STANDARD SPECIFICATION FOR SAFETY / THERMAL...

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STANDARD SPECIFICATION FOR

SAFETY / THERMAL RELIEF VALVES, RUPTURE DISCS & BREATHER VALVES

DOCUMENT NO : 44-LK-5100-00/J.02/0011-A4

Rev No. Issue Date Pages Rev Description Prepared

By

Checked

By

Approved

By

A 12.08.08 8 Issued for Comments / Approval

RCK GDR BSP

JACOBS ENGINEERING INDIA PRIVATE LIMITED

DOCUMENT NO : 44-LK-5100-00/J.02/0011-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR SAFETY / THERMAL RELIEF of 8 VALVES, RUPTURE DISCS & BREATHER VALVES Revision No. : A

TABLE OF CONTENTS 1.0 PURPOSE

2.0 SCOPE 3.0 TECHNICAL REQUIREMENTS 3.1 RELIEF VALVE AND DESIGN 3.2 BREATHER VALVE SIZING & DESIGN 3.3 RUPTURE DISC DESIGN 4.0 RELATED DOCUMENTATION

5.0 ATTACHMENTS


_________________________________________________________________________ DOCUMENT NO :44-LK-5100-00/J.02/0011-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR SAFETY / THERMAL RELIEF of 8 VALVES, RUPTURE DISCS & BREATHER VALVES Revision No. : A

1.0 PURPOSE

The purpose of this specification is to define the minimum requirements of design and manufacture of Safety / Thermal relief valves, Rupture Discs and Breather valves.

2.0 SCOPE The scope of work shall include design, manufacture, testing and supply of Safety /

Thermal relief valves, Rupture Discs and Breather valves. The inspection requirements shall be as per the inspection plan.

3.0 TECHNICAL REQUIREMENTS 3.1 RELIEF VALVE AND DESIGN 3.1.1 The vendor shall be responsible for the selection and sizing of the safety relief valves in

accordance with the supplied process data. 3.1.2 Safety relief valves shall be designed, manufactured and sized in accordance with the

recommendations of API RP526, API 527, API 520, API 521, ASME code for 'Boilers and Pressure Vessels' and Indian Boiler Regulations.

3.1.3 The calculated result should be used to select a relief valve whose effective flow area is

the nearest size larger than the calculated area, as limited by the standard orifice areas available.

3.1.4 Where Safety relief valves are provided on ASME coded boiler and pressure vessels,

they shall be manufactured in accordance with ASME VIII and shall carry the ASME VIII code stamp.

3.1.5 Lifting lever shall be specified for steam and air service 3.1.6 The percentage accumulation in case of pressure relief / safety valves shall be as follows

Steam Service - ASME SEC I 3% - IBR (Before steam let-down station) 5% - IBR (Distribution & Utilities) and 10% ASME Section VIII

− Gas, Vapour or liquid 10%

− Liquid for thermal Relief 20% or less

− Fire exposure on unfired vessels 21% 3.1.7 Safety Relief valves shall be of the direct spring loaded type. Pressure relief valves shall

be full nozzle full lift type except for thermal relief valves. 3.1.8 The spring in a pressure relief valve in service for pressures up to and including 250 psi

(1720 KPa) shall not be reset for any pressure more than 10% above or 10% below that for which the valve is marked. For higher pressures, the spring shall not be reset for any pressure more than 5% above or 5% below that for which the valve is marked.



3.1.9 Conventional valves shall be specified for constant back pressure while bellows seal type valves shall be specified for variable backpressure more than 10% of set pressure or for toxic / hazardous or corrosive fluids where conservation of the fluid is of utmost importance. Pilot operated pressure relief valves shall be used for special services and where set pressure is closer than 10% of the operating pressure, in general.

3.1.10 All Valves shall be flanged to ANSI B16.5 R.F. serrated finish unless otherwise specified.

Flanged connection shall be for standard sizes 1" or larger. Minimum flange rating shall be 150 # ANSI. Where permissible, screwed connections shall be used on sizes ¾" and below.

3.1.11 For API coded tanks pressure/vacuum relief valves shall be pallet/weight loaded, or pilot

operated. During hydrostatic testing of the equipment / pipe lines / systems Safety relief valve shall be removed and replaced by a blind flange.

3.1.12 Valve seat tightness shall be in accordance with the requirements of API STD 527. 3.1.13 The body material shall, as a minimum, be as per piping specifications. Nozzle and disc

material shall be SS316 as a minimum with machined stainless steel guide and spindle. Whenever semi nozzle designs are unavoidable, body material shall be at least same as nozzle material. The spring material of pressure relief valves shall be as follows unless otherwise specified in the datasheet, or required by the corrosive characteristics of the service:

-29ºC to 250ºC : Cadmium / Nickel-plated carbon steel. above 250ºC to 540°C : Tungsten alloy steel. below -29ºC : Stainless steel 316. Above 540°C : High Speed Steel

3.1.14 Pilot Operated Safety / Relief Valves

Pilot operated safety/relief valves use the process pressure acting on the topside of the disk as the closing force. The pilot valve, which is a spring loaded valve, connects the cavity above the disk either to the process or to the atmosphere, or a low-pressure system. Internal sensing for pilot shall be avoided as far as possible by providing remote pilot sense ports. The pilot operated safety/relief valve can operate at process pressure close to the set pressure because of the high positive closing force which increases with the process pressure. Normally pilot operated valves should be provided with soft seals, which give a better valve tightness. The design features of a pilot operated valve allows for larger orifice sizes than the maximum 8T10 size for spring loaded valves. A field connection for checking the set pressure shall be provided.

3.1.15 Mechanical requirements 3.1.15.1 The design shall incorporate guiding arrangements necessary to ensure consistent

operation and tightness. 3.1.15.2 The spring shall be designed so that the full lift spring compression shall be no greater

than 80% of the nominal solid deflection. The permanent set of the spring (defined as the difference between the free height and height measured 10 mins. after the spring has been compressed solid three additional times after presetting at room temperature) shall not exceed 0.5% of the free height.

3.1.15.3 The valve seat shall be fastened to the valve body such that the valve seat shall not lift. test

gag shall be provided for all pressure relief valves. 3.1.15.4 Valves shall be provided with provision for sealing of all external adjustments.



3.1.15.5 On valves where the design allows liquid to collect on the discharge side of the disk, the

valve shall be provided with a drain at the lowest point. 3.1.15.6 Stems shall be of AISI 416 except if the body is austenitic stainless steel, when it shall be

of 18.8% Cr.Ni. 3.1.16 Steam service 3.1.16.1 Pressure Relief Valves on steam service shall be provided with a lifting device to ensure

the valve is free. Pressure tight packing shall be provided around the lifting lever assembly, so that leakage will not occur when the valve is opened or under back pressure.

3.1.16.2 The lifting device shall not hold the valve disk in the open position when the exterior lifting

force is released. 3.1.16.3 Safety Relief Valves on steam service shall meet the requirements of the Indian Boiler

Regulations. 3.1.16.4 Valves for steam service shall be flanged to ANSI B16.5. Serrated R.F. and shall have an

open bonnet i.e. only with a yoke in place of a closed bonnet. They shall be provided with a weather hood \ when used in outdoor service.

3.1.16.5 Steam services above (750°F) 399°C shall be provided with a cooling spool between the

body and bonnet to minimise conduction of heat to the spring. 3.1.16.6 Vendor shall furnish sizing calculations based on IBR formula. In this connection, vendor

shall indicate the 'C' value as accepted by IBR. 3.1.17 Thermal Expansion Relief Valves 3.1.17.1 Relief valves without blow down ring shall be used for liquid thermal expansion purposes. 3.1.17.2 3/4" x 1" threaded (NPT) modified nozzle type valves with typically 0.38 cm2 orifice size

shall be specified for thermal relief. If the piping specification does not allow screwed connection then flange connection shall be used.

3.1.18 Relief Valve Installation 3.1.18.1 Safety and Safety Relief Valves shall always be mounted in a vertical position directly on

nozzles having a well-rounded approach that provides smooth, unobstructed flow from the vessel or line to the valve.

3.1.18.2 Safety valves shall not be mounted on nozzles having an inside diameter smaller than

the inlet connection to the valve, or on excessively long nozzles. 3.1.18.3 Discharge pipe work shall be piped upwards such that vapours or liquids are discharged

vertically. 3.1.18.4 For optimum safety valve performance, discharge piping shall be supported

independently of the valve.



3.1.18.5 For steam service slip joint drip pan elbows should be used, with the drip pan drain piped away to a safe location.

3.1.18.6 The installation of safety and safety relief valves shall be in accordance with the

recommendations of API RP 520 Part II. 3.1.19 Relief Valve Testing 3.1.19.1 Steam service valves shall be tested with steam. Where this facility is not available air

may be used. When steam valves are tested with air all necessary corrections for differential in popping pressure between steam and air shall be determined by the vendor and submitted to the purchaser for approval.

3.1.19.2 For steam service valves not covered by API Std. 527, when leak tested there shall be no

visible or audible leakage from the valve outlet when the inlet pressure is held at 95% of the set pressure after popping and reseating.

3.1.19.3 Valves marked for general service may be tested with air. 3.1.19.4 Liquid service valves shall preferably be tested with water but may be tested with air. 3.1.19.5 Valves shall be tested to demonstrate the popping point and tightness. 3.1.19.6 Pressure relief valves shall be type tested for capacity with 5% blowdown as per ASME

Sec VIII UG 131 and actual blowdown of the individual valves shall meet the process requirement. All Valves shall be provided with such type test certificates.

3.1.19.7 For all relief valves test records and test certificates to fully cover component materials

and the valve test details shall be provided. 3.1.20 Relief Valve Marking And Nameplates 3.1.20.1 The marks shall be placed on the valve or on a plate securely fastened to the valve. The marks shall be made in such a way that they will not be obliterated in service. 3.1.20.2 The markings shall include the following as a minimum for Safety / Thermal Relief

Valves:-

- Valve Tag number - Vendors name - Vendors design or type number (Model Number) - Size (mm) - Set Pressure kg/cm²g - Orifice (standard letter designations) - Cold setting - Back pressure (constant or variable) - Capacity at overpressure - Year of manufacture - ASME or IBR symbol as required. - Client’s (End user) name and Client’s code no.



3.2 BREATHER VALVE SIZING & DESIGN 3.2.1 The breather valves shall follow the listed specifications as a minimum during design.

There shall be sufficient margin between the set pressure of breather valve and tank's design pressure / vacuum. Also, there should be sufficient difference between the set pressure of N2 blanketing system and breather valve.

3.2.2 Breather valves shall generally be soft seated, dead weight type and shall have self-

draining body construction. The seating surfaces shall be shielded from condensates and the design shall prevent tendency of pallet to stick to the seat.

3.2.3 Vacuum breakers shall, in general, be sized and designed as per API 2000. 3.3 RUPTURE DISC DESIGN 3.3.1 Rupture discs shall be reverse buckling type, in general and shall be supplied in pre-

torqued holder assembly which shall fit inside the inner diameter of the bolt circle of standard flanges. Disc and holder material shall be compatible with the process fluid . Inconel discs shall be used above 100ºC if compatible with the process fluid.

3.3.2 When rupture disc is used upstream of a pressure relief valve, a pressure gauge shall be

provided on the downstream of the disc to indicate any rupture of the disc in addition to an excess flow check valve. In addition combination capacity factor of 0.9 shall be used for sizing unless the combination has been tested and approved for any other combination capacity factor. For such discs, a zero manufacturing tolerance shall be considered.

3.3.3 The total tolerance of the rupture disc shall be ± 5% of the specified bursting pressure or

less, unless otherwise specified. This shall include both the manufacturing tolerance and burst tolerance of the disc. All rupture discs shall be with ‘J’ bolt and tell tale assembly consisting of pressure indicator, pressure switch and excess flow check valve.

Rupture discs on ASME coded pressure vessels shall carry the ASME UD stamp.

3.3.4 Rupture Disc Testing 3.3.4.1 All discs shall be tested by bursting 2 discs of every batch with a ‘batch’ being defined as a

set of discs having the same size , material and set pressure. 3.3.4.2 All rupture discs and holders shall be provided with test records and test certificates to fully

cover component materials and the disc test details. 3.3.5 Rupture Disc & Breather Valve Marking And Nameplates 3.3.5.1 The marks shall be placed on a plate securely fastened to the disc and disc holder. The

marks shall be made in such a way that they will not be obliterated in service. 3.3.5.2 The markings shall include the following as a minimum for Rupture Discs / Breather

Valves:

- Tag number - Vendors name - Vendors design or type number (Model Number) - Size (mm)



- Set Pressure ( Set pressure for Vaccum / Gauge Pressure for Breather valves ) - Set Pressure at room temperature ( Not applicable for Breather valves ) - Back pressure (constant or variable) ( Not applicable for Breather valves ) - Capacity at overpressure ( Not applicable for Breather valves ) - Year of manufacture - Client’s (End user) name and Client’s code no.

3.3.5.3 ASME or IBR symbol as required. ( Not applicable for Breather valves ) 4.0 RELATED DOCUMENTATION

Standard name Description

API RP 526 Flanged steel safety relief valves.

API 527 Commercial seat tightness of safety Relief Valves with metal to metal seats

API 520 Design and installation of pressure relieving systems in refineries parts I & II.

API 521 Guide for pressure relief and depressurising systems.

ASME CODE SECTION VIII

Boiler and Pressure vessel code Div.1 and Div. 2

IBR Indian Boiler Regulations.

5.0 ATTACHMENTS Nil

STANDARD SPECIFICATION FOR SAFETY / THERMAL...

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