Bulldog probably had the best answer. bulldog - It is possible but I bet you would only do it once There are two or three big problems using the same tank for NH3 and LP. One is the problem Rupert mentions.rupert - I believe when going from nh3 to lp you have to have them cleaned real good. If i remember right the mixture of lp and nh3 creates some sort of lethal gas. Big no no when using tank for home/jobsite heating. Generally the cause is human error, either someone didn't do a good job of cleaning up before changing products or just put the wrong thing in the wrong place. Burning a mixture of the two may produce cyanide gas ... really nasty stuff. Not something you want to be around. Another is the effect NH3 has on brass. There was a relief valve failure on a propane storage tank several years ago at farm supply company. It sold both propane and NH3. Nobody could understand why it failed. The transport driver for the LP company I was working for said he knew what happened. He was setting in line one day with a driver from the company and got to talking about switching fromone product to another and how big a pain it was. Other driver said "Aw, you just blow off the pressure and change." They got some NH3 in the propane tank. Probably not a lot, but enough to eat up the brass in the relief valve. We routinely switched our trailer to hauling anhydrous in the Spring. Going to NH3 was simple, empty the tank, burn off the vapor, and load (I don't know about the relief valves. I assume either they worked for both products or were changed out). Going back to hauling propane we would empty it, depressurize it, partly fil it with water, drive it around to slosh it in the tank, drain it, blow fresh air in it, then once it was safe actually put someone inside with a pressure washer and rinse down the walls. After that we dried it, put the right amount of Methanol, and went back to propane. That is the RIGHT way to do it The third is a legal one. Rules and regs for propane and NH3 are different. I don't know if Fire Marshall approval is needed for an anhydrous bulk tank. I guarantee it is for propane. My friends at the OSFM have a great sense of humor, but not when folks blatantly and open violate safety rules. The inspector finds your NH3 tank being used for propane without the t's crossed and i's dotted, he may be courteous and smiling but you probably won't be smiling when he gets done. Oh, this doesn't relate to your bulk tank but fits the conversation. It may no longer legal to convert NH3 tanks to propane. This is a 5 year old edition of Pamphlet 58. Newer editions may have expanded the capacities. Also, states adopt 58 by date, so if your state has adopted and older version this may not apply to you. From Asmark Q. Can anhydrous ammonia nurse tanks that have been retired from service be converted and used for propane? A. The National Fire Protection Association (NFPA) formalized within NFPA 58, the Liquefied Petroleum Gas Code, a recommendation that except for containers used in cargo tank vehicle service, ASME containers of 3,000 gallons water capacity or less, and used to store anhydrous ammonia shall not be converted to LP-gas fuel service. NFPA recommendations are not considered to be a regulation unless adopted by a governing body, such as a city, state or federal municipality or agency.
Source: NFPA 58 Liquefied Petroleum Gas Code, 2008 Edition, Section 5.2.1.6 - 5.2.1.10, issued October 4, 2007.
Edited by Mike SE IL 6/17/2013 06:29
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Bulk NH3/LP tank question
