JASUBHAI GROUP      ABOUT CHEMTECH     ADVISORY BOARD     AWARDS       EVENTS     PUBLICATIONS     CONTACTUS    
Chemical & Processing
EPC
Oil & Gas
Refining
Automation
Pharma Biotech
Shipping
Power
Water
Infrastructure & Design

Ship-to-Ship Transfer of Hydrocarbon Products
Capt D N Banerjee, Lighterage Master, SCI Lighterage Cell A huge quantum of crude oil in the country is derived from foreign lands and is imported in Very Large Crude Carriers (VLCCs). Th ese VLCCs require deep drafted ports. Lightering becomes imperative as the operation reduces a vessel's draft for it to be able to enter port facilities, which cannot accept very large ocean-going vessels. Th e article details this, and more of interesting facts about lightering.

The history of oil tanker is a part of the evolution of the technology of oil transportation alongside the oil industry. Although man’s use of oil goes back to the prehistoric period, the first modern commercial exploitation dates back to James Young’s manufacture of ‘Paraffin’ in 1850. In the earlier days, oil from Upper Burma was moved in earthenware vessels to the river bank where it was then poured into boat holds. We have come a long way in terms of transportation of oil. Today’s modern Ultra Large Crude Carrier (ULCC) can be as long as 1,300 feet (400 m) long and have a capacity of about 500,000 DWT.

With the exception of pipeline, the most cost-effective way of transportation of oil is by shipping (tankers). Larger the oil tanker, cheaper it is to move oil. Larger tankers have contributed significantly to the growing demands for oil. Lighterage activity was born as an integral part in movement of crude oil to its ultimate destination; the Refineries. In the Indian subcontinent, at least 80 per cent of the domestic requirement of fossil fuel comes from other oil producing nations and it makes economic sense to import crude oil in larger ships such as VLCCs with capacities ranging from 200,000 to 300,000 metric tonnes. However these ships are too large and require deep drafted ports.

Lighterage or Lightering is the process of transferring cargo between vessels of different sizes. Lightering is undertaken to reduce a vessel’s draft in order to enter port facilities which cannot accept very large ocean-going vessels.

Effective manoeuvring controls are required on board both the vessel to be lightered and the lightering vessel. A few service vessels are equipped with bow thrusters, controllable pitch propellers, twin screws, and special rudders to aid in manoeuvring. Most also have engine controls on the Bridge and sometimes at other locations. Good systems for communications between key locations onboard each vessel and between vessels are critical.

Lightering vessels may be engaged by a variety of operators and shipping companies. These vessels have a range of design features that make them more or less suitable for lightering activities. Vessels that have been built or converted for lightering, usually service vessels that are dedicated solely to lightering, have standard mooring, fendering and hose transfer systems built in, and they engage in lightering on a regular basis.

On non-dedicated lightering vessels, the mooring lines, fenders and hoses are usually delivered to these vessels just before a lightering operation, used during the offloading of one Still to be lightered (STBL), and then removed by the service company that was engaged to provide this equipment, expertise and personnel for the lightering operation. These non-dedicated vessels are of varying designs, so the special equipment must be able to accommodate a variety of on-board arrangements.

STBLs exhibit an even greater variety of designs and arrangements of equipment. An STBL can be any vessel from the world tanker fleet with several possible places of construction, any age, any flag of registration, and crew nationality, and so forth.

Other than expertise, three categories of special equipment necessary for the safe transfer of oil cargo between two vessels on the open ocean, the same are listed below:
• A method of keeping the vessels together (i.e., a strong, well designed mooring system);
• A method of keeping the vessels apart and protecting them from each other (i.e., a fender system suitable for the individual operation);
• A reliable transfer system for moving the oil from one vessel to the other (i.e., hoses, connections, and equipment for connecting and disconnecting them).

Recommended Mooring Arrangements for Offshore Lightering
The side-by-side mooring arrangement used in a typical lightering operation is only practical in low-to-moderate seas under reasonably good weather conditions. If the weather turns severe and waves reach a certain height, the operations must be suspended and the vessels separated. Vigilance and good judgment on the part of all mariners are essential to avoid damaging either vessel.

The OCIMF (ICS and OCIMF, 1997) and individual company standards specify the types and testing of fenders. Before a lightering operation begins, the mooring master or lightering service company representative tests the pressure of pneumatic fenders, which must be inflated according to the manufacturer’s instructions (foam-filled fenders are sometimes used instead). Pneumatic fenders are most reliable when they are fitted with safety release valves to prevent them from bursting when compressed.

Primary fenders, which absorb the impact from the connection of the two vessels, must have the proper diameter in relation to the vessel’s freeboard to prevent the fenders from riding up the sides of the vessel and rolling onto the deck. The OCIMF recommends that fender diameter not exceed half the freeboard at any time. The fenders should also provide maximum protection along the hull, allowing for both approach and departure angles. Experience and skill are required to place fenders properly because vessels meet at different angles. The speed of approach significantly affects fender requirements, and it is prudent not to overestimate the approach speed when selecting fender size. The fender rigging system is also critical.

Secondary (or baby) fenders provide additional protection in case the angle between the vessels exceeds the protective capability of the primary fenders. Secondary fenders are placed fore and aft of the primary fenders to prevent steel-to-steel contact. The flare and counter of the two vessels



aggravated by motion, results in an almost infinite number of possible contact points. Tankers have extensive parallel midbodies, where fenders work best. However, some modern vessels have short parallel mid-bodies , s o secondary fenders must be available in appropriate locations.

Fenders may have to be moved or adjusted to suit the situation. Some vessels that are routinely engaged in lightering are fitted with permanent mounting points to facilitate the handling of secondary fenders. Some operators of dedicated lightering barges have placed permanent moulded-rubber fenders on the sides at these contact points, which eliminates the need to deploy fenders for each lightering operation.

Hoses
Many types of hoses are used in lightering. All of them must be approved by the administration for this service. The transfer hoses have a thick outer rubber jacket with an inner liner for reinforcement. Hoses are generally connected to the manifold by means of a fully bolted flange, which provides a strong and reliable connection. Hoses should be inspected regularly because they are exposed to more wear during lightering operations than when they are used at a terminal.

Weather
Weather is a major risk factor in lightering. Weather is both a safety factor, and a legal factor, because winds and sea state can affect vessel interactions, OCIMF guidelines specify the weather conditions under which lightering may take place in the designated lightering zones. Thus real-time information about the weather on the scene of the lightering operation, at locations six to eight hours away, and as much as 24 hours in the future should be available.

As the two vessels come together, vessel operators use information about winds, currents, and sea state to the best advantage. This information also ensures that the vessels will not be ‘peeled apart’ during the approach. Once the vessels are safely moored together, the weather is continuously monitored to ensure that conditions do not deteriorate to the point where safety is compromised. Sea state, winds, and currents also affect the unmooring of the two vessels.

If it appears that weather may become marginal, then the operators have several options. They may:

(1)Terminate cargo operations, drain the hoses, and keep the vessels together until the bad weather passes;
(2) Terminate cargo operations, drain the hoses, and separate the vessels with the intention of coming back together later to finish transferring the cargo; or
(3) Continue operations. Interrupting an operation and dismantling connections takes time, so the longer the lead time the lower the risk associated with unmooring. When the weather is deteriorating, it is important to have accurate forecasts that give operators sufficient time to unmoor and move the vessels apart before the weather becomes too severe to accomplish this safely.

Lightering is done most efficiently and safely while the STBL is at anchor.

SCI Pioneering Ship-to-Ship (STS) Transfer
The need for lightering on Indian shores led to the formation of a dedicated ‘Lighterage Cell’. In the year 1975, the B&T Division and the Lighterage Cell of SCI was formed. The responsibility of the Lighterage Cell is to lighter the larger import tankers into smaller tankers in the open sea beyond the port limits. Experienced loading masters were employed to conduct these high risk operations. The Lighterage Cell was answerable directly to the Oil Co-ordination Committee (OCC) that was created by the Govt of India to act as a link between the Ministry of Petroleum and the Ministry of Shipping.

The Lighterage Cell’s responsibility was also to plan the acquisition of necessary equipment and physically conduct open sea Ship-to-Ship (STS) lighterage operations on the coast of India. Offshore STS lighterage operations were thus introduced on the Indian coast by SCI in 1975, and developed to maximise utilisation of large tankers which could not enter the port at their fully laden draft.

The operations soon became the backbone of crude oil transportation and supplies to Indian refineries. In the years when there preceding deep drafted ports and SBMs, SCI has provided highly dedicated service to the nation for more than three decades in this field.

Over the years, SCI has gained vast expertise in offshore STS lighterage operations, which are conducted strictly in accordance with internationally accepted recommendations prescribed in the ICS / OCIMF Ship-to-Ship Transfer Guide (Petroleum). SCI has won international recognition by carrying out intensive operations, with an accident-free track record.

SCI maintains a stock of necessary STS equipment for these operations, viz: floating Yokohama Pneumatic Rubber Fenders (6.5 m x 3.3 m), cargo flexible hoses and other accessories. Suitable tugs are inchartered, as necessary.

At an average every year SCI conducted about 400 lighterage operations at various locations on the East and West coasts of India. However during the recent years due to the advent of SBMs, the number of lighterages has drastically come down.

SCI has played a key role in establishing tanker mooring systems for ONGCL’s numerous SBMs at Mumbai High and adjoining satellite oilfields. Since the commissioning of these oilfields in the seventies, SCI has worked in close co-ordination with ONGCL during the planning and deployment of tanker mooring systems, and has been physically conducting mooring operations of storage tankers for ONGCL ever since.

These operations are carried out by SCI throughout the year, including during the SW monsoon season, to facilitate uninterrupted production and storage of indigenously produced crude oil 1985-86, SCI commenced similar SBM mooring operations for M/s Enron Pvt. Ltd. at the Panna-Mukta oilfield, being jointly operated by ONGCL, Enron and Reliance. Subsequently, this service was continued with M/s British Gas India, who took over as the lead operator in this Joint Venture.

In 2006-07, SCI played an active role in the revival of the Dabhol Power Plant, by providing our expertise for conducting complete tanker handling operations of Product tankers at the Dabhol SBM, which had been lying idle for the previous five years.

SCI has conducted STS transfers at various locations in the East and West Coast of India viz., Sikka, Vadinar, Sagar, Dabhol, Vizag, Panna fields, Mumbai High and satellite locations, Goa, Sandheads, Kakinada etc. SCI’s Lighterage Cell also supervised Single Buoy Mooring (SBM) operations of storage tankers at Mumbai High and sateliite oil fields. SCI’s Lighterage Cell also carried out the inaugural ‘tandem mooring operation’ at FPSO ‘Dhirubhai,’ at the newly commissioned KG Basin offshore oilfield in the Bay of Bengal. SCI also supervises Ore transhipment with transhippers at Goa.

During the year 2011-2012, SCI has carried out 118 tanker lighterages (1.923 mmt), handled 28 SBM Mooring operation of (Crude handled 1.94 tmt) and 1.923 mmt of bulk iron ore cargo lighterages.