MSIV Plug 


The Preferred Engineering Main Steam Isolation Valve Plug is designed to allow for repairs on the main steam line isolation valve seats. The MSIV Plug is an aluminum plug designed to fit past the main steam isolation valve seats and seal on the ID of the valve body or pipe. The MSIV Plug is manually maneuvered past the valve seats and inserted into the valve with the use of handles and removable tubing handle extensions. Once in position, the Compression Nut is torqued which actuates the seal against the valve wall. 


  • Design pressure of 0.5 psi back pressure. 

  • Aluminum design precludes scratching or damage to the valve seats or guides. 

  • Designed to use plant equipment to actuate. No special tools needed.  

  • Air challenge tools provide instant verification that a complete seal is obtained and eliminate time consuming subjective video confirmation views.