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COMBUSTION GASES & PARTICLE HAZARDS
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
FILTERS, AIR for HVAC SYSTEMS
FILTERS, OIL on HEATING EQUIPMENT
FIRE SAFETY CONTROLS
FLOODED HEATING EQUIPMENT REPAIR
FUEL OIL TYPES & CHARACTERISTICS
FUEL UNIT, HEATING OIL PUMPS
GAUGES ON HEATING EQUIPMENT
HEAT TAPE HAZARD ON OIL TANK
HEATING OIL CLOUD WAX GEL POINT
HEATING OIL EXPOSURE HAZARDS, LIMITS
HEATING OIL - OLD, USEABLE?
HEATING OIL SHELF LIFE
HEATING OIL SLUDGE
HEATING OIL TANKS
HEATING OIL TYPES & PROPERTIES
HEATING OIL USAGE RATE
HEATING SYSTEM INSPECT DIAGNOSE REPAIR
MANUALS & PARTS GUIDES - HVAC
NO HEAT - BOILER
NO HEAT - FURNACE
ODORS FROM HEATING SYSTEMS
OIL FILL & VENT PIPING
OIL FILL PIPE LEAKS
OIL FILTERS on HEATING EQUIPMENT
OIL FILTER MISSING
OIL FUEL TYPES & CHARACTERISTICS
OIL HEAT FIRE SAFETY CONTROLS
OIL LINE CLOGGING FIX
OIL LINE LEAKS
OIL LINE PIPING LEAK CAUSES
OIL LINE QUICK STOP VALVES
OIL LINE SAFETY VALVES, OSVs
OIL ODOR SOURCES
OIL PIPING CONTROLS, DEFINITIONS
OIL PUMP FUEL UNIT
OIL SPILL CLEANUP / PREVENTION
OIL TANKS, DUAL PIPING
OIL TANK GAUGES
OIL TANK LEAK & ODOR CAUSES
OIL TANK LEAK POINTS
OIL TANK PIPING & PIPING DEFECTS
OIL TANK LEAKS & SMELLS
OIL TANK PIPING & PIPING DEFECTS
OIL TANK PRESSURE
OIL TANK SLUDGE
OIL TANK SPILL CLEANUP / PREVENTION
OIL TANK WATER REMOVAL
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks
SAFETY, HEATING INSPECTION
SOOT on OIL FIRED HEATING EQUIPMENT
Guide to OSVs - Oil Line Safety Valves: this article describes check valves and fusible link oil safety valves used on oil piping at heating appliances as both a fire safety device and to assist in oil burner servicing. We explain the purpose of OSVs, which way to turn the OSV or oil line safety valve to open or close it, and we describe common oil line valve installation or use mistakes.
This article series explains the installation & use of OSBs, or Fusible Link Oil Safety Valves. We describe and explain the differences in function and use among fusible link fire safety valves (OSVs) like the Firomatic®, vacuum operated OSVs like the Webster OSV and Suntec PRVs, oil line check valves, Tiger Loop and other oil system air removing devices, and oil delay valves or quick-stop valves that are also referred to as oil safety valves.
We explain where each valve is installed and what it does. We include oil safety valve and check valve troubleshooting advice, and we describe defects in heating oil piping & control valves.
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What are Fusible-Link Oil Safety Valves (OSVs) - definition
The OSV or oil safety valve controls flow of fuel oil to the oil burner of oil-fired heating boilers, furnaces, and water heaters. This inline oil valve is intended to close automatically and thus stop the flow of oil in the oil line in the event of a fire.
Some suppliers use other names for this valve including the "Firomatic" valve (R.W. Beckett) or the "Oil Safety Valve OSVA-38" (Capital City Tool, Inc.).
[Click to enlarge any image]
Fusible Fire Safety Valves are designed to reduce fire damage by shutting off the flow of oil from the oil tank in the event of a fire. These valves conform to UL/ULC 842 and are listed in the US and Canada. They are required by code in residential oil heating installations in conformance with NFPA 31. - R.W. Beckett [4a]
[Click to enlarge any image]
When the oil safety valve is open to permit heating oil to flow its movable stem and thus its internal stop valve are under spring tension.
Because the valve includes a fusible link (a lead or other soft metal core), in event of a fire the fusible link melts and the internal spring pushes the valve stem down, closing the valve and stopping oil flow.
Closing the oil valve or OSV means that we stop feeding oil to the oil burner in the event of a fire in the area.
Usually the OSV is installed close to the oil burner both for safety reasons (close to heating equipment means close to a more likely fire source) and also for service convenience (minimizes oil spillage and maximizes convenience for the heating service tech working on the burner or oil filter).
In our photo you can see from left to right the OSV, an oil filter, and the fuel unit (oil pump) and air intake for the oil burner.
That vertical pipe below the fuel unit is the return line - so we know this is a two-pipe or two line heating oil set-up.
Sometimes additional stop valves or OSVs may be installed at other locations (such as at the outlet of an above ground oil storage tank), but the critical location is at the oil burner since that's a more likely location at which a fire may occur.
Watch out: the Firematic™ fusible-link automatic oil line shutoff valve (photo at left) should only be present on the oil supply line. We explain below at FIRE SAFETY for OSVs on 2-LINE OIL PIPING SYSTEMS that installing an OSV on the return line of a two pipe oil system can lead to disaster. Instead, where it is necessary to prevent leakage from the return oil line during oil burner servicing we can install a simple one-way check valve on the oil return line (if the oil burner's fuel unit manufacturer permits.)
Our photo at below left shows an example of a Firematic™ safety valve right at the oil burner. Synonyms people use for this valve include OSV, fire safety valve, oil line valve, Fire-o-Matic valve, Fusible link valve, oil line shutoff valve, oil safety valve, and Fireomatic valve.
The standard oil safety valve used at the oil burner and often found also at the oil tank is the Firomatic™ fusible link safety valve. The Firomatic® oil line valve can be installed in ANY position - (vertical, horizontal, upside down) at least that's what we were taught and what we have seen - the valve is spring loaded.
In a fire the fusible link, a lead core, melts at 165°F and a spring in the valve assembly snaps the valve shut to assure that the heating system does not feed oil to a building fire. It has to work in any orientation.
This list provides some of the companies produce fusible-link inline oil safety valves (OSVs). The footnote links point to the companies' contact information in our References section, but generally you would purchase an OSV from your local heating equipment supplier or plumbing supplier.
The current fusible link valve product properly named Firomatic is so widely also called "Firematic" and "Fireomatic" that we include those terms to assist readers in finding this information. Who manufactures the Firomatic fusible link valve? R.W. Beckett. Who manufactures vacuum-operated OSVs? Webster & Suntec (the PRV). We explain the differences among these products in this article series.
See OIL TANK PIPING & PIPING DEFECTS for a table of normal running vacuum levels in heating oil piping installations.
In our OSV photos below, the first photo (below left) shows the oil line safety valve in the OPEN position - oil will flow when the threaded portion of the valve shaft extends fully up through the rotatable knob pointed to by my pencil. [Click any image to see an enlarged version. Thanks to reader Bernie Daraz for pointing out the need for these two photos]
In our heating oil line valve photo at above right the valve has been manually CLOSED - no oil will flow. The threaded valve stem has disappeared down into the valve body and has shut off the valve and oil flow.
Watch out: if (for example in case of a fire) the fusible link inside of an OSV has melted permitting the spring to close the valve, then from outside the valve may look as if it is in the open position - the threaded stem will still be poking out - but the valve has snapped and closed internally. Most likely you'll know this also because there will have been a fire or other horrible event that melted the OSV fusible link.
Which Way do I Turn the Oil Line Valve to Open or Close it to Permit or Shut Off Oil Flow?
Other Oil Safety Valve SNAFUS & Warnings
Watch out: A simple oil line shutoff valve may not be a fusible-link safety valve. The simple shutoff valve might be any plumbing valve that can manually stop oil flow in the line, but it is not a safety device.
Make sure you've installed a fusible-link safety valve at each location where it's most needed - at each oil burner. Even when one of these valves is installed at the oil tank the proper place for this protection is on the fuel oil supply line
right at the burner as well. Why?
Suntec points out in their installation literature for fuel units (oil pumps for oil burners) that pressures over 10 psi on an oil inlet line (normally running at a vacuum) may damage the shaft seal on the pump - i.e., leak heating oil. [See OIL TANK PIPING & PIPING DEFECTS for a table of normal running vacuum levels in heating oil piping installations.]
SAFETY warning: If the oil line fire safety valves are missing or are not at the right location, we recommend immediate installation of a Fire-o-matic™ type oil line safety valve on the oil line at the burner.
The concern is that should a fire occur in the building, and should an OSV on the oil return line close before the OSV on the supply line, the fuel unit may over-pressurize the oil lines, causing a burst oil line that then sprays high-pressure oil into the fire, increasing its size and spread-rate.
Use an oil line check valve instead. Or if the heating equipment manufacturer recommends against using a check valve in the oil piping system (Suntec prohibits, Webster recommends) then leave it out.
The automatic oil line shutoff valve should only be present on the oil supply line.
Further explanation of the use or prohibition of check valves in oil piping systems is at OIL LINE CHECK VALVES.
Our photo (left, red arrow) illustrates this hazard: you will see fusible link safety valves on both the oil feeder line (blue arrow, left side of photo before the oil filter canister) and the oil return line (red arrow, right side of the photograph).
SAFETY WARNING: If oil line valves are missing or are not at the right location there is risk of system malfunction, oil leaks, and fire damage.
We recommend installation of a Firematic™ fusible link (Fire-o-matic)™ type oil line safety valve on the oil supply line at the burner. This valve controls flow of fuel oil to the burner, and has a lead core which melts and shuts the valve, stopping the flow of oil in event of a fire in the building.
Even when a fusible link oil line valve is installed at the oil tank, the proper place for this fire protection is right at the ol burner as well. A valve in that location also makes servicing the heating equipment easier, faster, and cleaner.
Details about vacuum-operated OSVs and the Suntec PRV that combines the vacuum-operated valve with an oil filter are at OIL LINE VACUUM-ACTIVATED OSVs & PRVs.
Here is a brief summary:
Unlike a fusible link OSV that shuts in response to high temperature to provide fire protection at the oil burner, a vacuum operated OSV opens only in response to a "sustained vacuum" created at its outlet end when the oil burner's fuel unit pump is drawing oil from the supply.
Vacuum-operated safety valves offer protection against oil line leaks and against overpressure conditions on the supply side of the fuel unit. They are not a fire-safety valve.
Protection against over-pressure from the supply piping prevents leaks at the fuel pump inlet or seals that might occur when the fuel pump is not operating but the supply piping is under pressure from the oil source.
Details about check valves used (or not to be used) on heating oil piping systems are at OIL LINE CHECK VALVES. Excerpts are here.
If two oil lines are used to supply an oil burner, (a supply and a return) install an oil safety valve or OSV or fusible link oil line shutoff valve only on the oil supply line at the oil pump on the oil burner. Do NOT install an automatic oil line shutoff on the return oil line between the oil burner and the oil tank.
If a protection against oil back-flow at the return line is a concern, and if the manufacturer recommends it, use a check valve instead. Check valves like this one permit oil to flow just in one direction. They do not close down in event of a fire. Installed on the oil return line a check valve permits oil to flow from the oil pump in one direction only: back to the oil tank.
[Click to enlarge any image]
Or as reader T.R. clarifies:
... I've been reading about TigerLoop oil fuel line de-aerators.
When they are used, the manufacturer recommends that the fusible valve near the burner be attached at the inlet of their de-aeration device.
Typically the oil line de aerator device such as the Tigerloop is installed at the same location as the oil filter - just before oil enters the fuel unit (oil pump), as shown in our photograph at left, provided courtesy of reader E.I..
Our photo, left, shows a Tigerloop™ installed at a property discussed in the Q&A link given just above.
Gas Line Safety Valves
Fire safety valves for gas fuel lines that can shut off fuel supply in the event of a fire are also available - see our separate discussion at GAS SHUTOFF VALVES or select a topic from the More Reading links shown below.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs) about Fusible Link Oil Safety Valves (OSVs) on Heating Equipment
Question: Freeing up a stuck oil line control valve?
I think I have a valve that doesn't seem to turn off when fully turned counter clockwise. Any idea why? - P.C.
If you have a fusible link valve that doesn't seem to turn off you might try tapping the exposed end of the valve stem. I have found a stuck, or slow to close OSV on a few rare occasions. A gentle tap, not hard enough to damage threads, loosens it after which I open and close the valve a few times to convince myself it now moves freely. A burr on the brass interior or more likely internal sludge or debris could be the culprit.
Because at the oil burner the OSV is likely to be used at least once a year during service, that's a good opportunity to discover if the valve is not closing fully.
Questions & answers or comments about heating oil control valves and fusible link safety valves
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