Safe Operation of Liquid Evacuation Compressors

Written by Steve Watson

The compressor is a great piece of equipment to use in evacuating liquid propane from the storage tank.  However, it must be used in a safe manner while following the manufacturer’s procedures and federal regulations.  Along with the manufacturer’s procedures, refer to Pamphlet # 58 of the NFPA (National Fire Protection Agency) Liquefied Petroleum Gas Code.  Locate Chapter 7 LP-Gas Liquid Transfer 7.1.1, through 7.2.4.5 and follow through the process listed.  Also, keep in mind that when evacuating liquid from the tank you must always be on constant alert of your perimeter and, be aware of the wind direction.

Propane is stored in steel storage tanks under high pressures. In everyday operation different scenarios come into play when handling propane gas.

Scenario 1

For instance, when operating the evacuating compressor, removing the product from a propane storage tank must be performed by a technician that has been properly trained and certified to do so safely.  There are times when you have to remove an ASME tank from a customer location due to either the customer changing companies or it needs repairs that cannot be performed at the location. Another scenario could be because of an emergency where the liquid needs to be evacuated in order to keep the situation under control. Underground tanks are also equipped with valving used to evacuate liquid from the tank. By law, the Distance when performing this procedure must be 25 feet from all sources of ignition and 15 feet from internal combustion engines.  Oh yea, Absolutely NO Smoking!! Also, a Dry Chemical Fire Extinguisher with a minimum of 18 lb. B: C or A: B: C rating needs to be easily accessed.

Scenario 2

There are situations where the tank cannot be evacuated for repairs that are normally done on-site.  It is a very dangerous operation when a volatile and flammable product such as propane exceeds the pressure of 100 psi or more.  When possible, in a safe mode with no leaks, a permit from the local authority having jurisdiction should be obtained to remove the tank and delivered it to your bulk plant facility so the liquid can be evacuated under safe conditions.

The ASME tank is equipped with the most popular Chek-Lok Valve with a cap (Rego part # 7590U). Prior to July 1961 you were able to connect to a filler valve that ran from a tube at the bottom of the tank. After July 1961, tank manufacturers made a separate valve called an Actuated Liquid Withdraw Excess Flow Valve for the liquid evacuation of domestic storage tanks. The new valve also has a tube that goes to the bottom of the tank.

When preparing to connect this valve to the Chek-lok Liquid Evacuation Adapter you have to remove the cap from the Chek-Lok on the tank very carefully (about one turn) or until the liquid escapes from the small bleed port on the cap. Once the liquid is escaping from the valve cap STOP TURNING THE CAP!!  After approximately 30 seconds or less all the liquid will have escaped.  Once the flowing stops you are all set to connect valve. Make sure to use the hoses listed and approved for the Liquefied Petroleum Gas service of 350 psi with 1,750 psi bursting pressure.

Maintenance is key in the safe operation of your equipment. Make sure before you start the compressor and when you shut down the compressor you check the oil levels. Don’t trust the site glass at bottom of the compressor. A dip tube comes with the unit to check the crankcase oil level. Always store your equipment in an easily accessible place so it can be used quickly in case of an emergency. Keep all hoses, fittings, valves and fire extinguisher ready to go.

GOOD LUCK! SAFETY 1^st.

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