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Eliminating discharges in
oil/sea interfacesSeawater lubricated propeller shaft systems for
commercial ships
Presented by
Craig Carter, Thordon Bearings
Ship Efficiency: The Event 9 September 2015
Overview
• Problems with oil/sea interfaces in
propeller shaft lines
Operational Discharges
Accidental Discharges
• Regulations impacting ship owners US EPA – Vessel General Permit
Polar Code
• Options for Ship Owners
Air Seals / oil-based EAL’s
Seawater lubricated propeller shaft lines2
3
Propeller Shafts
Lubricated With Oil• Typical stern tube system has 1500 to 3000
litres of mineral oil
OIL
Oil to seainterface
Oil Lubricated Propeller Shafts
Tailshaft and pod seals do not operate in a perfect environment
• Pollution risk Seal must leak to lubricate its sealing lip
Oil pollution from leaking shaft or pod seal• Rope and fishing line damage seals
Escalating detection and enforcement
• MARPOL Annex I
• Satellite tracking
• Criminal fines
• Jail terms
Increased expectation of corporate
responsibility
• Damage to corporate brand and image
4
Oil discharges from commercial ships… a
serious problem
• Approximately 95% of commercial ships use oil lubricated metal propeller shaft
bearings.1
• Environmental Research Consulting (New York) study
“Total annual inputs of lubricating oil worldwide from stern tube leakage and other
operational discharges into port waters is estimated to be between 37 million to nearly 61
million litres. If the same rates of discharge occur at sea as they do in port, the estimated
worldwide annual inputs of lubricants to marine waters both in ports and harbours and at sea
might be estimated to be about four times the port estimate.
Total worldwide use of lubricants from operational leaks and discharges would then
be about 130 million to 244 million litres annually.2
51 Data related to Propulsion systems, IHS Fairplay database
2 Etkin, Dagmar Schmidt. Environmental Research Consulting “Worldwide Analysis of In-Port Vessel Operational
Lubricant ,” Arctic and Marine Oilspill Program Seminar of Environment Canada, 8 June 2010, Halifax, Canada
DNV Report – Operational Oil
Discharges Not Effectively Regulated
6
• Prepared for Norwegian Maritime Directoratefor consideration of Development of a Mandatory Code for Ships Operating in Polar Waters
• Discharges from shipping during regular operation in polar areas
• Presented at IMO DE 54 (Aug. 2010)
As a potentially relative large source of operational oil discharge, however still not effectively regulated and of unknown exact magnitude, stern tube leakage should be addressed as a particular environmental aspect in the polar environment as well as in other areas. Of particular importance under ice operation is the potential for especially high leakage rates, and the proximity to ice with regards to deposition of oil.
7
Accidental Oil Leakage
• Typical causes of increased oil leakage from stern tube
seal damage:
Fishing nets or rope caught in the propeller
Propeller shaft misalignment or bent shafts
Aged or worn lip seals
Propeller contact
with ice or striking bottom
Accidental Oil Leakage
8
Rope and fishing line damage aft seals.
Lloyd’s Register reports on shaftline defect
statistics over the last 20 years: “interestingly,
aft stern seal and forward stern seal represent
43% and 24% of shaftline failures respectively.”
3 Smith, Andrew, Lloyd’s Register Global Technology Leader-Engineering Systems .,
“Shaft Alignment Problems Analyzed,” Marine Engineers Review April 2009, pp. 16
9
Accidental Oil Leakage
• CleanSeaNet… Using satellite
imagery to detect oil spills-Apr. 2007
to Dec 2008 in European oceans/
seas.
“4,027 possible oil slicks were detected and reported to the authorities. The percentage of CleanSeaNet detections checked on site by aircraft or vessels confirmed as being mineral oil may vary from one region to the other but can reach values as high as 80%
Marc Journal, European Maritime Safety Agency Bulletin 2009 CleanSeaNet: Satellite-based monitoring service for marine oil spill detection and surveillance in European waters, pp 48-51
10
Oil Slick Detections
via Satellite: 2008
European Maritime Safety Agency Bulletin 2009 CleanSeaNet: Satellite-based monitoring service for marine oil spill detection and surveillance in European waters, pp 48-51
Trading in US Waters?
• 2013 Vessel General Permit (VGP) regulates
discharges from commercial vessels in ‘US
waters’ effective Dec. 19, 2013
• Section 2.2.9: All vessels must use an EAL
“Environmentally acceptable lubricant” in all oil to
sea interfaces, unless technically infeasible
• EPA recommends that all new build vessel
operators endeavor to use seawater-based
systems for their stern tube lubrication to
eliminate the discharge of oil from these
interfaces to the aquatic environment.12 http://www.epa.gov/npdes/vessels
New Polar Code
• Development of a Polar Code for ships operating in polar waters
• Polar waters will be “zero discharge” areas under MARPOL Annexes 1
and 2 (oil and noxious liquids).
• The Code states: “Any discharge into the sea of oil or oily mixtures
from any ship shall be prohibited.”
• Polar Code enters into force:
January 1, 2017
13
Complex Shaft Air Seals
Are they the answer?• A major seal manufacturer states the following related to air seals
on their website:
However, since it is not possible to rule out circumstances in which
there could be a leakage, EALs must be used on this type of seal as well.
• Depending on seal manufacturer and EAL, the EAL will need to
be replaced either at 2.5 or 5 year drydocking (aggressive nature
of the EAL on seals)
14
http://www.simplexturbulo.com/2013/07/12/vessel-general-permit-latest-news/
Typical Piping of Air Seal
15
Air control unitAir source
(Control Air)
L.O. tank unit
Floatswitch
Stern tube
Stern tubeL.O. pump unit
Filter
Pump
Draincollection unit
Flow meter
Air
Oil
Slight amount of air
is leaked from here.
Aft seal
Cooler
Needle valve
Oil and vegetable-based EAL’s…
Still considered a pollutant Oil-based EAL’s are still considered a pollutant under the
Oil Pollution Act of 1990 (OPA ‘90) and US Clean Water
Act (if there is a sheen)
Any discharges of oil-based EAL’s still require reporting
of the discharge to the U.S. Coast Guard, as well as
having clean-up and remediation costs, if required.
Even though biodegradable lubricants may be deemed
non-toxic by OECD testing, their presence on the water
surface is a threat to seabirds
16
Seawater Lubrication
• Seawater as a lubricant dates back to
earliest days of shaft driven propellers
• Today’s seawater lubricated propeller shaft
lines quite different than those of 1940’s
18
Elastomeric
Polymer Alloy Bearings
• Toughness, abrasion resistance, shock loading
• Typically, 2:1 L/D ratio for AFT bearing and 1:1
L/D ratio for FWD position
20
21
Water Quality Package
• Designed to provide a clean supply of
water to the water lubricated bearings
Controlled environment
• Flow is monitored and low flow alarms provided
Removes abrasives
Improves bearing wear life
Self contained unit
New Lloyd’s Register Rules
for Water Lubricated
Propeller Shaft Bearings
• New SCM (Screwshaft Conditioning
Monitoring) Notation
For water lubricated propeller shaft bearings
Effective Jan. 2013
• If vessel is compliant, no shaft
withdrawal until 18 years from newbuild
23
New Bureau Veritas Rules
for Water Lubricated
Propeller Shaft Bearings
• Revised MON-SHAFT Notation
For water (and oil) lubricated propeller shaft
bearings
Effective Jan. 1, 2014
• The tailshaft need not be withdrawn
provided that all condition monitoring
data are found to be within the
permissible limits and remaining
surveys are complied with 24
Who Uses Seawater Lubricated Propeller
Shaft Bearings?
Over 600 commercial ships including…• COSCO (China) - 12 bulk carriers, 3 car carriers, 20 On order
• ConocoPhillips (U.S.A.)- 5 oil tankers
• Flinter Group (Netherlands) – 24 dry cargo ships
• Disney Cruise Lines (U.S.A.) – 4 cruise ships
• BC Ferries (Canada) - 10 ferries
• Carisbrooke Shipping (U.K.) - 8 dry cargo ships
• CSL (Canada) - 9 bulk carriers
• Staten Island Ferries (U.S.A) - 3 ferries
25
26
Carnival Corp. (U.S.A.) – 17 Cruise ships (108,000 to
115,000grt) equipped with seawater lubricated propeller
shaft lines. Two more on order.
Grand Princess has used seawater lubricated propeller shaft lines since 1998
Long Predictable Bearing Wear Life
Lower Life Cycle Costs
27
Newbuild Aframax tanker (640mm shaft diameter)
25 year vessel life
Life Cycle Cost Analysis
Seawater Lubricated
COMPAC Propeller
Shaft Bearing System
Oil Lubricated White
Metal Prop Shaft
Bearing System
Bearings, shaft liners, seal(s)
and related shaft line equipment $286,750 $193,500
Cost of Acquisition & Installation $286,750 $193,500
Cost of Ownership (25 Years) $134,000 $535,840
TOTAL $420,750 $729,340
Operational & Performance
Benefits• Zero Pollution Risk
Eliminate oil from the stern tube
• Controlled Bearing Environment
Water Quality Package
Allows for SCM & T-MON Notation– No shaft
withdrawal for 18 years with monitoring
• Technical equivalence
Viable alternative to oil lubricated white metal
propeller shaft bearings
28
Operational & Performance
Benefits
• Reduced Operating Costs• No Aft seal to maintain as there is no Aft seal
(water lubricated FWD seal only)
• Eliminate oil or oil-based EAL’s from the stern
tube
no purchase of oil; no storage of oil
no sampling of oil; no disposal of oil
no labour required to top up header tanks
no complaints about bad odour
• Maintenance of seawater lubricated propeller
shaft bearing system is very low
29