The Motorship | VERSATILE NEW SERIES OF ETHYLENE TANKERS


Petredec’s new series of ethylene carriers will be an optimised version of the Empery type.(Photo: MarineTraffic/Ye Chia-Wei). Petredec’s new series of ethylene carriers will be an optimised version of the Empery type. (Photo: MarineTraffic/Ye Chia-Wei).



Advanced, handysized tonnage from China will afford considerable scope as to liquefied gas cargoes, writes David Tinsley.

Towards the end of 2019, Singapore-based Petredec Holdings exercised its options on two additional ethylene-capable liquefied gas carriers from Jiangnan Shipyard, augmenting the two-ship contract signed a few months earlier.

The newbuilds encapsulate an optimised and upgraded version of the 21,200m3-capacity Empery-class quartet completed by the Chinese yard over the course of 2016 and 2017. The nascent series offers a near-1,000m3 advance in cargo volume within a similar hull envelope, plus IMO Tier III NOx emissions compliance. The prospective fleet additions occupy delivery slots in 2021 and 2022, and the design perpetuates the considerable versatility in liquefied product transportation displayed by the initial quartet.

Imbuing the capability to transport ethylene necessitates design engineering to ensure and maintain a cargo temperature of minus 104degC.

As well as serving the niche, ethylene segment of the market, the ships will offer a very high degree of cargo carrying flexibility, extending trading opportunities and potentially minimising time in ballast. The payload scope embraces ethane (at minus 80degC), anhydrous ammonia, propylene, propane, vinyl chloride monomer (VCM), butadiene, butane and isobutane. Ethylene, propane and isobutane can be received aboard from either refrigerated or pressurised storage.

Given the potential product range, and as with the Empery generation, the vessels may be described therefore as LEG/LPG/ammonia/VCM carriers.

Having engaged TGE Marine Gas Engineering as the contractor for the cargo handling systems and tanks in the previous series of ethylene carriers from Jiangnan, and also for two 22,000m3 semi-refrigerated LPG/ammonia carriers built by the same yard in 2018, Petredec has retained the German company for the latest project.

Rather than the four-tank layout employed before, each of the 22,000m3 newbuilds will be configured with three cargo tanks of bilobe type, fabricated from 5% nickel-steel, and constructed to withstand a 5.3 bar maximum pressure. The gas plant will allow two segregations, with two liquid lines and two vapour lines feeding from and to the cargo manifold.

Cargo handling will be effected by six deepwell pumps, two per tank, located within the tank dome, and individually rated at 350m3/h. Loading and unloading is therefore anticipated at up to 2,100m3/h from refrigerated or pressurised storage, using vapour return. An LPG heater/vaporiser will be supplemented by a dedicated ethylene vaporiser.

The specified cargo boil-off and fuel gas system is of the cascade/direct cycle type, using three refrigerant (propylene) compressors and three cargo compressors.

Petredec’s preceding programme of four ethylene carriers at Jiangnan had received German financing from KfW IPEX-Bank working with credit insurance provider Euler Hermes. With EUR50 million-worth of gas and tank systems contracted to TGE Marine of Bonn, the funding reflected the German export component to the deal.

The propulsion system in each of the existing ships entails a 500mm-bore two-stroke engine providing direct drive to a fixed-pitch propeller. The MAN six-cylinder S50ME-C8.2 diesel has a specified rating of 7,170kW at 114rpm and operates on either very low sulphur fuel oil (VLSFO) or low sulphur marine gas oil (LSMGO). Consumption of VLSFO at maximum service speed is in the order of 25t per day.

The auxiliary outfit is substantial, as befits such an extensively-equipped vessel, and comprises four aggregates powered by Daihatsu DK-20e series engines manufactured under licence from the Japanese designer in China. Two six-cylinder models and two eight-cylinder versions are installed, yielding individual outputs of 950kW and 1,250kW respectively, giving a total availability of 4,400kW.

Two of the four gensets have to be run to provide the requisite power in port for taking on or discharging a full cargo, and two are needed at sea to maintain cargo tank pressure. When carrying ethylene, a third set has to be brought on-line so as to ensure refrigerated temperature control of the cargo. When no cargo machinery is being activated, as on a ballast leg, a single aggregate is sufficient to cover the ship’s sea-going electrical load.

Technical husbandry of the ethylene tanker flotilla is the province of Anglo Eastern Ship Management’s Singaporean company, which is also responsible for the crewing arrangements, whereby each vessel has a complement of 21.

Ethylene is a primary building block of the petrochemicals industry and is used in the production of polyethylene, ethylene dichloride, ethanol, styrene, glycols and many other products.

PRINCIPAL PARTICULARS – Empery-class ethylene carrier

Built

2016-2017

Length overall

159.99m

Length bp

152.81m

Breadth, extreme

24.80m

Depth, extreme

16.70m

Draught, scantling

9.40m

Corresponding deadweight

16,925t

Gross tonnage

17,235t

Cargo capacity @100%

21,220m3

Cargo capacity @98%

20,795m3

Main engine power

7,170kW

Speed, loaded

16kts

Auxiliaries

2 x 950kW + 2 x 1,250kW

Class

Bureau Veritas

Crew

21

Flag

Singapore

PETREDEC ethylene carriers

Jiangnan yard no.

Name

Capacity

Delivery

H2567

Empery

21,200m3

2016

H2568

Ellington

21,200m3

2016

H2569

Emilius

21,200m3

2017

H2570

Earth Summit

21,200m3

2017

H2669

Eclipse

22,000m3

2021

H2670

Electra

22,000m3

2021

H2671

Exhibitionist

22,000m3

2022

H2672

Enable

22,000m3

2022



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