What to Order
| Spare part | Commissioning stock | Two-year stock | Minimum quantity |
|---|---|---|---|
| Valve seat-and-seal kit | 2–5% | 5–10% | 1 per interchangeable group |
| Stem seal kit | Only when not included in the main kit | Match the planned maintenance work | 1 per unique packing design where needed |
| Complete valve overhaul kit | Selected valves only | Match the planned overhaul quantity | 1 for selected critical groups |
| Pneumatic actuator seal kit | 2–5% | 5–10% | 1 per actuator group |
| Hydraulic actuator seal kit | 1 per group | Planned use plus lead-time stock | 1 per actuator group |
| Complete solenoid valve | 2 per model or 2–5% | 5–10% | 2 per model |
| Solenoid coil | 2 per model and voltage | 5–10% | 2 per model and voltage |
| Limit switch box | 1 per model | 1 per model | Add 1 for critical or remote service |
| Proximity sensor | 2 per model and output type | 2 per model and output type | 2 per model |
| Filter-regulator | 1 per model or about 2% | 2–5% | 1 per model |
| Pressure gauge | 2 per range and connection | 5–10% | 2 per range |
| Positioner | 1 per model and protocol | 1 per compatible group | Add 1 for critical, remote or long-lead groups |
| Electric actuator module | Selected modules only | Based on lead time and failure effect | 1 when immediate replacement is required |
| Complete configured actuator | Critical groups only | 1 per selected critical group | Risk-based |
| Complete actuated valve | Rarely required | 1 for selected critical groups | Risk-based |
The two-year percentages are totals for the full two-year stock package. Do not multiply them by two again.
These percentages are purchasing allowances, not API, ISO or IEC requirements. API 6D covers valves within its stated scope, while API 6DX covers actuator sizing, mechanical integrity and mounting kits used with valves within its scope. Neither provides one spare-parts percentage for every project.[1][2]
Convert Percentages into Quantities
| Units in one interchangeable group | Commissioning kits | Two-year kits |
|---|---|---|
| 1–10 | 1 | 1 |
| 11–25 | 1–2 | 1–3 |
| 26–50 | 1–3 | 2–5 |
| 51–100 | 2–5 | 3–10 |
| 101–200 | 3–10 | 6–20 |
Use the lower end for clean, low-cycle service with fast local supply. Use the upper end for dirty service, special seal materials, frequent cycling, remote sites or long delivery.
Do not count a stem seal kit, seat-and-seal kit and complete overhaul kit as three separate requirements until the supplier confirms what each kit contains. One overhaul kit may already include the seats, body seals and stem packing.
Group Parts Before Counting
Parts are interchangeable only when they can be installed without changing the valve rating, seal material, temperature range, fail action, electrical approval or control connection.
| Equipment | Details that must match |
|---|---|
| Valve | Manufacturer, model, size, pressure class, floating or trunnion design, bore, seat material, stem packing, body seals and end connection |
| Actuator | Manufacturer, model, size, double-acting or spring-return action, fail direction, torque, supply pressure, seal grade, mounting flange and rotation |
| Solenoid | Voltage, AC or DC supply, three-way or five-way function, normally open or closed action, port thread, flow capacity and approval |
| Switch | Contact rating, NAMUR, PNP, NPN or dry-contact output, enclosure and hazardous-area approval |
| Positioner | Model, analog or digital protocol, single-acting or double-acting output, firmware, feedback option and approval |
| Electric module | Actuator model, voltage, hardware version, firmware, communication protocol and certification |
A 6-inch floating valve and a 6-inch trunnion valve do not normally use the same seats, bearings or stem parts. Compare a forged soft-seated floating ball valve with the parts shown in the trunnion ball valve structure guide before combining their spare lists.
Upstream and downstream trunnion seats may also be different. Check the approved drawing and the SPE and DPE seat guide before ordering seat assemblies.
ISO 5211 specifies attachment dimensions for part-turn valves and actuators. A matching ISO 5211 flange does not prove that the actuator has enough torque or that its coupling fits the valve stem.[4]
Use the approved valve torque data. The valve torque curve guide explains break torque, running torque and closing torque.
Calculate the Final Quantity
Use data in this order:
- Actual consumption from the same equipment model
- Records from similar plants
- OEM maintenance and warranty information
- Planning percentages when no better data exist
ISO 14224 provides a standard structure for recording equipment, failures and maintenance work in petroleum, petrochemical and natural-gas operations. It does not give a universal spare percentage.[3]
When annual consumption data are available, use:
Expected two-year use = Installed quantity × Annual use rate × 2
Lead-time stock = Installed quantity × Annual use rate × Supplier lead time in months ÷ 12
Final stock = Planned maintenance use + Expected two-year use + Lead-time stock
Round the result upward.
| Example | Calculation | Final stock |
|---|---|---|
| 18 standard valves | 18 × 5% = 0.9, rounded to 1; add 1 for a 14-week delivery | 2 kits |
| 64 process valves | 64 × 8% = 5.12, rounded to 6; deduct 2 unused commissioning kits | Order 4 additional kits |
| 12 high-temperature valves | 1 minimum special-seal kit; add 1 because replacement seals require 16 weeks | 2 kits |
| 40 pneumatic actuators | 40 × 2.5% annual use × 2 years = 2; add 1 for lead time | 3 seal kits |
Do not use this formula for one-off complete valves, large hydraulic actuators, matched metal-seat assemblies or unique electronic modules. Select those items by shutdown time, delivery time and repair ability.
Adjust for Delivery Time
| Supplier lead time | Stock action |
|---|---|
| Below 2 weeks | Minimum group stock may be enough for noncritical equipment |
| 2–8 weeks | Add stock equal to expected use during the delivery period |
| 9–16 weeks | Add at least one extra common repair item where a failure can stop operation |
| More than 16 weeks | Review complete modules and selected insurance spares |
| Custom or obsolete item | Agree an emergency supply, exchange or approved replacement plan |
For filters, seals and solenoids, calculate expected use during the delivery period. For a complete actuator or valve, keep the smallest quantity needed to cover one serious failure.
Commissioning Stock
Order the higher of one kit per interchangeable group or 2–5% of the installed quantity. Increase the quantity when valves are welded into the line, pipeline cleanliness is uncertain, special seals are used or delivery is longer than the commissioning period.
| Problem | Check before using a spare | Likely spare |
|---|---|---|
| Seat leakage after flushing | Debris, ball position and test direction | Seat-and-seal kit and drain seals |
| Actuator does not move | Air or power supply, solenoid and control signal | Solenoid, coil or filter-regulator |
| Actuator moves slowly | Supply pressure, blocked filter, air leakage and valve torque | Filter element, regulator or actuator kit |
| No open or closed signal | Actual valve position, switch cam, terminals and wiring | Switch box or proximity sensor |
| Coils fail repeatedly | Voltage, duty rating, temperature and moisture | Correct coil after fixing the cause |
| Early actuator shaft leakage | Coupling alignment and bracket stiffness | Coupling, mounting parts and seal kit |
| Positioner cannot be configured | Protocol, firmware and saved settings | Compatible configured positioner |
ISO 8573-1 classifies compressed-air contamination by particles, water and oil. The instrument-air requirement should state the required class and the point where it is measured.[5]
Dirty air can damage the regulator, solenoid and actuator while the valve body remains serviceable. See the electric versus pneumatic actuated ball valve guide for the different accessory and maintenance requirements.
The purchase order should also state whether the supplier must replace owner stock used to correct manufacturing, assembly or configuration defects during commissioning.
Two-Year Stock
Calculate planned maintenance first. If four actuators are scheduled for overhaul, order four kits plus lead-time stock. Do not apply another 5–10% to the same four overhauls.
| Service condition | Increase these parts | Do not increase automatically |
|---|---|---|
| Clean utility service | Minimum seals, solenoids and filters | Complete valves and large actuators |
| Dirty process media | Seats, drain seals and cavity fittings | Electronic control boards |
| Wet or oily instrument air | Filters, regulators, solenoids and actuator seals | Valve body parts |
| Marine or corrosive atmosphere | Switch boxes, solenoids, gauges, fittings and fasteners | Valve internals unless the process fluid also attacks them |
| High cycling | Dynamic seals, solenoids, couplings and positioners | Complete valves without evidence of internal wear |
| High or low temperature | Correct seal grade, lubricant and approved accessories | Standard-temperature kits |
| Remote site | Low-cost consumables and selected critical modules | Every complete valve assembly |
For high-cycle valves, use annual cycle count, OEM maintenance intervals and actual part life. A valve that moves once a month should not use the same stock rule as one that moves hundreds of times per day.
Repeated seat damage points to poor flushing or unsuitable service conditions. Repeated actuator seal damage points to dirty air, bad alignment, excessive speed or incorrect sizing. Buying more parts does not fix these causes.
Critical Stock
| Failure effect | Stock to consider |
|---|---|
| Safety function lost, hazardous fluid cannot be isolated, no bypass or full unit shutdown | Configured actuator, critical controls, mounting parts and valve repair kit |
| Reduced production, but a bypass or standby train is available | Repair kits, common controls and one actuator shared by compatible valves |
| Small production effect and fast local supply | Minimum repair kits and common accessories |
A complete configured actuator is useful when there is no bypass, supplier delivery is longer than the allowed outage, replacement is faster than repair, or the site cannot safely rebuild and test the actuator.
Do not automatically order a complete actuator, separate positioner, separate solenoid and separate switch box for the same failure. First check what is already included in the configured spare.
When a valve is part of a safety instrumented function, replacement, configuration, proof testing and return to service must follow the plant’s functional-safety procedure. IEC 61511 covers safety instrumented systems in the process sector; it does not apply automatically to every actuated valve.[6]
Electrical parts used in explosive atmospheres must keep the required protection type and marking. A solenoid with the correct voltage and thread is not acceptable when its hazardous-area approval is different.[7]
Valve Repair Kits
| Valve design | Parts commonly required |
|---|---|
| Floating ball valve | Two seats, stem packing, stem thrust washer, body seal, stem O-rings and gland parts |
| Trunnion-mounted ball valve | Seat rings or carriers, seat inserts, seat springs, stem and trunnion seals, body seals, bearings, injection fittings, drain seals and vent seals |
| Fire-safe valve | Normal seats, graphite secondary seals, fire-safe stem packing and body gaskets |
| Cryogenic valve | Low-temperature packing, stem seals, body seals and approved lubricant |
| Metal-seated valve | Matched ball-and-seat assembly, seat carriers, springs, seals and coating repair plan where applicable |
Ask whether each kit contains parts for one seat or both seats. Also ask whether the stem packing, body seals, bearings, springs and graphite seals are included.
Metal-seated balls and seats may be coated, lapped together and match-marked. Loose replacement seats may be unusable when the OEM requires a matched ball-and-seat set. Review the metal-seated valve maintenance guide before ordering loose seats.
ISO 10497 covers fire type testing of isolation valves. A soft-seal kit that does not include the secondary fire-safe seals may not restore the approved valve design.[8]
Anti-static parts should be checked separately. Anti-static continuity and fire-safe sealing are different functions.
For cryogenic valves, verify the extended bonnet, stem length, seal material and lowest design temperature. The cryogenic ball valve guide explains why these valves need separate spare records.
Actuator Parts
| Actuator type | Parts commonly stocked |
|---|---|
| Pneumatic actuator | Piston or vane seals, shaft seals, housing O-rings, bearing strips, gaskets and approved lubricant |
| Spring-return actuator | Seal kit and, for selected critical groups, a complete factory-built actuator or approved spring module |
| Hydraulic actuator | Cylinder seals, rod and piston seals, guide rings, filters, check valves, flow-control valves, pressure switches and accumulator parts |
| Electric actuator | Power module, control board, local display, terminal board, sensors, contactors, relays, fuses and heaters |
Order actuator parts by model, size, action and seal grade. Do not order by torque output alone.
Fail-open and fail-close spring-return actuators may use different spring sets even when the housings look identical.
An electric module may fit physically but still fail to work because its voltage, protocol, hardware, firmware or approval is different. Store the approved settings and parameter files outside the actuator.
Control Parts
| Part | What must match | Suggested minimum |
|---|---|---|
| Complete solenoid | Voltage, function, porting, flow, temperature and approval | 2 per model |
| Solenoid coil | Voltage, AC or DC supply, power and duty rating | 2 per model and voltage |
| Limit switch box | Switch type, contact rating, enclosure and shaft interface | 1 per model |
| Proximity sensor | NAMUR, PNP, NPN or other output, voltage and approval | 2 per model |
| Positioner | Protocol, action, feedback, firmware and approval | 1 per compatible group |
| Filter-regulator | Port, pressure range, filter size and material | 1 per model |
A spare coil covers an electrical failure only. A complete solenoid also covers blocked passages, internal leakage, corrosion and mechanical damage.
Repair or Replace
| Work | Typical planning time |
|---|---|
| Replace a solenoid coil | 15–30 minutes |
| Replace a complete solenoid | 30–60 minutes |
| Replace a switch box | 1–2 hours |
| Replace a configured pneumatic actuator | 2–6 hours |
| Open and rebuild valve internals | 8–24 hours or longer |
| Remove a valve for factory repair | Several days to several weeks |
These are planning ranges, not fixed labor standards. Actual time depends on isolation, access, valve size, lifting, piping work, permits and testing.
| Spare option | Included parts | Use when |
|---|---|---|
| Bare actuator | Actuator only | The bracket, coupling and controls can be reused |
| Mounted actuator | Actuator, bracket, coupling and fasteners | Mounting parts are custom or easy to damage |
| Configured actuator | Actuator, mounting parts, controls, tubing and settings | A critical valve must be restored quickly |
Before buying many internal kits, confirm that the site can dismantle, rebuild and test the equipment. Use the stem-leak and seat-leak guide to identify the leak location before opening the valve.
ISO 5208 specifies valve examinations and pressure tests used to check pressure-boundary integrity and closure tightness. The repair procedure should state which tests must be repeated after each repair.[9]
120-Valve Example
The project contains:
- 60 identical utility valves
- 24 normal process valves
- 12 high-temperature valves
- 12 dirty-service valves
- 8 emergency shutdown valves
- 4 large pipeline isolation valves
| Group | Commissioning stock | Two-year stock | Reason |
|---|---|---|---|
| 60 utility valve kits | 2 | 3 | Clean service and one standard design |
| 24 process valve kits | 2 | 3 | Special material and 10-week delivery |
| 12 high-temperature kits | 2 | 2 | One minimum kit plus one long-lead kit |
| 12 dirty-service kits | 2 | 2 | Higher risk of seat damage |
| 8 shutdown-valve kits | 1 | 2 | No acceptable bypass |
| 4 large-valve internal sets | 1 | 1 | Large and unique valve design |
| Pneumatic actuator kits | 1 per actuator group | 5–10% per group | Different sizes and seal grades |
| Solenoid valves | 2 per model | 5–10% per model | Low cost and quick replacement |
| Positioners | 1 per model and protocol | 1–2 per group | Protocol and settings must match |
| Two-year spare category | Example quantity |
|---|---|
| Valve seat-and-seal kits | 12 |
| Large-valve internal sets | 1 |
| Pneumatic actuator seal kits | 5–8 |
| Complete solenoids | 6–12 |
| Solenoid coils | 6–12 |
| Switch boxes | 2–4 |
| Positioners | 1–2 |
| Complete configured actuators | 1 |
The 120 installed valves do not require 12 complete spare valves. Most stock is held as seals, solenoids and a small number of complete critical modules.
The emergency shutdown group receives one configured actuator because actuator replacement is faster than field rebuilding. The four large pipeline valves receive one agreed internal set and an emergency supplier-support plan instead of four complete spare valves.
RFQ Checklist
| Required information | What it prevents |
|---|---|
| OEM part number | Unapproved substitution |
| Compatible valve tags | Issuing a part to the wrong valve |
| Exploded drawing and bill of materials | Missing components |
| Kit contents and overlap list | Buying the same seals twice |
| Material and temperature range | Mixing standard and special kits |
| Seat direction and quantity | Ordering the wrong trunnion seat |
| Hazardous-area approval | Loss of electrical compliance |
| Hardware, firmware and protocol | Receiving an unusable electronic module |
| Special tools and repair limits | Buying kits the site cannot use |
| Post-repair tests | Returning untested equipment to service |
| Shelf life and storage method | Parts expiring before use |
| Normal and emergency lead time | Insufficient replenishment stock |
| Superseded part numbers | Keeping obsolete stock with no replacement |
| Warranty replacement process | Owner stock paying for supplier defects |
Approve the final list after valve drawings, materials, actuator sizing and controls are confirmed. The industrial ball valve procurement guide provides additional bid-package checks.
For a complete actuator, state whether the price includes the bracket, coupling, fasteners, solenoid, switch box, positioner, regulator, tubing, configuration and factory test.
Storage Checks
ISO 2230 provides guidance for storing vulcanized and thermoplastic rubber products. Seal life depends on the material, packaging and storage condition, so one shelf-life figure should not be applied to every kit.[10]
| Stock item | Suggested review |
|---|---|
| Opened repair kit | Check immediately after use |
| Shelf-life-controlled seals | Review every 6–12 months |
| Electronic module compatibility | Review once a year |
| Complete stored actuator | Check preservation every 6–12 months |
| Overall stock quantity | Review after commissioning, after the first operating year and after each major shutdown |
Protect seals from sunlight, excess heat, ozone sources, moisture, chemicals, dirt and permanent deformation.
Warehouse records should show the OEM part number, compatible tags, receipt date, expiry or review date, storage location, packaging condition, issue history and reorder level.
Safety
An actuated valve may contain process pressure, pneumatic pressure, hydraulic pressure, electricity and stored spring energy. Isolate and release every energy source before maintenance.
For applicable United States general-industry work, OSHA 29 CFR 1910.147 covers servicing where unexpected start-up or stored-energy release could injure workers.[11]
The UK HSE has reported an emergency shutdown valve incident in which an end plate and springs were released because of stored spring energy. Spring modules should only be opened with the approved method and tools.[12]
After repair, check valve movement, fail position, seat and stem leakage, position indication, control response, opening time, closing time and mounting condition.
Finally
Use 2–5% for commissioning repair kits and 5–10% for two-year stock only when no better records exist. Apply the percentage to each interchangeable group, keep at least one kit per group and two complete solenoids per model, and deduct transferable commissioning stock before reordering. Check kit contents so seats, stem seals and body seals are not bought twice. A complete actuator or valve should be stocked only when repair or supplier delivery cannot meet the allowed shutdown time. Record every part used during the first year and replace the initial percentages with actual failure and delivery data.
