Attachment A - Boiler Safety Device Testing for Syracuse and Rome NY CBOC.pdf

1. INTRODUCTION

1.1 OBJECTIVE

The following testing requirements shall be performed on the four Fulton Vantage VTG- 4000 dual-fuel hot water boilers located at the Syracuse VA Medical Center, 800 Irving Avenue and the two Fulton Vantage VTG-4000 hot water boilers, one of which is dual-fuel. All boilers are served by natural gas as the primary fuel and dual-fuel boilers use fuel oil as the backup fuel. The four boilers at the Syracuse VA Medical Center are dual fuel capable, but the fuel oil pumping system has been taken out of service. Because the system could be re-activated at some future time, the fuel oil tests shall be completed to the fullest extent possible in the current configuration. Where testing of the fuel oil or other tests are not possible, the boiler testing technician shall note the reason for the test not being performed. These tests shall be performed every 6 months, unless otherwise noted. This scope represents a minimum standard for boiler and associated plant safety device testing. The text presents a concise and thorough treatment of boiler safety as applied to automatically-fired gas and oil, heating and process boilers and boiler support equipment servicing healthcare facilities. The text includes a description of each boiler safety device, how it works, what happens if it doesn’t work, what its purpose is, and how to test the device. Appendix A provides detailed step by step procedures for testing devices typically found on steam and hot water boilers. Some boilers will not include all of these devices, in which case the technician shall document. Appendix B provides detailed step by step procedures for testing devices applicable only to hot water boilers.

The testing contractor shall also perform tests recommended by the boiler manufacturer that are not indicated in this scope. Manufacturer specific tests shall be attached to the report.

Appendix F shall be used to provide comments for each individual safety test.

Appendix G lists the inspection testing frequency for hot water boilers.

Appendix C has been removed.

1.2 BACKGROUND INFORMATION

One must understand that the use of the term “boiler” may refer to the system that includes the generation of steam, hot water, or hot oil. There are many safety devices such as level alarms, safety valves, relief valves, etc. that are found on the components involved in the distribution and use of steam. The safety checks are necessary and must be conducted on all devices in the system in order to ensure that the system is safe.

It is important that one has the manufacturer’s manuals and wiring diagrams and on all equipment to be tested before beginning the tests described herein and have a customized testing procedure specific to the boiler plant.

1.3 REQUIREMENTS FOR SAFETY TESTING

1.3.1 Properly test and analyze each safety device to determine VA Compliance There are three questions that the person conducting the safety test must be able to answer affirmatively for a safety device to be VA compliant. IN THE TEST

PROCEDURES GIVEN IN APPENDICES A AND B, THIS SET OF QUESTIONS IS

CALLED THE “3 QUESTION CRITERIA”. IT IS SUCCINTLY STATED IN THE BOX

ON THE NEXT PAGE.

If any of the three questions are not answered affirmatively for a safety device, the device in question FAILS to be VA compliant. If there is a failure of any safety device that can’t be fixed immediately, the boiler must be removed from service or an Interim Safety Measure (ISM) developed, approved, and instituted until the repair is completed. In this situation the Medical Center Director must be notified of the situation.

THE 3 QUESTION CRITERIA

1. Is the correct device installed?

• A device approved by the VA that meets all VA requirements and standards

• The device is in the right location as defined by VA requirements and standards

• The device is set up to accommodate testing

• Any valve isolating the device is lockable only in open position

• If the device is a switch, it must open when it actuates.

• Any signal used in process control cannot be used as an input to a safety system.

• Independent safety control includes the fact that the safety control must be located in an enclosure that contains no other type of control.

• Any shunt on low water cutoffs (bypass switch) must be a non-latching device. No other shunts are allowed.

• The use of a snubber, dampener, pneumatic accumulator or other such device to dampen the pressure provided to a safety switch or gage used in testing the switch is not VA compliant.

2. Does the device activate at the proper set point that is in accordance with the criteria for the set point as defined herein and VA standards?

3. Does the device produce the proper result for its intended purpose (i.e. device must result in actions defined herein)?

1.3.2 REQUIRED CERTIFICATIONS FOR EACH SAFETY DEVICE TEST REPORT

A VA compliant test report will contain the following certification on the first page following the cover page of the report.

I certify that I have properly tested all applicable safety devices listed in this report for boiler # and its associated equipment and I certify that all of these tests confirm that every device tested “passed” as defined by the following question: Did the device fail or pass the 3 question criteria?

PRINTED NAME SIGNATURE DATE

Position Title Company

OR

I certify that I have properly tested all applicable safety devices listed in this report for boiler # and its associated equipment and I certify that some of these tests failed as defined by the following question: Did the device fail or pass the 3 question criteria? More details of these failures are given in Appendix F (Comments on each individual test)

PRINTED NAME SIGNATURE DATE

Position Title Company

1.3.3 Confirming That All Devices Actually Function for Intended Purpose In testing any safety device, it is paramount that the testing procedure verifies compliance with the three requirements listed above.

1.3.4 Lockable Valve Requirements

In order to facilitate testing of some types of safety devices, it is sometimes necessary to temporarily isolate the safety device and provide test ports by means of manual valves. However, these modifications cannot be allowed to increase risk by locking out a safety device during normal operation and must clearly indicate test and normal position. Any such manual valve that could isolate a safety device from its normal operating circuit must be lockable and the lock must be lockable only in the correct operating position. It is most important that in normal operation the valve is actually locked.

1.3.5 Confirming That Jumpers Are Removed and Valves Properly Locked In many cases in order to test a device, it will be necessary to either electrically jumper (bypass) a device or to valve out the device. The safety testing personnel should only carry a fixed number of jumpers and should make sure that at the end of a test that all jumpers being used are accounted for and that all lockable valves are locked in their correct position.

1.3.6 Adherence to Electrical Safety

The VA complies with the NFPA 70E Electrical Code. In executing the safety procedures described herein, it is sometimes necessary to open an electrical panel with a voltage sufficient to require various levels of protection. No personnel should perform such operations without being qualified with the proper training and gear. While this requirement will not be listed for each safety test, it must be understood that all personnel must rigidly adhere to the requirements of NFPA 70E.

1.4 NOMENCLATURE

AFOSV Automatic Fuel Oil Shutoff Valves ALWCO Auxiliary Low Water Cutoff on steam boilers ALWCOHW Auxiliary Low Water Cutoff on Hot Water Boilers APFGSOV Automatic Pilot Fuel Gas Shutoff Valves APFGSVV Automatic Pilot Fuel Gas Solenoid Vent Valve AMSOV Atomizing Media Shut Off Valve CAPI Control Air Pressure Interlock CAPS Combustion Air Pressure Switch DA Deaerator DAODS Deaerator Overflow Drain System DASV Deaerator Safety Valve ESPB Emergency Stop/Panic Button FDDWOPS Forced Draft Damper Wide-Open Pre-Purge Proving Switch FDMIS Forced Draft Motor Interlock Switches FGRDI Flue Gas Recirculation Damper Interlock AFGSOV Automatic Fuel Gas Shutoff Valves and Solenoid Vent Valve AFGSVV Automatic Fuel Gas Shutoff Solenoid Vent Valve FPI Furnace Pressure Interlock FS Flow Switch on Hot Water Boilers FSMFO Flame Scanner-for main flame out FSNSIS Flame Scanner Not Sensing Igniter Spark HFGPCS High Fuel Gas Pressure Cutoff Switch HFOPCS High Fuel Oil Pressure Cutoff Switch HWAB High Water Alarm on Boiler HWACT High Water Alarm on Condensate Tank HWTS High Water Temperature Switch on Hot Water Boiler HWADT High Water Alarm on Deaerator Tank IT Igniter Timing LAMDPS Low Atomizing Media Differential Pressure Switch

LAMFS Low Atomizing Media Flow Switch LAMPS Low Atomizing Media Pressure Switch LFGOLI Low Flue Gas Oxygen Level Interlock LFGPCS Low Fuel Gas Pressure Cutoff Switch LFOPCS Low Fuel Oil Pressure Cutoff Switch LFPS Low-Fire Proving Switch LPFGPCS Low Pilot Fuel Gas Pressure Cutoff Switch LRVE Liquid Relief Valve on Economizer LRVE\HW Liquid Relief Valve on Hot Water Boiler LRVOPS Liquid Relief Valve on Oil Pump Set LWA Low Water Alarm LWACT Low Water Alarm on Condensate Tank LWADT Low Water Alarm on Deaerator Tank LWCO Low Water Cutoff on Steam Boiler LWCOHW Low Water Cutoff on Hot Water Boiler MFIT Main Flame Ignition Timing MV Manual Valve NRBSPLS Non-Recycle Boiler Steam Pressure Limit Switch OADA Outside Air Damper Alarm OBPS Oil Burner Position Switch OSDPI Outlet Stack Damper Position Interlock Switch PAPS Purge Airflow Proving Switch POC_AFOSV Proof of Closure on Automatic Fuel Oil Shutoff Valves POC-AFGSOV Proof of Closure on Automatic Fuel Shutoff Valves PPT Pre-Purge and Post-Purge Timing PRV Pressure Reducing Valve RBSPLS Recycle Boiler Steam Pressure Limit Switch SVB Steam Safety Valves on Boiler SVFPRV Safety Valve Following PRV TP Test Port

1.5 PREPARATION OF SYSTEM FOR SAFETY TESTING

The normal boiler installation does not generally allow easy access and control for testing. Safety testing is an ongoing activity for safe boiler plant operation. In this section a discussion is given of system design considerations that will allow easy testing.

The discussion is organized around classes of different safety devices. For detailed drawings illustrating an appropriate test setup for each device, refer to the safety testing procedures given in the Appendices A and B. A list of test equipment that is satisfactory for conducting the safety tests is given in Appendix E. The list is an example, but many other comparable instruments could be utilized.

1.5.1 Setup for testing a Combustion Air Pressure Switch, Purge Air Proving Switch, Furnace Pressure Interlock, Control Air Pressure Interlock, High Fuel Gas Pressure Cutoff Switch, High Fuel Oil Pressure Cutoff Switch, Low Fuel Gas Pressure Cutoff Switch, and Low Fuel Oil Pressure Cutoff Switch.

In order to test these switches, it is necessary to be able to temporarily isolate these switches from the normal pressure source and either increase or decrease the pressure applied to the switch using the test port in order to determine the switch trip point. At the same time the piping must be such

LFGPC

S

LOCK OPEN

TP

AFGSOV AFGSOV HFGPCS FUEL FLOW

CONTROL

HFGPCS

AFGSVV

TP

LOCK OPEN

Main Gas Line TP TP that the actual pressure that the switch senses can also be measured. The arrangement is pictorially shown in Figures 1.2 for the case of a Combustion Air Pressure Switch. The other switches listed above should be set up in a similar manner as indicated in the respective test procedures in Appendix A.

Figure 1.2 Combustion Air Pressure Switch (CAPS) Setup

1.5.2 Setup for Leak Checking Oil and Gas Block Valves and Gas Bleed Vent Valve

In order to easily test for leaks in the block valves, a test port (TP) and calibrated pressure gage must be available both in the line between the valves and downstream of the second valve. Also in the case of gas, a lockable manual valve downstream of the solenoid bleed vent valve is required. A port and pressure gage in the line between the solenoid valve and lockable manual valve is also needed as shown in Figure 1.3. Note, there are two test ports (TP) for determining normal operating pressures and one test port (TP) for testing the automatic fuel gas vent valve for leaks. This arrangement is schematically shown for natural gas in Figure 1.3. The arrangement for testing the automatic fuel oil valves is the same with the exception the vent line is absent with its attendant test arrangement as shown in the test procedure for oil leaks in Appendix A.

(Note that some boiler manufacturers do include a liquid relief valve between the two automatic fuel shut off valves. If this relief valve is included it must be tested.)

BLOCK AND BLEED SYSTEM

Figure 1.3 Test setup for leak testing the two Automatic Fuel Gas Shut Off Valves and the Automatic Fuel Gas Vent Valve

1.5.3 Setup for Checking Dangerous Gas Detection System for the Building Sample gas with a level of CO and combustibles equal to the sensor set points should be available with a means to supply the gas to the sensor per the manufacturers test procedures.

1.5.4 Setup for Checking Proof of Closure Switches, Low Fire Proving

Switches, Force Draft Damper Vane Interlock, Outlet Stack Damper Interlock, Recycle Steam Pressure Switch, Non-recycle Pressure Switch, and Recirculation Damper Interlock

It is necessary to electrically isolate or jumper these switches for testing. Although not necessary, it may be convenient to have the two electrical leads from each of these switches wired into an electrical control panel where it is easy to either remove one lead from the terminal block to isolate the switch or to jumper across the two leads to simulate a switch in the closed position.

1.5.5 Setup for Low Water Cutoffs

A low water cutoff can be treated in the same way as those switches in section 1.5.4. It is more convenient to have independent, non-latching shunt test switches (Momentary bypass switch) for isolating the two low water cutoffs for steam boilers and hot water boilers that are fitted with two low water cutoffs. This shunt test switch is required for each low water cutoff by VA standards for boilers fitted with two low water cutoffs.

2 WATER LEVEL CONTROL

2.1 LOW WATER CUTOFFS

2.1.1 Description

A low water cutoff is a device that causes the automatic fuel safety shutoff valves to close if the water level in the boiler drops below a pre-set safe level. Low water causes about 50 percent of all boiler incidents. Low water can cause the boiler to overheat which could lead to the failure of the pressure vessel with enormous potential damage (explosion). Two low-water cutoffs are required for steam boilers while hot water boilers are required to have at least one low water cutoff. Low-water cutoffs operate either on a “float” system or electrode system (probe) for steam boilers. Any low water cutoff for hot water boilers must be a probe. In the float system there is a pipe connection to the boiler high and low connection points. Between these connection points there is a vertical section containing a volume sufficient to house the float. If the water level falls below a prescribed level, the falling float will cause a switch to actuate causing the automatic fuel valves to close. (See Figure 2.1)

LWCO

FLOAT

SHUNT

PROBE

Figure 2.1 Low Water Cutoff

In the electrode system, there is a similar piping arrangement as in the float system.

Probes extend vertically downward into the vertical pipe connecting the piping to the high and low boiler connection points or for hot water boilers directly into the boiler.

The electrodes are located at the bottom of the probe and are used to measure the conductivity of the media in which the electrodes are immersed. The conductivity of water is much higher than steam. Hence, if the water level drops below the probe, a drastic change in conductivity occurs. This change is used in an electrical circuit to cause the automatic fuel shut-off valves to close. Most safety codes require at least one float system be included to protect against low water for steam boilers. This is shown in Figure 2.1. The VA requires one float and one probe for steam boilers. True redundancy requires that the low water cutoffs be in two separate piping arrangements as shown. Placing both low water cutoffs in a single piping arrangement could lead to a situation in which blockage in the piping arrangement renders both level control safety devices useless.

Some low-water cutoffs are provided with non-latching “shunt” test switches by which the low water cutoff switch is bypassed. A non-latching shunt test switch means that the test switch must be manually held open in order to bypass the low water cutoff switch.

The VA requires individual shunt test switches for both low water cutoffs for steam boilers. Operators can use the shunt test switch in “testing” each low-water cutoff by simply by-passing one low water cutoff by holding in the other low water cutoff shunt test switch and allowing the active low-water cutoff to shut down the boiler. This procedure is then repeated for the other low water cutoff. Operators electrically check the low water cutoff using this method.

A boiler control system should never allow the boiler to automatically restart after a low-water cutoff has actuated to stop boiler operation and all trip points must occur with water clearly in the sight glass.

A detailed step by step test procedure is given in Appendix A for steam boilers and Appendix B for hot water boilers.

2.1.2 Consequences of Low Water Cutoff Failure

If the low water cutoffs both fail, the boiler would then be fired with no water in the boiler. This will cause the metal temperatures to rise rapidly and the metal strength to be significantly decreased. In fire tube boilers the main Morrison tube typically collapses which could allow steam onto the boiler fireside. The steam pressure has been known to blow the ends out of the boiler through concrete block walls a distance of hundreds of feet. Similar catastrophes could occur in water tube boilers.

2.1.3 Testing a Low Water Cutoff

Low-water cutoffs must be tested in a mode in which they fail. Testing is basically done by allowing the water level to lower in a “slow drain”. In order to be in a realistic mode, one must not follow a procedure that actuates the cutoff by rapidly blowing off a volume of water from the water column containing the switch. This is very important in testing a float type cutoff. The rate of decrease in water level is required to be a maximum of 1 inch/minute.

A detailed step by step test procedure is given in Appendix A for steam boilers and Appendix B for hot water boilers.

2.2 LOW WATER ALARM

2.2.1 Description

The low water alarm provides audible and visual warnings that the water level is approaching a dangerously low level. These alarms are based either on a conductivity probe or float as described in the previous section. These alarms are required on the steam boiler, deaerator, and condensate receiver tanks. On the boiler, the low water alarm must be set to activate before either of the low water level cutoff switches shuts off the boiler. On the deaerator and condensate receiver tanks, the alarm is the only indication of a low water problem. On these devices the setting should be above 1/3rd of the tank diameter and with visible water in the sight glass. The alarm should not be set so high that it causes excessive alarm activation. Of course lack of water in the deaerator or condensate receiver will quickly result in loss of water to the boiler with the problems described in the section of low water level control.

2.2.2 Consequence of Water Level Alarm Failure

Low water in a condensate or deaerator tank is a precursor to low water failure in a steam boiler with the problems described above. There is also the hazard of damage to a condensate transfer or boiler feed pump from running dry. A low water alarm on a boiler is a warning to operators of an impending potential problem of a “boil out” of water.

2.2.3 Testing Low Water Alarms

This alarm is tested by causing a drop in water level in the vessel being tested. The alarm should activate at the desired set point (the set point must be above the level at which the first low water cutout activates, at a level allowing operators time to restore the proper level, and visible in the appropriate sight glass).

A step by step procedure is given in Appendix A for three situations: steam boilers, deaerators, and condensate tanks.

2.3 HIGH WATER ALARM

2.3.1 Description

A high water alarm is required on a steam boiler, deaerator, and condensate tanks to aid in preventing overfilling. Due to the failure rate of float type devices used for this purpose, high water alarms must always be conductivity probe type devices for VA compliance.

2.3.2 Consequence of High Water Alarm Failure

High water in a condensate tank could lead to backup of condensate in condensate lines. High water in a deaerator will result in poor deaeration but also leads to violent shaking of the vessel. High water in a steam boiler could result in pushing liquid into the steam line. Slugs of water in the steam system can move at high velocity due to the motive force of steam causing water hammer. Water hammer can cause valves and other fittings to explode and steam piping to rupture. Death and injury from these events is a regular occurrence. This same effect could produce high water levels in the steam supply to a steam powered appliance connected to the system with detrimental effects on the process.

2.3.3 Testing the High Water Alarm

The high water alarm must be tested off-line. Slowly fill the vessel with water, observe the water level in the sight glass, and note the point at which the alarm sounds. Be careful not to overfill the system, above the level at which the alarm should actuate.

A step by step procedure is given in Appendix A for three situations: steam boilers, deaerators, and condensate tanks.

3 PRESSURE CONTAINMENT

3.1 RELIEF VALVES

3.1.1 Description

Relief valves are spring-loaded valves that open if the liquid pressure in the system that they control increases above a pre-set limit. They are similar to safety valves with the exception that they do not exhibit “popping” action or blowdown. (Relief valves do not incorporate the “huddling” chamber found on safety valves). These valves are connected directly to an exhaust pipe that conveys the fluid to the building exterior or storage tank. Three important pieces of equipment requiring relief valves in boiler applications are economizers, hot water boilers, and oil pump sets.

3.1.2 Consequences of a Relief Valve Failure

Failure of a relief valve could lead to a pressure vessel explosion with serious consequences. Failure could also lead to equipment damage due to overheating-e.g. in operation of an oil pump.

3.1.3 Checking a Relief Valve

A testing procedure for the relief valve on an oil pump set and economizer is given in Appendix A. A test procedure for hot water boilers is given in Appendix B.

3.2 BOILER HYDROSTATIC TESTING

3.2.1 Description

A hydrostatic test is performed on a boiler, deaerator, pressurized condensate receiver and economizer to determine if it is capable of withstanding the potential operating pressure. It is very important to understand that any leak is a sign of weakness in the vessel and should be thoroughly inspected by a professional and properly repaired before the vessel is put back into operation. (These leaks could represent small cracks or metal thinning/corrosion/etc. that is not discernable to the eye).

3.2.2 Consequences of Failure to Hydrostatic Test

If weak spots are present and the vessel is operated, a significant chance exists that a pressure vessel explosion could occur with tremendous loss of property and life. Failure to perform a proper hydrostatic test would allow a weakened vessel to be operated with the associated dangers of such operation.

3.2.3 Performing a Hydrostatic Test

To perform a hydrostatic test, fill the vessel completely full of water below 200 F.

Remove and/or isolate all safety and relief valves. Close all supply and discharge lines.

The boiler must be completely locked and tagged out from all energy sources following OSHA requirements and the fireside opened for inspection. The hydrostatic pressure for the test should be 1.5 times working pressure applied for several hours. The dry side must be checked for any sign of leaks. Any leaks must be professionally evaluated in terms of whether the vessel can be operated safely without repair.

In applying the hydrostatic pressure, care must be exercised not to overpressure the vessel. If the vessel were pressurized above its elastic limit, the vessel would not be fit for further use and should be scrapped!

4 FUEL TRAIN SAFETY DEVICES

4.1 LOW PRESSURE FUEL CUTOFF SWITCH

4.1.1 Description

The low-pressure fuel cutoff switch causes the automatic fuel shutoff valves to close if the fuel pressure is below the lower limit for safe operation. Low pressure fuel cutoff switches are found on the main gas line, main oil line, and pilot gas line. The switch in all three of these applications senses the supply fuel pressure after the pressure regulating valve and upstream of any fuel control valve (See Figure 4.1). For the main oil and gas supply lines, the switch is in continuous operation once the boiler is in the run mode. For the pilot gas supply, the switch operates continuously while the pilot flame is on. A common operational problem with a low pressure cutoff switch occurs due to the PRV allowing a “dip” in fuel pressure on startup. Some facilities have installed a snubber or accumulator between the fuel line and switch to prevent the switch from activating. Snubbers and accumulators are not allowed by VA requirements and standards.

Figure 4.1 Low Pressure Fuel Cutoff

4.1.2 Consequences of Low Pressure Fuel Cutoff Switch Failure Low fuel pressure can result in unstable burning or flameout conditions. When fuel pressure returns to normal, the combustion chamber can overfill with fuel before igniting. This can easily result in combustion explosions that are violent enough to blow the “ends” of the boiler and even through surrounding structures. Extensive property damage, injury, and even death can result.

4.1.3 Checking the Low Pressure Fuel Cutoff Switch

This switch is checked by isolating the switch and slowly venting gas until the switch activates. A step by step test procedure for the low pressure fuel cut out switch for the main gas and main oil supply systems as well as the pilot gas system is given in Appendix A.

4.2 HIGH PRESSURE FUEL GAS CUTOFF SWITCH

4.2.1 Description

The high fuel gas pressure cutoff switch is used to cause the automatic fuel shutoff valves to close if fuel pressure is above a given higher limit for safe operation. These switches are used for both the main gas and main oil fuel supply systems (See Figure 4.2). In both applications the switch should be located after the pressure regulating valve and upstream of the fuel control valve. The switch is in continuous operation once the boiler is in the run mode.

Figure 4.2 High Pressure Fuel Cutoff

4.2.2 Consequences of High Pressure Fuel Cutoff Switch Failure High fuel pressure can cause unstable flame conditions but more importantly it can result in over-firing the boiler. Over-firing can damage burner/boiler materials to the point of meltdown and explosion. The generation of steam can be so intense that a pressure vessel explosion can occur. High fuel pressure can easily occur if a pressure regulator and high-pressure cutoff switch were to fail.

4.2.3 Checking the High Pressure Fuel Cutoff Switch

The switch is checked by isolating the switch and using a hand pump or equivalent device (see Appendix E for equipment list) to raise the pressure until the switch trips out the boiler. A step by step test procedure for the high pressure fuel cut out switch for the main gas and main oil supply systems is given in Appendix A.

4.3 VENTING BETWEEN AUTOMATIC GAS SHUTOFF VALVES

4.3.1 Description

The volume between the automatic fuel gas shutoff valves should be vented to the atmosphere with a system as shown in Figure 4.3 for both the main gas and pilot line automatic shut off valves. While the boiler is running the solenoid valve is shut and gas flows through the two automatic shutoff valves to the burner. When the fuel shut-off valves close, the solenoid valve opens and vents any residual gas in the space between the valve and any leakage of gas through the first automatic shutoff valve.

The purpose of the vent system is to ensure that even if the first automatic shutoff valve leaks, the gas is vented rather than allowed to move through the second automatic fuel-shutoff valve and then into boiler. The vent line must be vented to the atmosphere outside of the building.

TP

AFGSOV AFGSOV HFGPCS FUEL FLOW

CONTROL

HFGPCS

AFGSVV

TP

LOCK OPEN

TP TP

BLOCK AND BLEED SYSTEM

Figure 4.3 Gas Train Vent Valve

4.3.2 Consequences of a Failed Vent Valve

Fuel leaks into the boiler are obviously dangerous because if both automatic shut off valves leak, gas would fill the boiler furnace while the boiler is off. Fuel mixed with air is a potentially explosive mixture that with any source of ignition could result in disaster.

On ignition if purging did not adequately vent this gas, a tremendous explosion would result when lighting the burner. This combustion explosion could easily wipe out all property and personnel within several hundred feet of the boiler.

4.3.3 Testing the Gas Train Vent Valve (solenoid valve)

Testing of the vent system includes doing a bubble test with the boiler running by attaching a tube to the test port downstream of the AFGSVV as shown in Figure 4.3 and letting the other tube end be slightly immersed in water with the manual valve above the AFGSVV closed. The other test is to see if the pressure between the two automatic shut off valves goes to zero when the boiler stops running and the manual valve is open.

A detailed step by step procedure to check all these aspects of the vent valve are given in Appendix A.

4.4 LEAK TEST OF AUTOMATIC FUEL SHUT OFF VALVES

4.4.1 Description

A block and bleed system is provided as discussed in section 4.3 to prevent fuel from entering and potentially collecting in the boiler while the boiler is off. This system is used on the main oil and gas supply lines to the burner as well as the pilot gas supply.

(On the main oil supply line a vent is not required. However, some manufacturers do use a vent and if one is provided, it must be equipped for testing and must be tested.)

The two automatic shut off valves used in either case are the means by which the boiler is automatically shut down in case any operating limit is not satisfied. It is essential that these valves do not leak when closed. For both oil and gas, NFPA code requires two automatic shut off valves.

4.4.2 Consequences of Leaking Automatic Shut Off Valves

If both automatic fuel shut off valves leak and the vent system does not function (in the case of gas), fuel would be introduced into the burner and into the boiler furnace while the boiler is off. This fuel would produce a combustible mixture in the boiler. Fuel leaks into the boiler are obviously dangerous because it allows the presence of a combustible air-fuel mixture that could explode when the fuel is ignited on startup. This combustion explosion could easily wipe out all property and personnel within several hundred feet of the boiler.

4.4.3 Testing the Automatic Fuel Shut Off Valves for Leaks

The testing for leaks can be done when the boiler is off. The test procedure for natural gas is measuring for a leak with a “bubble test”. This method involves connecting a tube to a confined space downstream of the valve being tested with positive pressure on the upstream side of the valve. The tube is placed approximately 1/16th of an inch below a water surface in order to have negligible back pressure. Any leak will show up as a bubble generated in the water at the tube exit. For oil a test port can be provided to visually observe whether oil drains from the test port.

A step by step procedure is given in Appendix A for both oil and gas.

4.5 OIL LOW ATOMIZING MEDIA PRESSURE AND DIFFERENTIAL

PRESSURE/FLOW SWITCHES

4.5.1 Description

An atomizing fluid (compressed air or steam) is usually used to aid in the combustion of the oil fuel (See Figure 4.4). A safety switch is required that shuts the boiler off in case of low atomizing media pressure. This switch measures pressure in the atomizing fluid line immediately after the pressure regulating system and causes the automatic fuel control valves to close if the atomizing pressure falls below its set point. If there is a differential pressure regulator, the sensor must be located upstream of that regulator.

In some cases where air is used to atomize, no atomizing media differential pressure switch is used. For this case only the low atomizing media pressure switch described above is needed. For all other cases, a second switch is needed to help ensure that atomizing media is flowing at a sufficient rate into the burner. For the case in which the atomizing media pressure at the burner is greater than the oil pressure for all firing rates, a differential pressure switch is needed. For the case where the atomizing media is less than oil pressure at some firing rates (“crossover”), a flow switch is required by the VA. The differential pressure switch must be located as shown in the figure. The flow switch must be in the atomizing media line before it enters the burner.

Figure 4.4 Low Atomizing Media and Differential Pressure Switches (Note Flow switch not shown)

4.5.2 Consequences of Low Atomizing Media Pressure, Inadequate Atomizing Media Differential Pressure or Inadequate Atomizing Media Flow

Low atomizing media pressure, low atomizing media differential pressure or low atomizing media flow could cause poor combustion leading to the production of carbon monoxide, flame instability, and possible combustion explosions leading to serious loss of property and injury/death.

4.5.3 Testing the Oil Low Atomizing Media Pressure Switch

The set point on the oil low atomizing pressure switch must not allow the atomizing media pressure to fall below 80% of the regulated pressure upstream of the switch testing is accomplished on-line by slowly lowering the oil atomizing media pressure and observing that the switch operates at the correct set point. If a low atomizing media flow switch is required, the testing is done on line by slowly closing the manual valve in the atomizing media line and observing the atomizing media pressure at point that the switch shuts off the boiler. The switch must shut off the boiler at a atomizing media pressure lower than 80% of the regulated pressure up stream of the switch.

4.5.4. Testing the Low Atomizing Media Differential Pressure Switch The set point on the oil low atomizing media differential pressure switch must not allow the atomizing media differential pressure to fall below 80% of the minimum differential pressure seen by the switch from low fire to high fire. Testing is accomplished on-line at low fire by slowly closing the manual valve in the atomizing media line upstream of the low atomizing media differential pressure switch and observing the differential pressure at which the switch closes.

4.5.5. Testing the Low Atomizing Media Flow Switch

The set point on the oil low atomizing media flow switch must not allow the atomizing media flow to fall below 80% of the minimum differential pressure across the flow switch seen by the switch from low fire to high fire. Testing is accomplished on-line at low fire by slowly closing the manual valve in the atomizing media line upstream of the flow switch and observing the differential pressure at which the switch closes.

A step by step procedure for all these switches is given in Appendix A.

4.6 AUTOMATIC FUEL SHUTOFF VALVE PROOF OF CLOSURE SWITCH

4.6.1 Description

The function of an automatic fuel shutoff valve is absolutely essential. All safety devices that require fuel shutdown rely on the two automatic fuel shutoff valves to perform this task. Proof of Closure switches must be present in both automatic shut off valves. Both oil and gas automatic shut off valves require proof of closure switches. The switches in the two valves should be wired in series so that an indicated failure in either valve will prevent the boiler from starting. The proof of closure switch is an integral part of the automatic fuel shutoff valve. It has a simple function to guarantee that the automatic fuel shutoff valve is closed before allowing the boiler to go through the burner startup sequence. If the automatic fuel shutoff valve is not closed, the proof of closure switch will be open, breaking the circuit and not allowing the burner to start. The proof of closure switch is active only during the startup sequence.

4.6.2 Consequences of a Failed Proof of Closure Switch

If either proof of closure switch fails, the switch could “stick” closed even with the valve open. This malfunction would present a false signal to the burner management system indicating that the valve is closed when it might not be closed. This malfunction could allow the fuel to be ignited with a large quantity of fuel in the furnace. Under this scenario, a combustion explosion would occur. The result could be a tremendous loss of property and death as well as physical harm to personnel within in the boiler area.

4.6.3 Testing the Automatic Fuel Shutoff Valve (Proof of Closure) Switch The proof of closure switch for the gas valves is tested by simultaneously looking at pressure downstream of the valve and the resistance across the switch that is isolated during the light off sequence. The resistance should change from a zero reading to an infinite reading before pressure is observed.

A detailed step by step procedure to testing the proof of closure switches is given in

5 BURNER AND AIR TRAIN SAFETY DEVICES

5.1 THE FLAME SCANNER

5.1.1 Description

A flame scanner is a device that continually monitors the flame to determine whether a flame is present in the combustion chamber. If the flame is extinguished for any reason, the scanner causes the two automatic fuel shutoff valves to close.

Modern flame scanners work by converting either the ultraviolet (UV) or infrared (IR) portion of the thermal radiation produced by the flame to an electrical signal. The UV scanner has some disadvantage in that it can sometimes see the igniter spark as a flame. The IR scanner has a disadvantage in that it can mistake glowing refractory for a flame. A self-checking UV scanner is required to be in compliance with the VA specifications. The “self-checking” feature detects a scanner failure and immediately shuts down the burner.” The strength of the electrical scanner signal is then the indication as to whether an adequate flame is present.

5.1.2 Consequences of a Failed Flame Scanner

If the flame scanner allows fuel to be supplied to the combustion zone when no flame exists, combustion explosions can occur. The combination of a spark due to some type of “glowing” material and a “pocket” of fuel/air mixture at an explosive ratio can result in an explosion. Another scenario is relighting the boiler with an explosive mixture of fuel and air present. There have been numerous accidents in which the front or back of the boiler have blown off and through masonry walls with loss of life and property damage.

5.1.3 Checking a Flame Scanner

There are many potential tests for a flame scanner depending on the situation. The guiding principle is to try to check the scanner operating in the same mode that a potential failure might occur. The required test is then to cause the flame to extinguish by shutting off the fuel supply and to determine whether the flame scanner then causes the two automatic fuel shut-off valves to close. It is very important that the flame scanner be checked on both oil and gas firing.

A detailed step by step procedure is given for testing the flame scanner in Appendix A.

5.2 LOW FIRE PROVING SWITCH

5.2.1 Description

In the startup procedure for the boiler, the safest way to light the main burner is with a minimum of fuel input. Low fire proving switches are required by the VA to be position switches that are closed only if the fuel valves and air damper are in the low fire position. These low-fire proving switches have the function of not allowing the main flame to be ignited if the firing positions for fuel and air are not a minimum. A low fire proving switch can be located in the drive motor that causes the movement of the fuel valve or air damper but, in that case, all linkages between the drive motor and valve/damper must be drilled and pinned. In some electronic control systems, a potentiometer is used to determine the position of the inlet damper by the output of a voltage level to the controller. This potentiometer is not compliant with VA requirements. Parallel position systems require separate proof of closure switches for the low fire position for air and both fuels while single point positioning systems require only a proof of closure switch on the fuel valve if linkages are properly drilled and pinned.

5.2.2 Consequences of a Failed Low Fire Proving Switch

Failure of the low-fire proving switch could allow the boiler to start in a high fire position. This result could easily lead to a violent combustion explosion with property loss as well as injury and death to individuals the area of the boiler.

5.2.3 Testing the Low-Fire Proving Switch

The low-fire proving switch should be tested during the boiler startup sequence. The switch is isolated and the switch set point is determined by a voltage measurement across the switch during boiler startup. A check to see if the boiler will attempt to light with the switch open is the final part of the test.

A detailed step by step procedure for testing the low fire proving switch is given in

5.3 COMBUSTION AIR PRESSURE SWITCH

5.3.1 Description

A combustion air pressure switch is used for the purpose of causing the two automatic fuel shutoff valves to close if the forced draft fan is not producing proper air pressure (See Figure 5.1). This switch uses a differential pressure measurement across the fan.

The switch is in the safety control circuit anytime the boiler is in the run position. For a constant speed fan, the set point for the switch is established by measuring the minimum pressure differential seen by the switch over the firing range and setting its switch trip point at approximately 80% or more of the minimum differential pressure.

For a variable speed forced draft fan, the set point is set by measuring the pressure differential across the fan during purge and setting the trip point at 35% or more of the pressure difference during purge. In order to meet the requirement for the variable speed forced draft fan, it will probably be necessary to limit the turn down on fan speed to 40 Hertz.

Figure 5.1 Combustion Air Pressure Switch

5.3.2 Consequences of a Failed Combustion Air Switch

If the fan fails to produce adequate combustion air, incomplete combustion will occur.

Incomplete combustion can result in a combustion explosion and the production of carbon monoxide with its attendant toxicity can easily cause death for operators.

5.3.3 Testing Combustion Air Flow Switch

The first step in the test procedure is to establish the pressure difference on which to base the switch trip point. Separate procedures in Appendix A are given for the cases of constant and variable speed forced draft fans. Once this pressure difference has been established, the high pressure side of the switch can be isolated as shown in Figure 5.1.

The pressure is then bled down and the set point determined.

A detailed step by step procedure for testing the combustion air flow switch is given in

5.4 PURGE AIR FLOW PROVING SWITCH

5.4.1 Description

The purpose of the purge airflow-proving switch (PAPS) is to ensure that during purging sufficient air volume is moved through the boiler. Four air changes are required for fire tube boilers and eight air changes are required for water tube boilers. Hence, the PAPS serves the role of proving airflow rate during purging. The PAPS works by measuring pressure change across a boiler. The switch should see a small pressure change at low fire with a much larger change in the purge (high fire) position. This pressure should be measured across the boiler without variable restrictions.

CAPS

TP

Lock Open

5.4.2 Consequences of a Failed Purge Airflow Proving Switch

If this switch were to malfunction, it would be possible to ignite the pilot or main flame with combustible gas mixtures present in the boiler. This could result in a combustion explosion.

5.4.3 Testing the Purge Airflow Proving Switch

The purge air flow proving switch should be tested during the boiler startup sequence.

It is tested with the same procedure as the combustion air pressure switch.

A detailed step by step procedure for testing the purge air flow proving switch is given in Appendix A.

5.5 BURNER POSITION SWITCH

5.5.1 Description

Some manufacturers of oil burners require a position switch to indicate that the burner is in the correct position before firing. The switch is generally a simple proximity switch that is electrically closed by depression of the switch by the burner as it is fully inserted into the boiler. For those boilers utilizing this switch it must be tested.

5.5.2 Consequences of Burner Position Switch Failure

If the boiler could fire on oil with the burner partly retracted, fire, production of carbon monoxide, flame instability, and combustion explosions could result.

5.5.3 Testing the Burner Position Switch

The switch is tested by determining if the boiler would fire on oil with the burner partially retracted. If the switch is properly set up, the boiler control will not allow the boiler to leave purge with the burner out of position.

A detailed step by step testing procedure is given in Appendix A.

5.6 FORCED DRAFT MOTOR INTERLOCK

5.6.1 Description

The forced draft motor interlock provides an extra level of safety relative to proving “purge air flow” and “combustion air flow” and protects the fan motor from running with an inadequate power supply such as single phasing. There are three types of interlocks currently being used. The simplest interlock is an auxiliary contact which is a single pole switch that “makes” when the main switch supplying 3-phase power to the fan is closed.

One could cut any or all of the power leads going to the motor and this switch would indicate acceptable operation. For this reason, this interlock is not acceptable. A second design utilizes phase monitors on all three legs that look at the incoming power characteristics that is able to detect a loss of incoming power to the panel. However, the fan motor could be disconnected electrically and the phase monitor would indicate acceptable operation. Again this interlock is not acceptable. The VA approved interlock is based on current relays in which current in all three legs supplying power to the motor is measured (See Figure 5.2). This interlock involves encircling each power lead with a current pickup. The lack of sufficient current through any of these current pickups will stop boiler operation. For testing, the VA requires the use of a type of current pickup around each lead that can be opened and removed without disconnecting the power lead from its terminal strip.

3 Phase Line In

Current Transformers feeding current relays

3 Phase Line Out

Figure 5.2 Forced Draft Motor Interlock

5.6.2 Consequences of a Failed Forced Draft Fan Motor Interlock If the fan fails to run or runs at a lower speed, the boiler would produce combustibles leading to the same problems discussed in section 5.5.2.

5.6.3 Testing the Forced Draft Fan Motor Interlock

The test for this interlock consists of determining whether the right type of switch (current relays as shown in Figure 5.2) is in place and then removing the current pickups, one at a time, and determining if the boiler shuts down.

A detailed step by step procedure is given in Appendix A.

5.7 FURNACE PRESSURE INTERLOCK

5.7.1 Description

The purpose of the high furnace pressure interlock (FPI) is to ensure that the furnace pressure does not exceed an acceptable limit due to impeded flow. The FPI works by measuring pressure in the boiler furnace while the boiler is running. A pressure that exceeds the FPI set point “breaks” the interlock to an open position and causes the boiler to shut down.

Motor Contactor

5.7.2 Consequences of High Furnace Pressure Interlock Failure A blockage in the exit portion of the boiler combustion gas circuit, leads to high furnace pressure and incomplete combustion. Under this condition carbon monoxide is generated and the combustion gases are potentially highly explosive. If the FPI were to malfunction two highly undesirable consequences might occur. First, high furnace pressure would cause incompletely combusted gasses internal to the boiler furnace to be expelled into the boiler room. Carbon monoxide levels in the boiler room could reach dangerous levels. Secondly, these incomplete combustion gases could explode if a supply of oxygen became available (For example the flame was temporary extinguished, and then explosively re-ignited by a “hot spot” in the boiler.) Therefore, the consequences of a failed FPI could be dangerous atmospheric conditions for the occupants of the plant and potential explosion.

5.7.3 Testing the Furnace Pressure Interlock

The FPI is tested by first determining the furnace pressure at high fire in order to establish a proper set point for the interlock. It can then be tested on line by isolating the switch and pressurizing the interlock with an air hand pump to determine its set point and action towards shutting off the boiler.

A detailed…