Why Bundling the Valve Scope Matters

A valve on its own is a self-contained part. On a piping line, it is the centre of a joint: two flanges, a gasket, a stud bolt set, a transition fitting on each side, and the line pipe on the other side of the fitting. If the valve is supplied to API 6D, the flanges to ASME B16.5, the gaskets to ASME B16.20 and the stud bolts to ASTM A193, every component in the joint has to clear the same hydrotest envelope. Splitting the scope across four or five vendors makes that envelope harder to enforce, not easier.

Bundled procurement groups the joint into a single line item, with one RFQ, one technical clarification cycle, one MTR set and one shipping schedule. The cost saving is not only in the unit price — the bigger saving is in the avoided rework when a flange facing does not match the gasket, or a stud bolt length does not clear the nut after the gasket is compressed.

Three drivers tend to push a project toward a bundled scope:

• Single line class on a high-pressure hydrocarbon or steam line, where the joint envelope is critical and the material consistency cannot be left to chance.
• Remote site with limited lay-down space, where staged deliveries of valve-then-flange-then-fitting create on-site handling and storage headaches.
• Large volume of identical line classes, where a single source can release a call-off order against a master agreement and absorb the price step that comes with volume.

Step 1: Freeze the Line Class, Not the Valve List

The first mistake is to write a valve list before the line class is frozen. The valve list then gets re-issued every time a line class is updated, and the MTR pile grows with each re-issue. The discipline that prevents this is to freeze the line class — pressure class, material, facing, gasket type, bolt specification, corrosion allowance — before any RFQ is sent out. Once the line class is frozen, the valve list becomes a count of part numbers within that class.

A typical hydrocarbon line class is written as:

• Service: crude oil, gas, NGL, refined product
• Design pressure / temperature: per project PFD
• Pipe: API 5L X65, ASTM A106 B, ASTM A312 TP304/316 as per line
• Valve: API 6D gate, globe, check, ball — body WCB / LCC, trim 13Cr or SS316, NACE MR0175 for sour service
• Flange: ASME B16.5 weld neck, raised face, ASTM A105 or A350 LF2
• Fitting: ASME B16.9 butt weld, same material family as the pipe
• Gasket: spiral-wound with graphite filler, ASME B16.20
• Stud bolt and nut: ASTM A193 B7 stud with A194 2H nut

When this line class is locked, the entire joint — valve, two flanges, gasket, bolt set and the fittings on either side — sits inside a single envelope, and the RFQ can be written against the envelope, not against the individual parts.

Step 2: Match the Valve Family to the Service Environment

Within the frozen line class, the next decision is which valve family fits which service. Not every valve in the bundle is a gate valve, and not every line is an isolation duty. The most common service-to-valve mapping on a real project is:

Isolation Duty (Mainline, Manifold, Block Valve)

On the main hydrocarbon and gas line, the isolation valve is almost always a gate valve (ASME B16.34 / API 600 / API 6D) or a trunnion-mounted ball valve. The gate is preferred for large bore on transmission lines; the ball is preferred for frequent operation and tight shut-off. Both go in the same line class envelope, with the same flange facing, the same gasket and the same bolt specification. Our industrial valves are released against this envelope with full MTR and traceability per API 6D.

Modulation and Trim Duty

On control and metering stations, the valve changes from a gate or ball to a globe or an angle globe with a control trim. The line class itself does not change — the pressure class, flange facing and bolt specification stay the same — but the valve is on a longer lead time, and the MTR has to cover the trim separately. Procurement should treat the control valve as a separate sub-line item, but keep it inside the same bundled package so the joint scope stays aligned.

Check and Anti-Surge Duty

On pump discharge, compressor discharge and turbine exhaust, a swing check, dual plate check or axial check valve is added in the same line. The check valve is typically smaller in face-to-face dimension than a gate of the same size, which affects the lay-out of the adjacent fittings. The fitting scope has to be adjusted to keep the joint centred and to keep the pipe support on the upstream side where the water hammer risk is highest.

Drain, Vent and Instrument Duty

Small-bore drain, vent and instrument root valves are usually needle, ball or double block-and-bleed. They sit on a different line class (typically Class 800 or Class 1500 socket weld) and use socket weld fittings rather than butt weld. The temptation is to exclude this scope from the bundle because it is small. In practice, leaving it out of the bundle almost always leads to a mismatch in material certification between the small-bore and the mainline scope, and the MTR pile ends up with a gap. Including it in the bundle closes that gap.

Step 3: Lock the Flange, Gasket and Bolt Scope

Once the valve list is in place, the pipe flanges on either side of each valve are dimensioned by the valve face-to-face. The flange count per valve is normally two on flanged valves, or one on butt-weld-end valves where the mating flange belongs to the pipe spool. Either way, the flange specification is shared: ASME B16.5 weld neck, raised face or RTJ as per service, ASTM A105 / A350 LF2 / A182 F304 / F316 as per material. The gasket and the stud bolt follow the same ASME B16.20 / ASTM A193 envelope.

Three details that are easy to miss in the bundled scope:

• Flange facing finish: a stock 125-250 Ra finish is fine for spiral-wound gaskets, but a soft-ring-joint gasket requires a smoother finish to seal. The finish is on the flange drawing, not the valve datasheet.
• Bolt length after gasket compression: the bolt has to clear the nut by at least two threads after the gasket is compressed to its target thickness. A 1/8-inch step on the gasket is enough to change the bolt length and to break the standard part number.
• Stud bolt material at low temperature: ASTM A320 L7 is the standard for -46 °C and below, and is the workhorse for cryogenic service. Forgetting to switch from A193 B7 to A320 L7 in the cold section is a classic line-class drift.

Our gasket, stud bolt and nut scope is released against the same ASME / ASTM envelope as the flanges, so the facing, the bolt pattern and the MTR are consistent across the joint.

Step 4: Adjust the Fitting Scope to the Valve Face-to-Face

The pipe fittings in the bundle are not picked in isolation. They have to absorb the dimensional change introduced by the valve — gate, globe, ball or check — and still ｄｒｏｐ the line pipe back onto the routing on the isometric. The most common fittings in a hydrocarbon line class are:

• Long-radius elbow (LR 90 / LR 45) for direction change on the main run.
• Straight tee and reducing tee for branch connections, with the branch diameter selected against the branch line class.
• Concentric and eccentric reducer for size transitions, with the eccentric reducer laid flat (flat-on-top) for two-phase flow to avoid gas pockets.
• Cap for future tie-in points and instrument root valves.

On a long mainline run, butt weld fittings dominate because they match the line pipe wall and the valve end without a thickness transition. On the small-bore side — drains, vents, instrument root — socket weld fittings are used for socket-weld-end valves in Class 800 and above. threaded fittings are restricted to utility air, water and low-pressure firewater, where the joint envelope is less critical.

The fitting scope has to be issued together with the valve list, not after, because the fitting centre-to-end dimension often has to absorb the gate or globe face-to-face. Re-issuing the fitting scope after the valve list is locked forces a re-quote on the fitting line item, and the MTR stack grows.

Step 5: Build a Single MTR Set Across the Bundle

The biggest hidden cost in a multi-vendor scope is the documentation pile. Every valve, flange, fitting and bolt has its own MTR, its own certificate and its own traceability record. When the parts arrive on site, the QA/QC team has to reconcile the MTR stack against the line class, and any mismatch stops the hydrotest.

A bundled scope is sold with a single MTR envelope per line class. The manufacturer issues one MTR per heat, with the valve, flange, fitting and bolt cast into the same document tree, and the same ASTM / ASME / EN standard referenced across the joint. When QA/QC asks for a sample MTR, the document is a single PDF, not a four-vendor pile.

Our delivery for valve-flangefitting-gasket-bolt bundles includes:

• One MTR per heat, covering the valve body, the flange, the fitting and the bolting.
• One dimensional inspection report per lot, covering the face-to-face, the flange bore, the gasket seating dimension and the bolt length.
• One hydrotest envelope, with the same test pressure applied to the valve, the joint and the fitting.
• One shipping list and one packing list, with parts marked against the same line-class code for site storage.

Step 6: Plan the Logistics Around the Joint

A bundled scope reduces site handling. Instead of four or five inbound deliveries, the project receives one delivery per line class per lot, with the parts packed in the joint sequence: valve, two flanges, gasket, bolt set, then the upstream and downstream fittings. Site erection opens the box and walks the parts to the right isometric without sorting.

For large projects, this approach is usually paired with a call-off schedule. The master agreement is signed for the full line-class volume, and individual call-offs are released against the project schedule. The manufacturer holds the raw material and the production slot; the project holds the inventory risk. This is the model that most EPC owners prefer for a multi-line-class refinery, petrochemical or gas processing project, and it is the model our team supports for industrial valves, pipe flanges and pipe fittings on a single MTR envelope.

Step 7: Spot the Line-Class Drifts Before They Reach Site

Even with a disciplined RFQ, line-class drift is common on real projects. The most common drift points are:

• Trim substitution: the valve is sold with 13Cr trim on the body, but the seat is upgraded to SS316 for sour service without a line-class ｕｐｄａｔｅ. The flange and gasket stay the same, but the MTR now references a different ASTM standard, and the QA/QC file has to be reconciled.
• Gasket substitution: the spec calls for spiral-wound with graphite filler, but a flexible graphite gasket is offered as a lower-cost alternative. The flexible graphite gasket is fine for low-pressure steam, but it does not handle the same thermal cycling on a hydrocarbon line.
• Bolt substitution: ASTM A193 B7 is replaced by ASTM A193 B7M (a lower-hardness variant) on a sour service line. B7M is correct for NACE MR0175, but the substitution has to be captured in the line class, not left as a one-off vendor selection.
• Flange facing substitution: a raised face flange is offered instead of an RTJ flange on a Class 600 sour line. The joint still passes the same hydrotest, but the gasket inventory is wrong, and the bolt length may no longer clear the nut after the gasket is seated.

A Practical Line Class for a Bundled Scope

The table below is a typical line class for a hydrocarbon transmission line, written as a bundle. The same line class can be extended to a gas processing train, a refinery block or a petrochemical plot by adjusting the design pressure and the temperature.

When the Bundle Stops Saving Money

A bundled scope is not the right answer for every project. It works when the line class is large and the parts share a single MTR envelope. It does not work when:

• The project has many small line classes (under 50 joints per class), where the RFQ overhead exceeds the joint savings.
• Utility and firewater lines, which use a different material family and a different flange standard, and are usually cheaper to buy from a regional stockist.
• Highly engineered one-off valves (e.g. control valves with a specific actuator package), where the valve manufacturer is the lead and the flange and fitting scope has to follow the valve schedule.

In those cases, a conventional split PO is fine, provided the line class is still frozen and the MTR envelope is still shared.

Closing the Loop with the Manufacturer

A bundled scope is only as good as the technical clarification cycle behind it. The first RFQ should ask for:

• Confirmation of the line class, including the pressure class, material, facing and gasket envelope.
• Sample MTR per heat, covering the valve, flange, fitting and bolt.
• Dimensional inspection report per lot, including the valve face-to-face and the flange bore.
• Hydrotest envelope and the test fluid (typically water, but air or nitrogen for cryogenic or hazardous service).
• Shipping sequence, packaging and labelling against the line-class code.

The clarification cycle is the place to lock the line class, not on the shop floor after the parts are made. Every clarification captured in the RFQ is one less rework later, and one less MTR reconciliation on site.