Oil line safty valve in the OPEN (oil flows) Position (C) 2013 Daniel FriedmanHow to Open or Shut an Oil Safety Valve
Operating guide for fusible link oil safety valves

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

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.

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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Green links show where you are. © Copyright 2017, All Rights Reserved.

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

Fusible link oil line valve (C) Daniel Friedman

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.

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 left) 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]

Oil line safty valve in the OPEN (oil flows) Position (C) 2013 Daniel Friedman Oil tank drain valve leak (C) Daniel Friedman

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 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


Continue reading at OIL LINE SAFETY VALVES, OSVs or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Suggested citation for this web page

OIL LINE SAFETY VALVE TURN DIRECTION to OPEN or SHUT at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman