by Hans | July 25th, 2011
Shipco Marine Constructors deliver their latest new build 15m tug PT May for sea trials and testing.
This is the first small tug of this type to be built in New Zealand for some time, standing out from its predecessors with a number of clever design features and performing more like a z drive ship handling tug than a workboat.
Bollard pull trials ahead and astern went without a hitch, the tug performing very well with minimal vibration, easily maintaining position and heading. Compared to existing tugs with hard mounted propulsion machinery PT May is a pleasure to operate, the engines being soft mounted with flexible couplings to hard mounted gearboxes, providing a very smooth outcome, commented on by a good number of people. Noise is of an acceptable level for such a small steel vessel with a big power plant, insulation fitted to a high standard.
Once all trials were completed to satisfaction of the GL surveyor the tug was handed over to the owner, Pacific Tug, Australia. We then delivered the tug to Auckland, where a number of towing jobs of all types were carried out to trial the vessel further for both Pacific Tug and Shipco, while awaiting shipping to Brisbane. PT May performed above expectation on all towing and workboat duties identifying how easy these jobs can be undertaken with modern, properly designed equipment.
Eventually a ship was found for transport to Australia, Pacific Tug contracting us to deliver the tug further down the coast to Tauranga. This voyage was carried out in less than ideal conditions, 25-35 knot wind and rough seas. The sea keeping ability of this little tug is exceptional and gives the feel of a larger vessel. We had a far more comfortable ride down the coast than we would have had in one of our larger tugs.
Fuel consumption free steaming appears to be very acceptable, 1700 rpm giving a solid average speed of 10 knots @ 94 LPH including gen set. In conclusion I feel that Shipco have developed an outstanding little tug that will be very suitable for a wide range of towing and workboat duties, being built and finished to a high standard.
Length overall (excluding fenders): 15 Metres; Beam (moulded): 6.5 Metres; Depth (moulded): 2.75 Metres; Draft Aft: 2.8 Metres; Fuel oil: 11.15 Cub M; Spare fuel oil: 10.04 Cub M; Fresh water; 3.04 Cub M; Sewage: 2.66 Cub M; Dirty lube oil: 2.59 Cub M; Clean lube oil: 1.3 Cub M;
Hull and Machinery design by : SHIPCO
Classification : Germanisher Lloyd : notation ( +) 100 A5 RSA (200) TUG MC
Safety, Lifesaving and navigation equipment : Australia CLASS 2B
Built For : Pacific Tug Pty Ltd – Brisbane Australia
Trials Performance : Bollard Pull ahead 17 tonnes – astern 14 tonnes; Speed : 10.5 Knots; Normal Manning 2 Persons; Crew accommodation for 4 persons.
For crew comfort the wheelhouse and accommodation floors are floating type, the engines are resiliently mounted with the main engines being on LOREZ spring type vibration isolators, Exhaust piping and mufflers are resiliently amounted all resulting in very good noise control. Air conditioning of the wheelhouse and accommodation areas are by Ocean Breeze using a chilled water system with the keel cooledchiller units in the engine room and the stainless steel air handlers in the living areas.
Generater sets Electrical power is generated by two Cummins generator sets; One set: 6B-CP80DM/5 rated 80 KW 380 volts 50 HZ Keel cooled electric started; One set :6C-CP136DM/5 rated 136 KW 380 volts 50Hz keel cooled air started. This set supplies the power necessary to drive the towing winch.
Fendering system : by SHIPCO
Around the bow and extending to the forward shoulders is a 1.1metre wide sweep of double loop tyre fendering 500mm deep. This fendering has very good energy absorbing characteristics together with good holding abilities. Aft of this is a section of aircraft tyres 1.00 metre dia 500mm wide secured to the hull without chains by way of steel rims. Aft of this are two rows of veregated single cut tyre fenders suitable for hard knocks that inevitably happen.
Towing winch—Manufacturer — SHIPCO
Electrically driven 37 Kw via an ABB variable speed drive Brake holding capacity 75 tonnes hydraulic operation; Line pull bare drum 11 tonnes at 15 metres a minute; Line pull 4th layer 8 tonnes at 22metres per minute; Drum diameter 610mm capacity 550 metres x 32mm diameter wire in 6 layers; Level wind equipment installed Controlled emergency quick release is provided at speeds of 48 to 88 metres per minute; The winch drive reductions are achieved firstly via a planetry drive with a reduction ratio of 25.6 to 1 then to a pinion and bull gear drive having a 4.58 to 1 reduction. The winch control console is positioned on the engine casing deck forward of the winch. This console houses the winch control joystick, The hydraulic towing pins and hold down push buttons, the steering jog levers and rudder indicators together with the engine and transmission control levers, allowing the winch operator full control.
The ABB variable speed drive uses ABB’s own direct torque control algorithm giving very smooth acceleration and deceleration to required speeds and providing for simple setup of user selected line speed and pull from 0 to 100% of winch capacity. The system incorporates the brake control features and does not release the brake until the drive has generated suffecient force (typically about 50%) against the brake before releasing it. These low harmonic electrical drives are built to class approval and are provided with special filtering achieving normally less than 5% current distortion.
Towing pins and stern roller Manufacturer — SHIPCO
Pins are electric/hydraulic operation 3 pin type with hold down. Each hardened pin slides up and down in bronze bushes and rotates on 4 roller bearings for each pin. The wire hold down lug is raised up and folded down hydraulically. The 400 mm dia stern roller is balanced, running in spherical bearings and has a SWL of 35 tonnes.
Capstan Manufacturer — SHIPCO
Hydraulically driven vertical type 500mm dia waist giving a 5 tonne pull at 20metres per minute. Foot switch operation.
Tow Hook Manufacturer —SHIPCO
35 tonne SWL rotating hook type with hydraulic release.
Propulsion Main engines are 2 off Cummins KTA 19 –M3 rated 600 BHP each at 1800 rpm, air started and keel cooled. Driving through ZF island mounted gearboxes model W 1800 ratio 6.160 to 1 and connected to the engines via a Centa CX-55-LFS2 input coupling. Propeller shafts are of mild steel running in oil lubricated bronze bushes with 1494mm dia 4 bladed propellors with a 20 degree blade skew and made from Manganese bronze. Engine and gearbox control is by a 3 station ZF controller with 1 MC2000 and 2 760 control heads. The propulsion train is remarkably free of vibration in both ahead and astern travel and at all speed ranges.
The excellent manouverability of the tug is obtained from the specially designed independently steerable nozzles. The nozzles are top hung and have 35 degrees of steerage to port and starboard in a total of 12 seconds.Steering gear is of SHIPCO manufacture with TQM auto pilot and electronic steering levers.Three steering stations are provided, one in the wheelhouse, one on the flybridge and one at the winch station.Kelvin HardiePO Box 24 Whangarei, New Zealand 0140PH: +649 4382219Fax: +649 4387845www.shipco.co.nz