A Sleeve plug valves is a valve that uses a rotary sleeve or stopper to open or close a medium. It is widely used in petroleum, chemical and natural gas industries. The focus of maintenance is sealing, flexible operation and corrosion resistance. Specific maintenance points and operational recommendations are as follows:
I. Daily Inspection inspections and maintenance
Sealing Performance Inspection
Leak Detection: Check regularly for leaks valve body/pipeline connection, stem packing boxes and the sleeve/plug sealing surfaces.
METHOD: Apply soapy water to the cover to see if there are bubbles. Alternatively, leak rate can be measured using pressure testing equipment (API 598 compliant).
Seal Surface Repair: If the sealing surface is worn or scratched, repair it using a dedicated grinding tool to maintain a surface roughness of Ra ≤ 0.8μm. Serious wear and tear requires replacement of sealing ring or sleeve.
Operational Flexibility Inspection
Rotational Resistance Test: Manual rotation of the stem to check for bonding or abnormal noise. Increased resistance may indicate insufficient lubrication or buildup of internal dirt.
Downtime adjustment: Make sure the valve opening match the actual position to avoid damaging the the sealing surface by rotating too hard. Appearance and Connection Inspection
Valve Body Corrosion: Check valve body surface for rust, cracks or peeling coating, focusing on welds and flange connections.
Fastener Inspection: Check regularly for loose bolts and nuts and refasten them according to required torque (e.g. M16 bolts torque 40-60 Nm).
II. Cleaning and preventing scale
Internal cleaning
Removal Residual Media: After closing the valve, remove the cover and remove impurities from the sleeve cavity, plug surface and flow path using a soft brush or compressed air (pressure ≤ 0.6 MPa).
Chemical cleaning: If the medium is highly viscous or contains particulate matter, soak the valve in a special cleaning agent (such as an alkaline cleaning solution) and rinse off. Avoid using strong acid or alkali to avoid corrosion of the valve body.
Anti-scale measures
Water quality control: If the medium is water or vapour, hardness (≤ 200 mg/L) should be controlled to prevent scale deposition.
Additional filters: Install Y filters upstream of valves to filter particles ≥ 50 microns. Lubrication and Anti-Seize
Valve Stem Lubrication
Lubricant selection: Use a high temperature and chemical resistant lubricating grease (such as molybdenum disulfide grease) suitable for conditions ranging from -20°C to 200°C.
Lubrication Interval: lubrication interval every 3 to6 months, high temperature or high frequency environment requires shorter lubrication interval.
Instructions: Remove the packing cover and inject grease with a grease grease gun until the stuffing box overflows. Replace glands and tighten evenly.
Containers and Plug Anti-Seize
Clearance Adjustment: Regular inspection of gaps between bushing and plug (usually 0.1-0.3mm). Too big a gap to replace.
Anti-scratch coating: Apply a polytetrafluoroethylene (PTFE) coating to the plug surface to reduce friction.
III Anti-Corrosion Measures
Material Selection
Valve body material: Materials such as 304 304/316 stainless steel for slightly the corrosiveness media) or hartensitic material (for strong acids and alkalis) are selected according to the corrosiveness of the medium. Sealants: Carbide (such as cobalt based alloys) or ceramic coatings are used to improve abrasion and corrosion resistance.
Coating protection
External Surface Coating: Spray-coated epoxy resin or polyurethane coating with thickness ≥ 100μm and salt resistance ≥ 1000 hours.
Inner Cavity Coating: For non-metallic sealing valves, ceramic coating may be applied to the inner cavity to prevent media corrosion.
Environmental controls
Humidity Management: Store in relative humidity ≤ 60% to avoid condensation on valve body surface.
Ventilation Requirements: Installation in a well-ventilated area to prevent the accumulation of corrosive gases.
