Terminology E. Operational Characteristics of Pressure Relief Devices

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=90 BGCOLOR="#000066" TEXT="#F7F7FF" bgproperties="fixed" background="66b00c10dkbliw.jpg"> <div> <FONT SIZE="2" COLOR="#FF6600" FACE="Arial" ><A HREF="index.htm" TARGET="_top" TITLE="PRD Technologies Inc."><U><B>HOME </B></U></A><B> </B></FONT><B>   </B><A HREF="id151.htm" TARGET="_top" TITLE="Pressure Relief Device Terminology"><U><B> </B></U></A><FONT SIZE="2" COLOR="#FF6600" FACE="Arial" ><A HREF="id151.htm" TARGET="_top" TITLE="Pressure Relief Device Terminology"><U><B> BACK </B></U></A></FONT><A HREF="id151.htm" TARGET="_top" TITLE="Pressure Relief Device Terminology"><U><B> </B></U></A><B>|  </B><FONT SIZE="7" COLOR="#FF6600" FACE="Arial" ><B> </B></FONT><FONT SIZE="7" COLOR="#FFFFCC" FACE="Arial" ><B>  </B></FONT><FONT SIZE="6" COLOR="#FFFFFF" FACE="Arial" ><B>PRD Technologies Inc.</B></FONT></div> <bR> <div> </div> </td> </tr><tr> <td valign="top" width=210 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> Terminology E. Operational Characteristics of Pressure Relief Devices</div> <bR> <div> <B><IMG SRC="41a9b3e0.png" border=0 width="155" height="62" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B><IMG SRC="26980500.jpg" border=0 width="128" height="80" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <div> <B><IMG SRC="57482420.jpg" border=0 width="130" height="66" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> </td> <td valign="top" height=390 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <I><B>Pressure Relief Solutions & Services</B></I></div> <bR> <div> <B>E. Operational Characteristics of Pressure Relief Devices</B></div> <bR> <div> <I><B>back pressure </B></I><I>- </I>the static pressure existing at the outlet of a pressure relief device due to pressure in the discharge system</div> <div> <I><B>blowdown </B></I><I>- </I>the difference between actual popping pressure of a pressure relief valve and actual reseating pressure expressed as a percentage of set pressure or in pressure units</div> <div> <I><B>blowdown pressure </B></I><I>- </I>the value of decreasing inlet static pressure at which no further discharge is detected at the outlet of a pressure relief valve after the valve has been subjected to a pressure equal to or above the popping pressure</div> <div> <I><B>breaking pressure </B></I><I>- </I>the value of inlet static pressure at which a breaking pin or shear pin device functions</div> <div> <I><B>built-up back pressure </B></I>- pressure existing at the outlet of a pressure relief device caused by the flow through that particular device into a discharge system </div> <div> <I><B>burst pressure </B></I>- the value of inlet static pressure at which a rupture disc device functions</div> <div> <I><B>chatter - </B></I>abnormal rapid reciprocating motion of the movable parts of a pressure relief valve in which the disc contacts the seat</div> <div> <I><B>closing pressure </B></I><I>- </I>the value of decreasing inlet static pressure at which the valve disc reestablishes contact with the seat or at which lift becomes zero</div> <div> <I><B>coefficient of discharge </B></I>- the ratio of the measured relieving capacity to the theoretical relieving capacity</div> <div> <I><B>cold differential test pressure - </B></I>the inlet static pressure at which a pressure relief valve is adjusted to open</div> <div> on the test stand. This test pressure includes corrections for service conditions of superimposed back pressure and/or temperature.</div> <div> <I><B>constant back pressure - </B></I>a superimposed back pressure which is constant with time</div> <div> <I><B>cracking pressure - </B></I>see <I>opening pressure</I></div> <div> <I><B>flow capacity </B></I><I>- </I>see <I>measured relieving capacity</I></div> <div> <I><B>flow-rating pressure </B></I><I>- </I>the inlet static pressure at which the relieving capacity of a pressure relief device is measured</div> <div> <I><B>flutter </B></I><I>- </I>abnormal, rapid reciprocating motion of the movable parts of a pressure relief valve in which the disc does not contact the seat</div> <div> <I><B>leak pressure </B></I>- see <I>start-to-leak pressure</I></div> <div> <I><B>leak test pressure </B></I><I>- </I>the specified inlet static pressure at which a quantitative seat leakage test is performed in accordance with a standard procedure</div> <div> <I><B>marked breaking pressure </B></I><I>- </I>the value of pressure marked on a breaking pin device or its nameplate</div> <div> <I><B>marked burst pressure </B></I><I>- </I>the value of pressure marked on the rupture disc device or its nameplate or on the tag of the rupture disc and indicates the burst pressure at the coincident disc temperature </div> <div> <I><B>marked pressure </B></I>- the value or values of pressure marked on a pressure relief device</div> <div> <I><B>marked relieving capacity </B></I><I>- </I>see <I>rated relieving capacity</I></div> <div> <I><B>measured relieving capacity </B></I><I>- </I>the relieving capacity of</div> <div> a pressure relief device measured at the flow-rating pressure, expressed in gravimetric or volumetric units</div> <div> <I><B>opening pressure </B></I>- the value of increasing inlet static pressure of a pressure relief valve at which there is a measurable lift, or at which the discharge becomes continuous as determined by seeing, feeling, or hearing </div> <div> <I><B>start-to-discharge pressure </B></I>- see <I>opening pressure</I></div> <div> <I><B>start-to-leak pressure </B></I>- the value of increasing inlet static pressure at which the first bubble occurs when a pressure relief valve is tested by means of air under a specified water seal on the outlet </div> <div> <I><B>superimposed back pressure </B></I><I>- </I>the static pressure existing at the outlet of a pressure relief device at the time the device is required to operate. It is the result of pressure in the discharge system from other sources.</div> <div> <I><B>test pressure </B></I><I>- </I>see <I>relieving pressure</I></div> <div> <I><B>theoretical relieving capacity </B></I>- the computed capacity expressed in gravimetric or volumetric units of a theoretically perfect nozzle having a minimum cross-sectional flow area equal to the actual discharge area of a pressure relief valve or relief area of a non-reclosing pressure relief device </div> <div> <I><B>vapor-tight pressure </B></I>- see <I>resealing pressure</I></div> <div> <I><B>variable back pressure - </B></I>a superimposed back pres-sure that will vary with time</div> <div> <I><B>warn </B></I>- see <I>simmer</I></div> <bR> <bR> <div> <B>For further assistance or information call (330) 253-4800or email: </B><A HREF="mailto:sales@prdtechnologies.com" TARGET="_top" TITLE="mailto:sales@prdtechnologies.com"><U><B>sales@prdtechnologies.com</B></U></A><A HREF="mailto:sales@prdtechnologies.com" TARGET="_top" TITLE="mailto:sales@prdtechnologies.com"><U> </U></A> </div> </td> </tr></table></body>