I. Tank Structure of Horizontal Dry Bulk Tankers
Horizontal structure is the most common configuration for dry bulk tankers. Based on their internal layout, they are classified into single-compartment, double-compartment, and triple-compartment horizontal powder tankers.
Due to stricter enforcement of overload regulations in recent years, the market has largely converged on 2 structural types:
- Single V-shaped body, also known as a single-compartment structure.
- Double V-shaped body, also known as double-compartment structure.
The triple-compartment horizontal powder tanker, once known as the “super large powder tanker,” has essentially been phased out.
- The single-compartment horizontal tanker tank is composed of standard butterfly-shaped or elliptical end caps and 2 or 4 sections of cone-shaped tank segments.
- The double-compartment horizontal tanker tank consists of standard butterfly-shaped or elliptical end caps, 2–3 sections of slanted cone tank segments for the front V-section, 2 slanted cone tank sections for the rear V-section, or a straight tank section.
The end caps and tank segments are welded together using dual-sided gas shielded welding.
II. Air Chamber and Fluidization Bed of Dry Bulk Tankers
Inside the tank, air chamber structures and fluidization beds are arranged. Their purpose is to use compressed air to fluidize the material stored in the sealed tank for unloading.
- The air chambers are located at the end caps or the connection points between the front and rear compartments in double-compartment tankers.
- A canvas hose-shaped fluidization bed is laid at the bottom of the tank.
In single- or double-compartment tanks without side baffles, the air chamber structure is lighter, easier to maintain, and requires less frequent maintenance. The fluidization bed provides stable performance, fast unloading speed, and low material residue.
III. Power System of Horizontal Dry Bulk Tankers
Currently, domestic horizontal powder tankers are generally equipped with onboard air compressors, mainly of 2 types:
- Swing-type
- Screw-type
Swing-type compressors are the first choice due to their lower cost and high air output. They are further divided into single-cylinder and twin-cylinder types. Single-cylinder swing compressors are lighter in weight and have become widely adopted in the context of overload and load restriction regulations.
Screw-type compressors offer benefits like lightweight design, high air output, long continuous operation time, and long service life. Examples include:
- Green Zhongfu XK18
- Ingersoll Rand CHH RAND CS90
- Domestic Lianhansheng screw compressors powered by vehicle PTO
However, due to being several times more expensive than swing-type compressors, screw compressors have limited market adoption.
The power source for onboard air compressors can be:
- Independent diesel engines
- Electric motors
- Dual-power setups (diesel + electric)
- PTO from the tractor unit
- Dual-power systems using both electric motors and PTO
Among these, PTO-driven systems (using the tractor’s engine) eliminate the need for additional engines or motors, offering advantages in both weight and cost.
IV. Discharge Performance of Horizontal Dry Bulk Tankers
Discharge performance is a key metric. According to QC/T 560 “Technical Conditions and Performance Test Methods for Bulk Cement Vehicles,” discharge must be tested under:
| Parameter | Value / Performance |
|---|---|
| Working Conditions | |
| Vertical Height | 15 meters |
| Horizontal Distance | 5 meters |
| Working Pressure | 0.2 MPa |
| Performance Requirements | |
| Discharge Rate (Standard Material) | ≥ 1.2 tons/min |
| Residual Rate (Standard Material) | ≤ 0.3% |
| Discharge Rate (Other Materials) | ≥ 1.0 m³/min |
| Residual Rate (Other Materials) | ≤ 0.3% |
| Current Horizontal Tanker Capability | |
| Tanker Type | 32m³ Single-Compartment Horizontal Tanker (No Baffles) |
| Actual Discharge Rate | 1.5–1.6 tons/min |
| Actual Residual | ≈ 50 kg |
| Actual Residual Rate | ≈ 0.15% |
V. Development Trends of Horizontal Dry Bulk Tankers
1. Lightweight Design
As the market demands lighter vehicles, tanker bodies are becoming thinner while still using high-strength steel. However, issues like tank collapse and denting have been reported. Thus, while reducing weight, it’s critical to maintain structural safety and quality.
Benefits of lightweight design:
- Lower fuel consumption
- Improved environmental performance
- Higher payload capacity
These are driving factors in the future development of horizontal powder tankers. With the rapid development of aluminum alloy special vehicles, all-aluminum horizontal single-compartment powder tankers have also started gaining market presence.
2. Faster Discharge and Lower Residue
Discharge rate and residual rate remain key performance indicators. Efforts to reduce material residue include:
- Minimizing the fluidization bed area
- Reducing dead zones in the tank
- Using bottom discharge systems
Such optimizations help to empty the tank during unloading and minimize residue.
