boiler safety valve testing made in china

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.

There are various safety valves available to meet various applications and performance criteria demanded by various industries. Furthermore, national standards determine many types of varied safety valves.

Standard ASME I and ASME VIII standards for boiler applications and vessels and ASME / ANSI PTC 25.3 standards for safety valves and relief valves provide the following definition. These standards set performance characteristics and define various types of safety valves used:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Notes; This additional strength (additional burden), which can be provided through foreign resources, is reliably released when the pressure on the safety valve inlet reaches the specified pressure. The amount of additional loading is very regulated that if the additional loading is not released, the safety valve will reach its certified discharge capacity at a pressure which is no greater than 1.1 times the maximum pressure that is permitted to be protected.

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

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

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

Once the valve starts to open, the effects of built-up backpressure also have to be taken into account. For a conventional safety valve with the spring housing vented to the discharge side of the valve.

Therefore, if the back pressure is greater than the overpressure, the valve will tend to close, reducing the flow. This can lead to instability within the system and can result in flutter or chatter of the valve.

In general, if conventional safety valves are used in applications, where there is excessive built-up backpressure, they will not perform as expected. According to the API 520 Recommended Practice Guidelines:

A conventional pressure relief valve should typically not be used when the built-up backpressure is greater than 10% of the set pressure at 10% overpressure. A higher maximum allowable built-up backpressure may be used for overpressure greater than 10%.

The European Standard EN ISO 4126, however, states that the built-up backpressure should be limited to 10% of the set pressure when the valve is discharging at the certified capacity.

For the majority of steam applications, the back pressure can be maintained within these limits by carefully sizing any discharge pipes. This will be discussed in Module 9.4. If, however, it is not feasible to reduce the backpressure, then it may be necessary to use a balanced safety valve.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Steam Safety Valve is designed to meet the rigorous process conditions which are essential for steam boilers. This spring loaded safety valve is used in superheater and reheater applications and is specially engineered to provide fast response to overpressure and blowdown requirements. The Starsteam safety valves are designed to provide high integrity performance and repeatability particularly at high pressure and high temperatures in power plants as well as oil and gas applications. This safety valve features a Stardisc design which guarantees perfect tightness at high temperatures as well as repeated and accurate positioning on the nozzzle.

Throughout the years, HZVALVE has developed its Quality System which is an integral part of our manufacturing policy. Our primary goal is to provide products that meet and exceed market standards. In this sense, HZVALVE is an ISO-9001 Audited and Certified Company that has achieved major certifications worldwide. Our system consists of a rigorous quality control as well as the selection of raw materials from approved vendors. Control over our manufacturing process is vital. Serial numbers allow HZVALVE to monitor and trace fabrication processes along with the materials of components.

HZVALVE owned independent quality department with over 25 experienced inspectors. Our target is to cover all vital point including material, procession, assembling, testing and package for overall quality controlling and supervision. We keep the understanding that the high quality products create more value to customers.

The Boiler and Pressure Vessel Safety Inspection Unit is responsible to ensure that all boilers and pressure vessels (BPVs) are inspected in accordance with Maryland Boiler and Pressure Vessel Safety Act & Regulations. This responsibility involves ensuring the safe operation, maintenance, repair and alterations of all pressure retaining objects. The Law also requires that any boiler or pressure vessel that will be installed in Maryland be built to American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code and be registered with the National Board of Boilers and Pressure Vessel Inspectors. The Law requires that boilers and pressure vessels be inspected annually or biennially depending on the type of equipment. Boilers shall not be operated without a Valid Certificate of Inspection.

All inspections shall be performed by an inspector commissioned by the National Board of Boilers and Pressure Vessel Inspectors and by the Maryland Commissioner of Labor and Industry and be employed by an Authorized Inspection Agency (AIA). There are about 20 AIAs active in Maryland. The owner shall contract with Insurer or Non-Insurer AIA. If an object is insured then the Insurer shall inspect.

A1: International special equipments are subjected to ML refer to boilers, pressure vessels, safety valves, bursting Discs, Valves of gas cylinders. The special equipment shall follow the stipulation of supervision administration regulation for manufacture of boiler and pressure vessel.

A2: Special Equipment Safety Administration Bureau (SESA), AQSIQ: is the authority in charge of special equipment manufacture licensing. Its main responsibilities include acceptance of manufacture licensing applications, approval of appraisal and assessment reports, issuance and management of manufacture licenses.Special Equipment Licensing Office (SELO), AQSIQ: is an office established by SESA to deal with daily routines of manufacture licensing. Its main responsibilities include reception of application documents and appraisal and assessment reports, printing and mailing of licenses, reception of Data Notice from overseas license holders, providing consultation for manufacture licensing procedures, policies and regulations. China Special Equipment Inspection and Research Institute (CSEI): is an appraisal and assessment organization for manufacture licensing authorized by AQSIQ. Its main responsibilities include organizing the appraisal and assessment team, making the appraisal and assessment schedule, carrying out the on-site appraisal and assessment, and drafting the appraisal and assessment report. Note: “appraisal and assessment” hereinafter will be idiomatically substituted by “audit”.

A3: Resources requirements: The manufacturer shall possess the necessary resources and capability required for the manufacturing of its products and the applied product level, including production site, manufacturing and processing facilities, inspection and test equipment and conditions as well as the suitable and appropriate human resources. For details, please refer to the Requirements for Boiler and Pressure Vessel Manufacture Licensing. Quality management system requirements: A quality management system shall be established and operate effectively according to TSG Z0004-2007 Basic Requirements for Special Equipment Quality Assurance System on Manufacture, Installation, Alteration and Repair. Product safety quality requirements: the design and manufacture of boiler and pressure vessel products to be manufactured and/or used inside China shall be subject to Chinese codes and standards. For details, please refer to relevant safety technical codes and standard, TSG G0001-2012 Boiler Safety Technical Supervision Administration Regulation and R0004-2009 Supervision Regulation on Safety Technology for Stationary Pressure Vessel.

A4: The relevant safety technical codes and regulations can be downloaded from SELO’s website http://www.cbpvi.org/laws.html. The codes and regulations which are not published on the website, should be purchased from the Periodical Office of China Special Equipment Safety. Tel: +86 10 59068615 Email: zzs@.csei.org.cn

A5: Firstly, confirm the category of the pressure vessel according to pressure and volume graph in ANNEX A, Supervision Regulation on Safety Technology for Stationary Pressure Vessel (TSG R0004-2009); secondly, confirm the level of the pressure vessel according to Attachment 1 of Supervision Administration Regulation for Manufacture of Boiler and Pressure Vessel.

A6:The overall procedure for obtaining the ML mainly consist of documents application and acceptance, type test (only refer to safety valves, bursting Discs, gas cylinders and accumulators), design approval (only refer to boilers, gas cylinders and accumulators), manufacture survey in site, audit report approval and license issue.

(6) Inspection of product safety quality: The appraisal and assessment team will inspect the product on the production site to assess its conformity with the applicable codes and standards, and its conformity with the requirements of China manufacture licensing on product safety quality.

By means of claw clamping the flanges of the valves, The test bench can be equipped with air booster upon request of the user to perform the high pressure test. The safety protection devices and Data management system can be selected by users upon request. The test bench can be customized according to the user’s detailed requirements.

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.

The installation of individual boilers or boilers connected to a common circulation manifold requires a permit if the individual or combined BTU input exceeds:

Due to a change in the interpretation of State Statute 326B.988 (a) (14), the department is suspending the need for a permit to install hot water supply boilers (water heaters). 500,000 BTUs for hot water supply boilers; (1) 500,000 BTU/hour input must be exceeded, but (2) 210 degree F or a (3) nominal water capacity of 120 gallons; or a pressure of 160 psig.

Apply or pay for a boiler installation permit. Note:  A new permit system launched June 22, 2020. Users must create a new account and link it to their mechanical bond to obtain and pay for permits.

All boiler installations require a hydrostatic test applied to the boiler. The test pressure should be approximately 75 percent of the safety valve set pressure. Example: 15 psi safety valve set pressure, 11 psi hydrostatic test pressure. The test pressure must hold for at least 10 minutes.

The Governor shall appoint 6 citizens of this State, 2 of whom shall be professional engineers licensed by this State, and who shall represent the following interests: one manufacturer of boilers, pressure vessels or refrigeration equipment; one authorized insurer of boilers, pressure vessels and refrigeration equipment in this State; one operator of boiler, pressure vessels or refrigeration equipment in this State and licensed by the Mechanical Inspection Bureau; 2 users of boilers, pressure vessels or refrigeration equipment in this State, and one resident of this State representing the general public.

All of these appointees shall serve at the pleasure of the Governor, and together with the commissioner and the examining board in the mechanical inspection bureau shall constitute a board of boiler, pressure vessel and refrigeration rules. This board shall meet at the call of the commissioner, or his designee, who shall be chairman, and it shall promulgate, after a public hearing, subsequent to the publication of notice of said hearing, rules and regulations for the safe and proper construction and installation and use of steam boilers, pressure vessels and refrigeration plants which are subject to the provisions of article 2, chapter 7 of this Title.

No unlicensed person shall operate a steam generator, similar equipment potentially capable of generating steam having relief devices set over 15 psig. and rated at or developing over 6 boiler horsepower or a steam power generator, if over 6 horsepower; a hoisting machine regardless of motive power, whenever the boom length exceeds 99 feet; a refrigerating plant of over 24 tons of refrigerating capacity, utilizing refrigerants of a flammable or toxic nature; or a steam or hot water heating plant of which the indicated or rated capacity exceeds either 499 square feet of heating surface or 100 boiler horsepower or 1,000 kilowatts or 4,000,000 British thermal units input regardless of pressure or temperature conditions; and no owner, agent, superintendent, manager or other person having charge of any building or work in which such equipment is located, or used, shall use, or cause or allow to be used, any such equipment described in this section unless the same is in charge of a properly licensed person, except in emergency, and then for no longer than 15 days unless the commissioner in writing extends such time, of which emergency the owner of such equipment, or the agent, superintendent, manager or other person in charge thereof shall promptly notify the mechanical inspection bureau in writing, stating fully the circumstances.

(4) any refrigerating plant utilizing refrigerants classified as being in Group 1 in the Safety Code for Mechanical Refrigeration of the American Society of Refrigerating Engineers approved by the American Standards Association, Inc., or

(6) Any steam generating equipment having relief devices set at or under 15 pounds per square inch gage or hot water equipment reliably regulated to operate automatically at a temperature not greater than 250 degrees F, and having relief devices set at or under 160 pounds per square inch gage when serving a heating plant other than in a building of public assembly providing (a) the equipment shall be protected by such type of automatic safety control system which is approved by the State mechanical inspection bureau for automatic operation; and (b) the boiler plant and its safety components are inspected operationally at reasonable intervals, when the building is occupied, by a person designated by the owner, agent, superintendent, or manager, which person"s qualifications to operate such equipment have been certified by the State mechanical inspection bureau on the basis of 90 days" experience and reasonable examination by that bureau in respect of such equipment. The "operational inspection" referred to in this subparagraph shall mean visual inspection of all indicators, gages, thermometers, external connections and other items which may be viewed by an external inspection. A log book shall be maintained on the premises recording such inspections, which log book shall be open to inspection by any designated representative of the State mechanical inspection bureau.

Any license may be revoked or suspended by the commissioner upon receiving evidence of incompetence, negligence, intoxication while on duty or other reason establishing that the licensee is unfit to hold a license, after notice is given to the licensee and a hearing afforded him before one or more members of the examining board. In case revocation or suspension is recommended by the member or members conducting the hearing, it shall not be acted upon by the commissioner until at least 15 days" notice of the recommendation shall be given to the licensee and an opportunity afforded him within that time period to ask for a rehearing before the commissioner. After rehearing, if requested, the commissioner may affirm, modify or dismiss such recommendation. Pending a hearing or rehearing as provided in this paragraph, the commissioner may authorize the suspension of a license in the interest of health and safety.

a. All steam or hot water boilers or similar equipment potentially capable of generating steam, except steam boilers having adequate relief devices set to discharge at a pressure not greater than 15 pounds per square inch, gage, or hot water boilers having adequate relief devices set to discharge at a pressure not greater than 160 pounds per square inch, gage, and which hot water boilers are reliably limited to temperatures not exceeding 250 degrees Fahrenheit, when such steam or hot water boilers serve dwellings of less than six-family units or other dwellings with accommodations for less than 25 persons, shall be inspected and be subject to a hydrostatic test, if necessary, at least once in each year, at 12-month intervals, by an inspector of the Division of Workplace Standards, excepting, however, such as may be insured after having been regularly inspected in accordance with the terms of this article by insurance companies, whose inspectors shall have satisfactorily passed an examination or received certificates of competency approved by the commissioner. Such inspection shall be as completely internal and external as construction permits, except that in the case of a steam or hot water boiler or similar equipment, the operation of which is an integral part of or necessary to a continuous processing operation, internal inspections may, at the discretion of the commissioner, be performed at intervals in excess of 12 months as permitted by the shutting down of the processing operation. The inspection of any equipment described in this chapter by a certified inspector of an insurance company shall be acceptable in lieu of State inspection. This article shall not apply to any boiler having less than 10 square feet of heating surface or a heat input of less than 10 kilowatts or 40,000 British Thermal Units per hour or to equipment under the jurisdiction and control of the United States Government, the inspection of which is actively regulated by a federal agency, or to equipment used solely for the propulsion of motor vehicles regulated by Title 39 of the Revised Statutes.

c. The Division of Workplace Standards shall maintain an inspection service for the purpose of providing shop inspection of those vessels regulated by Chapter 7 of Title 34 of the Revised Statutes, which are under construction or new, or which are to be used for a purpose other than that for which originally approved, or which have never been subject to a previous inspection in New Jersey. This service shall be provided for New Jersey builders, owners or users of such vessels upon their request only. The fees for this service shall be set by the commissioner and shall be: (1) not more than $50.00 for each vessel inspected, provided that he may establish a charge for each visit, for the purpose of inspection, of not less than $100.00 nor more than $300; (2) for construction review of vessel not designed in accordance with standards set by the Board of Boiler, Pressure Vessel and Refrigeration Rules, not less than $500 nor more than $1,500. The fees established under this subsection pursuant to the amendatory provisions of P.L. 2003, c. 117 shall be in effect for State fiscal years 2003-04 and 2004-05 and thereafter may be adjusted by the Commissioner of Labor in accordance with fee schedules adopted by regulation.

The fees shall be payable by and collected from the owner, lessee or operator by the insurer or inspector at the time of inspection for each boiler insured within the State. It is further provided that payment of these fees may be made by the insurer through other methods when required or allowed by the commissioner, as provided in R.S. 34:7-18.

No steam boiler, pressure vessel or refrigeration system shall be sold, installed or used in this State unless it conforms to such rules, regulations and standards as are from time to time adopted by the Board of Boiler, Pressure Vessel and Refrigeration Rules and approval by the commissioner under authority of R.S. 34:1-47.

All refrigeration systems using flammable or toxic refrigerants of over three tons of refrigerating capacity or requiring over six driving horsepower, and all refrigeration systems using nonflammable and nontoxic refrigerants of over 18 tons of refrigerating capacity or requiring over 36 driving horsepower, having relief devices set over 15 pounds per square inch gage and used in a plant of any size or storage capacity, shall be inspected annually by an inspector of the Mechanical Inspection Bureau or of an insurance company, as provided in subsection a. of R.S. 4:7-14; and the owner, lessee or operator shall comply with the recommendations of the inspector in conformity with the rules and regulations adopted by the Board of Boiler, Pressure Vessel and Refrigeration Rules of the Mechanical Inspection Bureau and approved by the commissioner. The fees for such inspection by an inspector of the Mechanical Inspection Bureau shall be as follows:

Any owner, lessee, seller or operator of any steam or hot water boiler or similar equipment specified in R.S. 34:7-14, pressure vessel or refrigeration system who shall sell, use, cause or allow to be used such steam or hot water boiler or similar equipment specified in R.S. 34:7-14, pressure vessel or refrigeration system in violation of any provision of this article shall be liable to a penalty of not less than $500.00 nor more than $10,000.00 for each first offense and not less than $500.00 nor more than $25,000.00 for each subsequent offense, to be collected by a civil action or, in the commissioner"s discretion, to be imposed by the commissioner as a compromise. All civil actions shall be brought by the Department of Labor as plaintiff, and may be brought in the Special Civil Part, Law Division of the Superior Court of the county, or municipal court of the municipality, wherein such violation shall occur. Any sum collected as a penalty pursuant to this section shall be applied toward enforcement and administration costs of the Division of Workplace Standards in the Department of Labor.

These rules are promulgated pursuant to the authority of the Operating Engineers and Firemen Licensing Act, N.J.S.A. 34:7-1 et seq. and the Boiler, Pressure Vessel and Refrigeration Act, N.J.S.A. 34:7-14 et seq.

"Alteration" means any change in the item described on the original manufacturer"s data report which affects the pressure containing capability of the boiler or pressure vessel. Nonphysical changes such as an increase in the maximum allowable working pressure (internal or external) or design temperature of a boiler or pressure vessel shall be considered an alteration. A reduction in minimum temperature such that additional mechanical tests are required shall also be considered an alteration.

"ASHRAE 15" means the Safety Code for Mechanical Refrigeration published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

"ASHRAE 34" means the standard on Designation and Safety Classification of Refrigerants published by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.

An inspection agency authorized to write boiler and pressure vessel Insurance and having inspectors that are authorized with a valid certificate of competency to inspect; or

An owner-user of pressure vessels who maintains an established inspection department, whose organization and inspection procedures comply with the requirements of the National Board or the American Petroleum Institute, as applicable, and which is registered with the Bureau of Boiler and Pressure Vessel Compliance (BBPVC).

"Boiler" means a closed vessel in which water is heated, steam is generated, steam is superheated, or any combination thereof, under pressure or vacuum for external use by the direct application of heat. The term "boiler" shall include fired or waste heat units for heating or vaporizing liquids other than water where these units are separate from processing systems and are complete within themselves.

"Heating boiler" means a steam or vapor boiler operating at a pressure not exceeding 15 psig, or a hot water boiler operating at a temperature not exceeding 250 degrees Fahrenheit.

"Hot water heating boiler" means a boiler in which no steam is generated, from which hot water is circulated for heating purposes and then returned to the boiler; and which operates at a pressure not exceeding 160 psig or a temperature of 250 degrees F or both at or near the boiler outlet.

"High pressure boiler" means a power boiler in which steam or other vapor is generated at a pressure of more than 15 psig. High pressure boiler also means a high temperature, high pressure water boiler or heat recovery steam generator.

"Heat recovery steam generator" means a high pressure boiler in which steam or other vapor is generated and where steam is super heated. The term heat recovery steam generator" shall include both fired and indirect fired units whose heat source is derived from duct burners and/or waste exhaust gasses.

"Hot water supply boiler" means a low pressure hot water boiler having a volume exceeding 120 gallons or a heat input exceeding 200,000 BTU/Hour (58.6 KW) or an operating temperature exceeding 200 degrees Fahrenheit, that provides hot water to be used externally to itself.

"Unfired boiler" means an unfired pressure vessel in which steam is generated except for evaporators, heat exchangers or vessels in which steam is generated by the use of heat resulting from operation of a processing system containing a number of pressure vessels such as used in the manufacture of chemical and petroleum products.

"Boiler horsepower" means the evaporation of 34.5 pounds of water from and at 212 degrees Fahrenheit or its equivalent and in the absence of reliable means of determination shall mean five square feet of boiler heating surface, or 10 kilowatts input, or 40,000 BTU input.

"Bureau of Boiler and Pressure Vessel Compliance" means the Bureau of Boiler and Pressure Vessel Compliance of the Division of Public Safety and Occupational Safety and Health, New Jersey Department of Labor and Workforce Development.

"Chief engineer" means a properly licensed person who, to establish responsibility, supervises or takes the lead over one or more of the licensed operators of high pressure boilers, power plants or refrigeration systems working in the same plant.

"Continuous processing operation" means a continuously operating processing or environmental control unit within the petroleum refining or chemical manufacturing industry where an associated boiler or similar equipment cannot be taken out-of-service outside of a scheduled, pre-planned periodic shut down of the entire continuous processing operation without incurring significant safety, environmental or economic harm.

"Division of Public Safety and Occupational Safety and Health" means the Division of Public Safety and Occupational Safety and Health of the New Jersey Department of Labor and Workforce Development.

"Insurance company inspector" means an employee of an insurer who is trained and specializing in the inspection of boiler or pressure vessels for safety reasons to represent the interests of the insurer.

"Internal inspection" means as complete an examination as can reasonably be made of the internal surfaces of a boiler or pressure vessel when manhole plates, handhold plates, or other inspection opening closures are removed.

"Mechanical Inspection Bureau" means the bureau established pursuant to N.J.S.A. 34:1-38.1 et seq. (1917) and is synonymous with the Bureau of Boiler and Pressure Vessel Compliance.

"Model steam boiler" means a boiler that is individually fabricated for non-commercial use, and is used primarily for demonstration, exhibition or education purposes, including antique boilers or steam pumpers.

"National Board Commission" means the commission issued by the National Board of Boiler and Pressure Vessel Inspectors to a holder of a certificate of competency who desires to make shop or field inspections in accordance with the National Board for such commission.

"National Board Inspection Code" means the manual for boiler and pressure vessel inspectors published by the National Board of Boiler and Pressure Vessel Inspectors.

"Occurrence" means any event which reduces the pressure-containing capability of, or requires immediate repair to, a boiler or pressure vessel, exclusive of normal wear on the equipment.

"Owner or user" means any person, firm or corporation legally responsible for the safe operation of any boiler, pressure vessel, or refrigeration system.

"Owner-user inspector" means an inspector who possesses an owner-user Certificate of Competency issued by the Bureau of Boiler and Pressure Vessel Compliance and is employed by a registered owner-user inspection agency.

"Shop inspection" means an inspection performed when any boiler or pressure vessel is being constructed, fabricated or undergoing welded repair. Such inspections shall include audits and joint reviews as required and assigned by the ASME, API, and National Board including owner-user certification audits.

"State inspector" means an employee of the Bureau of Boiler and Pressure Vessel Compliance who is authorized to inspect boilers or pressure vessels or other equipment.

"Total capacity" means the sum of the horsepower at ratings of all boilers comprising the system based on the minimum safety valve relieving capacity as required by the ASME Code.

"Welded repair" means work necessary to restore a boiler or pressure vessel to a condition suitable for safe operation at the design conditions. If any repair changes the design temperature or pressure, the requirements for rerating shall be satisfied. A repair can be the addition or replacement of pressure or non-pressure parts that do not change the rating of the boiler or pressure vessel.

This subchapter shall apply to the administrative functions required to be performed by the owner or user of any boiler, pressure vessel or refrigeration system within the scope of this chapter, including, without limitation, model steam boilers.

(a) For the purpose of examination or inspection of any boiler, pressure vessel, refrigeration plants, power plant or other equipment, the Commissioner may enter such premises at all reasonable hours in accordance with N.J.S.A. 34:1-15.

Any steam boiler, steam generator, hot water boiler for service over 250 degrees Fahrenheit, or similar equipment potentially capable of generating steam having a safety valve or valves set higher than 15 pounds per square inch gauge and rated over six horsepower;

A steam or hot water heating plant with an indicated or rated capacity that exceeds either 499 square feet of heating surface or 100 boiler horsepower or 1,000 kilowatts or 4,000,000 BTU input regardless of pressure or temperature conditions, and only when the building or building being served is deemed occupied;

(a) When more than one licensed person is required to operate a high pressure boiler, refrigeration plant or power generating plant, whether or not the operators are employed on the same shift, the management of the plant shall designate one lead person, commonly called a chief engineer to establish responsibility for operations. Chief engineers are not required for low pressure plants.

(b) The engineer designated as chief engineer shall be permitted to serve as chief engineer in one plant location only and must be a full-time employee of the company responsible for the operation of the high pressure boilers, power generating or refrigeration plants. In the case where the chief engineer is a contract employee, the employee shall be under full time control of facility management responsible for the equipment. The designation shall be in writing and be on file at the plant location where the chief engineer is employed.

(e) The Bureau of Boiler and Pressure Vessel Compliance may recognize an engineer holding a license one grade lower than that required to serve as acting chief engineer on a temporary basis provided:

(f) A boiler operator holding a boiler operator in charge license may act as chief engineer of an installation of 500 boiler horsepower or less. He or she may assume charge of a shift, under the supervision of a properly licensed chief engineer, in installations not over 1,000 boiler horsepower. When the total capacity exceeds 1,000 boiler horsepower, he or she may act as boiler operator, under the direction of, and responsible to, a properly licensed engineer in charge of his or her shift. (See Tables 3.4 and 3.7)

(g) An engineer holding a C or third grade license of the proper classification may act as chief engineer of any plant where the total capacity of the equipment involved does not exceed 1,000 boiler horsepower, 100 engine horsepower or 65 tons refrigerating capacity. He or she may also act as operating engineer, under the supervision of a properly licensed chief engineer, in installations exceeding the above limits. (See Tables 3.4, 3.7 and 3.8)

(h) An engineer holding a B or second grade license of the proper classification may act as chief engineer of any plant where the total capacity of the equipment involved does not exceed 3,000 boiler horsepower, 500 engine horsepower or 300 tons refrigerating capacity. He or she may also act as operating engineer, under the supervision of a properly licensed chief engineer, in installations exceeding the above limits. (See Tables 3.4, 3.7 and 3.8)

(b) Licensed persons on watch shall give constant attention and remain within sight and/or natural sound of high pressure boilers and refrigeration plants or be stationed in a control room where the licensed person has direct and immediate intervention capabilities.

(d) The length of time that the licensed person can be away from the equipment varies according to its nature, size and load conditions. At a minimum, the operator shall monitor the conditions of the low pressure boiler plant twice every 24 hours, with no less than seven hours between each equipment check.

(f) A boiler operator"s log shall be maintained in each plant containing over 100 horsepower. Every operator on the shift shall review the log and, at the end of each shift, shall sign the log. All logs shall include the date, name of the operator(s) on duty, and time of relief. Any personnel who are training to obtain their licenses under the requirements of N.J.A.C. 12:90-8.4 shall include within the log the actual time spent as a trainee. When the operator of a low pressure plant is not in the boiler room, as permitted in (c) above, the operator shall indicate in the log periodic tours of the boiler plant as required in (d) above.

High pressure boiler operator logs shall contain at a minimum the