Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

S.G. Meijer Pompen voor het lossen van chemicaliëntankers vanaf de wal.
Literature survey, Report 2003.TT.6752, Transport Technology.

Within the current distribution structure of chemical products, parcel tankers have to stay in port for long periods of time due to the large range of products that has to be loaded and unloaded at multiple terminals. By building dedicated terminals and tankers for certain chemical products with large transport volumes, these port times could significantly be shortened.

To examine the possibility of putting pumps on the terminal instead of having them placed aboard, as is currently the case with chemical tankers, research has been done on the different pump types and their characteristics. Most of the work has been done on centrifugal pumps and piston pumps, as these are the most suitable pumps for the given task.

From analysis the main advantages and disadvantages of centrifugal pumps and positive displacement pumps are drawn and put in the following overview:
advantages diadvantages
Centrifugal pumps + High capacities possible
   (> 5000 m3/hr)
+ Cheap
+ Simple
+ Pulsless capacity
- Small heads (< 500 m)
- Not self priming
- Not suitable for viscous liquids
   (>200 cSt)
Positive displacement pumps + High heads (>5000 m)
+ Suitable for high viscosities
   (150-10,000 cSt)
+ Variable speed with constant
+ Mostly self priming
- Low capacities (<100 m3/hr)
- Complicated and heavy
- Not leak free
- Relatively expensive

For unloading tankers from ashore, an analysis has been done based on methanol as this product is responsible for a large part of the transported volume of chemicals. The following boundary conditions are given:
       Capacity: 500 m3/hr
       Vertical distance between tanker bottom and quay: 20 m
       Total head (including friction head): 60 m
       Viscosity methanol (25 &grad;C): 0,69 cSt (water = 1 cSt)

For unloading the tankers with the given conditions there has been chosen for a centrifugal pump, based on capacity, head, viscosity, toxicity and price.

For unloading the parcel tankers from the quay there are three possible solutions. In order of preference these are:
  1. Placing a centrifugal pump on the sore and pressurizing the ship tanks to 2.5 - 2.8 bar with an inert gas like nitrogen. The nitrogen can be produced with the use of nitrogen generators.
  2. Placing a centrifugal pump on the sore and pressurizing the ship tanks with normal air. A membrane or some kind of other solution should be used to keep the air and the methanol separated in the tanks.
  3. Lowering a centrifugal pump in the ship, which then has to be connected to the tanks.

Reports on Transport Engineering (in Dutch)
Modified: 2003.04.10; , TU Delft / 3mE / TT / LT.