how many safety valve in boiler free sample

Boiler explosions have been responsible for widespread damage to companies throughout the years, and that’s why today’s boilers are equipped with safety valves and/or relief valves. Boiler safety valves are designed to prevent excess pressure, which is usually responsible for those devastating explosions. That said, to ensure that boiler safety valves are working properly and providing adequate protection, they must meet regulatory specifications and require ongoing maintenance and periodic testing. Without these precautions, malfunctioning safety valves may fail, resulting in potentially disastrous consequences.

Boiler safety valves are activated by upstream pressure. If the pressure exceeds a defined threshold, the valve activates and automatically releases pressure. Typically used for gas or vapor service, boiler safety valves pop fully open once a pressure threshold is reached and remain open until the boiler pressure reaches a pre-defined, safe lower pressure.

Boiler relief valves serve the same purpose – automatically lowering boiler pressure – but they function a bit differently than safety valves. A relief valve doesn’t open fully when pressure exceeds a defined threshold; instead, it opens gradually when the pressure threshold is exceeded and closes gradually until the lower, safe threshold is reached. Boiler relief valves are typically used for liquid service.

There are also devices known as “safety relief valves” which have the characteristics of both types discussed above. Safety relief valves can be used for either liquid or gas or vapor service.

Nameplates must be fastened securely and permanently to the safety valve and remain readable throughout the lifespan of the valve, so durability is key.

The National Board of Boiler and Pressure Vessel Inspectors offers guidance and recommendations on boiler and pressure vessel safety rules and regulations. However, most individual states set forth their own rules and regulations, and while they may be similar across states, it’s important to ensure that your boiler safety valves meet all state and local regulatory requirements.

The National Board published NB-131, Recommended Boiler and Pressure Vessel Safety Legislation, and NB-132, Recommended Administrative Boiler and Pressure Vessel Safety Rules and Regulationsin order to provide guidance and encourage the development of crucial safety laws in jurisdictions that currently have no laws in place for the “proper construction, installation, inspection, operation, maintenance, alterations, and repairs” necessary to protect workers and the public from dangerous boiler and pressure vessel explosions that may occur without these safeguards in place.

The documents are meant to be used as a guide for developing local laws and regulations and also may be used to update a jurisdiction’s existing requirements. As such, they’re intended to be modifiable to meet any jurisdiction’s local conditions.

The American Society of Mechanical Engineers (ASME) governs the code that establishes guidelines and requirements for safety valves. Note that it’s up to plant personnel to familiarize themselves with the requirements and understand which parts of the code apply to specific parts of the plant’s steam systems.

High steam capacity requirements, physical or economic constraints may make the use of a single safety valve impossible. In these cases, using multiple safety valves on the same system is considered an acceptable practice, provided that proper sizing and installation requirements are met – including an appropriately sized vent pipe that accounts for the total steam venting capacity of all valves when open at the same time.

The lowest rating (MAWP or maximum allowable working pressure) should always be used among all safety devices within a system, including boilers, pressure vessels, and equipment piping systems, to determine the safety valve set pressure.

General guidance on proper installation may seem like common sense to experienced installers and inspectors. A few of the most important guidelines and best practices include:

Avoid isolating safety valves from the system, such as by installing intervening shut-off valves located between the steam component or system and the inlet.

Contact the valve supplier immediately for any safety valve with a broken wire seal, as this indicates that the valve is unsafe for use. Safety valves are sealed and certified in order to prevent tampering that can prevent proper function.

Avoid attaching vent discharge piping directly to a safety valve, which may place unnecessary weight and additional stress on the valve, altering the set pressure.

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Operating controls for boilers could be broadly defined to include burner management controls; however, this inspector guide will be limited to the pressure and temperature operating controls required by the ASME BPV Code for steam and hot water boilers.

Steam boilers require a device which senses steam pressure and cycles the burner or other source of heat in order to maintain a consistent, predetermined operating pressure. A second device is used to prevent the boiler from exceeding the maximum allowable working pressure (MAWP) indicated on the boiler nameplate.

Hot-water boilers require a device which senses water temperature and cycles the burner or other source of heat in order to maintain a consistent, predetermined operating temperature. A second device is used to prevent the boiler from exceeding the design temperature of an ASME BPV Code Section I boiler or the maximum water temperature indicated on an ASME BPV Code Section IV boiler nameplate.

The secondary device referenced above for both steam and hot-water boilers is referred to as a high-limit control and under normal conditions, would never be called upon to operate. However, if the primary, or operating, control should fail, the high-limit control must operate, stopping the burner or other source of heat. Some high-limit controls incorporate a manual reset. The purpose of this is to alert the operator that the high-limit control has been activated. The operator should then look for the problem which caused the high-limit control to activate before resetting the device and restarting the boiler.

ASME BPV Code Section I does not specifically mandate pressure or temperature controls but they will be found, in one form or another, on almost all ASME BPV Code Section I boilers. In addition, ASME Standard CSD-1 (if applicable) requires the controls on boilers with input ratings up to 12,500,000 Btu/hr. Jurisdictional regulations will specify the use of ASME Standard CSD-1 if it is mandated.

A pressure control must be installed so as to always sense pressure from the steam space of the boiler. The ASME BPV Code requirements and device manufacturer"s instructions should be followed for any installation details. When a siphon or pigtail is used to prevent live steam from entering and damaging the device, the orientation of the siphon loop is critical to the proper operation of a device containing a mercury switch. If the siphon loop is installed in the incorrect orientation shown in Figure 1, movement of the loop caused by heat and/or pressure can cause the mercury switch in the device to activate or deactivate at other than the set pressure.

A temperature control must be installed as required by the ASME BPV Code and the manufacturer"s instructions. Temperature controls are designed and manufactured in different configurations to sense temperature on the surface of a pipe (sometimes called a surface mount device), in a thermo-well, or directly in the water.

Either type of operating control can be bypassed electrically with jumper wires. Jumper wires can be used legitimately by qualified service personnel during maintenance and testing, but must be removed before returning the boiler to normal operation. Jumper wires could be used inappropriately in an attempt to permanently bypass a control which has malfunctioned and will not allow the boiler to operate.

While inspecting low-pressure or high-pressure boilers, the inspector will be observing operating controls. The inspector must take the time necessary to completely evaluate the condition and operational effectiveness of these controls. The inspector should:

Compare the pressure gage reading on a steam boiler with the set pressure of the primary operating control. If the pressure gage reading is higher than the set pressure of the control, request the installation of a second, reliable pressure gage in order to determine the accuracy of the first pressure gage. If the second pressure gage reading agrees with the operating control set pressure, the first pressure gage must be recalibrated or replaced. If, however, the second pressure gage reading agrees with the first pressure gage, the boiler should be removed from service until the primary operating control can be repaired or replaced.

Compare the thermometer reading on a hot-water boiler with the set temperature of the primary operating control. If the thermometer reading is higher than the set temperature of the control, request the installation of a second, reliable thermometer in order to determine the accuracy of the first thermometer. If the second thermometer reading agrees with the operating control set temperature, the first thermometer must be recalibrated or replaced. If, however, the second thermometer reading agrees with the first thermometer, the boiler should be removed from service until the primary operating control can be repaired or replaced

Request the owner or owner"s representative test the high-limit control in accordance with the control manufacturer"s instructions. This test may involve disabling the primary operating control or setting the primary control"s pressure or temperature, as applicable, higher than the setting of the high-limit control. Since each installation can be unique, the inspector should rely on the control manufacturer"s instructions for guidance. Before returning the boiler to its normal operating condition, ensure all operating controls are enabled and set to the proper pressure or temperature.

Additional information to aid inspections of operating controls, including installation requirements, can be found in the following publications and sources:

In order to ensure that the maximum allowable accumulation pressure of any system or apparatus protected by a safety valve is never exceeded, careful consideration of the safety valve’s position in the system has to be made. As there is such a wide range of applications, there is no absolute rule as to where the valve should be positioned and therefore, every application needs to be treated separately.

A common steam application for a safety valve is to protect process equipment supplied from a pressure reducing station. Two possible arrangements are shown in Figure 9.3.3.

The safety valve can be fitted within the pressure reducing station itself, that is, before the downstream stop valve, as in Figure 9.3.3 (a), or further downstream, nearer the apparatus as in Figure 9.3.3 (b). Fitting the safety valve before the downstream stop valve has the following advantages:

• The safety valve can be tested in-line by shutting down the downstream stop valve without the chance of downstream apparatus being over pressurised, should the safety valve fail under test.

• When setting the PRV under no-load conditions, the operation of the safety valve can be observed, as this condition is most likely to cause ‘simmer’. If this should occur, the PRV pressure can be adjusted to below the safety valve reseat pressure.

• Any additional take-offs downstream are inherently protected. Only apparatus with a lower MAWP requires additional protection. This can have significant cost benefits.

Indeed, a separate safety valve may have to be fitted on the inlet to each downstream piece of apparatus, when the PRV supplies several such pieces of apparatus.

• If supplying one piece of apparatus, which has a MAWP pressure less than the PRV supply pressure, the apparatus must be fitted with a safety valve, preferably close-coupled to its steam inlet connection.

• If a PRV is supplying more than one apparatus and the MAWP of any item is less than the PRV supply pressure, either the PRV station must be fitted with a safety valve set at the lowest possible MAWP of the connected apparatus, or each item of affected apparatus must be fitted with a safety valve.

• The safety valve must be located so that the pressure cannot accumulate in the apparatus viaanother route, for example, from a separate steam line or a bypass line.

It could be argued that every installation deserves special consideration when it comes to safety, but the following applications and situations are a little unusual and worth considering:

• Fire - Any pressure vessel should be protected from overpressure in the event of fire. Although a safety valve mounted for operational protection may also offer protection under fire conditions,such cases require special consideration, which is beyond the scope of this text.

• Exothermic applications - These must be fitted with a safety valve close-coupled to the apparatus steam inlet or the body direct. No alternative applies.

• Safety valves used as warning devices - Sometimes, safety valves are fitted to systems as warning devices. They are not required to relieve fault loads but to warn of pressures increasing above normal working pressures for operational reasons only. In these instances, safety valves are set at the warning pressure and only need to be of minimum size. If there is any danger of systems fitted with such a safety valve exceeding their maximum allowable working pressure, they must be protected by additional safety valves in the usual way.

In order to illustrate the importance of the positioning of a safety valve, consider an automatic pump trap (see Block 14) used to remove condensate from a heating vessel. The automatic pump trap (APT), incorporates a mechanical type pump, which uses the motive force of steam to pump the condensate through the return system. The position of the safety valve will depend on the MAWP of the APT and its required motive inlet pressure.

This arrangement is suitable if the pump-trap motive pressure is less than 1.6 bar g (safety valve set pressure of 2 bar g less 0.3 bar blowdown and a 0.1 bar shut-off margin). Since the MAWP of both the APT and the vessel are greater than the safety valve set pressure, a single safety valve would provide suitable protection for the system.

However, if the pump-trap motive pressure had to be greater than 1.6 bar g, the APT supply would have to be taken from the high pressure side of the PRV, and reduced to a more appropriate pressure, but still less than the 4.5 bar g MAWP of the APT. The arrangement shown in Figure 9.3.5 would be suitable in this situation.

Here, two separate PRV stations are used each with its own safety valve. If the APT internals failed and steam at 4 bar g passed through the APT and into the vessel, safety valve ‘A’ would relieve this pressure and protect the vessel. Safety valve ‘B’ would not lift as the pressure in the APT is still acceptable and below its set pressure.

It should be noted that safety valve ‘A’ is positioned on the downstream side of the temperature control valve; this is done for both safety and operational reasons:

Operation - There is less chance of safety valve ‘A’ simmering during operation in this position,as the pressure is typically lower after the control valve than before it.

Also, note that if the MAWP of the pump-trap were greater than the pressure upstream of PRV ‘A’, it would be permissible to omit safety valve ‘B’ from the system, but safety valve ‘A’ must be sized to take into account the total fault flow through PRV ‘B’ as well as through PRV ‘A’.

A pharmaceutical factory has twelve jacketed pans on the same production floor, all rated with the same MAWP. Where would the safety valve be positioned?

One solution would be to install a safety valve on the inlet to each pan (Figure 9.3.6). In this instance, each safety valve would have to be sized to pass the entire load, in case the PRV failed open whilst the other eleven pans were shut down.

If additional apparatus with a lower MAWP than the pans (for example, a shell and tube heat exchanger) were to be included in the system, it would be necessary to fit an additional safety valve. This safety valve would be set to an appropriate lower set pressure and sized to pass the fault flow through the temperature control valve (see Figure 9.3.8).

A little product education can make you look super smart to customers, which usually means more orders for everything you sell. Here’s a few things to keep in mind about safety valves, so your customers will think you’re a genius.

A safety valve is required on anything that has pressure on it. It can be a boiler (high- or low-pressure), a compressor, heat exchanger, economizer, any pressure vessel, deaerator tank, sterilizer, after a reducing valve, etc.

There are four main types of safety valves: conventional, bellows, pilot-operated, and temperature and pressure. For this column, we will deal with conventional valves.

A safety valve is a simple but delicate device. It’s just two pieces of metal squeezed together by a spring. It is passive because it just sits there waiting for system pressure to rise. If everything else in the system works correctly, then the safety valve will never go off.

A safety valve is NOT 100% tight up to the set pressure. This is VERY important. A safety valve functions a little like a tea kettle. As the temperature rises in the kettle, it starts to hiss and spit when the water is almost at a boil. A safety valve functions the same way but with pressure not temperature. The set pressure must be at least 10% above the operating pressure or 5 psig, whichever is greater. So, if a system is operating at 25 psig, then the minimum set pressure of the safety valve would be 30 psig.

Most valve manufacturers prefer a 10 psig differential just so the customer has fewer problems. If a valve is positioned after a reducing valve, find out the max pressure that the equipment downstream can handle. If it can handle 40 psig, then set the valve at 40. If the customer is operating at 100 psig, then 110 would be the minimum. If the max pressure in this case is 150, then set it at 150. The equipment is still protected and they won’t have as many problems with the safety valve.

Here’s another reason the safety valve is set higher than the operating pressure: When it relieves, it needs room to shut off. This is called BLOWDOWN. In a steam and air valve there is at least one if not two adjusting rings to help control blowdown. They are adjusted to shut the valve off when the pressure subsides to 6% below the set pressure. There are variations to 6% but for our purposes it is good enough. So, if you operate a boiler at 100 psig and you set the safety valve at 105, it will probably leak. But if it didn’t, the blowdown would be set at 99, and the valve would never shut off because the operating pressure would be greater than the blowdown.

All safety valves that are on steam or air are required by code to have a test lever. It can be a plain open lever or a completely enclosed packed lever.

Safety valves are sized by flow rate not by pipe size. If a customer wants a 12″ safety valve, ask them the flow rate and the pressure setting. It will probably turn out that they need an 8×10 instead of a 12×16. Safety valves are not like gate valves. If you have a 12″ line, you put in a 12″ gate valve. If safety valves are sized too large, they will not function correctly. They will chatter and beat themselves to death.

Safety valves need to be selected for the worst possible scenario. If you are sizing a pressure reducing station that has 150 psig steam being reduced to 10 psig, you need a safety valve that is rated for 150 psig even though it is set at 15. You can’t put a 15 psig low-pressure boiler valve after the reducing valve because the body of the valve must to be able to handle the 150 psig of steam in case the reducing valve fails.

The seating surface in a safety valve is surprisingly small. In a 3×4 valve, the seating surface is 1/8″ wide and 5″ around. All it takes is one pop with a piece of debris going through and it can leak. Here’s an example: Folgers had a plant in downtown Kansas City that had a 6×8 DISCONTINUED Consolidated 1411Q set at 15 psig. The valve was probably 70 years old. We repaired it, but it leaked when plant maintenance put it back on. It was after a reducing valve, and I asked him if he played with the reducing valve and brought the pressure up to pop the safety valve. He said no, but I didn’t believe him. I told him the valve didn’t leak when it left our shop and to send it back.

When it came back, I laid it down on the outlet flange and looked up the inlet. There was a 12″ welding rod with the tip stuck between the seat and the disc. That rod was from the original construction and didn’t get blown out properly and just now it got set free. The maintenance guy didn’t believe me and came over and saw it for himself (this was before cell phones when you could take a picture).

If there is a problem with a safety valve, 99% of the time it is not the safety valve or the company that set it. There may be other reasons that the pressure is rising in the system before the safety valve. Some ethanol plants have a problem on starting up their boilers. The valves are set at 150 and they operate at 120 but at startup the pressure gets away from them and there is a spike, which creates enough pressure to cause a leak until things get under control.

If your customer is complaining that the valve is leaking, ask questions before a replacement is sent out. What is the operating pressure below the safety valve? If it is too close to the set pressure then they have to lower their operating pressure or raise the set pressure on the safety valve.

Is the valve installed in a vertical position? If it is on a 45-degree angle, horizontal, or upside down then it needs to be corrected. I have heard of two valves that were upside down in my 47 years. One was on a steam tractor and the other one was on a high-pressure compressor station in the New Mexico desert. He bought a 1/4″ valve set at 5,000 psig. On the outlet side, he left the end cap in the outlet and put a pin hole in it so he could hear if it was leaking or not. He hit the switch and when it got up to 3,500 psig the end cap came flying out like a missile past his nose. I told him to turn that sucker in the right direction and he shouldn’t have any problems. I never heard from him so I guess it worked.

If the set pressure is correct, and the valve is vertical, ask if the outlet piping is supported by something other than the safety valve. If they don’t have pipe hangers or a wall or something to keep the stress off the safety valve, it will leak.

There was a plant in Springfield, Mo. that couldn’t start up because a 2″ valve was leaking on a tank. It was set at 750 psig, and the factory replaced it 5 times. We are not going to replace any valves until certain questions are answered. I was called to solve the problem. The operating pressure was 450 so that wasn’t the problem. It was in a vertical position so we moved on to the piping. You could tell the guy was on his cell phone when I asked if there was any piping on the outlet. He said while looking at the installation that he had a 2″ line coming out into a 2×3 connection going up a story into a 3×4 connection and going up another story. I asked him if there was any support for this mess, and he hung up the phone. He didn’t say thank you, goodbye, or send me a Christmas present.

Pipe dope is another problem child. Make sure your contractors ease off on the pipe dope. That is enough for today, class. Thank you for your patience. And thank you for your business.

A ship’s engine room is a complex arrangement of machinery and systems, which is used in carrying out various operations on board. One such important machinery, which has been assisting ships since the start of shipping, is the marine boiler.

Earlier, marine boilers were primarily installed on a ship for the propulsion plant, which used to run on steam (steam engine).  Today, the steam generated by the boiler is utilized in various systems in the engine room, including heating of fuel for the main engine. Considering the importance of marine boilers and the risks involved with its operation on ships, there has been constant development in the industry to enhance boiler safety on board. Some even consider it one of the “deadliest” machinery systems on board.

Boiler Explosion: Many cases of boiler explosion in the past have shown how dangerous marine boiler can be if not operated professionally. Accidents happen when the fuel system within the boiler is mishandled, or when the steam pressure inside the boiler drum is not regulated.

Boiler Fire/ Meltdown: The boiler fire is another type of accident which can destroy all the tubes inside the boiler and lead to an explosion or spreading of fire within the ship.

Scalding: Scalding is a type of burn caused by high-temperature steam. Steam burn is one of the most common accidents seafarers experience on board. It is said that 8 out of 10 seamen, who work with the steam system, have experienced scalding (major or minor) in their careers at least once.

Hot Surface: The boiler and the associated pipes, valves, and auxiliaries have a very hot surface as they carry steam to different parts of the ship. A direct skin contact with any of the exposed surface will lead to severe burn.

Other Risks: Other risks such as high pressurized parts, handling harmful chemicals, moving machinery etc. are also associated with operating marine boilers.

Needless to say, safety is a critical aspect when operating a high or even a low-pressure boiler on a ship and therefore different marine boiler devices are provided.

Boiler Safety System and Instruments: A modern marine boiler is fitted with several safety devices for the protection of the operator. For easy understanding, let us divide these instruments/devices as per the system they are fitted in –

Steam Safety System: The steam system in the boiler is a high pressure, high-temperature area. To safeguard the operator and the boiler itself, it is fitted with the following safety features:

Pressure gauge: Multiple pressure gauges are fitted to ensure the operator has an idea of the current value of pressure inside the boiler. Usually, two pressure gauges are fitted on the boiler and one line is taken from the steam drum to the engine control room, to display the steam pressure remotely.

The pressure gauges are also incorporated with cut-in and cut-out automation systems, i.e. the input from the pressure gauges are used to operate the boiler burner. When the pressure reaches the set value, the boiler burner will stop firing and when the pressure drops to a lower set value, the burner will be switched ON to raise the boiler pressure.

Safety Valve: Boiler safety valve is an extremely important safety equipment fitted on the steam drum of the boiler. As per SOLAS chapter II-1, every steam boiler and every un-fired steam generator shall be provided with not less than 2 safety valves of adequate capacity. However, with regards to the output or any other feature of a boiler or un-fired steam generator, the administration may permit only one safety valve to be fitted if adequate protection against overpressure is thereby satisfactorily provided.

Usually, an improved high lift is one of the most popular types of safety valves used on a ship. They are set to lift at the blow-off pressure and shut when the pressure reduces to the safe limit. They are set to open at 3 % above working pressure. The lift of valve is one-twelfth of the valve diameter.

Easing Gear: The easing gear is attached to the boiler safety valve. Every individual safety valve is provided with its own easing gear, which is a pulley and wire arrangement (connected to the lever of the safety valve) with an accessible handle at the lower operating boiler platform. It is used to lift the boiler safety valve in case of an emergency (without getting near to the safety valve) and to regularly test the operation of the safety valves.

Steam Pressure Alarm and cutout: An audio-visual alarm is also provided for the steam pressure system to remind the operator about the steam pressure. Once the alarm activates and the pressure continues to rise (or decrease), the cut-out will get activated and it will shut off the fuel burner. The cutout functioning is different and independent of the automation which operates the burner. The low-pressure cutout has an option to override it, but the high-pressure cutout will stop the burner and should never be overridden in any case

Boiler Vent: Vent on the boiler drum is required to ensure boiler does not implode once it is shut down. It is normally opened when the pressure gauge shows the reading below 0.5 bars.

Water Safety System: The water system is a high-temperature system and the level and quality of the water inside the water drum plays a crucial role in the safe operation of the boiler. Following are the equipment/system fitted on the water side of the marine boiler:

Low / high water level alarm and cutout: The boiler water drum is fitted with a level sensor, which will continuously monitor the level of water inside the drum. A full drum will carry over the water or will have no space to generate steam, thus reducing the efficiency of the boiler; whereas low or no water level in the drum will lead to over-heating of tubes and can lead to fire or meltdown of the complete boiler.

The low/ high water level provides an early warning to the operator for taking appropriate action to manage the water level inside the boiler water drum.

Too low water level alarm and shut down: The initial warning provided by the above arrangement (low/high water level alarm), may not be sufficient for the operator as there can be a major leak in the tubes, leading to a reduction in the water level. A secondary safety is therefore provided i.e. Too low water level alarm and shut down, which will stop the burner firing to control the overheating of the boiler internal parts.

Water level indicators: The boiler is fitted with multiple water level indicators to make it easy for the operator to see the water drum level and ensure operational safety of the boiler.

Local gauge glasses are provided in a duplex on the boiler drum to ensure at least one gauge glass is operational in case one stops showing the level. Remote water level indicators such as a differential pressure water level sensor, probe level sensor etc. are also provided to indicate the current level in the drum at a remote position such as the engine control room.

Salinity Sensor: The boiler drum is fitted with a salinity sensor, which continuously monitors the dissolved solids content in the water. If the solid (e.g. salt) content exceeds the set value, it trips the boiler to ensure the tubes and boiler internals does not get affected due to the contamination. The operator should either blow down the boiler and feed fresh water to the drum to eliminate the cause which is resulting in high salinity (for e.g. leakage in the condenser)

Fuel Safety System: The boiler is provided with heavy or marine gas fuel oil for generating the heat in the furnace. To ensure the fuel system is operating efficiently, it is fitted with the following boiler safety features:

Low fuel oil pressure alarm: The fuel to the burner is provided using a fuel oil pump. Two pumps areinstalled (one kept as standby) to ensure there is no operational hindrance in case of failure of one pump. If the fuel supply pressure is less than required, the atomization of fuel will not happen, leading to dripping of fuel inside the furnace. This can lead to blow-back of the burner and can seriously injure the operator. Once the low-pressure alarm is sounded, the operator must ensure to eliminate the cause behind it.

Low / high fuel oil temperature alarm: Modern marine boilers are meant to operate in different grades of fuel due to the port / ECA regulations for minimizing the air pollution from the ship. The oil temperature is an important factor as it controls the viscosity of the fuel which is directly related to atomization and efficient combustion inside the furnace. If the fuel temperature is not at its set value (which will vary for different grades), the alarm will sound. The operator must stop the alarm and the oil temperature should be brought to normal before restarting the boiler.

Flame failure alarm: The burner unit which is a photocell (also known as the flame eye) is used to detect the flame inside the furnace. If the burner is abruptly stopped, or during starting the main burner is not producing flame, the photocell will detect the absence of the flame and sound an audio-visual alarm.

Smoke Density alarm: With more stringent rules coming up for environmental protection, the boiler exhaust is fitted with a smoke density sensor which detects the post-combustion product, especially during starting of a boiler and at low loads. If the smoke density is higher than the required value, it will sound an alarm to which the operator needs to check the combustion of the boiler

Force draught fan stop alarm:To have an efficient combustion, a proper mixture of air and fuel is needed. The air is provided to the burner assembly using a forced draught fan (FDF). If the fan is not operational due to any reason, it will generate an alarm.

Operational Safety: Automation, alarms, and warnings have made the life of seafarers on ships a lot easier than what it used to be in terms of boiler safety. However, professional engineers rarely depend on them and always rely on the best practice for efficiently running the machinery.

Efficient hot well/ cascade tank function: Maintaining the correct hot-well temperature will decrease the steam production time of the boiler compared to a low-temperature water supply by the cascade tank

Routine furnace inspection: Boiler furnace is responsible to contain the heat within the boiler and to reduce the surface heat loss. Maintaining the furnace refractory will lead to efficient boiler steam production

Lagging: Once the steam comes out of the boiler via main steam stop valve, it is supplied to several systems via pipes and distribution valves. A proper lagging on the pipes and valves will ensure the boiler need not run extra as the steam loss will be contained. Also, it ensures the safety of ship staff from surface burns.

Maintenance: On-time maintenance such as testing of safety valve, cleaning of boiler tubes etc. will result in safe and efficient working of the marine boiler.

Disclaimer:The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

An ardent sailor and a techie, Anish Wankhede has voyaged on a number of ships as a marine engineer officer. He loves multitasking, networking, and troubleshooting. He is the one behind the unique creativity and aesthetics at Marine Insight.

Years ago, it was not uncommon to read news about tragic boiler explosions, sometimes resulting in mass destruction. Today, boilers are equipped with important safety devises to help protect against these types of catastrophes. Let’s take a look at the most critical of these devices: the safety valve.

The safety valve is one of the most important safety devices in a steam system. Safety valves provide a measure of security for plant operators and equipment from over pressure conditions. The main function of a safety valve is to relieve pressure. It is located on the boiler steam drum, and will automatically open when the pressure of the inlet side of the valve increases past the preset pressure. All boilers are required by ASME code to have at least one safety valve, dependent upon the maximum flow capacity (MFC) of the boiler. The total capacity of the safety valve at the set point must exceed the steam control valve’s MFC if the steam valve were to fail to open. In most cases, two safety valves per boiler are required, and a third may be needed if they do not exceed the MFC.

There are three main parts to the safety valve: nozzle, disc, and spring. Pressurized steam enters the valve through the nozzle and is then threaded to the boiler. The disc is the lid to the nozzle, which opens or closes depending on the pressure coming from the boiler. The spring is the pressure controller.

As a boiler starts to over pressure, the nozzle will start to receive a higher pressure coming from the inlet side of the valve, and will start to sound like it is simmering. When the pressure becomes higher than the predetermined pressure of the spring, the disc will start to lift and release the steam, creating a “pop” sound. After it has released and the steam and pressure drops below the set pressure of the valve, the spring will close the disc. Once the safety valve has popped, it is important to check the valve to make sure it is not damaged and is working properly.

A safety valve is usually referred to as the last line of safety defense. Without safety valves, the boiler can exceed it’s maximum allowable working pressure (MAWP) and not only damage equipment, but also injure or kill plant operators that are close by. Many variables can cause a safety valve on a boiler to lift, such as a compressed air or electrical power failure to control instrumentation, or an imbalance of feedwater rate caused by an inadvertently shut or open isolation valve.

Once a safety valve has lifted, it is important to do a complete boiler inspection and confirm that there are no other boiler servicing issues. A safety valve should only do its job once; safety valves should not lift continuously. Lastly, it is important to have the safety valves fully repaired, cleaned and recertified with a National Board valve repair (VR) stamp as required by local code or jurisdiction. Safety valves are a critical component in a steam system, and must be maintained.

All of Nationwide Boiler’s rental boilers include on to two safety valves depending on the size; one set at design pressure and the other set slightly higher than design. By request, we can reset the safeties to a lower pressure if the application requires it. In addition, the valves are thoroughly checked after every rental and before going out to a new customer, and they are replaced and re-certified as needed.

My name is Kelly Paffel, Technical Manager for Inveno Engineering, LLC, located in Tampa, Florida. We are an engineering firm focused on steam and condensate systems. Today I want to talk about steam safety valves: sizing, selection, installation, best practices. Steam safety valves installed wherever the maximum allowable working steam pressure of a system or over pressurizing a containing vessel is likely to be exceeded. In particular under fault conditions due to a failure of another piece of equipment in the system.

The typical system we have a pressure inducing valve here. We have a pressure 200 PSI here. And our equipment down here is only rated for 150 PSI, then we need to protect it with a safety relief valve. And typically, that safety relief valve will be set for the lowest rated equipment or component in the system; pressure and temperature rating.

The codes for this steam safety valve is governed by the American Society of Mechanical Engineers (ASME). ASME, through its committees, has established Boiler and Pressure Vessel Codes for safety though rules and formulas indicating a good practice. The National Board of Boiler and Pressure Vessel Inspectors has the authority to verify, administer and enforce this ASME code wherever it has been adopted. Therefore any safety valve that we must follow the code set out by ASME and under the jurisdiction of the national report.

Steam safety valve codes. In the steam system, we look at section one which is for the boilers or power boilers. Section 4 is for heating boilers and section 8 is for pressure vessels out there away from the boiler in the steam system. So, anything away from the boiler, we’re typically looking at section 8, safety valves. The example shows right here, this picture here shows the safety valve located on the boiler, which is going to be section 1.

The code stamps and it’s meaning, we have A, M, N, PP, S, U, U2, UV, and V. So these are the codes and these are the meanings of the code. For example, PP is pressure piping, S is for power boilers, U is for pressure vessels, and V is for boiler safety valves.

We’re going to discuss sizing and selection of a safety valve. We’re looking at the design type. The design type can be the standard safety valve, which is shown here, or we can use pilot operated. Then we have body drains, a lifting device here. Some people prefer to have a lifting device, some people do not prefer. Of course the materials here have to be rated for the max pressure and temperature of the system. So that depends on the material, so if we get in to the higher pressures, when we’re dealing with super heat, then materials have to be selected for that super heat pressure and temperature.

The sealing adjustments typically is adjustments here for the over pressurization in blow down, and the set point tolerance has got to be come up with on safety valves. Now, we’re now getting into the details on the internals of the safety valve and we’re going to talk about the selection process.

So here’s a typical application, we’re going to do this for pressure reduction. So we’re reducing steam pressure here, downstream here. Our equipment downstream, we have a device that only rated for 100PSI, 338 degrees. So we’re going to have to put in a safety valve here. So we’re reducing the pressure here to 50PSI for our operation, but we have to protect the system which is going to be 100PSI chain.

Now, the thing is that we typically have a 10 percent differential between the operating set pressures recommended, and the thing is that this pressure differential would be, if we’re operating at 100PSI, or our safety valve is set for 100PSI and we want to operate at 90PSI or lower. That’s due to, the safety valve can go into, what we call simmer[inaudible 00:05:27] so we want to be at least 10 percent away from our set pressure of our safety valve for the operating pressure of the system. Now, some people recommend 20 percent, and that gets into the lower pressure operation where we’re reducing pressures down to 10 or 12 PSI and we have our safety valve set there for 5PSI. So if my system safety valve is set for 15PSI, it would operate the system at 10PSI to stay away from that simmer effect of the safety valve and that’s per code that the safety valve can go into simmer.

The total capacity of a safety valve at set pressure must exceed the control valve or pressure-reducing valve’s maximum capacity, if the valve were to fail in a fully open position. So if this valve were to fail in the fully open position, this safety valve has to be able to discharge the total capacity. Now, total capacity of the boilers, is the maximum BTU fuel input on the boiler. So the safety valve must be able to relieve the maximum steam output with the maximum BTU input to that boiler, depending on the type of fuel that you’re using for that boiler. Multiple safety valve installation is possible if the capacity can not be reached with one safety valve. It’s common to find that with boilers that we have two or three safety valves to get to the capacity that’s required for that operation.

The steam safety valves sizing designation is designated by numbers. Excuse me. Letters. So up here you’ll see the letters, here. K, L, M, N, P. That gives us the effective orifice area. So if I have a set pressure here 100 PSI, and a P orifice, we have this capacity here, which is around 37012 pounds per hour. So we look up the safety valve and see 4 by 6 P. P means the orifice inside the safety valve.

Now, a safety relief valve must be mounted in the vertical position. The reason mounted in the vertical position is a safety valve is set up as assembled or manufactured in the vertical position, so you must duplicate how the position is of the safety valve. The system must be free of dirt of course. Upstream piping connection must be at least equal to the valve, so if the end of the valve is 6 inches, then this connection valve here needs to be 6 inches.

With the steam safety valve no shutoff valve can be installed down here, and do not plug the drain valves, and the discharge lines should be no less than the full area of the valve. In the [inaudible 00:08:38] that make sure we have a drip pan elbow put onto the valve, and this just changes direction from horizontal to vertical, and increases the pipe on pipe diameter, and then the vent pipe can come down but does not make contact with the drip pan elbow. The outlet always must discharge where no one can be at harm’s way, typically to the top of the building or the unit, and cut it at a 45 degree angle to signify it’s a steam safety valve. So you cut it at a 45 degree angle, it used to be 7 feet, and this has recently changed, it’s now 10 feet above. That’s a typical installation of a safety valve.

We also have best practices up on the website, to go into more detail on safety valves, but this is just a short version to give you some idea. So if we can be of service, here is out contact information, and have a great day.

A series of anomalies occurred in the boiler room that evening. The steel compression tank for the hydronic loop flooded, leaving no room for expansion. Water will expand at 3% of its volume when heated from room temperature to 180° F. When the burner fired, the expansion of the water increased the system pressure within the boiler. The malfunctioning operating control did not shut off the burner at the set point which caused the relief valve to open.

The brass relief valve discharge was installed with copper tubing piped solid to a 90° ell on the floor and the tubing further extended to the floor drain. The combination of hot water and steam from the boiler caused the discharge copper tubing to expand, using the relief valve as a fulcrum. The expansion of the copper discharge tubing pressing against the floor was enough to crack the brass relief valve, flooding the boiler room. The damage was not discovered until the next morning, several hours after the leak occurred. Thousands of dollars in damage was sustained and luckily no one was injured.

Each boiler requires some sort of pressure relieving device. They are referred to as either a safety, relief or safety relief valve. While these names are often thought of as interchangeable, there are subtle differences between them. According to the National Board of Boiler and Pressure Vessel Inspectors, the following are the definitions of each:

• Safety valve— This device is typically used for steam or vapor service. It operates automatically with a full-opening pop action and recloses when the pressure drops to a value consistent with the blowdown requirements prescribed by the applicable governing code or standard.

• Relief valve— This device is used for liquid service. It operates automatically by opening farther as the pressure increases beyond the initial opening pressure and recloses when the pressure drops below the opening pressure.

• Safety relief valve— This device includes the operating characteristics of both a safety valve and a relief valve and may be used in either application.

• Temperature and pressure safety relief valve— This device is typically used on potable water heaters. In addition to its pressure-relief function, it also includes a temperature-sensing element which causes the device to open at a predetermined temperature regardless of pressure. The set temperature on these devices is usually 210°.

• Relief valve piping— The boiler contractor installed a bushing on the outlet of the safety relief valve. Instead of 1 1/2-in. pipe, the installer used 3/4-in. pipe. When asked about it, he answered that he did not have any 1 1/2-in. pipe but had plenty of 3/4-in. pipe. I explained and then had to show the disbelieving contractor the code that states that the relief valve discharge piping has to be the same diameter as the relief valve outlet (see 2012 International Mechanical Code, 1006.6). By reducing the discharge pipe size, the relieving capacity of the safety valve may not be adequate to properly relieve the pressure inside the boiler, causing a dangerous situation.

The code also states that the discharge material shall be of rigid pipe that is approved for the temperature of the system. The inlet pipe size shall be full diameter of the pipe inlet for the relief valve. Some manufacturers suggest using black iron pipe rather than copper tubing. If using copper, it should have an air space that allows expansion should the relief valve open to avoid the accident that I referenced above. The discharge piping has to be supported and the weight of the piping should not be on the safety relief valve. Valves are not permitted in the inlet piping to or discharge piping from the relief valve. If you are using copper tubing on discharge piping, verify that there is room for expansion.

• Installation— Read the manufacturer’s installation manual as each may have different requirements. For instance, Conbraco requires that the discharge piping must terminate with a plain end and use a material that can handle temperatures of 375° or greater. This will preclude PVC or CPVC pipe for the discharge piping. The instruction manual for its model 12-14 steam relief valve stipulates that you cannot use a pipe wrench to install it. That would be good to know.

I once visited Boiler Utopia as the floor was clean and waxed. All the pipes were covered and exposed pipes were painted. There were large stickers detailing what was inside each pipe as well as directional arrows. Nothing was stacked next to the boilers. Yellow caution lines were painted on the floor around each boiler. I was in heaven. As I walked around the rear of the boiler, something clicked and triggered a warning bell. The discharge of the relief valve piping was about 6 in. from the floor but instead of a plain or angled cut end, the pipe had a threaded pipe cap on the termination. I asked the maintenance person about it and he said that the valve was leaking all over his newly waxed floor and this was the only way he could stop it. When I said that the discharge pipe should not have been threaded, he explained that it was not threaded and he had to take it to the local hardware store to thread it. I informed him that the cap had to be removed. We cut the pipe on an angle to prevent this.

• Steam boiler— Most manufacturers recommend a drip pan ell on the discharge of the steam boiler relief valve to eliminate the weight of the discharge piping on the relief valve. Some codes require the discharge to be vented outdoors.

• Testing— I will ask the attendees in my classes, “How often do you test the relief valves?” Most do not make eye contact and when I follow up with, “Why are they not tested?” I often hear that opening the relief valve will cause it to leak. I suggest that you refer to each manufacturer’s directions for testing. For instance, one will recommend once a year while another recommends twice a year. One manufacturer says, “Safety/relief valves should be operated only often enough to assure they are in good working order.” I am not sure what that even means. You want to also verify the proper test procedure as some will only want the relief valve tested when the boiler is at 75% of the rated pressure or higher of the relief valve.

A boiler valve kit is a must-have for any homeowner with a boiler system. This brass valve kit features a vent safety valve that helps to protect your home from dangerous gas build-up. The included instructions make installation easy, and the durable brass construction ensures lasting performance. Keep your family safe with this essential boiler valve kit.

6. Stable outlet pressure and High reliability, Perfect seal at low and high pressure, and wear-resistant, solid and reliable for lifetime use. Easy to install.

9. When the calibrated pressure is reached, the valve opens automatically and discharges the atmosphere to protect the whole system from safe caused by overpressure

10. This brass boiler valve kit is perfect for any steam-powered project. The kit includes a pressure gauge, safety valve, and two shut-off valves. The pressure gauge helps you monitor the pressure in your boiler, the safety valve keeps your boiler from exploding, and the shut-off valves let you turn off the steam supply without having to drain the boiler.

This brass boiler valve kit is perfect for any steam-related projects you may have. It includes a durable boiler and vent safety valve to keep your project safe and functional. The included instructions make it easy to install this kit in no time. This boiler valve kit is the perfect addition to your tool collection with its high-quality construction and affordable price. This brass boiler valve kit is ideal for any steam-based appliance. The kit includes a boiler valve, vent safety valve, and all the necessary fittings for a quick and easy installation. The included vent safety valve helps to ensure safe operation by releasing excess pressure in the event of a malfunction. This kit is ideal for use with any boiler, including cast iron, steel, or copper boilers.

Vent safety valves are required for all direct-fired appliances; this kit includes everything you need to install one. The boiler valve is brass and has a 1/2-inch pipe thread fitting that can be connected to the vent pipe. It also features an adjustable pressure relief valve with a gauge, protecting your home from high-pressure steam or air from the system. This kit comes with two elbows (1 in., two in.), four nipples (3/4 in., 1/8 in., 3/8 in.), three straight fittings (5/16 inches), and five pipe connectors (3 ways).

This boiler kit includes a brass pressure relief valve with an air vent, which is required by law. It also has a 1/2″ discharge elbow and two unions connecting the pipe inlet to your water heater. The safety valves are designed to prevent excess pressure from building up inside the tank, which can cause dangerous boil-overs or even potential explosions. This kit is excellent for homeowners with existing water heaters without this equipment installed.

Stainless Steel Safety Relief Valve is a safety mechanism deployed in applications to prevent them from bursting under pressure. Suraj Metal Corporationis a leading manufacturer and supplier of the different types such as the Brass Safety Valveand others in various sizes and dimensions. The valves are fitted with the pipelines in a way that when the pressure goes above the threshold level, the Stainless Steel Air Safety Valveopens up and relieves the system of pressure.

This is important to prevent the pipes from being damaged or bursting under high pressure. The Stainless Steel Safety Exhaust Ball Valveis used in the exhaust systems where the temperature plays major role. When the temperature exceeds certain point, it increases pressure and the safety valve opens and balances the pressure in the system. The spring loaded boiler safety valveis used in boilers and heat exchanger systems where steam and hot water are circulated through pipes. There are different gas safety valvetypes and each of these differ in their purpose and functions. Please feel free to contact us for more information on the different types of air compressor pressure relief valveand others with pricing.

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