel-pipe version.
• Nominal sizes: 200 / 250 / 400A / 400B → select by SWL, rope basis, and installation geometry.
• Safe working load: 294–1,177 kN (30–120 t reference) → confirm the approved load direction and hull support.
• Reference rope diameter: 30–60 mm → load-basis reference, not an automatic maximum rope size.
• Calculated weight: 16.1–96.1 kg for Type B → supports handling, installation, packing, and freight planning.
• Installation: Recessed side-shell welded fitting → coordinate shell opening, reinforcement, welds, and coating.
• Surface treatment: Sa 2.5 blasting + epoxy shop primer as reference → final finish follows the project specification.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm ISO 13798 Type B and nominal size 200, 250, 400A, or 400B according to the required SWL and vessel towing arrangement.

Step 2: Confirm the intended towing or mooring function, towline direction, maximum lead angle, reference rope diameter, and whether the fitting is for newbuilding or replacement.

Step 3: Provide the side-shell opening, recess arrangement, surrounding structure, internal reinforcement, and shipyard welding interface drawing.

Step 4: Confirm material grade: C-Mn steel plate, stainless steel, or special low-temperature / ice-service material, together with traceability and impact-test requirements.

Step 5: Confirm surface treatment, coating repair after installation, SWL marking, inspection scope, and classification society requirement before quotation.

Step 6: Provide quantity, vessel type, installation position, delivery destination, required delivery time, and an approved drawing or reference photo if available.

Structure

Steel plate fabricated recessed body | Rounded rope-contact contour | Side-shell welded interface | Connection to local hull reinforcement | SWL identification area | Drainage and corrosion-protection details to project drawing

Fabrication, Installation & Engineering Advantages

• The recessed side-shell position provides a practical lower attachment point for tug lines when the vessel’s freeboard or mooring deck height limits direct access to deck fittings.
• Type B steel plate construction allows the body geometry, thickness, weld preparation, and dimensional repeatability to be controlled through forming, fitting, and fabrication jigs.
• Rope-contact areas should be rounded, dressed, and free from harmful sharp edges so the towline is not exposed to unnecessary local chafing during ship-assistance operations.
• The fitting load is transferred into the side shell and internal supporting structure. Hull reinforcement, weld size, load direction, and permissible lead angle therefore require approval by the vessel designer and class society.
• Because the fitting is recessed in the ship side, drainage, coating continuity, access for inspection, and corrosion control should be reviewed as part of the installation design.
• For stainless steel or special low-temperature steel, the exact grade, welding consumables, dissimilar-metal interface, heat input, NDT, and post-installation surface treatment should be agreed before production.

Custom Attributes

• Standard: ISO 13798:2020 → reference for recessed bitt designation, nominal sizes, dimensions, SWL, and construction type.
• Construction Type: Type B steel plate fabricated → differentiated from Type A steel-pipe construction.
• Nominal Size: 200 / 250 / 400A / 400B → select according to required SWL, rope basis, and side-shell arrangement.
• SWL: 294 / 491 / 687 / 1,177 kN → do not substitute MBL, breaking load, test load, or unrestricted multidirectional capacity.
• Material: Exact grade to be confirmed → C-Mn steel plate, stainless steel, or special steel should follow project temperature, welding, and class requirements.
• Installation: Side-shell recessed and welded → local reinforcement and load path are part of the vessel structure and must be checked separately.
• Certificate Requirement: Available according to order scope → material certificates, maker documentation, class inspection, and witness testing should be agreed before quotation.

How It Works

Towline is led to the recessed side-shell position → Line is secured around the bitt contact surface → The approved towing load is transferred through the fabricated fitting and welded interface → Local hull reinforcement distributes the load into the vessel structure → Fitting is inspected and maintained as part of the towing arrangement

Applications

High-freeboard vessels | Cargo ships | Tankers | Bulk carriers | Ship-assistance and harbor towing positions | Side-shell towing stations | Newbuilding and replacement projects

Certifications & Advantages

Certificates and inspection can be arranged according to project requirement, material traceability, approved drawing, test scope, and classification society procedure. Compliance should not be assumed until the required documentation and witnessing scope are confirmed.

Certification: CCS, NK, BV, ABS, DNV, LR, KR, IRS, RS, RINA, CRS, Makers Test Certificate.

Drawing & Photos

FAQ

Q1: What is the difference between ISO 13798 Type A and Type B recessed bitts?

A1: Type A is manufactured from steel pipe, while Type B is fabricated from steel plate. The same nominal size may therefore have different outside diameter, wall thickness, and calculated weight. This page and its main table apply to Type B.

Q2: Can the listed SWL be used for any towline direction?

A2: No. The SWL must be applied within the load direction and installation conditions defined by the applicable standard and approved vessel arrangement. Side-shell reinforcement, weld details, towline lead angle, and supporting structure must be checked before use.

Q3: What information is required before quotation?

A3: Confirm ISO 13798 Type B, nominal size, SWL, vessel type, side-shell installation drawing, towline direction and rope diameter, material grade, surface treatment, quantity, class requirement, destination, and required delivery time.

Zhongyuan Ship Machinery Manufacture (Group) Co., Ltd. was founded in the 1990s and has developed into an integrated marine equipment manufacturer and project supply partner combining manufacturing, technical support, and export services. The group consists of four factories and one export trading company, with more than 300 employees, including over 20 experienced technicians and engineers. Our export company supports global customers with project communication, technical documentation, logistics coordination, and after-sales service.

Our factories are certified to ISO 9001, ISO 14001, ISO 45001, and related occupational health and safety management standards. We also hold type approval certificates from major classification societies such as DNV, LR, BV, and ABS, as well as works approval certificates, class-approved WPS procedures, and qualified welders. Our products can be supplied with certificates from IACS classification societies including DNV, ABS, LR, BV, CCS, RINA, KR, NK, IRS, and RMRS, depending on project requirements.

We manufacture a wide range of marine and offshore equipment, including deck equipment and machinery, mooring and towing equipment, deck outfitting, shafting components, rudder stocks, shaft and rudder systems.

In addition to our manufactured products, we also supply selected marine equipment through qualified partner manufacturers, including hydraulic cylinders, hydraulic power units, marine hardware, lifting and lashing equipment, hoisting and rigging products, lifeboats, rescue boats, launching appliances and davits, life-saving equipment, fire-fighting equipment, rubber fenders, rubber packing, marine pumps, valves, pipe fittings, multi-core pipes and accessories, steel wire ropes, mooring ropes, rope nets, anchors, anchor chains, and various marine chains.

Our main production facilities include CNC machining centers, CNC machine tools, CNC cutting machines, boring and milling machines, hydraulic presses, plate rolling machines, welding robots, welding equipment, shot blasting equipment, and dust-free painting workshops. These facilities enable us to support customized manufacturing and project-based production for shipbuilding, ship repair, offshore, and marine engineering projects.

We are committed to providing reliable, high-quality, and cost-effective marine equipment to customers worldwide. With our manufacturing capability, technical support, qualified supply network, and export coordination experience, Zhongyuan aims to be a trusted partner for shipyards, shipowners, offshore companies, and marine equipment distributors.