oil safety valve location brands

R.W. Beckett’s burner controls were created with customer satisfaction and safety in mind. Our entire suite of burner controls utilizes the most current technology to safely control the combustion process.

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.

How & Where do We Install a Fusible-Link Firomatic™ Type Oil Safety Valve? 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.

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.).

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]

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.

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

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.

In particular, the OSV shown here is installed between the oil filter canister and the fuel unit intake port. That means that it would be impossible to service the oil filter without spilling heating oil unless the service technician finds another oil line shutoff valve somewhere between the oil tank and the inlet side of the oil filter.

With the shutoff valve between the filter canister and the oil burner (above right), changing the oil filter in the canister will require the service tech to go to the more distant oil tank to find and close a valve in that location (if one is even present).

The technician moved the Fire-o-matic OSV to its proper location at the inlet side of the oil filter, and he also installed a Firomatic oil line check valve between the oil filter and the oil burner.

This is an important fire-safety detail as in event of a fire a closed valve on the return line (if it closes before the OSV on the supply line) could cause blowing seals on the oil pump or a blown oil line fitting, spewing fuel oil over the building fire.

In sum, the proper place for the fusible link oil valve (Fire-o-Matic Safety Valve™ for example) is on the oil supply line just before the inlet to the oil filter canister (red arrow, below left), not between the canister and the oil burner as shown at below right (orange arrow).

Below is another two-line oil system showing the OSV on the inlet side of the fuel filter canister just ahead of the oil burner and the oil return line exiting from the bottom of the fuel unit.

Regarding "the best location of an oil filter", NFPA 31 (2011): 7.5.8, for indoor tanks up to 330 gallons, requires that a thermally activated shutoff valve be placed inline as close as practical to the outlet from a tank and that a proper filter or screen be installed downstream and WITHIN SIX INCHES of the required thermally actuated valve. If it"s required in the code, it doesn"t have to "the best" - it just has to comply with the code.

Many oil heat technicians sensibly want to install a fusible-link oil supply line valve at the oil burner, not only because this makes servicing the oil burner easier but because it also recognizes that the most-likely location of a fire is at the oil burner rather than possibly at a more distant oil storage tank.

The photograph above shows the right location for this safety device: at the input end of the oil filter. This permits the service technician to conveniently turn off the oil supply inorder to change the oil filter cartridge.

The writers of NFPA 31 (2011) 7.5.8 as specified above were focused on safety including wanting to avoid oil spills from the tank, but they might also have recognizede that putting an oil filter at the oil tank protects the oil line (between tank and oil burner) from sludge-clogging.

(Jan 23, 2014) oilman said: Your info is wrong. The filter belongs on the tank so it also protects the oil line. If you must install at the burner, it must be piped at least 12" from the pump. Hence why they make 12" flexible oil lines.

Reply: We agree that there is an advantage to protecting the oil line. However some HVAC instructors (including mine) teach that if the filter is not installed by the burner it is too often forgotten at service time.

When the oil tank is a bit more remote - across the garage and buried by the homeowner"s stored surfboards and hiking boots and boxes of tax receipts, the service tech enjoys being able to find the oil burner. Having inspected several thousand heating systems, my [DF] experience is that most of the time the OSV and filter are installed where they are convenient for service - which is usually close to the burner, notwithstanding the very good reasons for locating a filter at the inlet end of the oil line.

Our OPINION [DF] is that if the technician installs an OSV at the oil burner (and ahead of a filter if one is installed there), s/he should install a second OSV on the same oil supply line at the outlet from the oil tank, particularly if the oil tank outlet piping exits at the tank bottom, and ahead of the oil filter (if that"s where it"s installed).

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.

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

In the event of a fire, if the return oil line valve closes before the supply line oil valve your oil burner pump may burst the oil line or it may cause a fuel pump gasket or seal to fail, leading to uncontrolled oil flow and perhaps worse, spray heating oil everywhere, possibly feeding the building fire.

Thanks to Dave Ferris for this fire safety tip and thanks to reader Rick Johnston for adding clarification. (Note that not oil burners use both an oil supply and oil return line between the oil tank and oil burner.)

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.

Watch Out: 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

Recommended (red arrow, photo above left): an automatic oil line shutoff valve on the oil supply line right at each and every individualoil burner: (a type that will shut off oil supply to the heating equipment in the event of a fire, such as a Fire-o-Matic™ valve) is shown in our photo at left.

By every oil burner, we mean for example that if your heating system and also your hot water heater each has its own oil burner then each burner should have an oil safety valve. (As in our photo above left).

A common but poor practice is to install an oil valve just at the oil tank or perhaps installing a single oil safety valve at the oil burner for the heating boiler but omitting the oil safety valve for the oil fired water heater in the same building.

A second oil line shutoff valve on the oil supply line at the oil tank (photo above right) is ok as long as you have also provided the first oil safety valve at the oil burner(s).

Some service technicians install a second oil safety valve at the oil tank or at another remote location away from the oil burner, such as at the building wall where an outdoor oil tank line enters the building, or right at the oil tank (photo at above right - this oil tank valve is leaking).

This second valve is helpful if it becomes necessary to replace the oil line between oil tank and oil burner. Although our photo above shows a fusible link oil valve at the oil tank, the oil line shutoff valve at the oil tank or at a location remote from the oil burner or other more likely fire sources can be a normal plumbing stop valve.

However a common exception we see in the field is an OSV at the oil burner and a second OSV (or perhaps a simple shutoff valve, not thermally linked) at the oil tank end of the oil line.

Teflon tape at OSV threaded oil line or fuel unit connections: Webster"s instructions and some other manufacturers also specifically warn: Do Not Use Teflon Tape. Use of teflon tape voids all warranties. (Webster 2011)

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.

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).

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.

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.

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..

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.

AFL Industries, AFL OIL STOP VALVE PRODUCT BULLETIN [PDF] AFL Industries, 1101 West 13th St., Riviera Beach FL 33404 USA, Tel: 561-844-5200 includes OSV installation instructions for the contractor.

Bursey, Charles, "The Oil Safety Valve (Service)", Charles Bursey, Sr., Fuel Oil News, February 2006 (Still trying to get the full article - October 2008 - DF) Charles W. Bursey Sr. can be reached at F.W. Webb Co. www.fwwebb.com/

Cleanburn Energy CLEANBURN MULTI-OIL FURNACE OPERATORS MANUAL [PDF] (2009) Clean Burn Energy Systems, CLEAN BURN, INC. 34 Zimmerman Road Leola, PA 17540 U.S.A. includes Oil Safety Valve Installation Instructions

R.W. Beckett (U.S. & Canada) Firomatic Fire Safety Valves Beckett Corporation produces /distributes a wide range of oil burners & oil burner accessories * equipment including the oil safety valve (OSV) referred to as Firomatic® fusible fire safety valves, oil line check valves, and fusible link thermal switches

Beckett"s Firomatic® OSVs are provided in both 3/8" and 1/2" sizes and in flare and threaded designs. OSVs are provided designed for installation at the oil burner and in a different model at the oil storage tank.

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 U.S. and Canada. They are required by code in residential oil heating installations in conformance with NFPA 31.

All[Firomatic® fire safety] valves are embossed with the direction of oil flow and include unique part number identification ring on each valve. The seal stem uses a double seal washer/o-ring system with high grade Viton® equivalent materials suitable for No. 2 fuel oil, kerosene, and jp to 205 biodiesel blend.

Oil under pressure or vacuum is supplied to the inlet of the PRV valve. Vacuum is required at the outlet of the PRV valve to open it and to allow oil to flow. When a burner starts, the pump will supply the vacuum necessary to open the valve. Any leak in the system which prevents vacuum from being exerted on the outlet port of teh valvewill prevent oil from flowing.

ISP Automation, Firomatic Globe Type Oil Line Valves & Lever Type Fusible Link Control Valves: ISP Automation, Inc., 1035 Old Georges Road, North Brunswick, NJ 08902, Phone: 866-383-3481, FAX 866-383-3482, Email: support@ispautomation.com http://www.ispautomation.com/

Webster "Service Technician"s Handbook, Webster Fuel Pumps & Valves" [handbook]. Webster Fuel Pumps & Valves, Capitol City Tool, Inc., http://www.websterfuelpumps.com/ , Division of Capital City Tool, Inc., Op. Cit.

Webster, OSV SERIES OIL SAFETY VALVES DIMENSIONS & SPECIFICATIONS [PDF] Fuel oil safety valves, Webster Fuel Pumps & Valves, web search 10/12/2011 original source http://www.websterfuelpumps.com/pdffiles/osv1.pdf

Webster, "Dimensions & Specifications, OSV Series Oil Safety Valves, OSVA 38, OSVA 50", Webster Fuel Pumps & Valves, (1980), Op. Cit. retrieved 2/24/2014, original source: http://www.websterfuelpumps.com/pdffiles/osv1.pdf

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.

RW BECKETT RECALL for FIROMATIC 1/2" FEMALE PIPE THREAD FUSIBVLE SAFETY VALVE [PDF] P/N 12130 - the stem may not travel far enough to shut off the flow of fuel if exposed to trip point temperature. Posted until 4/1/2017, retrieved 2019/10/09 original source: https://static.globalindustrial.com/site/pdf/RW_Beckett_Firomatic_Female_Pipe_Thread_Recall.pdf

Excerpt: Recently, we became aware of a design deficiency in our ½” ‘Firomatic’ Fusible Safety Valve part number 12130. This bulletin covers ONLY the ½” FPT version p/n 12130, previous p/n B200F.

Under certain conditions, if the valve is exposed to temperatures exceeding the handle’s temperature rating and the valve ‘fires’ or actuates, the stem may not travel far enough to properly seat the valve and shut off the flow of fuel. This could result in a dangerous situation if there is a ruptured fuel line downstream of the valve. There have been no reports of this situation arising, but the potential for this issue to occur does exist. This does not affect the valve’s operation when used as a manual shut off valve.

The current design of the 12130 – ½” FPT valve and handle assembly was in production prior to R W Beckett’s acquisition of the Firomatic® product line. We have been unable to determine exact dates for any changes made to the design by previous manufacturers. Therefore this bulletin covers all Firomatic® ½” FPT valves, whether using our part number 12130 or the obsolete part number B200F, used by Highfield Manufacturing. Suspect valves can be identified by the name ‘Firomatic’ cast into the body of the valve. See illustration below.

A re-design of the 12130 valve will be available pending agency approvals and manufacturing process lead times. We are anticipating the re-designed valve to be available by January 1, 2017.

RW BECKETT RECALL for FIROMATIC 1/2" FEMALE PIPE THREAD FUSIBVLE SAFETY VALVE [PDF] P/N 12130 - OLDER COPY - the stem may not travel far enough to shut off the flow of fuel if exposed to trip point temperature. Posted until 4/1/2017, retrieved 2019/10/09 original source: https://static.globalindustrial.com/site/pdf/RW_Beckett_Firomatic_Female_Pipe_Thread_Recall.pdf

It might matter tremendously which way your OSV or oil safety valve is installed and in any event we ought to follow the manufacturer"s instructions including the flow arrow.

Here"s just one example. Some OSVs such as sold by Webster include a pressure-isolating feature that protects the fuel unit (the oil pump) from additional pressures that might come from the oil feed such as from an overhead oil feed line or even an elevated oil tank. Typically codes specify that the input pressure from the oil delivery piping ahead of the burner"s fuel unit not exceed 3 psi.

Those Webster OSVs include an internal valve that is designed to OPEN in RESPONSE to the FUEL UNIT OPERATION. So if the valve is installed backwards that feature will not work and the fuel unit may not pump oil properly to the burner nozzle.

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.

All valves are embossed with the direction of oil flow and include unique part number identification ring or each valve. The seal stem uses a double seal washer/ o-ring system with high grade Viton® equivalent materials suitable for No. 2 fuel oil, Kerosene and up to 20% Biodiesel blend.

Watch out: That"s because in the event of a fire a lead core in the valve is intended to melt to allow the valve to close - to stop feeding oil to a possible building fire. So if the valve is jammed it"s unsafe.

My concern is the stem does not go back into the valve or come out of it any further than it currently is no matter which direction I turn the valve or how many turns I make. Since the valve does not STOP turning in either direction, I"m concerned the valve is faulty.

If the stem pokes up out of the valve handle you"ve screwed the valve "down" and it is "open" to pass oil. Remember that these valves are threaded opposite of most others.

The knob on my OSV does not tighten up no matter how many times I turn it in either direction. The threaded stem in the center is protruding out about 2mm so I"m not sure if the valve is fully opened or closed. Is there a fix for this or do I need to replace the OSV?

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.

In my opinion painting a fusible link is potentially unsafe - paint may interfere with mechanical operation of the valve. Most likely the manufacturer will agree, though they may not have imagined that event.

there must be an exception to the rule. my firematic valves open counter-clockwise and close clockwise and are definitely firematic valves because of their construction. they are just like the photos above but turn in the opposite direction you describe

I have a Themopride oil furnace that loses prime over night when the thermostat is lowed. It has a tigerloop installed. Why is there oil in the tigerloop if it loses prime?

Also, how do you recommend trouble shooting this? There are several valve one at each end of the supply line and one before the tigerloop that I could close for a few hours and see if it solves the problem (that would atleast narrow it down to a few fittings)

On a manual 1" fireomatic valve where the bonnett section joins the valve body, is that a brass on brass fit or is there suppose to be an o-ring or gasket? Does the OEM (Fireomatic) permitt valve disassembly for installation purposes? Thanks.

Mike I"ve installed these valves but have not tried disassembling one. If your unit is from Beckett, who currently provides the Fireomatic oil safety valve as well as the "New England Safety Switch" that uses a similar mechanism, then you might give them a call to ask.

Is there a inspection protocol for these valves like Morrison has on there fusible link valves (some quarterly inspections some yearly) and are they fine to use on gasoline lines I see only oil mentioned.

Watch out: do not use an oil line safety valve in ANY application other than those listed by UL and by the manufacturer - in this case, on heating oil supply lines.

Continue reading at OIL LINE SAFETY VALVE TURN DIRECTION to OPEN or SHUT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

OIL LINE SAFETY VALVES, OSVs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

[1]AUDELS OIL BURNER GUIDE, INSTALLING, SERVICING, REPAIRING, [PDF online copy of this book] Frank D. Graham, Theo. Audel & Co., New York 1946, 1947, 1955 (out of print, copies occasionally available from antique book dealers and on EBay). Use THIS LINK to read a free online copy of this helpful classic textbook.

[2] Beckett Model SR Oil Burner Instruction Manual, R.W. Beckett Corporation, PO Box 1289, Elyria OH 44036 and R.W. Beckett Canada, Ltd., 430 Laird St., Guelph, Ontario, Canada N1G 3x7

[17] Newmac Furnaces & Boilers, "Installation, Operating, and Service Manual, Oil Fired Boiler Model NBR-2001 NBR 2002", (2007) Newmac Manufacturing, Inc., Debert Air Industrial Park, Lancaster Crescent, PO Box 9, Debert, Nova Scotia, BOM 1GO Canada, Tel: 902-662-3840, retrieved 2/23/2014

Thanks to Rick Johnston for pointing out that the more likely cause of a fire safety valve in the return oil line is a burst seal on the fuel unit 4/6/2009

Thanks to reader Bernie Daraz for suggesting the need for clear photographs illustrating the OSV or oil line safety valve in the open and closed positions. Personal correspondence 2/15/2013.

Thanks to reader T.R. for suggesting clarity on where oil safety valves should or should not be installed and for discussing the proper hook-up location for the Tigerloop and similar oil line prime protection & air removal devices. April 2011.

Thanks to reader Anonymous by request 2/23/2014, for requesting clarification of the safety hazards involved in placing an OSV on the return line of a two-pipe oil system.

TECHNICAL REFERENCE GUIDE to manufacturer"s model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop Weldon & Associates

Surface-controlled subsurface safety valves (SCSSVs) are critical components of well completions, preventing uncontrolled flow in the case of catastrophic damage to wellhead equipment. Fail-safe closure must be certain to ensure proper security of the well. However, this is not the only function in which it must be reliable—the valve must remain open to produce the well. Schlumberger surface controlled subsurface safety valves exceed all ISO 10432 and API Spec 14A requirements for pressure integrity, leakage acceptance criteria, and slam closure.

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Here in Massachusetts we had a new law passed on Jan. 8, 2009 and I’m very excited about it and the great things that it will hopefully do. It’s called M.G.L. Chapter 453 and its alias is the ‘Oil Tank Law,” but many also call it the ‘Oil Line Law.”

It states that before July 1, 2010 insurers will have to make casualty insurance available to Massachusetts homeowners, and at a reasonable rate, for a spill caused by a leaking oil tank or failed line. This is the first time in many years that oil heated homes will be covered in the event of just normal wear and tear and aging of a fuel tank.

Homeowners must do their part. Every property owner of a one to four family residence must either replace his oil line in a non-metallic sleeve, or upgrade the line through the use of an oil safety valve. If the entire tank and line are below the pump nothing has to be done, but those jobs are very rare.

The absolute best way to upgrade an existing system is a new sleeved line, but the prv/osv valve makes a good option for many. Finally, oil companies and heating contractors can gain some much needed work and a simple permit signed by the installer and filed with the local fire department is all that is needed to comply. The permit must be made out, but the fire department doesn’t have to inspect it since the technician is the inspector, per se.

Sunstrand originally created the concept for these valves in the 1960s for high head and pressurized applications’the PRV-38, Pressure Reducing Valve – 3/8″‘and they were followed by Webster with their model. In 1976 Webster changed the name to OSV® (oil safety valve). Sundstrand bowed out of the PRV market in the mid-1970s since they just weren’t selling enough of them to keep making them, Suntec brought them back in the 1980s for use as the PRV/OSV.

The oil safety valve is a dynamic pressure reducer; it requires pressure or vacuum to work. As a pressure reducer (PRV), it’s invaluable in protecting pump seals under the high pressures needed to get oil up to burners located high overhead. Working with booster pumps, the PRV does a great job. As an OSV®, the valve works to protect us against underground oil line leaks. I was first introduced to these devices while working on oil lift jobs in the Air Force and found them everywhere, especially in aircraft hangers.

Basically, what most of us knew was if you put 30 psi on a PRV/OSV the pressure goes to about 10 psi. If you put three psi on it you’ll get about one psi out of it. That wasn’t new, but what Sam found was that if you put zero psi on it you got nothing out, but apply vacuum to it and it would open. Pressure is a positive force, vacuum is a negative force. If you have a PRV/OSV at zero pressure and you exert two inches of vacuum, it will open. As long as you keep a vacuum on it the valve stays open. Imagine your finger on a straw filled with liquid, the liquid stays inside because you’ve trapped it in a vacuum. But, if you lose vacuum, the valve closes and the OSV was born.

If you do a search of the PRV/OSV you’ll find the PRV/OSV mentioned all over the place because they work and do the job. Several states, Massachusetts and Maine, now have legislation mandating them and yet the industry still wonders about them. The Europeans use them and even have models that can be adjusted based on the height of the oil level and the pump, Figure 4. So what gives? Well, it’s like a lot of things; if we don’t understand, it we knock it. But the PRV/OSV is a device that can help you and truly do a lot to clean up oil heat’s image. By using the PRV/OSV you can prevent unseen, underground oil line leaks, and that’s a big deal today, as it always has been.

If you still can’t get the PRV/OSV to work look at your system. The purpose of the PRV/OSV is to protect property against oil line failures, but if there’s too much vacuum you probably don’t need it. Remember, when being used as an oil safety valve, it’s a gravity (vacuum) device, not a pressure device. Make sure you power vacuum bleed that pump too, and you can find the directions for that at my website, it’s my Field Note No. 6.

*George Lanthier is the owner of Firedragon Enterprises, a teaching, publishing and consulting firm. He is the author of over 25 books on oil heating and HVAC subjects. He can be reached at 608 Moose Hill Rd., Leicester, MA 01524. His phone is 508-421-3490, fax at 508-421-3477

Industry leading pressure and safety relief valve designs with over 140 years of technical and application expertise providing custom engineered solutions for O&G, Refining, Chemical, Petrochemical, Process and Power applications. Our designs meet global and local codes and standards (API 526; ASME Section I, IV & VIII; EN ISO 4126; PED & more). Gain insight into the performance of your pressure relief valves with wireless monitoring.

There is a wide range of safety valves available to meet the many different applications and performance criteria demanded by different industries. Furthermore, national standards define many varying types of safety valve.

The ASME standard I and ASME standard VIII for boiler and pressure vessel applications and the ASME/ANSI PTC 25.3 standard for safety valves and relief valves provide the following definition. These standards set performance characteristics as well as defining the different types of safety valves that are used:

ASME I valve - A safety relief valve conforming to the requirements of Section I of the ASME pressure vessel code for boiler applications which will open within 3% overpressure and close within 4%. It will usually feature two blowdown rings, and is identified by a National Board ‘V’ stamp.

ASME VIII valve- A safety relief valve conforming to the requirements of Section VIII of the ASME pressure vessel code for pressure vessel applications which will open within 10% overpressure and close within 7%. Identified by a National Board ‘UV’ stamp.

Full bore safety valve - A safety valve having no protrusions in the bore, and wherein the valve lifts to an extent sufficient for the minimum area at any section, at or below the seat, to become the controlling orifice.

Conventional safety relief valve -The spring housing is vented to the discharge side, hence operational characteristics are directly affected by changes in the backpressure to the valve.

Balanced safety relief valve -A balanced valve incorporates a means of minimising the effect of backpressure on the operational characteristics of the valve.

Pilot operated pressure relief valve -The major relieving device is combined with, and is controlled by, a self-actuated auxiliary pressure relief device.

Power-actuated safety relief valve - A pressure relief valve in which the major pressure relieving device is combined with, and controlled by, a device requiring an external source of energy.

Standard safety valve - A valve which, following opening, reaches the degree of lift necessary for the mass flowrate to be discharged within a pressure rise of not more than 10%. (The valve is characterised by a pop type action and is sometimes known as high lift).

Full lift (Vollhub) safety valve -A safety valve which, after commencement of lift, opens rapidly within a 5% pressure rise up to the full lift as limited by the design. The amount of lift up to the rapid opening (proportional range) shall not be more than 20%.

Direct loaded safety valve -A safety valve in which the opening force underneath the valve disc is opposed by a closing force such as a spring or a weight.

Proportional safety valve - A safety valve which opens more or less steadily in relation to the increase in pressure. Sudden opening within a 10% lift range will not occur without pressure increase. Following opening within a pressure of not more than 10%, these safety valves achieve the lift necessary for the mass flow to be discharged.

Diaphragm safety valve -A direct loaded safety valve wherein linear moving and rotating elements and springs are protected against the effects of the fluid by a diaphragm

Bellows safety valve - A direct loaded safety valve wherein sliding and (partially or fully) rotating elements and springs are protected against the effects of the fluids by a bellows. The bellows may be of such a design that it compensates for influences of backpressure.

Controlled safety valve - Consists of a main valve and a control device. It also includes direct acting safety valves with supplementary loading in which, until the set pressure is reached, an additional force increases the closing force.

Safety valve - A safety valve which automatically, without the assistance of any energy other than that of the fluid concerned, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed to re-close and prevent further flow of fluid after normal pressure conditions of service have been restored. Note; the valve can be characterised either by pop action (rapid opening) or by opening in proportion (not necessarily linear) to the increase in pressure over the set pressure.

Direct loaded safety valve -A safety valve in which the loading due to the fluid pressure underneath the valve disc is opposed only by a direct mechanical loading device such as a weight, lever and weight, or a spring.

Assisted safety valve -A safety valve which by means of a powered assistance mechanism, may additionally be lifted at a pressure lower than the set pressure and will, even in the event of a failure of the assistance mechanism, comply with all the requirements for safety valves given in the standard.

Supplementary loaded safety valve - A safety valve that has, until the pressure at the inlet to the safety valve reaches the set pressure, an additional force, which increases the sealing force.

Note; this additional force (supplementary load), which may be provided by means of an extraneous power source, is reliably released when the pressure at the inlet of the safety valve reaches the set pressure. The amount of supplementary loading is so arranged that if such supplementary loading is not released, the safety valve will attain its certified discharge capacity at a pressure not greater than 1.1 times the maximum allowable pressure of the equipment to be protected.

Pilot operated safety valve -A safety valve, the operation of which is initiated and controlled by the fluid discharged from a pilot valve, which is itself, a direct loaded safety valve subject to the requirement of the standard.

The common characteristic shared between the definitions of conventional safety valves in the different standards, is that their operational characteristics are affected by any backpressure in the discharge system. It is important to note that the total backpressure is generated from two components; superimposed backpressure and the built-up backpressure:

Subsequently, in a conventional safety valve, only the superimposed backpressure will affect the opening characteristic and set value, but the combined backpressure will alter the blowdown characteristic and re-seat value.

The ASME/ANSI standard makes the further classification that conventional valves have a spring housing that is vented to the discharge side of the valve. If the spring housing is vented to the atmosphere, any superimposed backpressure will still affect the operational characteristics. Thiscan be seen from Figure 9.2.1, which shows schematic diagrams of valves whose spring housings are vented to the discharge side of the valve and to the atmosphere.

By considering the forces acting on the disc (with area AD), it can be seen that the required opening force (equivalent to the product of inlet pressure (PV) and the nozzle area (AN)) is the sum of the spring force (FS) and the force due to the backpressure (PB) acting on the top and bottom of the disc. In the case of a spring housing vented to the discharge side of the valve (an ASME conventional safety relief valve, see Figure 9.2.1 (a)), the required opening force is:

In both cases, if a significant superimposed backpressure exists, its effects on the set pressure need to be considered when designing a safety valve system.

Once the valve starts to open, the effects of built-up backpressure also have to be taken into account. For a conventional safety valve with the spring housing vented to the discharge side of the valve, see Figure 9.2.1 (a), the effect of built-up backpressure can be determined by considering Equation 9.2.1 and by noting that once the valve starts to open, the inlet pressure is the sum of the set pressure, PS, and the overpressure, PO.

In both cases, if a significant superimposed backpressure exists, its effects on the set pressure need to be considered when designing a safety valve system.

Once the valve starts to open, the effects of built-up backpressure also have to be taken into account. For a conventional safety valve with the spring housing vented to the discharge side of the valve, see Figure 9.2.1 (a), the effect of built-up backpressure can be determined by considering Equation 9.2.1 and by noting that once the valve starts to open, the inlet pressure is the sum of the set pressure, PS, and the overpressure, PO.

Balanced safety valves are those that incorporate a means of eliminating the effects of backpressure. There are two basic designs that can be used to achieve this:

Although there are several variations of the piston valve, they generally consist of a piston type disc whose movement is constrained by a vented guide. The area of the top face of the piston, AP, and the nozzle seat area, AN, are designed to be equal. This means that the effective area of both the top and bottom surfaces of the disc exposed to the backpressure are equal, and therefore any additional forces are balanced. In addition, the spring bonnet is vented such that the top face of the piston is subjected to atmospheric pressure, as shown in Figure 9.2.2.

The bellows arrangement prevents backpressure acting on the upper side of the disc within the area of the bellows. The disc area extending beyond the bellows and the opposing disc area are equal, and so the forces acting on the disc are balanced, and the backpressure has little effect on the valve opening pressure.

Bellows failure is an important concern when using a bellows balanced safety valve, as this may affect the set pressure and capacity of the valve. It is important, therefore, that there is some mechanism for detecting any uncharacteristic fluid flow through the bellows vents. In addition, some bellows balanced safety valves include an auxiliary piston that is used to overcome the effects of backpressure in the case of bellows failure. This type of safety valve is usually only used on critical applications in the oil and petrochemical industries.

Since balanced pressure relief valves are typically more expensive than their unbalanced counterparts, they are commonly only used where high pressure manifolds are unavoidable, or in critical applications where a very precise set pressure or blowdown is required.

This type of safety valve uses the flowing medium itself, through a pilot valve, to apply the closing force on the safety valve disc. The pilot valve is itself a small safety valve.

The diaphragm type is typically only available for low pressure applications and it produces a proportional type action, characteristic of relief valves used in liquid systems. They are therefore of little use in steam systems, consequently, they will not be considered in this text.

The piston type valve consists of a main valve, which uses a piston shaped closing device (or obturator), and an external pilot valve. Figure 9.2.4 shows a diagram of a typical piston type, pilot operated safety valve.

The piston and seating arrangement incorporated in the main valve is designed so that the bottom area of the piston, exposed to the inlet fluid, is less than the area of the top of the piston. As both ends of the piston are exposed to the fluid at the same pressure, this means that under normal system operating conditions, the closing force, resulting from the larger top area, is greater than the inlet force. The resultant downward force therefore holds the piston firmly on its seat.

If the inlet pressure were to rise, the net closing force on the piston also increases, ensuring that a tight shut-off is continually maintained. However, when the inlet pressure reaches the set pressure, the pilot valve will pop open to release the fluid pressure above the piston. With much less fluid pressure acting on the upper surface of the piston, the inlet pressure generates a net upwards force and the piston will leave its seat. This causes the main valve to pop open, allowing the process fluid to be discharged.

When the inlet pressure has been sufficiently reduced, the pilot valve will reclose, preventing the further release of fluid from the top of the piston, thereby re-establishing the net downward force, and causing the piston to reseat.

Pilot operated safety valves offer good overpressure and blowdown performance (a blowdown of 2% is attainable). For this reason, they are used where a narrow margin is required between the set pressure and the system operating pressure. Pilot operated valves are also available in much larger sizes, making them the preferred type of safety valve for larger capacities.

One of the main concerns with pilot operated safety valves is that the small bore, pilot connecting pipes are susceptible to blockage by foreign matter, or due to the collection of condensate in these pipes. This can lead to the failure of the valve, either in the open or closed position, depending on where the blockage occurs.

The terms full lift, high lift and low lift refer to the amount of travel the disc undergoes as it moves from its closed position to the position required to produce the certified discharge capacity, and how this affects the discharge capacity of the valve.

A full lift safety valve is one in which the disc lifts sufficiently, so that the curtain area no longer influences the discharge area. The discharge area, and therefore the capacity of the valve are subsequently determined by the bore area. This occurs when the disc lifts a distance of at least a quarter of the bore diameter. A full lift conventional safety valve is often the best choice for general steam applications.

The disc of a high lift safety valve lifts a distance of at least 1/12th of the bore diameter. This means that the curtain area, and ultimately the position of the disc, determines the discharge area. The discharge capacities of high lift valves tend to be significantly lower than those of full lift valves, and for a given discharge capacity, it is usually possible to select a full lift valve that has a nominal size several times smaller than a corresponding high lift valve, which usually incurs cost advantages.Furthermore, high lift valves tend to be used on compressible fluids where their action is more proportional.

In low lift valves, the disc only lifts a distance of 1/24th of the bore diameter. The discharge area is determined entirely by the position of the disc, and since the disc only lifts a small amount, the capacities tend to be much lower than those of full or high lift valves.

Except when safety valves are discharging, the only parts that are wetted by the process fluid are the inlet tract (nozzle) and the disc. Since safety valves operate infrequently under normal conditions, all other components can be manufactured from standard materials for most applications. There are however several exceptions, in which case, special materials have to be used, these include:

Cast steel -Commonly used on higher pressure valves (up to 40 bar g). Process type valves are usually made from a cast steel body with an austenitic full nozzle type construction.

For all safety valves, it is important that moving parts, particularly the spindle and guides are made from materials that will not easily degrade or corrode. As seats and discs are constantly in contact with the process fluid, they must be able to resist the effects of erosion and corrosion.

The spring is a critical element of the safety valve and must provide reliable performance within the required parameters. Standard safety valves will typically use carbon steel for moderate temperatures. Tungsten steel is used for higher temperature, non-corrosive applications, and stainless steel is used for corrosive or clean steam duty. For sour gas and high temperature applications, often special materials such as monel, hastelloy and ‘inconel’ are used.

Standard safety valves are generally fitted with an easing lever, which enables the valve to be lifted manually in order to ensure that it is operational at pressures in excess of 75% of set pressure. This is usually done as part of routine safety checks, or during maintenance to prevent seizing. The fitting of a lever is usually a requirement of national standards and insurance companies for steam and hot water applications. For example, the ASME Boiler and Pressure Vessel Code states that pressure relief valves must be fitted with a lever if they are to be used on air, water over 60°C, and steam.

A test gag (Figure 9.2.7) may be used to prevent the valve from opening at the set pressure during hydraulic testing when commissioning a system. Once tested, the gag screw is removed and replaced with a short blanking plug before the valve is placed in service.

The amount of fluid depends on the particular design of safety valve. If emission of this fluid into the atmosphere is acceptable, the spring housing may be vented to the atmosphere – an open bonnet. This is usually advantageous when the safety valve is used on high temperature fluids or for boiler applications as, otherwise, high temperatures can relax the spring, altering the set pressure of the valve. However, using an open bonnet exposes the valve spring and internals to environmental conditions, which can lead to damage and corrosion of the spring.

When the fluid must be completely contained by the safety valve (and the discharge system), it is necessary to use a closed bonnet, which is not vented to the atmosphere. This type of spring enclosure is almost universally used for small screwed valves and, it is becoming increasingly common on many valve ranges since, particularly on steam, discharge of the fluid could be hazardous to personnel.

Some safety valves, most commonly those used for water applications, incorporate a flexible diaphragm or bellows to isolate the safety valve spring and upper chamber from the process fluid, (see Figure 9.2.9).