Fire Safety Guidelines Regarding Hydrocarbon Solvents May 23 2017, 0 Comments

Guidelines are prepared by Terpp Extractors technical staff to assist users in reading and understanding safe practices, however, are no formal interpretations issued. Any opinions expressed are the personal opinions of the author(s), and do not necessarily represent the official position of Terpp Extractors. In addition, the guidelines are neither intended, nor should be relied upon, to provide professional consultation or services. The (AHJ) Authority Having Jurisdiction will determine the facility requirements for operation of extractors.

Butane is classified as Liquefied Petroleum Gas (LPG) by the International Fire Code (IFC), which invokes NFPA 58: Liquefied Petroleum Gas Code.

When working with any flammable solvents a potentially explosive environment can be created in the area. This stresses the importance of safety procedures that should be implemented to prevent potential accidents. These guidelines only pertain to fire/explosion hazards and do not encompass all safety procedures that should be integrated into the extraction process.

 

(1) Do not allow the flammable solvent to mix with air (oxygen).

  • A seal (such as a gasket) that does not leak under vacuum may leak with positive pressure.
  • A positive (air or nitrogen) pressure test should be performed on the entire closed loop system each time the extractor is assembled to ensure leak-free operation. If air can leak from the extractor, gas can leak out during operation and mix with air to possibly become an explosive mixture in the area.
  • A full vacuum should be pulled on the entire closed loop system before solvent introduction to ensure an oxygen-free environment is maintained in the system. Without oxygen, combustion cannot occur even in the presence of an ignition source.


(2) Eliminate all potential ignition sources in the environment.

  • Only intrinsically safe equipment should be allowed in the environment.
  • All electrical equipment should be rated for Class 1 Division 1 or Division 2 environments.  Electrical devices designed for laboratory use in a Class 1 environment will carry a NEMA 7 rating.
  • Ancillary equipment should be located in a separate room.
  • Take steps to reduce static electricity.
  • N-Butane's autoignition temperature is approximately 550 degrees Fahrenheit.

 

(3) Install an appropriate ignition-proof hazardous exhaust system.

  • The facility must provide adequate ventilation/exhaust as determined by the Engineer of Record in order to maintain the local atmosphere below 25% of the Lower Explosion Limit (LEL).
  • N-Butane's explosion limit ranges from 1.6% - 8.4%.
  • At a concentration in air lower than the LEL, gas mixtures are "too lean" to burn. Butane gas has an LEL of 1.8%. If the atmosphere has less than 1.8% butane, an explosion cannot occur even if a source of ignition is present. Flammable limits, like flashpoints however, are intended as guides not as demarcation lines between safe and unsafe.
  • Butane is heavier than air which means it can collect in low spots in the area.
  • If ventilation is inadequate, vapors can settle and collect in low areas like sumps, sewers, pits, trenches and basements. The vapor trail can spread far from the liquid. If this vapor trail contacts an ignition source, the fire produced can flash back (or travel back) to the liquid. Flashback and fire can happen even if the liquid giving off the vapor and the ignition source are hundreds of feet or several floors apart.

 

(4) Employ a hydrocarbon leak detector during operation.

  • An alarming hydrocarbon leak detector rated for the LP-Gas solvent being utilized should be used throughout the entire extraction process to ensure the local atmosphere is maintained below 25% of the LEL. 

 

(5) Appropriate PPE should be worn at all times.

  • Refer to LP-Gas solvent's Material Safety Data Sheet for more detailed information.

 

(6) Always have a fire extinguisher in the area.

  • A fire extinguisher should be available in the area at all times.