Re: dechmounted propane tank?
Posted by: IDUNA
Date: May 5, 2011 11:25AM
Re: LPG Mechanicl ON/OFF Acturated Valve
Posted by: dwkayaks (IP Logged)
Date: May 4, 2011 08:49AM
Ahoy Rod ,,, It is V important that you also state just why you went to all this work , to be able to "shut off or turn on" , the outside gas supply, from inside the cabin .
You must have already discovered that a 1/4 turn on the tank valve was enough to allow a full supply of gas , but I would like to know why I have always been opening the valve fully, for so many years ?
Was it just habit or poor instruction from gas suppliers ?
What ever,,,, it is still important that you bring this subject to the attention of all owners .
Re: LPG Mechanicl ON/OFF Acturated Valve
Posted by: IDUNA (IP Logged)
Date: May 4, 2011 10:22AM
IDUNA is fitted with two 20 lb horizontal mounted LPG tanks (came with boat).
The starboard tank is connected to the galley stove. This system is fitted with a Blue Seas solenoid shutoff valve. ABYC specifies a LPG shutoff valve must be mounted outside the cabin and the shutoff control must be within arms reach of the service. Considering the galley is located by the companionway and the LPG tank is forward of the cabin house, we opted to using a solenoid shutoff valve instead of designing and building a complex mechanical shutoff. The control switch for the solenoid in located by the stove, i.e. within arms reach of the service.
The port tank supplies the Dickinson P-9000 heater. This is located on the port side of the cabin and is mounted on the bulkhead separating the fo'c's'le from the main saloon. We choose to use a mechanical actuated shutoff valve for this service for the following reasons:
1) Required no amps,
2) Could be located within arms reach of the service,
3) Was failure proof compared to a solenoid shutoff valve
4) I like to design and build mechanical "stuff"
5) Because of where the LPG tank and heater were located, it was practical to install a mechanical shutoff.
The amount of work to build the system was less than you may imagine. Designing the system probably took more time than building and install the system. I also have a friend who had access to a machine shop. He offered to make the yoke for me. I could have made the yoke out of brass, garolit, delrin, etc. using a drill, hacksaw, files and taps. I receive great joy from solving engineering problems and building solutions. It's just my makeup. The system is not complicated and is not difficult to build.
The valve on an LPG tank is not a throttling valve, i.e. it's either "open" or closed. In the chemical business, the standard for these valves is to open them all the way then close the valve 1/4 to 1/3 turn. This practice allows "back and forth play" on the valve should it become stuck. I recommend this practice for LPG valves. I suspect, the recommendation to always open a LPG valve fully, came into practice to ensure the valve was open.
As I stated before, gasses have very low viscosity and require only a small differential pressure across a valve or restricted opening to achieve a high volume of flow. The amount of fuel a galley stove or cabin heater requires is minimal. You can demonstrate this by lighting a stove burner then turning off the solenoid valve. It take awhile before the burner goes out. Considering the volume of the gas line from the solenoid valve to the stove is small, the burner requires very little fuel. This also holds true for the P-9000 heater. The P-9000 burns 20 lb of fuel per 100 hours when set on high or 0.05 oz of fuel per minute. At standard temperature and pressure, the volume occupied by 0.05 oz of propane is 0.7 l (700 ml) about the volume of 1 wine bottle. This is the reason 1/4 turn open works - low volume demand.
Thought about LPG systems:
When we purchased the boat, the stove shutoff valve was located in the cabin near the stove - simple, cost effective and almost failure proof. The only reason we installed a ABYC system was for insurance purpose.
We always turn off the shutoff valve to a service and burn the fuel in the supply line up. The practice also tests if the shutoff valve is operational or has failed.
Should we every go cruising, I plan to have a spare gas regulator and solenoid valve on the boat.
When we purchased our Blue Seas LPG solenoid valve and breaker switch, The breaker switch was fitted with a 5 amp breaker. LPG solenoid valves require less than 1 amp to open. It takes about 10 to 20 seconds for a breaker to open. Should a short occur in the solenoid, the solenoid will "burn up" before the breaker opens. I discussed this with Blues Seas They sent me a 2 amp breaker.