Oil Line Safety Valve (OSV) controls: this article explains how to open or shut the oil line safety valve used on oil fired heating equipment.

In our oil safety valve photo at page top the OSV is in the OPEN position - the telltale indicator is that the screw is visible protruding up through the top of the silver-gray valve handle.

We illustrate how to determine if the valve is already open or shut and we explain which way to turn the valve control knob to open or close the OSV.

Which Way do I Turn the Oil Line Fire Safety Valve (OSV or Firematic Valve) to Open or Close it?

Reader Question: Can you tell me what position the stem should be in to use the valve as a manual shutoff

— when the handle is turned to screw the stem IN the handle comes off as the stem goes into the valve body

— when the handle is turned to move the stem out of the body it reaches end of travel with ~1/4’ of stem exposed

— I want to shut the valve to change the filter feeding the furnace

- Thanks S.N.

 

Reply: Which Way do I Turn the Oil Line Valve to Open or Close it to Permit or Shut Off Oil Flow?

S.N. Our pair of photos just above at OPEN or SHUT POSITION of OSVs show how to tell if the OSV is open or shut. Details are below.

Fusible-link oil line valves such as the Fire-o-Matic valve work opposite from usual plumbing valves - that is, internally, because of the "reverse-threaded" valve stem, these oil line control and safety valves seem to operate backwards from what you'd expect.

• To Open the OSV - let oil flow: turn the oil line valve counter-clockwise (left to right - in the direction of my finger to OPEN heating oil fuel flow. The threadsOn this part are cut opposite from usual plumbing shutoff valves. As you turn the valve handwheel in this direction the threaded valve stem will protrude upwards through the rotating knob. Oil will flow when the valve is open. In my photo the valve was about half-way open.
  
  When the valve stem protrudes fully up through the turn-knob as far as possible you have compressed an internal spring inside the valve, and the valve is open to let oil flow. The handwheel actually feels "tighter" (as you are compressing the spring) and the handwheel moves down against the valve body as the valve opens.
• To Close the OSV - stop oil flow: rn the Firematic type OSV clockwise (right to left) to close the valve and stop oil flow. As you turn the valve handwheel or knob in this direction (opposite to the direction my finger is pointing) the valve stem will disappear down into the valve body, pushed by its internal spring. You are closing the valve - oil will not flow.
  
  The handwheel feels increasingly loose as you close the valve and it moves up away from the valve body.
  
  When the turn knob is rotated so that the valve stem moves down through the knob until the stem end is flush with the knob top and the knob is loose, the valve is fully closed and oil will not flow.

Watch out: if the control valve on a heating oil line is not a fusible-link safety valve such as the Fire-o-Matic™, it will probably be an ordinary plumbing stop valve that works as all plumbing valves: clockwise closes those valves by moving the valve stem down and counter-clockwise to move the valvestem up opens them. Sometimes we find a common stop valve on the oil line at the oil tank and a fusible-link safety valve just at each oil burner.

Details About Fusible Link Oil Line Valve Turning Directions to Open & Close the Valve & How the Valve Works Internally

An internal spring pressure, combined with a fusible link in the valve stem are what shut the oil line valve in event of a fire. In this design, when the valve is open to permit heating oil to flow it is also under spring tension. Because the valve includes a fusible link, 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.

Oil Line Valve Turned fully CCW (left to right) to Open Position = oil can flow

As you turn the handle on the oil piping safety valve counter-clockwise you will feel increasing spring tension as you are opening the valve (lifting the stem out of the valve body) against the spring pressure.

Because of the use of "reverse" threads on the valve stem, when you turn the OSV knob counter-clockwise the underside of the control knob, remaining in contact with the surface of the valve body, causes the valve stem to move up (against pressure of the valve's internal spring) until the threaded stem protrudes fully through the knob and you cannot turn the knob any more. In my photo the valve is about half-way open.

When the valve is fully open to permit fuel flow, the valve stem is "all the way out" of the valve body and the valve is being pushed-on by the internal spring. In this position the valve's knob has been turned clockwise, all the way down against the body of the valve.

When this oil line fusible-link valve is completely open to heating oil fuel flow, the valve stem is screwed all the way up "out" of the valve body. As you turn the valve knob clockwise you'll feel it moving against the internal valve spring pressure and you will see the valve stem moving up and out through the center of the oil valve knob.

Oil Line Valve Turned fully CW (right to left) to Closed Position = oil cannot flow

When the oil safety valve handle is screwed clockwise (right to left) so that the threaded rod has disappeared fully down into the valve body the valve handle will become loose and the valve internal components will be in the closed position - heating oil fuel will not flow.

Because of the use of "reverse threads" on the valve stem, when you turn the OSV knob clockwise , as the knob itself remains in contact with the valve body, the spring-loaded valve stem will move down into the valve body, closing off the oil flow.

As you turn the oil valve knob clockwise you will see the valve stem move back into the valve body and you will feel the spring tension on the device lessen.

For the last few counter-clockwise turns on the valve stem/screw you should feel a complete release of tension of the spring mentioned just above and if you keep turning the valve knob counter-clockwise it will unscrew and come off. Don't panic if this happens. The threaded portion of the valve stem protrudes up through the valve body and you can simply screw the knob back on.

How to Tell if the Oil Line Safety Valve (OSV) is OPEN or SHUT

In our OSV photos below, the first photo (below) shows the oil line safety valve in the OPEN positin - 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 below 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 likelyl you'll know this also because there will have been a fire or other horrible event that melted the OSV fusible link.

Summary of Oil Line Control Valve Open & Closed Positions

Put another way: if you turn the oil line valve until the handle begins to come off, the valve is in the CLOSED position. You will see that at this point you have removed all tension against the valve's internal spring and the spring has pushed the valve shut or closed. The valve stem has moved into the valve body.

If you turn the valve against its spring tension the valve is in its OPEN position. You will see that in this position you have turned the valve against its spring tension - the spring tension is increased - and the valve is open. The valve stem has moved out of the valve body.

We discuss using this valve for service to shut off the oil supply in our article on heating fuel oil filters found

at OIL FILTERS on HEATING EQUIPMENT where during heating equipment oil filter servicing the valve is used to close and later open the oil line feeding the oil burner

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

OSV Position: "No stem showing = no oil"

This is such a helpful article ! Thank you . After reading it I've concluded - ' no stem , no oil ' so I just remember that as I gently turn the valve handle ;
if the stem is up out of the valve then I know the oil will flow .

When I want to do work on my furnace I then gently turn the valve handle until there is no
more stem/threads above the turn handle - hence 'no stem, no oil flow ' and I know the oil flow is stopped so I can safely change the filter , etc . On 2020-09-21 by Skip

by (mod) - OSV stem position: NO-STEM = NO OIL

Skip

Thanks so much; what a great way to remember which way to turn the fire-o-matic valve stem: NO STEM = NO OIL - if you don't see the valve stem poking up through the knob then the valve has been closed.

What's the best way to bleed out the air from the oil filter?

What's the best way to bleed out the air from the filter? I've bled the burner which is after the filter, should I also bleed the filter/filter housing as well by getting the furnace to call for oil, or does bleeding the burner essentially take out any air in the loop? On 2020-06-25 by Jeff

by (mod)

Jeff

Please take advantage of the INDEX to RELATED ARTICLES given above as there you'll find articles giving a much more complete and better organized answer to your various questions than I can offer by typing it over again "off the cuff" here.

For example you'll find OIL FILTER CHANGE STEPS

and you'll see that there is usually an air bleed screw right on the oil filter,

but there is also an air bleeding procedure used by a service tech right on the fuel unit itself. That procedure will eventually remove all of the air from the filter and piping provided that there are no leaky fittings. But in my training we learned to first bleed at the filter manually, probably just to get a big part of the air out of the system first, avoiding having to keep forcing the burner to run without ignition (that's potentially dangerous).

Watch out: if you are not trained and familiar with how to perform all of those steps correctly you risk not only poor oil burner operation but a possible puffback explosion that can be caused by leaving air in the oil system or by an improperly-adjusted oil burner. In the old days we could "tune" an oil burner by eye and a bit of spit but modern high speed burners need to be adjusted using training and equipment such as CO2 or O2 measurement, smoke measurement, draft measurement, and temperature measurement.

If you're up for those steps, that's great.

by Jeff

Thanks! I kind of freaked out a bit after changing the filter wondering why when i opened the valve no oil was coming through. I thought I just turned my dollar saving filter changing exercise into an expensive service call....

When my oil burner OSV is "OPEN" oil doesn't seem to flow

My valve looks the same as this but when it is in the Open position it doesn't seem that oil flows through on it's own, but when I turn the boiler on and there is a call for oil it is definitely going through.

I discovered this as I went to change the filter and wanted to open the valve to release any air that may have been in the line, but with the valve open no oil was flowing, only when the boiler is on and calls.

Is there something special about how this has been setup that it would do this? On 2020-06-25 by Jeff -

by (mod) -

Is the oil tank oil level below the fuel unit?

Is there a check valve?

Was there a vacuum test of the fuel line?

Is it a 1 line or 2 line system?

Is the valve open as per the article above?

by Jeff

I don't know if I know the answers to those.

The oil tank level may in fact be slightly below the boiler. Tank is in the garage, the mechanical room I believe is slightly elevated above that.

Where would a check valve be located? The system looks like it is a 2 line system.

I don't know what a vaccum test is =(

I believe it is tank->supply line-> OSV -> in to filter -> out to the burner, then another line that appears to go out (which seems to me to be a 2 line?), no other valves in that setup that I saw.

Sorry forgot to add yes I have turned the valve completely counterclockwise all the way to the point it does move anymore and the stem is fully exposed. I've also turned the furnace on and bled the burner so it appears that there is absolutely oil going thru the lines when the furnace is calling.

by (mod) -

Jeff

In a two-line oil pipe system one line supplies oil to the fuel unit and the other is a return back to the oil tank. On that installation you to actually C300 oil pipes the supply of oil coming in through the filter, the return line to the tank, and a smaller-diameter high pressure line that feeds oil at high pressure out of the fuel unit and into the oil burner.

My point about tank elevation was that It's Perfectly Natural that if the take oil height is not above the height of the fuel unit you won't feed oil by gravity to the fuel unit but when the unit runs is perfectly capable of lifting oil, typically up about 6 feet at Max, or lifting even higher in a two line system.

OSV valves work in the opposite direction from a typical water valve

So....left to right is CLOCKWISE,,,,,right to left is COUNTERCLOCKWISE.....to CLOSE the valve you rotate counterclockwise and allow the inner spring to close the valve.

To OPEN the valve you would rotate clockwise and provide a counterbalance to the spring. On 2020-04-12 by Lou

by (mod) -

Sounds right; in sum these valves open & close opposite of a normal water valve.

Clarify: "tightening the OSV" is "opening" the valve

I think you've got your open and closed backwards, you seem to say the same thing for both normal valves and firematic valves ( See under watch out Clock wise is open ccw is closed ?) Confusing. While under summary, you have it correct. On 2016-10-19 by Kathy Sandlin

by (mod) - the OSV valve feels like it's being tightened when you're actually opening it - against spring pressure

Thanks for the note Kathy. It is confusing.

Counter-clockwise turning of the handwheel on an OSV feels as if you are "tightening" the valve and the valve stem moves "up" through the handwheel - fully CCW opens the valve and oil can flow. The valve stem is "reverse threaded" compared with normal plumbing valves.

A plumbing valve also "opens" in the counter clockwise direction but its threads are cut in a standard direction.

OSV leaking around the valve stem

I have a valve that is leaking around the stem. Is it possible to rebuild or repair the valve with out taking it off ?On 2016-04-07 by brian

by (mod) -

The valve core may be replacable but you'd need a way to shut off the oil supply, make the repair, then bleed the air from the whole system.

Typically it's quick and easy to ask your heating service company to handle the job.

First try GENTLY tightening the valve stem nut.

Watch out: if you break it off you'll have a financially ruinous oil tank flood in your home so take great care. If some fool does snap off an oil valve and can't otherwise shut off oil flowing from an above ground oil tank, for an emergency repair just bent and crimp the copper tubing to stop the oil flow.

How to work on oil piping when you can't shut off oil flow from the tank

Question: I have a fire-O-matic valve attached directly to the oil tank: it's now open and the furnace is running fine. I would like to close the valve and replace the downstream filter element.

But when I turn the handle in either direction the stem turns with the handle.

In other words, I cannot close the valve. I've tried the tapping on the end of the stem approach mentioned in the stuck valve section, but to no avail.

I'm thinking that vice grip pliers on the stem threads is a bad idea, but I also think that holding the stem to prevent it from turning will be necessary to free the handle to allow it to turn relative to the stem.

The only thing I can think of is carefully using a hack saw to cut a screwdriver slot in the end of the stem. Thoughts? Other ideas? On 2014-09-18 by RC in VT

by (mod) -

RC

You describe an irritating problem indeed. If the oil safety valve simply won't close you're at least lucky to continue to have heat. The solution is to use up oil in the tank, have its remains pumped out, then replace the valve.

But a service tech might try this stopgap measure to allow you to continue to service the oil burner before that repair:

- the oil line is "frozen" using an appropriate spray such as liquid CO2

- the line is cut near the oil tank (or near the oil burner where an OSV valve should be anyway) and a second new working valve is installed on the lines.

I suppose a very confident plumber with help from an assistant might try putting down a pan, trying to fix the valve while spilling oil, but given the trouble of cleaning up an oil spill that live approach makes me nervous.

I haven't seen it used on an oil line and there might be problems, but plumbers also use a heat soluble plug that can be jammed into a pipe to permit repairs, then dissolving the plug with heat.

Finally, in San Miguel de Allende I met a clever city plumber who showed me how he was able to replace a broken water supply pipe between the water main and the building by using a clever home made tool that inserted into the "live" pipe.

Turning a tee handle the plumber could enlarge a rubber grommet to stop water flow, allowing compression fittings or other connectors to be installed around and on the damaged pipe.

You can see the tool I describe at

https://inspectapedia.com/plumbing/De_Winterize_Buildings.php#PipeRepair

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.

Reply:

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.\

 

Question: What is the difference among all these different kinds of valves used on oil piping and at the oil burner or oil tank

What is the difference among all these different kinds of valves used on oil piping and at the oil burner or oil tank: check valve, fusible link valve, fire-o-matic type valve, vacuum operated valves, quickstop valves, solenoid valves, and oil delay valves. It's really confusing.

Reply:

We agree that there are enough valves and enough similarity in their names that the controls used at oil tanks, on oil piping, and at the oil burner to manage the flow of oil can be confusing. Worse, valves that do different things and have different purposes may all be called "oil safety valves" in marketing and technical literature.

Don't confuse the built-in check valve in the fuel unit with external check valves, fusible link oil safety valves, solenoid operated quick-stop oil valves, and their sisters, solenoid operated oil delay valves.

• See OIL SUPPLY & RETURN LINE CONTROLS & VALVES for details

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Continue reading at OIL SUPPLY LINE SAFETY VALVES, OSVs - home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• OIL SUPPLY LINE SAFETY VALVES, OSVs - home
• OIL SUPPLY LINE CHECK VALVES

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING OIL, OIL BURNERS, OIL FIRED HEATERS, OIL TANKS

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