Common Valve Mistakes: 15 Errors to Avoid

Valve selection and specification errors cause leaks, premature failure, and safety incidents. These 15 mistakes cover the most frequent technical and commercial errors in oil and gas valve engineering and procurement.

Technical Mistakes

1. Throttling a Ball Valve

Error: Using a ball valve in a partially open position to regulate flow. Risk: High-velocity flow erodes the soft seat, causing leakage within weeks. The valve loses its shut-off capability. Fix: Use globe valves or control valves for throttling; ball valves are for on/off service only.

2. Installing a Check Valve Backwards

Error: Ignoring the flow direction arrow and installing the valve in reverse orientation. Risk: The valve blocks forward flow and allows backflow; the exact opposite of its purpose. Fix: Always verify the cast flow arrow on the body. See check valve types and orientation.

3. Confusing API 600 and API 602

Error: Specifying API 600 for small-bore gate valves or API 602 for large-bore. Risk: API 600 (cast, NPS 2+) and API 602 (forged, ≤NPS 4) have different body designs, face-to-face dimensions, and wall thicknesses. Wrong standard = wrong valve. Fix: Use API 602 for small-bore (≤2”) and API 600 for larger sizes. Review gate valve specifications.

4. Mixing Pressure Classes in the Same Line

Error: Installing a Class 150 valve in a Class 300 piping system because “it fits.” Risk: The Class 150 component becomes the weakest link. At higher pressures, the valve body or flange joint fails first. Fix: Match the valve class to the piping class specification. See ASME B16.34 valve ratings.

5. Using Gate Valves for Frequent Cycling

Error: Specifying gate valves in applications requiring frequent open/close operations. Risk: Gate valves are slow-operating (multi-turn) and the wedge/seat contact wears with repeated cycling, causing galling and seat damage. Fix: Use ball valves or butterfly valves for frequent cycling duty.

6. Ignoring Fugitive Emission Requirements

Error: Not specifying low-emission packing for valves in environmental-regulated facilities. Risk: Standard packing allows stem leakage above regulatory limits (EPA, TA-Luft). Retrofit is expensive and requires shutdown. Fix: Specify ISO 15848-certified low-emission packing upfront for hydrocarbon services.

7. Wrong End Connection in the Purchase Order

Error: Ordering flanged-end valves for a butt-weld system, or vice versa. Risk: Requires adapters, additional welds, or complete reorder; delays and cost overruns. Fix: Cross-check end connections (RF, RTJ, BW, SW) against the piping isometric and valve datasheet.

8. Specifying Floating Ball Valves in High-Pressure Service

Error: Using floating-ball design above Class 600 or in large bore sizes (>8”). Risk: Line pressure pushes the floating ball into the downstream seat with excessive force, causing seat deformation and high operating torque. Fix: Use trunnion-mounted ball valves for high-pressure (≥Class 600) and large-bore applications.

9. Omitting Fire-Safe Certification in Hydrocarbon Service

Error: Not requiring API 607 / ISO 10497 fire-safe testing for ball and plug valves in flammable service. Risk: In a fire, non-fire-safe soft seats melt, causing uncontrolled leakage and escalation. Fix: Always specify fire-safe certification for ball and plug valves in hydrocarbon lines.

10. Forgetting Stem Orientation for Globe Valves

Error: Installing a globe valve with the stem horizontal or in inverted position without verifying design allowance. Risk: Packing leakage, difficult operation, and potential for debris accumulation in the bonnet. Fix: Install globe valves stem-up unless the datasheet explicitly permits other orientations. See globe valve design.

Commercial Mistakes

11. Skipping Factory Acceptance Test (FAT) for Actuated Valves

Error: Not requiring FAT for actuated valve assemblies (valve + actuator + accessories). Risk: Discovering misalignment, incorrect torque, or wiring errors at site; where rework costs 5-10× more than at the factory. Fix: Include FAT requirements in the PO for all actuated valves, especially fail-safe and ESD valves.

12. Not Specifying Valve Tag Numbers in the PO

Error: Ordering valves by generic description without tag numbers tied to the valve datasheet. Risk: Wrong configuration delivered; impossible to trace valves to their intended service during installation. Fix: Include tag number, datasheet reference, and piping class in every valve line item.

13. Accepting “Equivalent” Materials Without Review

Error: Allowing the vendor to substitute materials (e.g., A351 CF8M instead of A351 CF3M) without engineering approval. Risk: The substitute may not meet corrosion, low-temperature, or hardness requirements for the specific service. Fix: Require written material deviation requests with supporting data. See valve materials.

14. Ordering Without Face-to-Face Dimensions Check

Error: Not verifying that the valve face-to-face dimension matches the piping spool design. Risk: Valve doesn’t fit the spool; requires spool rework or spacer addition at site. Fix: Confirm face-to-face per ASME B16.10 and match against piping GA drawings.

15. Missing Spare Parts in the Purchase Order

Error: Not ordering spare seat rings, gaskets, and packing sets with the main valve order. Risk: When maintenance is needed, OEM spares have long lead times. Generic spares may not seal properly. Fix: Order a recommended spare parts kit (typically 10-20% of valve quantity) at the time of the main PO.

Frequently Asked Questions

Can I use a ball valve for throttling?

No. Ball valves are designed for full-open or full-closed (on/off) service. Partial opening exposes the soft seat to high-velocity flow, which erodes the sealing surface and causes leakage. Use a globe valve or a control valve for flow regulation.

What happens if I install a check valve backwards?

The valve blocks flow in the intended direction and allows reverse flow; the exact opposite of its purpose. Always check the flow direction arrow cast into the valve body before installation. See check valve types.

What is the difference between API 600 and API 602 gate valves?

API 600 covers bolted-bonnet cast steel gate valves, typically NPS 2 and above. API 602 covers compact forged steel gate, globe, and check valves for small-bore lines (NPS 4 and below). Using the wrong standard results in incorrect body design and dimensions.

Do I need fire-safe certification for all ball valves?

Not for all services. Fire-safe certification (API 607 / ISO 10497) is required for ball and plug valves handling hydrocarbons and flammable fluids. Utility services like cooling water and instrument air typically do not require it.

What is the difference between a floating and trunnion ball valve?

In a floating design, the ball moves slightly downstream under pressure, pressing against the seat for sealing. In a trunnion design, the ball is fixed by upper and lower bearings (trunnions), and spring-loaded seats press against the ball. Trunnion is preferred for high-pressure and large-bore applications.

Why shouldn't I mix Class 150 and Class 300 valves in the same piping system?

The pressure-temperature rating of the entire system is limited by the lowest-rated component. A Class 150 valve in a Class 300 system will fail first, creating a safety risk. All components must match the piping class specification.