ASME PCC-1-2013

We recommend and incorporate the methods and suggestions of ASME PCC-1-2013 Guidelines for Pressure Boundary Bolted Flange Joint Assembly.

Flange stresses are determined and limited by Appendix 2 of ASME Section VIII, Division 1. The methods are clear and most engineers understand the basics of Appendix 2 flange design. Unfortunately Appendix 2 does not address many factors which affect seal integrity, especially over a long service life.

For example, problems arise from an inherent disconnect between the flange designer and installer. The assembly intentions of the designer are often not effectively communicated to shop and field personnel.

Also, gasket technology is constantly advancing through dedicated research by sealing industry professionals such as Garlock Sealing Technologies. Our company recommends Garlock due to a long history of excellent quality and responsiveness.

In 2010 ASME Standards & Certification replaced standard PCC-1-2000 with PCC-1-2010 to reflect advances in calculation methods, gasket technology, bolting procedures, and to address the designer-installer disconnect. The goals of the specification are safety, consistency, and to ensure seal integrity through all stages of an extended service life. Additions and modifications were added in 2013 by issuance of PCC-1-2013.

Historically engineers used simple rules of thumb to calculate flange bolt load. Applying 50 KSI stress to all steel bolts or 60 percent of bolt yield worked generally well; however, not in all cases and these simplified methods are dangerous in critical applications.

For improved safety and consistency the emphasis must be placed on gasket stress for a given gasket (type, geometry, and material), and flange facing. PCC-1-2013 provides methods for determining an optimum "target" bolt load to achieve the desired gasket stress.

Torque is usually the most efficient and cost effective method of applying the target bolt load; therefore, PCC-1-2013 provides methods for determining the target torque.

Thread friction is a significant variable affecting the translation of torque into load. Relatively small thread imperfections can significantly affect the torque-load relationship. For this reason bolt and nut threads must be visually inspected and checked for free run nuts during the lubrication process. Yes, more labor is involved; however, these installation steps are critical.

Acceptable flange face flatness and imperfections depend on gasket type and material. Appendix D Guidelines for Allowable Gasket Contact Surface Flatness and Defect Depth provides guidelines for both based on gasket experience.

PCC-1-2013 recommends temporary gaskets for pressure testing and replacement with new service gaskets after testing.

PCC-1-2013 recommends that service gaskets not be reused after dis-assembly for maintenance.

A few of the benefits of incorporating PCC-1-2013 include:

   passing pressure tests on the first application, 

   leak-free plant start-ups and run cycles,

   lower maintenance costs, and

   eliminates process emissions (carcinogens, flammables, greenhouse gases, etc.)