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Exploring all the options

Tue 18 Apr 2017

Exploring all the options
Installation in progress of Erma Firstís BWMS. The new piping can be seen in blue (credit: Erma First)

When Erma First was invited to tender for a ballast water management system on an LPG carrier, three options were explored, explains managing director Konstantinos Stampedakis

Designing and installing a ballast water management system (BWMS) on board a 35,000m3 LPG/NH3 carrier without affecting its safe operation was a challenging prospect. We had to find a location in the shipís machinery space that would keep modifications to the existing piping systems and structural members to a minimum yet allow enough space around the equipment for maintenance. And it had to be the most cost-effective installation possible.

The shipís total ballast capacity is 12,000m3, served by a pair of main ballast pumps mounted in the engineroom, each rated at 500 m3/h at a pressure of 2.5 bar. They serve ballast tanks to port and starboard, along with a forepeak tank so our initial onboard survey reviewed the existing ballast piping arrangements and the pressure drop in the system, as well as the space availability. Equally important was an assessment of the available power.

Erma First Fit BWMS uses a combination of separation and electrochlorination and has two concepts available: the Erma First BWMS, which uses the most efficient filtration device available, a multi hydrocyclone, and the Erma First Fit arrangement, which is an advanced modular system that combines a high-end backwash filter and an electrolytic cell.

For the LPG carrier, the two main options we considered were based on the Erma First Fit arrangement. Option One used a single 1,000 m3/h treatment system while Option Two was based around two 600 m3/h systems. A third option was also considered, also using two 600 m3/h systems but with a different piping layout.

One of the early considerations was whether there was enough generator power. The ship has three generators: two of 1,215kW each and one of 740kW and its power consumption during unloading is 1,365kW. If one of the larger generators is kept on standby and the other two operate at 85 per cent load, that leaves 305.75kW of available power. This compares with power demand for Option One of 71kW and, for Option Two, 178kW. So there would be enough power for either choice.

After reviewing the complexity of the ballast lines for each option and the available space, the eventual choice was Option Two since it required the least piping. This minimised the pressure drop through the system which was calculated to be 0.3 bar, with a further 0.3 bar Ė at most Ė from the filter. This meant that no ballast pump upgrade was required.

The whole job took a year, from vendor selection in January 2016 through to installation in December, followed by commissioning. In fact, the design and plan approval of the installation was completed in nine months: it was the vesselís operational obligations that determined the installation dates.

Those final stages involved just two Erma First staff and a total of 21 days and the only problems they faced were with some minor electrical components. It completed a successful project, on time, on budget and with minimal impact on the shipís machinery space.

Components needed for proposed BWMS options

Component

Option One

Option Two

Electrolytic cell

1

2

40μm Filter

1

2

Transformer/rectifier

1

2

TRO sensors

2

3

Control board

1

2

Repeater panel

1

2

Flow meter

1

2

Dosing pump

1

2

Neutralising unit

1

1

Back flushing pump & valve

1

2

The projectís timeline

  • Vendor Selection: January 2016
  • Approval Drawings submission: 15 January
  • Kick-off meeting with class: 10 March
  • Submit first drawings to class: late March
  • Further submissions to class: until August
  • Final installation plan approval: August
  • Complete detailed specifications: October
  • Installation: December

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