Product Overview

Spirax Sarco Spira-trol Plug Stem and Seat Kit is a dedicated internal trim replacement assembly for Spira-trol series two-port globe control valves. It restores precise fluid metering and shut-off integrity across steam, gas, and liquid systems where operating wear, wire drawing, or surface impingement has compromised sealing. The kit provides matched parabolic plug profiles and precision-machined seats that mount directly into the valve body using the host valve cage-retained seating mechanism.

Available across nominal sizes DN15 to DN100 (½” to 4”) and larger sizes DN125 to DN300 (5” to 12”), these trim sets serve both unbalanced and balanced valve assemblies. Multiple metallurgy choices, including stainless steel 431, 316L, Stellite 6 hard facing, and soft PEEK/PTFE seating options, allow operators to renew control performance according to original specification without replacing the entire valve body.

Key Features

• Standardized parabolic plug contours available in Equal Percentage (50:1 rangeability), Linear (30:1 rangeability), and Fast Opening (10:1 rangeability) profiles.
• Cage-retained seat architecture held by duplex stainless steel cage (ASME A994 CD4MCuN), allowing in-line trim servicing without removing the valve body from the pipework.
• Multiple seating options supporting IEC 60534-4 Class IV metal-to-metal shut-off (with optional Class V) and Class VI bubble-tight shut-off via PEEK or PTFE soft seats.
• Full port and multi-stage reduced trim options (Reduction 1 through Reduction 5, plus microflute linear trims down to Kv 0.01) to adapt flow capacity to actual process demand.
• Metallurgy options covering stainless steel 431, 316L, Stellite 6 hard facing for erosive duties, and reversible PEEK (Steam-Tight C) configurations.
• Balanced plug options for DN65 to DN300 incorporating dynamic balance seals to minimize required actuator thrust.

Technical Specifications

Specification Parameter	Technical Detail / Value
Compatible Valve Series	Spira-trol K Series (KE73, KE71, KE43, KE61, KE63, KEA) and L Series (LE31, LE33, LE43, LE63, LEA)
Valve Size Coverage	DN15 to DN100 (½” to 4”), DN125 to DN300 (5” to 12”)
Plug Geometry	Parabolic contour
Flow Characteristics	Equal percentage (E), Linear (L), Fast opening (F)
Rangeability	50:1 (Equal percentage), 30:1 (Linear), 10:1 (Fast opening)
Rated Travel / Stroke	20 mm (DN15–DN50), 30 mm (DN65–DN100), 70 mm (DN125–DN300)
Plug & Stem Metallurgy	Stainless steel 431 (Trim T), 316L (Trim S), 316L with Stellite 6 (Trim W), 431 / 316L (Trim C, G, P)
Seat Ring Metallurgy	Stainless steel 431 (T), 316L (S), 316L + Stellite 6 (W), PEEK (C, P), 316L + PTFE insert (G)
Seat Cage Retainer	Duplex stainless steel ASME A994 CD4MCuN
Shut-off Class (IEC 60534-4)	Class IV (Standard metal-to-metal), Class V (Optional metal), Class VI (PEEK / PTFE soft seats, unbalanced), Class IV (Balanced soft seat)
Maximum Seat Operating Temperature	400 °C (Metal: 431, 316L, Stellite 6), 220 °C (PEEK Option C and P), 152 °C (PTFE soft seat Option G)
Saturated Steam Limit (Seat)	19 bar g (PEEK Option C/P), 4 bar g (PTFE Option G)

Applications

• Routine preventive overhaul or scheduled turnaround maintenance of Spira-trol globe control valves.
• Remediation of control loop degradation caused by seat erosion, cavitation pitting, wire drawing, or foreign debris entrapment.
• Correction of gland packing leaks resulting from stem scoring, scaly deposits, or mechanical misalignment.
• Re-rating valve capacity or characteristic via installation of reduced trim sets or alternative throttling profiles.
• Modulating and on/off service on saturated and superheated steam, condensate, compressed air, and Group 2 process fluids.

Removal and Refitting Procedures

Internal trim replacement can be executed with the valve body installed in the pipeline once the system is isolated, depressurized, drained, and cooled to ambient temperature.

Disassembly and Inspection

1. Disconnect the actuator and unfasten the bonnet nuts (27) or bolts according to the maintenance instructions.
2. Lift off the bonnet assembly and withdraw the plug/stem assembly (8).
3. Lift out the seat retaining cage (5), followed by the seat ring (6) and seat gasket (7). Take care not to damage the machined body recess.
4. Clean all internal surfaces thoroughly, removing all residual graphite from the body seat recess and mating faces.
5. Inspect the valve stem and sealing faces: score marks or scaly deposits on the stem accelerate packing failure, while seat or plug erosion prevents specified shut-off.

Assembly and Alignment Checks

1. Place a new seat gasket (7) into the body recess, then insert the seat ring (6).
2. Refit the cage (5), ensuring that the flow windows face downward and that the cage sits squarely on the seat without impinging against the valve body wall.
3. On balanced models, fit a new balance seal (31) into the plug groove and insert the plug/stem assembly into the cage using moderate hand force without snagging the seal.
4. Fit a new bonnet gasket, extend the plug stem fully so upper threads do not score the packing, and locate the bonnet assembly over the body studs.
5. Tighten the bonnet nuts progressively across diameters: tighten finger tight, raise and briskly lower the stem to center the plug, then apply torque in increments of 10%, 20%, 40%, 60%, 80%, and 100% of the specified torque (Table 1: 50 N m for DN15–25, 70 N m for DN32–50, 130 N m for DN65–80, 100 N m for DN100 on standard versions).
6. Verification test: pull the plug off its seat, rotate 120°, and push slowly back down into the seat checking for binding. Repeat this check three more times to ensure exact concentric alignment.

Ordering References

When specifying spare trim kits, state the exact valve model nomenclature, nominal bore, seat type, and flow coefficient (Kv/Cv) stamped on the valve body nameplate. Trims are supplied as matched sets (plug, stem, and seat ring; gaskets are ordered separately under gasket set B, G unless ordered as a conversion package).