boiler safety valve testing procedure made in china

As soon as mankind was able to boil water to create steam, the necessity of the safety device became evident. As long as 2000 years ago, the Chinese were using cauldrons with hinged lids to allow (relatively) safer production of steam. At the beginning of the 14th century, chemists used conical plugs and later, compressed springs to act as safety devices on pressurised vessels.

Early in the 19th century, boiler explosions on ships and locomotives frequently resulted from faulty safety devices, which led to the development of the first safety relief valves.

In 1848, Charles Retchie invented the accumulation chamber, which increases the compression surface within the safety valve allowing it to open rapidly within a narrow overpressure margin.

Today, most steam users are compelled by local health and safety regulations to ensure that their plant and processes incorporate safety devices and precautions, which ensure that dangerous conditions are prevented.

The principle type of device used to prevent overpressure in plant is the safety or safety relief valve. The safety valve operates by releasing a volume of fluid from within the plant when a predetermined maximum pressure is reached, thereby reducing the excess pressure in a safe manner. As the safety valve may be the only remaining device to prevent catastrophic failure under overpressure conditions, it is important that any such device is capable of operating at all times and under all possible conditions.

Safety valves should be installed wherever the maximum allowable working pressure (MAWP) of a system or pressure-containing vessel is likely to be exceeded. In steam systems, safety valves are typically used for boiler overpressure protection and other applications such as downstream of pressure reducing controls. Although their primary role is for safety, safety valves are also used in process operations to prevent product damage due to excess pressure. Pressure excess can be generated in a number of different situations, including:

The terms ‘safety valve’ and ‘safety relief valve’ are generic terms to describe many varieties of pressure relief devices that are designed to prevent excessive internal fluid pressure build-up. A wide range of different valves is available for many different applications and performance criteria.

In most national standards, specific definitions are given for the terms associated with safety and safety relief valves. There are several notable differences between the terminology used in the USA and Europe. One of the most important differences is that a valve referred to as a ‘safety valve’ in Europe is referred to as a ‘safety relief valve’ or ‘pressure relief valve’ in the USA. In addition, the term ‘safety valve’ in the USA generally refers specifically to the full-lift type of safety valve used in Europe.

Pressure relief valve- A spring-loaded pressure relief valve which is designed to open to relieve excess pressure and to reclose and prevent the further flow of fluid after normal conditions have been restored. It is characterised by a rapid-opening ‘pop’ action or by opening in a manner generally proportional to the increase in pressure over the opening pressure. It may be used for either compressible or incompressible fluids, depending on design, adjustment, or application.

Safety valves are primarily used with compressible gases and in particular for steam and air services. However, they can also be used for process type applications where they may be needed to protect the plant or to prevent spoilage of the product being processed.

Relief valve - A pressure relief device actuated by inlet static pressure having a gradual lift generally proportional to the increase in pressure over opening pressure.

Relief valves are commonly used in liquid systems, especially for lower capacities and thermal expansion duty. They can also be used on pumped systems as pressure overspill devices.

Safety relief valve - A pressure relief valve characterised by rapid opening or pop action, or by opening in proportion to the increase in pressure over the opening pressure, depending on the application, and which may be used either for liquid or compressible fluid.

In general, the safety relief valve will perform as a safety valve when used in a compressible gas system, but it will open in proportion to the overpressure when used in liquid systems, as would a relief valve.

Safety valve- A valve which automatically, without the assistance of any energy other than that of the fluid concerned, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed to re-close and prevent further flow of fluid after normal pressure conditions of service have been restored.

Safety valves are an arrangement or mechanism to release a substance from the concerned system in the event of pressure or temperature exceeding a particular preset limit. The systems in the context may be boilers, steam boilers, pressure vessels or other related systems. As per the mechanical arrangement, this one get fitted into the bigger picture (part of the bigger arrangement) called as PSV or PRV that is pressure safety or pressure relief valves.

This type of safety mechanism was largely implemented to counter the problem of accidental explosion of steam boilers. Initiated in the working of a steam digester, there were many methodologies that were then accommodated during the phase of the industrial revolution. And since then this safety mechanism has come a long way and now accommodates various other aspects.

These aspects like applications, performance criteria, ranges, nation based standards (countries like United States, European Union, Japan, South Korea provide different standards) etc. manage to differentiate or categorize this safety valve segment. So, there can be many different ways in which these safety valves get differentiated but a common range of bifurcation is as follows:

The American Society of Mechanical Engineers (ASME) I tap is a type of safety valve which opens with respect to 3% and 4% of pressure (ASME code for pressure vessel applications) while ASME VIII valve opens at 10% over pressure and closes at 7%. Lift safety valves get further classified as low-lift and full lift. The flow control valves regulate the pressure or flow of a fluid whereas a balanced valve is used to minimize the effects induced by pressure on operating characteristics of the valve in context.

A power operated valve is a type of pressure relief valve is which an external power source is also used to relieve the pressure. A proportional-relief valve gets opened in a relatively stable manner as compared to increasing pressure. There are 2 types of direct-loaded safety valves, first being diaphragms and second: bellows. diaphragms are valves which spring for the protection of effects of the liquid membrane while bellows provide an arrangement where the parts of rotating elements and sources get protected from the effects of the liquid via bellows.

In a master valve, the operation and even the initiation is controlled by the fluid which gets discharged via a pilot valve. Now coming to the bigger picture, the pressure safety valves based segment gets classified as follows:

So all in all, pressure safety valves, pressure relief valves, relief valves, pilot-operated relief valves, low pressure safety valves, vacuum pressure safety valves etc. complete the range of safety measures in boilers and related devices.

Safety valves have different discharge capacities. These capacities are based on the geometrical area of the body seat upstream and downstream of the valve. Flow diameter is the minimum geometrical diameter upstream and downstream of the body seat.

The nominal size designation refers to the inlet orifice diameter. A safety Valve"s theoretical flowing capacity is the mass flow through an orifice with the same cross-sectional area as the valve"s flow area. This capacity does not account for the flow losses caused by the valve. The actual capacity is measured, and the certified flow capacity is the actual flow capacity reduced by 10%.

A safety valve"s discharge capacity is dependent on the set pressure and position in a system. Once the set pressure is calculated, the discharge capacity must be determined. Safety valves may be oversized or undersized depending on the flow throughput and/or the valve"s set pressure.

The actual discharge capacity of a safety valve depends on the type of discharge system used. In liquid service, safety valves are generally automatic and direct-pressure actuated.

A safety valve is used to protect against overpressure in a fluid system. Its design allows for a lift in the disc, indicating that the valve is about to open. When the inlet pressure rises above the set pressure, the guide moves to the open position, and media flows to the outlet via the pilot tube. Once the inlet pressure falls below the set pressure, the main valve closes and prevents overpressure. There are five criteria for selecting a safety valve.

The first and most basic requirement of a safety valve is its ability to safely control the flow of gas. Hence, the valve must be able to control the flow of gas and water. The valve should be able to withstand the high pressures of the system. This is because the gas or steam coming from the boiler will be condensed and fill the pipe. The steam will then wet the safety valve seat.

The other major requirement for safety valves is their ability to prevent pressure buildup. They prevent overpressure conditions by allowing liquid or gas to escape. Safety valves are used in many different applications. Gas and steam lines, for example, can prevent catastrophic damage to the plant. They are also known as safety relief valves. During an emergency, a safety valve will open automatically and discharge gas or liquid pressure from a pressurized system, preventing it from reaching dangerous levels.

The discharge capacity of a safety valve is based on its orifice area, set pressure, and position in the system. A safety valve"s discharge capacity should be calculated based on the maximum flow through its inlet and outlet orifice areas. Its nominal size is often determined by manufacturer specifications.

Its discharge capacity is the maximum flow through the valve that it can relieve, based on the maximum flow through each individual flow path or combined flow path. The discharge pressure of the safety valve should be more than the operating pressure of the system. As a thumb rule, the relief pressure should be 10% above the working pressure of the system.

It is important to choose the discharge capacity of a safety valve based on the inlet and output piping sizes. Ideally, the discharge capacity should be equal to or greater than the maximum output of the system. A safety valve should also be installed vertically and into a clean fitting. While installing a valve, it is important to use a proper wrench for installation. The discharge piping should slope downward to drain any condensate.

The discharge capacity of a safety valve is measured in a few different ways. The first is the test pressure. This gauge pressure is the pressure at which the valve opens, while the second is the pressure at which it re-closes. Both are measured in a test stand under controlled conditions. A safety valve with a test pressure of 10,000 psi is rated at 10,000 psi (as per ASME PTC25.3).

The discharge capacity of a safety valve should be large enough to dissipate a large volume of pressure. A small valve may be adequate for a smaller system, but a larger one could cause an explosion. In a large-scale manufacturing plant, safety valves are critical for the safety of personnel and equipment. Choosing the right valve size for a particular system is essential to its efficiency.

Before you use a safety valve, you need to know its discharge capacity. Here are some steps you need to follow to calculate the discharge capacity of a safety valve.

To check the discharge capacity of a safety valve, the safety valve should be installed in the appropriate location. Its inlet and outlet pipework should be thoroughly cleaned before installation. It is important to avoid excessive use of PTFE tape and to ensure that the installation is solid. The safety valve should not be exposed to vibration or undue stress. When mounting a safety valve, it should be installed vertically and with the test lever at the top. The inlet connection of the safety valve should be attached to the vessel or pipeline with the shortest length of pipe. It must not be interrupted by any isolation valve. The pressure loss at the inlet of a safety valve should not exceed 3% of the set pressure.

The sizing of a safety valve depends on the amount of fluid it is required to control. The rated discharge capacity is a function of the safety valve"s orifice area, set pressure, and position in the system. Using the manufacturer"s specifications for orifice area and nominal size of the valve, the capacity of a safety valve can be determined. The discharge flow can be calculated using the maximum flow through the valve or the combined flows of several paths. When sizing a safety valve, it"s necessary to consider both its theoretical and actual discharge capacity. Ideally, the discharge capacity will be equal to the minimum area.

To determine the correct set pressure for a safety valve, consider the following criteria. It must be less than the MAAP of the system. Set pressure of 5% greater than the MAAP will result in an overpressure of 10%. If the set pressure is higher than the MAAP, the safety valve will not close. The MAAP must never exceed the set pressure. A set pressure that is too high will result in a poor shutoff after discharge. Depending on the type of valve, a backpressure variation of 10% to 15% of the set pressure cannot be handled by a conventional valve.

When I teach my steam classes, I ask the attendees, "Do you test the pop safety valve?" Most do not. When I ask why, they tell me the same reason; the safety valve will leak. I joke during the classes that you do not want to test the pop safety valve on a Friday afternoon because it will almost certainly leak. I then ask, Do you check the low water cutoff? They look at me like I have a third eye and say they always check the low water cutoff. If you test the low water cutoff, you should test the pop safety valve. It is the last line of defense against a potential catastrophe. One of the things I do when performing a boiler service call is to explain the duty of the pop safety valve and ask the customer if they would like to have it tested. I explain that it could leak and if they refuse to test it, I will notate it on my service call in case something happens. In this way, my company is protected.

The best way to understand the pop safety valve is to read the instructions which came with the valve. I don"t have a life, and while you are watching the Masked Singer, I read O & M manuals. I know, I"m weird. I figure it"s my job to share things I find while reading these page-turners. The manufacturer hides all sorts of useful tidbits on the installation and maintenance of their valve. I have enclosed some information I gleaned while reading the instructions for a Conbraco/Apollo pop safety valve.

The valve must be mounted in a vertical, upright position directly to a clean, tapped opening in the top of the boiler. I see many safety valves installed horizontally and wonder if that voids the warranty. There should be no restrictions or valves in the piping to or from the safety valve. The installation instructions require the discharge piping to be schedule 40 pipe. They specifically say not to use schedule 80 pipe, which is 50% thicker than schedule 40 pipe. Many installers use copper tubing for the discharge, which does not meet the instructions. The other thing which confuses me the manufacturer instructs you not to use a pipe wrench to install the safety valve. I would wager 99% of all valves are installed using a pipe wrench. I wonder what kind of valve they want you to use.

I consult the pop safety manufacturer or the building insurance company to determine the frequency of tests. Apollo recommends quarterly testing using the Try Lever Test unless the valve is located in a severe service condition, and then it should be done more often. They further state the pop safety valve should have a Pressure Test annually before the heating season or at the end of any non-service period. This test will check your courage as you have to jump out the pressure controls and watch the operation of the boiler as the pressure builds. If the pop safety valve opens at the set pressure, the valve is working properly. This is not a test a novice should do alone.

Apollo suggests checking the pop safety valve at or near the maximum operating pressure by holding the test lever fully open for at least 5 seconds and letting it pop closed. On a low-pressure steam system, the pop safety valve is set for 15 psi. I like to run the boiler steam pressure up to 12 psi or higher to check the pop safety valve. After the test, I drop it to the operating pressure the owner requires. If the valve does not open, the boiler should be shut down until it is checked by a licensed contractor or qualified service person.

The pop safety manufacturer requires a minimum pressure differential of five psi between the pressure relief valve set pressure and the boiler operating pressure. It further states, Under no circumstances should the margin be less than five psig. On a low-pressure steam boiler, the pop safety valve will be set for 15 psi. That means the boiler steam pressure should be ten psi or lower. In breweries, it is common to see the boiler pressure set at 12-14 psi. This is less than the five psi differential and could create a dangerous condition.

Boilers operate under extreme pressure and extreme fluctuations in temperature, often undergoing swings in temperature of hundreds of degrees Fahrenheit.

This guide to boiler inspections covers the basics of what a boiler is and does, what happens during a boiler inspection, the work that an inspector of boilers does, and how industries that use boilers can benefit from employing a drone for their inspections.

A boiler is a closed vessel whose purpose is the creation of hot water or steam. This steam is then used as a power source for various purposes (see the next section for some examples).

Typically, in order to create steam in a boiler, coal, oil or gas is converted into heat by combustion. That heat is then applied to the water contained in the boiler and, as the water is heated, it turns into steam.

But boilers don’t simply heat water in order to produce steam. Conditions within a boiler are also optimized to increase the boiling point of water through pressurization. This works the same way in a pressure cooker, where an airtight seal speeds up the time it takes to boil water, or to cook in general.

Through the combination of pressure, an efficient fuel source, and an efficient mechanism for transferring heat to the water, boilers are able to create huge amount of energy in the form of steam.

There are many different types of boilers out there. The difference between them has to do with the way heat is conveyed to or through the water in order to turn it into steam.

Fire-Tube Boiler.In a fire-tube boiler, fuel is burned inside the furnace and then the heat produced is transferred by tubes through the water in the tank to generate steam. Fire-tube boilers are one of the cheapest types of boilers to create since their design and construction is fairly straightforward. For the same reason, they are typically limited to low and medium pressure applications because their shell is not thick enough for higher pressures.

Recovery Boiler. Recovery boilers are used in the pulp and paper industry. They burn black liquor (a pulping byproduct) and recover inorganic elements in order to generate superheated steam.

Water-Tube Boilers. Water-tube boilers are similar to fire-tube boilers, but in water-tube boilers water tubes are heated inside the furnace to create steam instead of heating fire tubes that then transfer heat to the water inside of a tank. Water-tube boilers are more efficient than fire-tube boilers, but also more complex and therefore more expensive.

Biomass Boiler. Biomass boilers are similar to gas-fueled boilers except that they use bio fuel, such as wood chips, wood pellets, logs, or other forms of biomass to create heat instead of using fossil fuels.

But these plates can crack and buckle over time, which is why proper maintenance procedures are so important. If a problem goes undetected for too long, the boiler could suddenly explode with a force equivalent to a bomb going off.

Another concern is preserving the longevity of the boiler. Even if a disaster is not imminent, allowing a flaw to persist without maintenance could lead to a shorter lifespan for the asset, which will lead to increased costs for the company.

Most laws and insurance company guidelines recommend an annual inspection of large boilers. This inspection would be a thorough internal and external inspection, with the boiler cool and under no pressure.

Studies have shown that increasing the frequency of boiler inspections can lead to an increase in the asset life and a reduction in the release of greenhouse gases, but companies have to weigh these benefits against the cost of doing more inspections.

Boiler inspections are done by trained and certified technical specialists who are experts in the inspection of boilers. Given the high degree of specialization required for boiler inspections, companies usually contract out this type of work instead of using someone in-house.

Because boilers can be extremely dangerous if not properly maintained, the processes for inspecting them are rigorous and required by law in most countries.

The American Society of Mechanical Engineers (ASME) has created standards and codes for the installation of boilers, and the American Petroleum Institute (API) has created standards for boiler inspections, both of which are followed all over the world.

One aspect of these requirements is that inspections must be conducted by certified steam boiler inspectors, usually in the presence of a representative from a formal inspection body.

The goal for both the external and the internal inspection is to conduct a visual review of each part of the boiler in order to identify potential problems that could require maintenance.

While external inspections are straightforward and do not require any special preparation beyond making sure the boiler is cool and depressurized, internal boiler inspections can be difficult because of limitations with accessing various parts of a boiler.

In a manual internal boiler inspection, an inspector must physically enter the boiler, which requires the company to build scaffolding for the inspector to stand on during the inspection. Once the inspection is complete, the scaffolding must then be taken down after the inspection.

Boiler room condition. As part of a boiler inspection inspectors will usually inspect the room in which the boiler sits to make sure there is no flammable debris or other encumbrances that could present a safety hazard.

Nameplate. Inspectors will often begin their work at the nameplate, where they can find out the boiler type, when the boiler was made, the maximum pressure allowable in the boiler, and the types of controls needed for the boiler according to ASME manufacturing code and NBIC (National Board Inspection Code) requirements.

Safety valve. From a safety perspective, the safety valve is arguably the most important part of a boiler and will be an important device to review during a boiler inspection. If a problem develops in the boiler, the safety valve (also called the Relief Valve) will help prevent over-pressurization, which can lead to an explosion.

Control safety devices. Also of high importance for safety are control safety devices. Examples include the fuel train, the emergency shut off switch, and operating switch. All of these devices must be visually examined during a typical boiler inspection to ensure continued safe use of the boiler.

Piping. Boiler room piping is used to move water and fuel in and out of the boiler. The condition of the piping must be reviewed during any boiler inspection, both to ensure that it is still in good condition and also to ensure that it is the right kind of piping for the ways it’s being used according to ASME standards. Flue pipe connections must also be inspected to ensure that carbon monoxide is being expelled properly, and not building up in the boiler room.

Fresh air for combustion. Burners within a boiler must receive the correct ratio of fuel to air, which is why inspectors will review the combustion air requirements of the boiler during an inspection to make sure the air pathway is open and providing enough fresh air for the boiler to work properly.

Walls and surfaces. All internal walls and surfaces are inspected, looking for any signs of leaks, corrosion, overheating, or other structural issues within the boiler.

Using a drone instead of a person for collecting visual data in a boiler inspection has several benefits, the biggest of which are safety and savings.

Boilers present many challenges for flying, since the space within them is tight and full of objects for a drone’s blades to hit, which would immediately bring a normal drone crashing down.

Flyability drones are designed specifically for inspections inside confined spaceslike boilers, and help address all of these challenges. Flyability’s

Sending a drone into a confined space instead of an inspector keeps people out of potentially dangerous scenarios, improving the overall safety for those involved in the boiler inspection process.

Using a drone made just for indoor inspections, such as the Elios 3, inspectors can get a close view of burners, tubes, and other parts of the boiler that are typically hard to access during a manual inspection.

Safety valves or pressure relief valves are pressure regulating devices that are responsible for expelling excess pressure from the system when the maximum pressure levels for which they have been designed are exceeded, usually due to a

Safety valves perform their function when the pressure of the system where the fluid is contained, becomes higher than the maximum set pressure of the valve previously adjusted. When the system pressure is higher than the valve’s set

pressure, this opens, releasing the excess pressure to the atmosphere or to containment tanks, depending on the toxicity of the fluid. After releasing the excess, the valve closes again and the system pressure returns to normal.

To ensure total safety of personnel and installation, make sure that the valves have passed all safety tests and meet the requirements of the system where they are to be installed. All our valves are supplied with certificates of materials, cas-

What is the difference between the instantaneous full opening safety valve AIT (PSV) and the normal opening relief valve AN or progressive opening relief valve AP (PRV)?

The Pressure Safety Valve (PSV) opens instantaneously and fully upon reaching the set pressure for which it is designed, expelling the excess pressure from the system immediately. They are optimised for use with steam or gases.

In contrast, the normally or progressively opening Pressure Relief Valve (PRV) opens gradually as the system pressure rises above the set pressure of the valve above its setting. They are optimised to work with liquids.

At VYC Industrial we are specialists in the design and manufacture of all types of safety valves. We have a wide range of safety valves to cover all the needs of the sector.

The Mod. 496 EN safety valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The Mod. 495 EN pressure relief valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The relief valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open, at the fi rst proportional to the pressure increase, and after instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open, at the fi rst proportional to the pressure increase, and after instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open, at the fi rst proportional to the pressure increase, and after instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open proportional to the pressure increase.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open proportional to the pressure increase.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

The valve works as an automatic pressure releasing regulator activated by the static pressure existing at the entrance to the valve and is characterized by its ability to open instantly and totally.

They are used in places such as power, chemical and petrochemical plants to discharge safety valves, control valves, etc. in pressure lines and equipment that convey compressible substances such as steam, air, carbon dioxide, helium, methane, nitrogen, oxygen and other gases.

Test bench for regular inspections and setting and resetting safety valves. Ideal for distributors, maintenance companies or with in-house maintenance. It allows safety valves to be adjusted, tested and/or checked to the test pressure (setting) Pe wile cold (simulating service conditions), matching the opening pressure Ps and the closing pressure Pc, in accordance with the standard regulations.

Controlled safety pressure relief system CSPRS valves are mainly used where conventional direct-loaded spring action valves cannot guarantee the opening and closing margins that certain specifi c conditions of service demand.

The objective is to help the closure by means of pressure so that the valve remains completely watertight until reaching the set pressure and/or to activate the opening with pressure.

Increase the operating pressure of the system up to 99.9% of the set pressure.The control safety pressure relief system CSPRS device can be used with any safety valve available in the market and in particular, with models VYC Mod. 485, 486, 494, 495 and 496.

Manufacturers outside China, who have difficulties to completely carry out the above-mentioned regulations, are allowed to adopt the technical codes and standards, which is conventional and complete in system and are used by most countries after having approved by Boiler and Pressure Vessel Safety Supervision Administration of AQSIQ. But, in this case, they must meet the requirement as stipulated from article 45 to 50 onwards simultaneously.

Steel for pressure components of the boiler (including staying components) must be killed-steels. The designations of the steel should be those listed in foreign boiler steel standards, or of conventional boiler steels.

The results of visual inspection of boiler, mechanical property testing of welded joint, metallograpy and fractography, hydrostatic pressure test, and the NDE items and detective rate must satisfy the requirements of above-mentioned Chinese boiler codes and regulations.

4. Two independent water-level gauges should be mounted on the drum of every steam boiler. Only one gauge may be mounted if one of the following conditions is met:

5. For boilers with a rated capacity not less than 2 t/h, the low/high water level alarms and low water level interlock-protection device should be provided. For boilers with rated capacity not less than 6 t/h, the over-pressure alarm and the over-pressure interlock device should be provided.

7. For hot water boilers with rated temperature of outlet water not less than 120 °C or with rated heating capacity not less than 4.2 MW, the over-temperature alarm should be provided.

2. Strength Calculation sheets for pressure components and the calculation sheets for relieving capacity of safety valves (or selected from operational manual of the safety valves) or a summary of above mentioned calculation results.

A metallic nameplate should be put on the conspicuous place on the boiler. The contents on the nameplate should include at least the following items (in Chinese or English and using SI units):

Pressure vessels produced by pressure vessel manufacturers should meet the requirements of the following Chinese pressure vessels" safety technical codes and regulations:

Manufacturers outside China, who have difficulties to completely carry out the above-mentioned regulations, are allowed to adopt the technical codes and standards, which is conventional and complete in system and are used by most countries after having approved by safety supervision administration under AQSIQ. But, in this case, they must meet the requirement as stipulated from article 52 to 58 onwards simultaneously.

3. Calculation sheets for the required safe relieving capacity of pressure vessel, relieving capacity of safety valves and/or the discharge area of bursting or a summary of above calculation results.

In general, the safety factor for steel pressure vessel shall not be less than 3 if the design is based on the tensile strength at ambient temperature. The factors should normally not less than 1.6 for carbon steel and low alloy steel and not less than 1.5 for high alloy steel if the design is based on the yield strength at ambient temperature. Otherwise, it should subject to prior approval by the safety supervision administration of AQSIQ.

The safety factor for stress analyzing design should normally not be l;ess than 2.6 if the design is based on the tensile strength at ambient temperature and should normally not be less than 1.5 if the design is based on the yield strength both at ambient and design temperatures. Otherwise, it should subject to prior approval by the safety supervision administration of AQSIQ.

3. If the pressure vessel is designed by the strength calculation method other than those in the relevant standards or designed by proof testing, the manufacturer should register at the safety supervision administration of AQSIQ.

c. The words “by other means having the same quality as full penetrating double welding “ in the Table means the welded joint welding by one side which can assure good weld appearance at both side. In this case, it should be qualified with the same measures as for welding by both sides (including the qualification of welding testing plate). The welds by using argon shielded arc welding in backing welding or using ceramic or copper backing pads are the examples.

3). Weldablity test report and welding procedure qualification report of the material should be provided, and report safety supervision administration of AQSIQ for review and approval.

minimum tensile strength in the relevant standard is equal to or greater than 540MPa, the phosphor and sulfur contents shall not be greater than 0.020% and 0.015% respectively. The welding cracking sensitivity coefficient Pcm shall not be greater than 0.25%, and the weldablity test report and welding procedure qualification report of the material shall be provided to safety supervision administration of AQSIQ for review and approval.

1. All gas cylinders must be designed and manufactured in accordance with the Chinese national standards. In addition, the design documents of them shall be appraised before type testing. In the case of lack of Chinese standards, the manufacturer should report the applied standard and related technical document to the safety supervision administration of AQSIQ for review and approval. Among them, the key items related to the safety quality of gas cylinder, such as, design temperature, design pressure, bursting testing, NDE, mechanical properties, must not lower than the requirements as specified in the corresponding Chinese national standard.