Cage control valve leakage treatment

An Overview

    FV-201 anti-surge control valve is concentrated nitric workshop production of a very important field of a regulating valve , if leaking spool valve, process gas in the NO ₂ gas directly into the exhaust through the regulating valve, so that the exhaust gas in NO ₂ gas concentration excessive emissions, reach environmental requirements. In the November 3, 2010, concentrated nitric sudden increase in the concentration of exhaust workshop, rising from about 100ppm to 600ppm or so, after professional and technical staff to discuss, analyze, judge, agreed that the exhaust gas concentration causes the spool valve FV-201 causing a leak. In order to discharge the requirements of environmental protection, it is necessary to FV-201 control valve for maintenance treatment, the regulating valve leakage reached Ⅴ grade level requirements.

    2 valve structure

    Valve FV-201 manufactured by CCI cage cylinder straight travel valve, the medium flow is low prices, in use, because the original balanced valve plug easily damaged O-ring problem, after the factory will balance structure changed to a non-balanced, and by calculating the existing double-acting cylinder diameter and supply pressure used under unbalanced, still meet the conditions regulating valve under pressure in grade Ⅴ leakage class requirements. Regulating valve seal in the form of single-seat metal seal, linear flow characteristics, nominal diameter DN250, CV value of 900, the cage is designed to reduce the fluid noise porous buck. Double-acting cylinder actuator is equipped with a gas tank, make sure the valve in case of interruption of gas supply can also be emergency opening, to prevent compressor surge occurs.

    3 FV-201 control valve leaks and leakage checks

    3.1 leak check

    Produced in the process with the maintenance stop condition, the FV-201 with inlet and outlet valve regulating valve inlet flange removal separate blind blind flange with DN250 good regulator valve inlet, and add 0.30MPa instrument air source, valve seat, valve parts with soapy water leak, leak observed to determine whether the spool wire seal leaks, or leakage at the valve seat gasket.

    Through the inspection, there is no leakage at the valve seat gasket, leak hole in the cage, and are therefore determined to be in the spool seal leakage.

    3.2 Water pressure leak test

    According GB/T17213.4-2005 "Industrial Control Valves inspection and routine testing in Part IV: Inspection and routine testing" standard leak test, control valve inlet valve cavity to be 0.30MPa irrigation water pressure leak test, collected at the outlet valve leakage of water (see Figure 1), the leakage amounted to 2200ml/min, a large amount of the control valve leakage.

Figure 1 just off valve leaks when pressure test

    According GB/T17213.4-2005 "Industrial Control Valves inspection and routine testing in Part IV: Inspection and routine testing" in 7.3.3 leak specifications, calculate FV-201 control valve hydraulic test Ⅴ grade level requirements leak leak volume. Table 1.

Table 1 FV-201 control valve hydraulic test Ⅴ grade level leakage leakage

    Since FV-201 hydraulic test amount of leakage is 2200ml/min, far greater than Grade Ⅴ valve leakage level required amount of leakage 0.225ml/min, so the need for valve leakage for processing.