General RV Repair Procedure

[Bader]

Greeting all,

Would you please advice; is there any general repair procedure that we can use for different kind of relief valve defects , beside if there is something concerning welding & coating limitation.

I would appreciate your assistance.



I am always ready for help as much as i can .. so just let me know your Problem .

 

[BigInch]

Defects of any kind rarely fall under a general repair procedure.

If its a weld, grind and repair.

If its coating, remove and replace.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[gerhardl]

Advice from our workshops most skilled and experienced instrument mechanics:

...Clean everything carefully, taking as little as possible apart. Inspect visually. If no apparant cause for failure is found: put together again and see if it is working properly now....

An amazingly effective procedure!

Will work for more than 60% of all apparantly mechanical undamaged instruments and for instance pilot operated valves exposed to fluid for some periode.

 

[JAlton]

General Repair Procedures are available in the NBIC, Part 3, Supplement 7, Para. S7.14 for both Direct Spring & Pilot Operated PRV. This document is available for purchase at

http://www.nationalboard.org.

Specific Repair Procedures are documented in PRV Manufacturer's Maintenance Manuals, which in many cases are available on their websites: (See website info below)
Specific Critical Dimensions (Inspection Points and Acceptance Criteria, Tolerances) include:
Spring Range needs to be verified correct. Overall Spring Free Height is critical. Spring Squareness is important. Spring Footprint needs to be checked. Uneven Spring Coil Spacing is unacceptable.
Check Stem/Spindle Runout (Concentricity). Look for wear or galling.
Check Guide & Disc Holder Clearance for minimum/maximum
dimensions (overall clearance). Check Surface Finish. (Replace if worn or galled).
Check Nozzle Overall Height (Replace if under minimum). Check Nozzle Bore Diameter (Critical to Flow Capacity). This info is available in NB-18, Pressure Releif Device Certification, available for free download at

http://www.nationalboard.org.

Check Nozzle ID & OD, Check Nozzle Inside & outside Steps. Machine and/or Lap to Proper Finish.
Check Disc Overall Thickness (Replace if under minimum). Check Disc Steps. Check Disc Inside & Outside Steps. Machine and/or Lap to Proper Finish.

General repair is covered by NBIC, Part 3, S7.14, (see gerhardl comment re 60%). Specific Dimensions & Procedures are necessary to cover the remaining 40%. Many repairable PRVs are scrapped and replaced due to insufficient inspection while some unacceptable PRV Parts are reinstalled due to ineffective insecption.

http://www.dresser.com/internet/pages/documentwarehouse/documentsearchresults.cfm

http://www.tycoflowcontrol-na.com/literature.asp

JAC

 

[JAlton]

Regarding Welding & Coating, there are specific parameters. NBIC, Part 3, Supplememnt 7, Para. S7.12, addresses weld repairs to Pressure Releif Valves including repairs by an "R" Stamp Holder. Spring Coatings are not nearly as common as they were just a few years ago, but it is permissible to paint springs in a repaired valve to protect it from corrosion. Other coatings may be applied to springs by the OEM or Assembler. It is also acceptable to paint the Body & Bonnet of a PRV. Internal Parts are typically corrosion resistant due to ASME requirements.

JAC