LOUISIANA OFFICE FLORIDA OFFICE 3501 HOLIDAY DRIVE, SUITE #314 OCEAN-OIL P. O. BOX 47188 NEW ORLEANS, LA 70114 ST. PETERSBURG, FL 33743-7188 CELL (24 HOURS): (504) 367-4072 EXPERT WITNESS, INC. 566 VILLA GRANDE AVE. S. FAX: (504) 367-3790 ST. PETERSBURG, FL 33707 NAVAL ARCHITECTS and MARINE ENGINEERS PH: (727) 347-2556 Email: oceanoilpazos@bellsouth.net MARINE CONSULTANTS FAX: (727) 343-9717 www.siterrific.com/pazos CELL (24 HRS): (727) 415-7192 Email: hectorpazos75597@aol.com SLIPS AND FALLS IN THE MARINE AND OFFSHORE OIL FIELDS By: Hector V. Pazos, P.E., Naval Architect and Mechanical Engineer (www.siterrific.com/pazos) Copyright 2011 All Rights Reserved Because the exposure to the marine and offshore environments, slips and falls are a significant source of personal injuries on floating vessels and offshore equipment, probably the rate of personal injuries due to slip and falls in a marine environment is substantially greater than most industry groups. Although there are a good number of publications, books and articles written regarding the subject of slips and falls, there are almost none addressing the conditions found in a marine and offshore environment, which influence slips and falls. In floating vessels, the motions and the trim and list, influence the basic cause of slips and falls, and on offshore platforms or jack-up rigs, slips and falls are related to the oily environment that some times extends further than the drill floor. In both cases, the normally high humidity contributes to slips and falls and in some locations dust from coal or from chemical creates slippery environments. Glossary: The following glossary is included to avoid misinterpretations of the terminology used: Friction The force, which resists the relative movement of two surfaces in contact with one another, such as between your shoes and the surface you walk on. Static Friction The resisting force at the instant relative motion begins. Dynamic Friction The resisting force when movement is occurring without interruption. Dynamic friction is usually less than static friction. Anti-Slip Coefficient of Friction The ratio of the force required to move one surface over another to the total force vertically applied to the two surfaces.
The anti-slip coefficient of friction, is commonly identified as u : U = HORIZONTAL FORCE VERTICAL FORCE The static anti-slip coefficient of friction occurs at the point of action where the heel of the shoe makes contact with the walkway surface. In this case, if the anti-slip coefficient of friction is too low, the person generally falls backwards onto the buttocks. The dynamic anti-slip coefficient of friction involves the sole of the shoe coming in contact with the walking surface. and velocity. Momentum: The quantity of motion is a body as measured by the product of its mass Consensus: The generally accepted industry standard is that a static anti-slip coefficient of friction of.50 or above is safe on a dry walkway surface. A value below.50 indicates an unsafe walkway surface. There are some exceptions: The American with Disabilities Act Accessibility Guidelines indicates a minimum Coefficient of Friction of.6 for level surfaces and.8 for ramps. But this guideline should not be used alone when evaluating slip resistance. The influence of the footwear must be included. Also, the above consensus applies to same-level falls in floors that are, for all practical purposes, horizontal. But the floors or decks on a vessel are rarely horizontal. There is almost always some trim and list/sheer and camber and there are motions. Furthermore, there are localized structural deformations created during and after construction, which may affect the anti-slip coefficient of friction, and finally the presence of water, oily substances or powder, mostly on exterior walking/working areas is more common than in land-based facilities. Standards: The American National Standards Institute (ANSI) has recently created (2001) a standard for work place slips and falls, which was drafted by the American Society of Safety Engineers (ASSE) and is designated as A126.42: Standard for the Provision of Slip Resistance on Walking/Working Surfaces. 2
The American Society for Testing and Materials (ASTM) has a standard method for static coefficient of friction determination: ASTM C 1028-84, and several related standards developed thru many years, such as ASTM Standard F1677-96. There are other organizations such as Underwriter s Laboratories (U.L.) that have developed similar standards. Measurement: Over the years there have been several approaches to measure the anti-slip coefficient of friction. The simplest method is drag a shoe or boat filled with heavy items using a scale equipped with a large dial, and document the horizontal force required to drag the shoe or boat with a video camera to record the static and dynamic coefficients of friction. Various organizations in the USA and overseas have developed apparatus to measure slip resistance. Some measure the dynamic rather than the static coefficient of friction. The hard fact is that different machines may yield different results on the same test surface. Furthermore, the dynamics of a pedestrian s foot is quite different from the dynamics of a weighted object or a shoe being dragged across a surface. Instruments: There are many devices for measuring frictional forces. ANSI standard A1264.2 discussed the slip resistance testing of floors using four approved slip measurement instruments: Horizontal pull slipmeter (HPS). The HPS can be used only on dry floors Brungraber Mark II Portable Inclinable Articulated Slip Tester (PIAST) Brungraber Mark I Portable Articulated Sliptester (PIAST) Variable Incidence Tribometer (VIT) Despite of the above, it should be mentioned that no two-walkway material industries uses the same method of measuring slip resistance. The resilient tile industry method is different from the commercial floor polish industry. To attempt to correct this situation, the National Floor Safety Institute (NFSI - Beford, Texas) has developed a tester for wet Static Coefficient of Friction (SCOF) and provides a certification status when the value of the SCOF meets 0.6 or better. Other factors: There are other factors that have to be kept in mind when dealing with slip resistance. If an object such as a meter 3
(tester) is allowed to remain unmovable on a wet surface for a period of time, adhesion can develop between the object and the surface, resulting in high readings of the static coefficient of friction. Seemingly indicating that the wet surface is more slip resistant than the same surface dry. The Marine Environment in Dry Areas of a Vessel: There are at least three factors that affect any coefficient of friction that may be attempted to obtain in any dry area of a vessel, besides other factors in wet areas. 1. Fabrication tolerances of the decks on steel or aluminum vessels: The American Society for Testing and Materials has developed a standard guide for steel hull construction tolerances designated as: ASTM F1053/F 1053M-94, which presents permissible deviations, distortions, unfairness and construction inaccuracies in principal strength members in new construction of steel hulls. This guide is restricted to principal strength members and there is almost no provision for local waviness of deck plates. The waviness of deck plates can result in an increase or decrease of the measured coefficient of friction of 5 to 10%, when superimposed to alignment and distortion of the hull. 2. List, Trim, Sheer and Camber: The walk areas of a vessel are intended to be as horizontal as possible when the design condition is being developed. But there are infinite loading conditions, which result in any deck of a vessel not being horizontal at almost anytime due to list and trim. Additionally, most vessels decks have some sheer and camber. The combination of these factors may affect the measurement of the coefficient of friction by a substantial amount, depending on the location and the type of vessel. The forensic investigator should use plum bobs, protractors and levels to determine the influence of the trim, list, camber and sheet when investigating the condition of an area where a slip and fall occurred. 3. Vessel motions: A floating vessel is never at rest. Even alongside the dock, there are constant motions created by wind, currents, waves and wake of other vessels. The roll and pitch motions will affect the coefficient of friction being measured. Additionally, on the inside of the crew quarters, most of the slip and fall accidents occur in the kitchen, on vinyl floors that are usually waxed. In these cases, the victims appear to slip as they make a slight change in direction. 4
Very often, the presence of a mirror like shine is a tip off that the floor is too slippery. There are also dry locations where dust is a factor in slip and fall accidents, such as: a. The mudroom of drilling rigs, where dust from various dry chemicals spill from 50 lb. Bags resulting in slippery areas. b. Every location associated with transportation of coal. Coal dust is commonly found on decks of coal barges, tugboats, floating cranes transferring the coal from barges to vessels, and on the bulk carries transporting coal. The Marine Environment in Wet Areas of a Vessel: In addition to the factors mentioned for dry areas, there is one more factor of importance regarding slip and fall in wet areas where the amount of water is substantial: hydroplaning. The problem of hydroplaning has been carefully investigated both experimentally and analytically regarding rubber tires on pavement surfaces, but there have not been any mention regarding slip and fall on a wet deck of vessels, although the sole of a shoe in motion will have similar pressure buildup on the sole surface due to his collision with the standing fluid, than the pressure buildup on the tire surface, and therefore, hydroplaning can occur when a person moves fast on a deck where standing water is significant. The Shoe Selection: Footwear is critically important. A shoe s outsole is an important component in prevention of slip and falls. Shoes should be selected to be both, slip and oil resistance. The shape of the sole and the tread design of the outsole should create a condition that minimizes the possibility of hydroplaning. When the outsole squeezes the water away from the shoe, the possibility of hydroplaning is reduced. The outsole should have incisions that act as virtual hinges, resulting in a tread that feels as if it were composed of 3 or 4 movable sections. The incisions help to squeeze or move most liquid to the out edges of the outsole. Summary: The marine environment introduces several additional factors in the analysis of slip and fall accidents, not normally considered in studies of slip and fall situations in other industries. Therefore, the generally accepted industry standard that a value of 0.5 and above for the static anti-slip coefficient of friction may be safe on a dry walkway surface, in a non-marine 5
environment, but it may not be sufficiently safe in most marine environments. In general, floors should be textured for increased slip resistance. We have investigated a large number of slip and fall cases on vessels, offshore structures and marine related items such as containers. When the characteristics of the walking area do not support the contention that slip and falls occurred, other possible explanations for a fall must be considered. For instance, a passenger of an excursion vessel complained that the condition of the deck caused her fall and related injuries. Our investigation indicated that the area of the deck where the passenger claimed that the slip and fall took place could not be the cause of a slipping situation. The deck was textured, had practically no deformation and the motions of the vessel at the time of the accident were negligible. The vessel was alongside the dock. The finding triggered further investigation resulting in the final conclusion that the passenger was inebriated and fell to the deck when he was not walking. Several witnesses supported this fact, after finding that there was nothing wrong with the deck. Lesson learned: A slip and fall accident should not always be blamed on the condition of the deck. There are situations in which human interactions are the primary cause of slip and falls. About the Author: Hector V. Pazos is a Naval Architect, Marine Engineer and a Registered Mechanical Engineer and has been engaged in Accident Investigation/Reconstruction for more than 40 years. He has been retained as an Expert Witness in over 1,200 Maritime cases, related to both commercial vessels and pleasure crafts, for both defense and plaintiff. He has offices in St. Petersburg, FL and New Orleans, LA. He can be reached by phone at (727) 347-2556 or (504) 367-4072 or by email at: hectorpazos75597@aol.com and oceanoilpazos@bellsouth.net. For more information, please visit our website at: www.siterrific.com/pazos. 6