BPRV? Buckling Pin Relief Valve

Buckling            Pin technology offers an accurate and reliable means of calibrating            pressure relief devices. BS&B has developed the BPRV? Buckling Pin Relief Valve for            in-line pressure or vacuum relief offering quick and simple external            resetting. The BPRV is suitable for both gas and liquid            applications, and provides a full relief opening at a pre-determined            set pressure.

• Simple in-line installation

• Maximum relief capacity

• Convenient external reset

• Set pressure is unaffected by cycling/pulsating              pressures

• Standard set pressures up to 275 psi

• Set pressure is unaffected by valve              orientation

• The buckling pin is totally protected with a rugged              enclosure

Set Pressure Range—Buckling pin technology is used            for overpressure or vacuum relief at set pressures from a few            inches of water column to over 1000psig.
         
          Size Range—Valves are available for installation            between all international standard flanges.
         
          Temperature—Because the buckling pin mechanism is            located in an external enclosure, the set pressure is unaffected            by process temperature; only the ambient atmospheric temperature            needs to be considered.
         
          Operating Ratio—A 90% operating ratio permits            process pressures up to 90% of the set pressure.
         
          Service—Suitable for gas or liquid service. The            selected seal material must be compatible with the process            fluid.
         
          Vacuum—Valves can be supplied to withstand vacuum.            Inverted styles of the BPRV may be used for vacuum            relief.
         
          Pressure Cycling—Accuracy and reliability are            maintained under pressure cycling conditions.
         
          Leak Tight—As the operating pressure increases, the            seal is progressively energized to maintain leak tightness. The            seal is bubble-tight and offers minimal resistance to opening,            permitting low set pressures and tight pressure            tolerances.

Specifications

U.S.            Patent Number 6,367,498 applies; other international patents            pending.

The            Buckling Pin Relief Valve (BPRV?) offers quick and simple field reset            without removal from the            piping system.

The            Buckling Pin Relief Valve (BPRV?) can improve productivity within a            facility by dramatically reducing the down time that can be caused with            other non-reclosing pressure relief devices.

The BPRV is            an in-line pressure relief device which offers quick and simple field            reset without removal from the piping system. This non-reclosing pressure            relief device provides practical technology for the protection of            applications containing one or more of the following conditions:

Continuous Processing  (fast reset in the line)

• Hazardous Service (limits operator exposure)

• Large Line Size (convenient reset in the Line) 

• Inaccessible Location (external reset in the line)

• Frequent Operation (fast reset in the line)

Design

(U.S.            Patent #6,367,498 applies; Worldwide Patents Pending)

The design            of the BPRV? is based upon the offset shaft butterfly valve concept. The            offset of the shaft results in a turning moment being generated about the            valve shaft when a pressure differential is applied across the device. A            Buckling Pin mounted externally to the process normally resists this            turning moment. By calibrating the Buckling Pin to collapse at a load            coincident with that resulting from the shaft torque at a predetermined            differential pressure, the BPRV provides accurate pressure relief.

Buckling            Pin technology provides an accurate and reliable means of calibrating a            pressure relief device. When an axial load is applied to a straight            cylindrical pin, it will buckle at a specific load according to Euler's            Law. Buckling Pins that are manufactured from the same material and have            the same configuration will buckle at predictable and repeatable            loads.

Three  Primary BPRV            Components

1-Rotating Disc.             A rotating disc normally closes the flow path and turns through 90 degrees            in response to an overpressure/underpressure condition. The rotating disc            is constructed from metal and has a hollow design. This maximizes the flow            path through the BPRV and ensures the stability of the disc during normal            service and at the time of opening. (See catalog cover photo).

2-Flanged Body.  A            flanged body contains the rotating disc, holding it in place using shaft            connections that are sealed within the body and pass through bearings to            permit free rotation of the disc within the body. The body is a 1-piece            design with no constructional welds or other potential external leak            paths.

3-External Enclosure and            Mechanism.  The external enclosure and mechanism provides the set            pressure control for the BPRV. The mechanism is designed to resist the            turning moment of the disc shaft during normal service pressure            conditions. When the desired set pressure is reached, the mechanism            releases the disc due to the function of a Buckling Pin which has been            built with sufficient strength to resist disc rotation until that point.            The mechanism is contained within a stainless steel enclosure. The            enclosure door includes a seal to permit service under severe            environmental conditions.

Three Set Pressure Calibration            Controls

1-The            Offset of the BPRV Disc Shaft from the Center Line. 

A large            offset will generate a higher shaft load; a small offset will generate a            lower shaft load. For BPRV devices supplied for applications within the            ANSI 150/DIN PN10 flange pressure range, a standard offset is used that            does not exceed 1"/25mm, even for the largest installation.

2-The            Buckling Strength of the Buckling Pin. 

This is a            function of the 4th power of the pin diameter, the Modulus of Elasticity            of the Pin material, and the inverse of the Pin length. Buckling Pin            diameter is used for significant set pressure tuning, length adjustment is            used for fine tuning.

3-The            Enclosure Mechanism Uses a Lever Principal. 

This            enables a wide range of BPRV set pressures to be obtained with modest            Buckling Pin lengths and diameters while using a standard disc shaft            offset. This enables the mechanism to be compact and results in a simple            Pin installation procedure that can be completed by a single operator            without special tools.  Note:  The BPRV is calibrated before            shipment to meet the users required set pressure and tolerance.

Size and Set Pressure            Capability

The BPRV is            available with a standard range of sizes and set pressures designed to            suit applications that are compatible with ANSI 150, DIN PN 10 or similar            flange specifications as shown in Table 1.

In addition            to these standard specifications, the BPRV is capable of meeting a wide            range of dedicated customer requirements that have already             included:

High Set            Pressures: Over 2000 psi/138 Bar in a 6"/150mm  nominal size            installed between ANSI 900 flanges.

Low Set            Pressure: 20" Water Column/50 mBar in a 24"/600mm  nominal size

Please            consult BS&B Safety Systems with your special applications.

Table            1-Set Pressure Capability: Standard

Size                                                        Set Pressure

                                                              Minimum          Maximum

in                               mm                       psig      barg     psig       barg

1"                   25                         40        2.76                275      18.96

1            1/2"             40                         10        0.69                275      18.96

2"                   50                          5         0.34                720      49.64

3"-6"              80-150                   5         0.34                275      18.96

8" -            16"          200-400                 3         0.21                275      18.96

18" -            24"        450-600                 1         0.07                150      10.34

26" -            36"        650-900                 1         0.07                125        8.62

38" -            60"        950-1500               1         0.07                100        6.89

Set Pressure Certification and            Tolerance

In line            with International Standards, the BPRV is certified at the customer            requested set pressure. This certification is a result of Buckling Pin            tests conducted in the BPRV to confirm compliance with set pressure and            tolerance expectations. The BPRV is certified with a single set pressure            tolerance, as indicated in Table #2. For set pressures between 20 psi/1.38            Bar and 40 psi/2.76 Bar, the BPRV provides a superior set pressure            tolerance option of +/-5% compared to other non-reclosing pressure relief            devices.

When            certified according to ASME/North American standards, the BPRV is marked            with the customer requested set pressure (Table #1). When certified            according to European (PED) standards, the BPRV is marked with the            customer requested set pressure and the tolerance based upon Table 2.            Alternatively, European certification allows for marking the BPRV with a            minimum/maximum set pressure (which will also be calculated from Table            2).

Table            2-Set Pressure Tolerances

Pressure                                                          Tolerance

Over            40psi/2.76            Bar                                        +/-5% Standard

From 1-40            psi/0.07-2.76            Bar                          +/-0.14 Bar/2 psi Standard

Over 20            psi/1.38            Bar                                       +/-5% Upon Request

Operating Pressure Ratio

Buckling            Pin technology provides outstanding resistance to operating pressure            conditions. The BPRV can be operated up to 95% of minimum set pressure.            This is called the 'Operating Pressure Ratio'. Subject to special testing,            there is the ability to increase this ratio further.

Note:             Remember to subtract the negative set pressure tolerance in the case of a            BPRV marked with 'set pressure' rather than a defined min/max.

Pressure Cycling Service

Buckling            Pin devices are well suited to cyclic service pressure conditions.            Operating under compression, the Buckling Pin is not subject to tensile            fatigue failure. The BPRV can be cycled to its maximum operating pressure            ratio thousands of times.

Materials of Construction

The user            may specify the material of construction for each of the three major BPRV            components: Standard materials are as follows:

Valve            Body. The standard materials are carbon steel and

stainless            steel. Alternate materials include Hastelloy?* C-276, Monel?*, Alloy 20,            and metals that can be obtained in the form of cut plate or a forging            (depending upon the size of the device to be fabricated).

Valve            Disc.  The minimum material is stainless steel. The disc provides            the valve sealing surface, therefore a resistant surface must be ensured.            Alternate materials are the same as for the valve body.

Enclosure.  The standard            material is stainless steel with Viton door seals. Alternates may be            requested.

Seals

The primary            seal in the BPRV is mounted in the 1-piece body, held in place by a            sealing ring. This seal engages a curved surface on the leading edge of            the disc and has a profile that provides a tight shut-off from both the            inlet and outlet sides of the device. The standard seal material is            fluoropolymer (alternates are available upon request).

On the            outlet side of the disc, there are two shaft connections that hold the            disc freely within the body. These are also fitted with standard fluoropolymer            seals. Free rotation of the disc about the shaft is assured by the use of            either bushings or bearings (depending upon size and set pressure)            installed with a fluoropolymer seal on either side. The shaft seals are not in            process contact from the inlet side when the BPRV is in the closed            position. (Alternate shaft seals are available upon request).

Installation

The BPRV is            designed for “in-line” installation between pipe flanges. Each device is a            'full face' design with the pipe flange bolting typically passing through            the perimeter of the body. Some flange specifications have a compact            bolting pattern that would interfere with the bushings or bearings if            through bolt holes were used; in these cases, a threaded blind bolt hole            is provided on both sides of the BPRV so a full set of flange bolts is            installed.

The piping            may run horizontally, vertically, or at an oblique angle. The BPRV can be            supplied set-pressure certified for any of these orientations. The user            must identify the installation configuration at time of order to ensure            appropriate calibration testing of the BPRV.

The BPRV            body can be fitted with lifting lugs to ease maneuver of the device into            place between pipe flanges.

Field Reset

When a            Buckling Pin has functioned and the BPRV is to be reset, this can            typically be accomplished while the device remains installed in the piping            system. The enclosure is opened, the used Buckling Pin removed, the disc            rotated back into the closed position, a replacement Buckling Pin            installed and the mechanism reset. This takes only a few minutes and can            be completed by a single operator, even with the largest size BPRV.

Temperature

The            materials of construction for the BPRV permit a wide range of service            temperatures. Each device has two different temperature considerations:

1.                Compatibility of service temperature with seal materials.

2. Buckling                Pin coincident temperature at time of function.

The            standard fluoropolymer seals can be operated between -40oF/-40oC and            +400oF/260oC. While flowing, temperatures down to cryogenic conditions can            be handled. Seal performance is regained once the fluoropolymer seal has returned            to the recommended operating range.

With the            Buckling Pin installed in the enclosure, the process temperature does not            reach the pin. In general, the Buckling Pin will be at ambient temperature            making certification of the Pin lot at 72oF/22oC appropriate.

Variation            of ambient temperature causes minimal change in Buckling Pin performance -            as little as 1% over the range -40oF/-40oC to 200oF/93oC. Ambient            temperature conditions for each application should be reviewed with            BS&B Safety Systems, L.L.C.

Enclosure and Mechanism            Construction

Three            standard mechanisms are employed to met the torque requirements of the            BPRV nominal sizes 1”- 60” (25 mm-150 mm). In all cases, the mechanism is            fitted to a solid stainless steel baseplate to ensure rigidity. The            mechanism is either installed inside a stainless steel enclosure or has an            enclosure bolted to the baseplate (see M4200 photo). The M16000 mechanism            handles low torque applications typical of BPRV sizes 1”-6” (25 mm-150            mm). The more substantial M4200 mechanism handles the torque range typical            for higher pressure 4” (100 mm) BPRV devices through low pressure 24” (600            mm) size. The M1600 mechanism is designed to handle the very high torque            requirements of BPRV devices sized 24”-60,” nominal size. (The light duty            M600 mechanism for small size BPRV devices is offered with an economic,            light-weight glass fiber enclosure as an option).

The            mechanism front cover is provided with a latch tongue that aligns with            another on the side to allow the user to add a preferred locking            mechanism. Turn latches mounted on the front of the enclosure energize the            door elastomer seal.

All            mechanisms comprise of stainless steel and protective coated high tensile            steel components. This combination avoids seizing of moving parts through            the use of similar metals, and provides excellent corrosion resistance.            The mechanism is fully sealed within the enclosure when the door is            latched shut.

Mechanism Function

The BPRV            mechanisms use a lever principal to balance input load from the rotating            disc against output load applied to the Buckling Pin. When the (input            load) x (distance from lever load input to the fulcrum) > the (Buckling            Pin collapse load) x (distance from fulcrum to the lever load output), the            BPRV will open.

The input            load is provided by the pressure generated torque on the disc shaft This            loads the input side of the lever arm. When the Buckling Pin operates, the            lever is free to move, allowing the shaft to rotate through 90 degrees            into the full open position. At most set pressures, the BPRV will latch in            the full open position to ensure the greatest flow rate through the            device.  The location of the fulcrum is tailored by BS&B Safety            Systems, L.L.C. during the calibration of each BPRV. This set pressure            control feature of the BPRV design is used for fine tuning. The fulcrum            location is factory set and wire sealed for tamper evidence.

Customized BPRV Units/Command            Activation

The BPRV            can be user command activated in two different configurations:

BPRV-CAE

If it is            known that the BPRV will always sense a positive differential pressure, an            actuator (e.g. solenoid or pneumatic piston) installed adjacent to the            buckling pin can be used to buckle the pin on demand. This will release            the BPRV mechanism and allow the disc to rotate freely under pressure.

This is            known as a “command activated enclosure,” or CAE, and allows the valve to            be used as both a pressure relief device and a command actuated quick            opening valve.

BPRV-CAS

If command            actuation is desired in an application where positive differential            pressure cannot be guaranteed, a powered actuator can be installed on the            free shaft of the BPRV. When the operating conditions require the valve            open, the actuator is powered to overcome both the buckling pin and any            back pressure induced torque on the BPRV shaft to open the device.

This is            known as a “command activated shaft,” or CAS, and allows the BPRV to be            used as both a pressure relief device and a command actuated quick opening            valve.

The            BPRV-CAE and BPRV-CAS are examples of customized design options that can            be satisfied with this versatile pressure relief technology. BS&B            Safety Systems welcomes the opportunity to develop solutions to unique            applications.

Information Required to Order the            BPRV

General

•   Tag              Number

•   Line Size

•   Flange Specification

Operating            Conditions

•   Set              Pressure and Tolerance Requested

•   Set              Temperature (Pin Conditions)

Service            Conditions

•   Fluid

•   Vapor/Gas: Molecular Weight

•   Liquid: Specific Gravity

•   Required Flow Capacity (if known)

•   Normal Service Pressure

•   Vacuum Conditions

•   Back Pressure Conditions

•   Normal Service Temperature (Process)

•   Flowing Temperature (Process)

•   Static or Pulsing Service Pressure

Materials

•   Valve Disc

•   Valve Body

•   Disc Seal

•   Enclosure

Installation/Flow            Path

•   Vertical, Horizontal, Oblique (specify angle to Horizontal)

Accessories

•   Sensor — Visual/Electrical

•   Sensor Electrical Requirements

•   Buckling Pin or Buckling Pin Cartridge

•   Quantity of Pins/Cartridges

Note: When            the BPRV opens, the disc may project beyond the body cavity within which            it is retained when closed. When installing or removing the BPRV from            service it is essential the disc is in the closed position to avoid damage            to the disc and mechanism. Please seek advice from BS&B Safety Systems            when the BPRV is to be installed close to a “T-piece” or other piping path            that may present an unusual flow pattern to the device.

Quality Assurance

Every BPRV            is thoroughly tested before shipment. Pre-delivery

inspection            can be divided into:

• Dimensional Inspection

• Leak Tightness Verification

• Buckling Pin Calibration and Set Pressure Testing

Before the            BPRV is assembled from component parts, each component is dimensionally            verified for its critical features. After assembly, the performance of the            seals is checked. ANSI standard B16.104 is typically followed with a            minimum test standard of Class IV established. Many BPRV devices are            supplied to the stricter Class V and Class VI limits which require a            'bubble tight' construction.

All            Buckling Pins that are supplied as a lot are manufactured from a             single batch of raw material at the same time. The BPRV set pressure is            established through Buckling Pin destructive testing. Once the appropriate            Pin configuration has been achieved for the required set pressure, the lot            of Pins is completed within very tight dimensional tolerances. BS&B            Quality Assurance personnel witness set pressure tests for certification            purposes. All Buckling Pins are supplied tagged with a traceable lot            number, set pressure and the serial number of the BPRV unit for which they            have been calibrated.  SAF-T-PIN? Buckling Pin Cartridges are            recommended for optimum control and traceability.

When fully            calibrated and certified, wire seals are installed at the

following            key locations:

• Junction of the Body and the Enclosure

• Fulcrum Connection to the Enclosure Baseplate

• Junction of the Sensor to the Shaft (where fitted)

Codes and Standards

Several            International standards recognize Buckling Pin devices and provide            guidelines for their certification. These include ASME, in the form of            code case 2091, and TUV AD Merkblatt A1 and the European Pressure            Equipment Directive (PED). The BPRV can be supplied to all established            standards.

Maintenance

If desired,            the Buckling Pin can be removed and the BPRV tested by rotating the disc            into the open position triggering the mechanism.  There must be no            pressure on the device.  The Buckling Pin can then be            reinstalled.

Occasionally it will be            necessary to replace the disc seal. This can be accomplished quickly and            easily. The disc seal is held in place by a seal ring that inserts into            the inlet of the one-piece body. This seal ring is simply removed using            simple tools and the used seal pulled out from the BPRV body. After            inspecting the seating area and clearing away any debris, the BS&B            replacement seal is installed and the seal ring put back in place. Seal            replacement does not require disassembly of the BPRV body or mechanism. It            is recommended a spare disc seal is purchased for each BPRV.

Testing            In Place

Since the            BPRV might be interpreted as a relief valve, many users wish to perform            scheduled maintenance to ensure the set pressure has not been compromised            while the valve is in service. The normal procedure for testing of many            types of relief valves is to remove the valve from service and send to a            valve repair shop for a pop test and re-certification. The advantage of            the BPRV is that the valve can be re-tested in-situ. The offset shaft is            designed with a hexagon drive in the enclosure. The user can leave the            valve in service between the flanges and attach a torque wrench to the            hex. All the user needs to do is load the shaft with a torque wrench until            the valve opens. BS&B Safety Systems, L.L.C. can supply a torque value            range which, when applied to the hex drive of the offset shaft, will            buckle the pin and activate (open) the valve. Once the value recorded on            the torque wrench lies within this torque range supplied by BS&B, the            user knows that the valve set pressure has not been compromised and the            product is now re-tested. This allows users to re-check the valve within            10-15 minutes, without having to remove it from service.

Testing in            place greatly reduces the maintenance expenses compared with relief valves            by dramatically reducing the time and labor involved with the            re-validation process.

Optional SAF-T-PIN? Buckling Pin            Cartridge

The BPRV            can be provided with Buckling Pin Cartridges that are installed like an            electrical fuse. The SAF-T-PIN? Buckling Pin Cartridge allows a            "Quick-Change" option of Buckling Pins with a simple push-in/pull-out            design for installation within the enclosure. Each SAF-T-PIN? Cartridge            contains a calibrated Buckling Pin that is perfectly mounted for optimum            performance.

The            SAF-T-PIN cartridge locates into the BPRV mechanism in one direction only            ensuring fail-safe installation.

The            transparent cartridge permits visual inspection of the Buckling Pin, and            the stainless steel ends of the cartridge are marked with full set            pressure and traceability information including the serial number of the            BPRV device. The SAF-T-PIN cartridge avoids the need for  special            installation procedures and any concern of handling bare Buckling            Pins.  Worldwide patents pending.

Sensor/Indicator Option

Both a            visual and electrical signal to confirm BPRV status is available. Mounted            on the free shaft not used by the mechanism, the BPRV sensor comprises a            sealed enclosure (typically to Nema IV standard) that houses a colored            dome indicating 'Open' (colored Red) or 'Closed' (colored Green). The dome            is rotated by a shaft extension that moves in unison with the disc of the            BPRV. Electrical switching compatible with the users requirements can be            added to the enclosure to provide a remote signal or alarm when the BPRV            operates. This can be provided to meet intrinsically safe requirements.

SmartDisk? Compatible

The BPRV            can be supplied with SmartDisk? wireless sensor technology that allows an            electrical signal to be generated at a monitoring station located up to            several thousand feet away from the BPRV without the cost of hard wiring.            Please refer to catalog 77-1016 for more information.