PVC Piping and Electrostatic Discharge in Hazardous or Classified Areas

On assessments performed in the last year, WEST has found many vessels have improper use of PVC piping in a classified or hazardous area. PVC presents an explosion hazard because it is non-conductive and susceptible to surface electrostatic buildup capable of igniting an atmosphere containing explosive gas or liquid mixtures. These installations were mostly on third party equipment, such as mud cleaning equipment. In some instances, the use of PVC was found as a permanent fixture of the rig's mechanical installation. This material has been found in drains, vents, waterlines, mud vacuum suctions, and chemical injection lines. Each of these installations has a distinct and dangerous effect on vessel safety.

Classification Societies have defined rules on the use of PVC material in hazardous areas. Vessel management and ship owners were not aware that the hazard existed. All of these installations had been passed by the various classification societies, and none had reported or listed the installations as a deficiency. Below are the rulings from the main classification societies prohibiting its use.

DNV Rules for Steel Ships 2002 Edition.
Pt.4 Ch.6 Sec.6 A
708 Plastic pipes are normally made of electrically insulating materials and are as such not acceptable for service in gas hazardous areas. Special conductive qualities can be permitted if in accordance with the following principles:

- Piping systems in or through gas hazardous areas, carrying conductive fluids are to be electrically conductive on the outside
-Piping systems in or through gas hazardous areas carrying non-conductive fluids, e.g. refined oil products and distillates, are to be electrically conductive on the inside and outside.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS 2002.

5.15 Electrical Conductivity
5.15.1 Pipe Conductivity
Piping conveying fluids with conductivity less than 1000 pico siemens per meter are to be electrically conductive.
5.15.2 Hazardous Areas
Regardless of the fluid being conveyed, plastic pipes are to be electrically conductive if the piping passes through a hazardous area.

USCG has several publications on the issue to try to make all ships in US waters aware of the danger of using PVC piping in hazardous or classified areas. Several of the occurrences are discussed in these publications:

Two other explosions occurred on tank barges at the pier. The first event was caused by a foreign non-conductive object in the tank that exploded while the barge was loading gasoline at the pier. The second occurred due to a non-conductive PVC wand was used for vacuuming operations while the tanks were being cleaned.

IMO MODU code issued later this year will include a section on electrostatic discharge. They are also publishing a specific formula to calculate and measure a safe conductivity level in plastic piping. DNV is currently working on a "world wide safety alert" to bring more awareness to the problems. This should be in publication in March of this year.

What is safe?

All regulatory bodies have regulations permitting the use of plastic in hazardous areas if they adhere to some specific specifications. PVC (polyvinyl chloride) is not approved. CPVC (post-chlorinated polyvinyl chloride) has a chlorine content high enough to meet the conductive standards of all the regulatory bodies.

This piping has the same ease of installation and looks of PVC; the writing on the side of the pipe has to be read to verify the composition of the material. Be sure the fittings are of the same materials. Remember on the Hollywood 1034, it was only a coupling!

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