Engineering Standard. Fig 707 Safety Relief Valve Installation and Maintenance Instructions

Transcription

1 ES/707/0/003 ES/707/0/003 June 2007 Engineering Standard Fig 707 Safety Relief Valve Installation and Maintenance Instructions Sharp Street, Worsley, Manchester M28 3NA: Tel +44 (0) Fax +44 (0) safetysystemsuk.com Safety Systems UK Ltd.

2 Revisions Date Section Amendment Signature 13/06/07 Original issue Michael J Gray CONTENTS Specification 1.0 Scope Pressure and Temperature Design Limits Size Range Preparation Installation Set Pressure adjustment Changing Spring Valve Maintenance 4 Page 2 of 6

3 1. Scope This Standard covers Installation and maintenance procedures for fig 707 safety relief valve, covering resilient and metal seated versions. Note Valve range not suitable for sea water applications 2. Pressure and Temperature Design Limits Pressure Temperature o C Bar St Steel/EPDM(WRAS) to 95 St Steel/AFLAS to 200 St Steel/PTFE to 224 St Steel to Size Range DN15 x DN15 DN20 x DN20 DN25 x DN25 DN32 x DN32 DN40 x DN40 DN50 x DN50 4. Preparation 4.1 Remove all packing materials. 4.2 Check that set pressure and other details on the valve nameplate are correct. 4.3 Use suitable pipe thread sealant or fit appropriate inlet and outlet flange gaskets (ensure that the gaskets do not impede flow). 4.4 Pipework leading to the valve should be thoroughly cleaned to remove all foreign matter, debris, pipescale etc, as this will lead to valve leakage if trapped between seat and disc. 4.5 Fluid discharge should not create any bending forces on the valve inlet connection. All discharge piping should be adequately supported. 5. Installation Valve installation should conform to good engineering practice to ensure safe and efficient operation. To facilitate access, a union joint is recommended near to the valve outlet. Note : Fluid discharge must not create a hazard to persons or property. 5.1 Position The valve should be mounted vertically in the pipeline with the adjusting screw uppermost. The branch leading to the valve shall be of sufficient size to prevent a pressure drop in excess of 3% of the set pressure when the valve is discharging its rated capacity. 5.2 Discharge Piping The discharge pipe should be equal to the valve outlet for pipe lengths up to 50 diameters (including 1 right angled bend). Pipe lengths should be restricted and fittings should be of sufficient size so as to limit the built up back pressure to 10% of the valve set pressure. Greater pipe lengths or the use of pipe with more bends should be carefully calculated, contact the factory for further advise. 5.3 Drainage If there is a risk of condensate accumulating on the discharge side of the valve, a small drainpipe should be led away from the lowest point. 6 Set Pressure adjustment 6.1 With no inlet pressure applied to the valve, remove padlock (17) and Lever (9) (where fitted) and remove dome (8, 16). 6.2 Slacken Locknut (11). 6.3 Increase inlet pressure slowly to defined valve set pressure. Increasing pressure slowly will give a precise opening point without risk of valve popping. Set Pressure Definition Air, Gas, Steam First Audible Discharge Liquids First Steady Stream 6.4 To increase valve set pressure turn adjusting screw (2)clockwise (downwards) and to reduce set pressure turn adjusting screw (2) anticlockwise (upwards). 6.5 Once correct set pressure has been established retighten locknut (11) and replace dome (8, 16), lever (9) and padlock (17) where fitted. Page 3 of 6

4 7.0 Changing Spring 7.1 With no inlet pressure applied to the valve, remove padlock (17) and Lever (9) (where fitted) and remove dome (8, 16) 7.2 Slacken Locknut (11) 7.3 Slacken and remove adjusting screw (2) by turning anticlockwise (upwards) 7.4 Remove spring (4) and replace with new spring 7.5 Refit adjusting screw (2) and apply a nominal load to the spring by turning the adjusting screw anticlockwise (downwards) 7.6 Adjust set pressure as described in section Once correct set pressure has been established retighten locknut (11) and replace dome (8, 16), lever (9) and padlock (17) where fitted Fit spring end cap (5) and spring (4) onto spindle Screw adjusting screw into valve body Load ball (15) into disc (7) and assemble into body locating on spindle Screw seat (16) into body Screw pinning screw (3) into body and lock into seat Adjust set pressure as described in section Once correct set pressure has been established retighten locknut (11) and replace dome (8, 16), lever (9) and padlock (17) where fitted Note : If set pressure changes are being made, ensure that the pressure temperature limitations for the valve trim have not been exceeded. Where set pressure changes have been made a new nameplate will be required which has been stamped with the revised valve set pressure. 8.0 Valve Maintenance 8.1 Strip-down With valve removed from system, remove padlock (17) and Lever (9) (where fitted) and remove dome (8, 16) Slacken Locking ring (11) Slacken and remove adjusting screw (2) by turning anticlockwise (upwards) Remove spring (4), spindle (6), spring end cap (5) Remove pinning screw (3), Seat (16), Disc(7), ball (15) 8.2 Refurbishment Clean components and inspect for signs of excessive wear, galling, erosion etc. Resilient Valve discs should be replaced during regular maintenance Check spring for pitting or corrosion. Light marks can be polished out, however components with excessive deterioration should be replaced The valve seat and metal disc should not be lapped together. These can be lapped separately using a flat cast iron lapping plate and fine carborundum or diamond lapping compound If marks cannot be lapped out they may require machining. When re machining seat faces it is important to maintain the original profile and seat width. If in doubt consult factory for required dimensions. 8.3 Re-Assembly Assemble locking ring (11) to the adjusting screw (2) Fit spindle (6) into upper part of valve body Page 4 of 6

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