Oil and Gas Procurement: The Sector Requirements a Generic Process Misses

Oil and gas procurement follows the same process as any other industrial procurement, and then carries four requirements that exist nowhere else.

Sour service material compliance. API specification and Monogram verification. Hazardous area certification. Contractor safety prequalification.

Each of those is treated as an engineering requirement, and each of them actually fails at a procurement step. A specification omitted from the purchase order cannot be enforced at inspection, and an inspector cannot reject material against a clause nobody wrote.

This article covers what belongs on an oil and gas purchase order, how to verify an API Monogram licence in two minutes, what NACE MR0175/ISO 15156 does and does not protect against, and why the generic direct, indirect and service classification is the wrong model for this sector.

Scope note: this covers equipment, materials and services procurement for upstream, midstream and downstream facilities. It does not cover crude oil, condensate or product trading, which is commodity dealing and a different discipline entirely.

What Makes Oil and Gas Procurement Different

Oil and gas procurement is the acquisition of equipment, materials and services for facilities where the process fluid is flammable, frequently toxic, and often under pressure, which means the specification carries a safety consequence that most industrial procurement does not.

Three conditions drive the difference.

The fluid can crack the metal. Hydrogen sulphide in the process stream causes sulfide stress cracking in susceptible steels, producing sudden brittle failure with no visible warning. Material selection is therefore governed by a dedicated international standard rather than by ordinary strength calculations.

The atmosphere can ignite. Facilities are divided into classified hazardous areas, and every item of electrical equipment installed in one must carry certification matching that area's zone, gas group and temperature class.

The equipment is regulated by product specification, not just by quality system. The American Petroleum Institute publishes product specifications and licenses manufacturers to mark conforming equipment, which creates a verifiable check that has no equivalent in most sectors.

Get any of the three wrong at the purchase order stage and you have bought equipment that cannot be legally installed, cannot be safely operated, or will fail in service. For the underlying procurement process that all of this sits on top of, see our guide to the industrial procurement process. More on Prismecs's work across the sector is on the oil and gas page.

Sour Service: NACE MR0175/ISO 15156

NACE MR0175/ISO 15156, "Petroleum and natural gas industries, Materials for use in H2S-containing environments in oil and gas production," governs the selection and qualification of metallic materials for service where hydrogen sulphide is present, and compliance is mandatory on sour projects worldwide.

The standard was first published by NACE International in 1975 following catastrophic sour field failures. It was adopted by ISO in 2003 and redesignated ISO 15156. The two designations are technically equivalent and referenced interchangeably, which is why most purchase orders name both.

The standard gives requirements and recommendations for carbon and low-alloy steels, corrosion-resistant alloys and other alloys used in oil and natural gas production and natural gas treatment plants in H2S-containing environments, where failure could pose a risk to the health and safety of the public and personnel or to the environment.

Sour or sweet

Sour service is the operating condition where H2S is present above a defined threshold. The commonly applied trigger is H2S partial pressure in the gas phase exceeding 0.05 psia, equivalent to 0.0003 MPa.

Sweet service contains no H2S above that threshold, and standard materials such as ASTM A105 or A106 are acceptable without NACE compliance.

Whether a given service is sour depends on H2S partial pressure, in-situ pH, temperature and chloride content together. A frequently cited field rule is that H2S partial pressure above 0.0003 MPa combined with pH below 3.5 indicates sour service, but always confirm against the governing project specification rather than the rule.

The three parts

Most purchase orders reference both designations and the applicable part, for example "NACE MR0175 / ISO 15156 Part 3," to remove ambiguity.

The hardness limit that governs everything

For carbon and low-alloy steels the core requirement is a maximum hardness of 22 HRC, approximately 248 to 250 HV10, in the parent metal, the weld metal and the heat affected zone.

The heat affected zone is the region of parent metal adjacent to a weld whose microstructure has been altered by welding heat, and it is typically the hardest and most vulnerable region. Post-weld heat treatment is the primary means of bringing HAZ hardness back within the limit, and welding procedure qualification must include a hardness survey across the weld cross-section.

Two failure mechanisms are qualified by test. Sulfide stress cracking resistance is qualified per NACE TM0177, using Method A constant load tensile testing or Method D four-point bend testing. Hydrogen induced cracking resistance is qualified per NACE TM0284.

What the hardness limit excludes

The hardness requirement eliminates specific material grades from sour service. In oil country tubular goods, J55 and N80 Type 1 are excluded because their hardness is uncontrolled and may exceed the limit. Compliant grades under ISO 15156-2 include L80, C90, T95 and C110 when manufactured to the chemistry and heat treatment requirements of API 5CT and tested per the standard.

OCTG means oil country tubular goods, the casing, tubing and drill pipe used in well construction.

What NACE MR0175 does not cover

This is the most common misunderstanding among buyers. The standard addresses only the resistance of materials to environmental cracking caused by H2S. It does not address loss of material by general corrosion, and it does not address localized corrosion such as pitting or crevice attack.

A NACE-compliant material can still corrode away. Corrosion allowance, inhibitor programmes and CRA cladding are separate decisions made under different criteria, and assuming NACE compliance covers them is a design error that shows up years later.

If H2S content changes over field life

Many fields sour over time as production progresses or as water injection begins. Where a field is expected to sour, specifying to sour service from the outset is almost always cheaper than replacing equipment later. Establish the design basis with reservoir engineering at specification, not at first sample.

Lead time and cost

Sour service materials carry longer lead times and higher cost than sweet service equivalents, driven by controlled chemistry, heat treatment requirements and the additional testing and documentation burden. Treat NACE-compliant items as long-lead by default and raise the requisition accordingly.

API Specifications: Which One Applies to What

The American Petroleum Institute publishes product specifications that define how oilfield and process equipment is designed, manufactured, tested and documented, and naming the correct specification on the purchase order is what makes conformity verifiable.

API standards are formal requirements governing design, manufacture, testing and documentation, and they apply across drilling and production operations. Equipment meeting an API standard has been evaluated against a recognized industry benchmark rather than against manufacturer-defined criteria alone.

Name the specification and its edition on the purchase order. A bid offered "to API 610" without an edition can be quoted against a superseded revision, and the difference between editions is frequently where the cost sits.

The API Monogram and How to Verify It

The API Monogram is a voluntary licensing programme under which API authorizes a manufacturer to apply the API Monogram registered mark to equipment conforming to an applicable API product specification, and any buyer can verify a licence in about two minutes.

Licensees must demonstrate a quality management system compliant with API Spec Q1, and licensing follows a successful on-site audit of the facility's quality management system and product designs against API Spec Q1 and the relevant product specification. Licenses run for three years with renewal audits, licensees undergo on-site audits by API auditors as a condition of maintaining the licence, and API reserves the right to conduct unscheduled audits.

The mark is stamped directly onto eligible equipment and cannot lawfully be used without an active licence.

The verification step almost nobody takes

API maintains the API Composite List, an online directory of Monogram and Repair and Remanufacture licensees and management system registered organizations. It is searchable by company name, certificate number, product type, keywords in the registration scope and status, and it shows real-time licence status.

Across the Monogram, APIQR and Repair and Remanufacture programmes, API recognizes more than 4,300 organizations in 75 countries.

Three checks to run before award:

Is the licence active? Status is shown in the directory, and a lapsed or suspended licence means the mark cannot be applied.

Does the scope cover the product you are buying? A manufacturer licensed for one product specification is not licensed for another. Search the registration scope, not just the company name.

Does the certificate number on the offer match the directory entry? This is the check that catches misrepresentation.

Counterfeit and expired marks

An API Monogram applied without an active licence is unlawful, and unauthorized-channel equipment bearing an API mark is a documented risk in this sector. Require the certificate number in the bid, verify it against the Composite List, and require full traceability to the manufacturing source for critical items.

Monogrammed versus non-monogrammed

Non-monogrammed equipment can be perfectly fit for purpose where the application does not require it, and monogrammed equipment typically carries a premium reflecting the audit and quality system burden behind it. The decision is application-driven: where the equipment is safety-critical, pressure-containing or subject to operator or regulatory specification, the monogram is generally not optional.

For refurbished or repaired equipment, API operates a separate Repair and Remanufacture licensing programme, and the same directory verification applies.

Quality Systems: ISO 29001, API Q1 and API Q2

Oil and gas supplier qualification uses sector-specific quality management standards that sit above general ISO 9001 certification, and specifying the right one is what makes the qualification meaningful.

The practical difference is that API Spec Q1 explicitly requires compliance with applicable legal and regulatory requirements relevant to the oil and gas industry, and carries a product-specific licensing programme behind it. ISO 9001 mentions compliance generally and has no equivalent product licensing mechanism.

Specify API Spec Q1 for equipment manufacturers, API Spec Q2 for service suppliers, and ISO 9001 as the floor rather than the qualification. Check that the certificate scope covers the product or service category you are buying, because a certificate with the wrong scope is common and easy to miss.

Regulatory and operator approval

Many operators maintain their own approved vendor lists and technical specifications that sit above the published standards. Where you are supplying into an operator's facility or a joint venture, confirm which operator specifications apply before issuing the enquiry, because retrofitting them after award is a change order.

Hazardous Area Certification: IECEx, ATEX and Ex Marking

Every item of equipment installed in a classified hazardous area must carry certification matching that area's zone, gas group and temperature class, and equipment arriving with the wrong marking cannot be legally installed.

A hazardous area is a location where a flammable atmosphere may be present. Areas are classified by how often and how long that atmosphere occurs.

Gas group classifies the ignition characteristics of the flammable substance, running IIA, IIB and IIC in increasing order of ignition sensitivity, with IIC covering hydrogen and acetylene. Temperature class, T1 through T6, defines the maximum surface temperature the equipment may reach, with T6 the most restrictive at 85°C.

The certification schemes

IECEx is the IEC System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres, an international scheme issuing Certificates of Conformity recognized across many jurisdictions.

ATEX refers to EU Directive 2014/34/EU, covering equipment and protective systems intended for use in potentially explosive atmospheres. ATEX certification is required for equipment placed on the EU market.

Both reference the IEC 60079 series, Explosive atmospheres, with IEC 60079-0 covering general equipment requirements, IEC 60079-10-1 covering classification of areas for explosive gas atmospheres, and IEC 60079-14 covering electrical installations design, selection and erection.

In North America, the National Electrical Code, NFPA 70, provides the Class and Division system under Article 500 and the Zone system under Article 505. Confirm which system the site uses, because certification under one does not automatically satisfy the other.

The purchase order check

Specify the zone, gas group and temperature class on the purchase order, not just "hazardous area rated." Then verify on receipt that the Ex marking on the nameplate matches the specification and that the certificate number is traceable to an issuing body.

Equipment with a marking that does not match the classified area for which it was bought is not a documentation problem. It is equipment that cannot be installed, and it usually surfaces during commissioning when the schedule has no room.

The Three Procurement Types, Corrected for This Sector

Direct, indirect and service procurement is an accounting taxonomy. It is useful for reporting and close to useless for designing an oil and gas procurement process.

Direct procurement covers materials and equipment forming part of the producing or processing asset: wellhead equipment, OCTG, valves, piping, pressure vessels, rotating equipment and instrumentation. Each category carries its own API specification and, in sour fields, its own NACE requirement.

Indirect procurement covers goods supporting operations without forming part of the asset. It is genuinely lower risk and genuinely lower value, and it should not consume the same process rigour.

Service procurement covers the specialist contracted work that dominates oil and gas spend. It is addressed in the next section, because it is nothing like the software licences and temporary staff that generic guides describe.

The classification that actually drives the process

Three questions design your process path, and none of them is direct versus indirect.

Sour or sweet? This determines material specification, testing, documentation and lead time.

Classified or unclassified area? This determines Ex certification requirements.

Safety-critical or not? This determines inspection level, documentation type and whether third-party witness is required.

Classify each item against those three questions, then apply full process rigour to the items that answer yes to any of them. For the full step-by-step process those categories run through, see our guide to the industrial procurement process.

Contractor and Service Procurement: Safety Prequalification

Service procurement is one of the largest spend categories in oil and gas, and it carries safety prequalification obligations that do not exist in most other sectors.

The category covers drilling and well intervention services, turnaround and shutdown contractors, non-destructive testing and inspection, rope access and specialist maintenance, marine logistics and vessel charter, helicopter transport, and catering and camp services.

What prequalification assesses

Safety performance history including recordable incident rate and any regulatory enforcement. Written safety management system and its audit history. Competency and training records for the personnel who will attend site. Insurance at the limits your contract requires. Financial standing sufficient to survive the contract term. And where applicable, API Spec Q2 certification for service supply organizations.

Prequalification typically takes 4 to 12 weeks for a new contractor, longer where a facility or system audit is required. Many operators use third-party prequalification platforms to maintain this data across a supply base, which reduces duplication but does not remove your obligation to assess suitability for the specific scope.

If a contractor's safety record is poor

A poor record is not automatically disqualifying, but it must be assessed rather than noted. Look at trend rather than a single year, at the severity distribution rather than the count alone, and at what changed after any serious incident. A contractor with a serious incident and a documented, audited response is often a better risk than one with a clean sheet and no system behind it.

Contract the competency, not just the company

Require named personnel with verifiable competency records for safety-critical roles, a minimum notice period and handover overlap on replacements, and the right to remove individuals who do not meet the standard. Company-level prequalification does not guarantee who turns up.

Turnaround Procurement: The Fixed-Date Problem

Turnaround procurement is scheduling, not purchasing, because materials that arrive after the shutdown window are worthless until the next one.

A turnaround, also called a shutdown or TAR, is a planned period during which a process unit is taken offline for inspection, repair and replacement work that cannot be performed while running. The window is fixed months or years in advance and is extremely expensive to extend.

What that changes

Work backward from the window, not forward from approval. Every long-lead item must have a required-on-site date that precedes the window with contingency, and the enquiry date is that date minus lead time minus shipping minus inspection.

Freeze the scope early. Turnaround scope growth is the single largest driver of materials arriving late, because a late scope addition inherits no lead time.

Order the inspection-driven items on assumption. Some replacement needs are only confirmed when the unit is opened, which means the choice is between pre-ordering on a probability basis and extending the window. Pre-ordering and returning unused items is almost always cheaper.

Hold consumables and gaskets locally. The items that stop a turnaround are rarely the expensive ones.

For the maintenance planning side of the same window, see our guides to outage planning and rotating equipment maintenance.

Supplier Risk and Supply Chain Mapping

Supply chain mapping is the exercise of identifying where each component originates and which facilities and subcontractors it passes through, and its value is that it lets you assess an exposure before it becomes a shortage.

Mapping matters most where sourcing is concentrated in one location or country, because concentration converts a local disruption into a project delay. Map to sub-tier level for critical items, since the constraint is frequently a forging, a casting or a specialist coating rather than the prime supplier.

What to do with the map

When a disruption occurs, organizations with a current map can determine within days which of their items are affected and act while options still exist. The practical responses are alternative sourcing from a pre-qualified second source, reallocating existing inventory, reserving capacity at an alternative supplier, or resequencing the work that depends on the item.

All four require the alternative to be identified in advance. A map produced after the disruption tells you what you lost.

Supplier benchmarking

Assess contractors and suppliers continuously across dependability, delivery performance, quality non-conformance rate and safety performance, rather than only at tender. Contract and supplier relationship management is a recurring weakness in this sector, and the usual symptom is non-compliance with agreements that nobody is monitoring.

Insurance and liability

Your insurer prices on the integrity of the assets and the competence of the parties working on them. Sourcing non-compliant material into a sour or classified installation is a coverage question as well as a safety one. Where a failure traces to a specification omitted from the purchase order, the liability position is materially worse than where the specification was stated and the supplier failed to meet it.

What Belongs in an Oil and Gas Purchase Order

The purchase order is where sector compliance becomes enforceable, because an inspector can only reject material against a requirement the order actually stated.

For EN 10204 certificate types, Incoterms selection, inspection and test planning, expediting and milestone payments, all of which apply here and are not sector-specific, see our guide to the industrial procurement process.

If you receive non-compliant material

Reject on the documentation before you accept the goods. Accepting delivery and raising the issue later weakens your position considerably. The common non-conformances are the wrong EN 10204 certificate type, a certificate with no heat traceability, missing hardness or heat treatment records, and an API mark with no verifiable licence behind it.

Third-party inspection

Where you cannot attend, appoint a third-party inspection agency with the relevant sector experience and accreditation. Name the agency or the approval process in the purchase order, define what they witness, and require that hold points are not released without their sign-off.

Documentation at handover

The certificates, test reports, heat treatment records and Ex certificates form part of the asset record and are required for operation, future maintenance, regulatory inspection and any eventual sale. Establish that they are delivered in a native exportable format and that a defined portion of payment depends on their acceptance.

Upstream, Midstream, Downstream

The four sector requirements apply across the value chain. Which one dominates changes with the segment.

Upstream

Sour service and API specification compliance dominate, because the produced fluid is uncontrolled and the equipment is pressure-containing. API Spec 6A for wellhead, API Spec 5CT for tubulars, and NACE MR0175/ISO 15156 across the board where H2S is present or expected.

Midstream

Pipeline valves under API Spec 6D, compression under API Std 617 or 618, and metering. Hazardous area classification is extensive across compressor stations and terminals. Long linear assets make logistics and Incoterm selection more consequential than elsewhere.

Downstream and petrochemicals

Turnaround procurement dominates the calendar, and the scale of shutdown material requirements is the defining challenge. Rotating equipment under API Std 610, 617, 618 and 682, plus extensive piping, valves and heat exchangers. See our petrochemical engineering services page for the adjacent engineering scope.

Offshore versus onshore

Offshore adds weight and footprint constraints, marine logistics, certification for the flag or coastal state, and a far higher cost of getting it wrong, because a replacement item requires a vessel or helicopter rather than a truck. Specification discipline and documentation completeness matter more offshore than anywhere else.

Smaller operators

Full process rigour on every item is uneconomic below a certain spend. Apply it selectively: full specification, verification and inspection on anything that is sour service, in a classified area, or safety-critical, and a simplified process for everything else.

Outside the United States

API specifications, NACE MR0175/ISO 15156, IECEx and the ISO standards apply internationally without change. What differs is the national regulatory regime, local content requirements, customs and tariff treatment, and in some jurisdictions a requirement for local agents or in-country manufacturing content. In the EU, ATEX applies to equipment placed on the market. Confirm these before shortlisting, because they can eliminate a technically qualified supplier after award.

What Prismecs and eINDUSTRIFY Do

Prismecs delivers industrial procurement for oil and gas alongside engineering, construction management and O&M, through eINDUSTRIFY, its dedicated procurement platform.

eINDUSTRIFY provides Procurement-as-a-Service covering RFQs, sourcing, vendor coordination and delivery, plus digital marketplace access for industrial supplies with streamlined procurement workflows. It is backed by Prismecs for turnkey support including logistics, installation and operations.

The integration matters for one reason specific to this sector. A procurement organization that never sees the equipment installed has no feedback on whether its supplier qualification held. A procurement organization whose own engineering and field teams receive, install and commission the equipment finds out, and the approved vendor list reflects it.

Prismecs serves oil and gas and petrochemicals as named verticals, and supports sourcing, vendor coordination and delivery through supply chain solutions.

Apply this article's criteria to any procurement partner, including us. Ask how NACE requirements are carried into the purchase order. Ask whether API Monogram licenses are verified against the Composite List before award and who does it. Ask which EN 10204 certificate type is specified by default. Ask who attends inspection.

To request a specification and sourcing review, send your equipment list, service conditions including H2S content, area classification and required on-site dates to sales@prismecs.com or call +1 (888) 774-7632. We return a specification checklist, a compliance gap list and an indicative lead-time position.

Frequently Asked Questions

What is oil and gas procurement?

It is the acquisition of equipment, materials and specialist services for upstream, midstream and downstream facilities, where the process fluid is flammable, often toxic and usually under pressure. It follows the same process as other industrial procurement and adds four sector requirements: sour service material compliance, API specification and Monogram verification, hazardous area certification, and contractor safety prequalification. It does not include crude or product trading, which is commodity dealing.

What is NACE MR0175 / ISO 15156?

It is the international standard governing selection and qualification of metallic materials for equipment used in oil and gas production and natural gas treatment where hydrogen sulphide is present. First published by NACE International in 1975, adopted by ISO in 2003 and redesignated ISO 15156, the two designations are technically equivalent. It is published in three parts covering general principles, carbon and low-alloy steels, and corrosion-resistant alloys.

What is sour service and what is the threshold?

Sour service is any operating environment where hydrogen sulphide is present above a defined threshold, commonly applied as H2S partial pressure in the gas phase exceeding 0.05 psia, equivalent to 0.0003 MPa. Sweet service falls below that threshold, where standard materials such as ASTM A105 or A106 are acceptable. Whether a service is sour depends on H2S partial pressure, in-situ pH, temperature and chloride content together.

What hardness limit applies to sour service steel?

Carbon and low-alloy steels must not exceed 22 HRC, approximately 248 to 250 HV10, in the parent metal, weld metal and heat affected zone. Post-weld heat treatment is the primary means of reducing HAZ hardness within limit after welding, and welding procedure qualification must include a hardness survey of the weld cross-section. Hardness records should appear on the material test certificate.

What does NACE MR0175 not protect against?

It addresses only resistance to environmental cracking caused by H2S, specifically sulfide stress cracking and hydrogen induced cracking. It does not address loss of material by general corrosion, and it does not address localized corrosion such as pitting or crevice attack. A fully NACE-compliant material can still corrode away, so corrosion allowance, inhibition and cladding are separate decisions under different criteria.

Which OCTG grades are excluded from sour service?

J55 and N80 Type 1 are excluded because their hardness is uncontrolled and may exceed the limit. Compliant grades under ISO 15156-2 include L80, C90, T95 and C110 when manufactured to the chemistry and heat treatment requirements of API Spec 5CT and tested to the standard. Qualification requires sulfide stress cracking testing per NACE TM0177, using Method A constant load or Method D four-point bend.

What is the API Monogram?

It is a voluntary licensing programme under which API authorizes a manufacturer to apply the API Monogram registered mark to equipment conforming to an applicable API product specification. Licensees must hold a quality management system compliant with API Spec Q1 and pass an on-site audit of that system and their product designs. Licences run three years with renewal audits, and API may conduct unscheduled audits.

How do I verify an API Monogram licence?

Search the API Composite List, API's online directory of Monogram, Repair and Remanufacture licensees and management system registered organizations. It is searchable by company name, certificate number, product type, registration scope keywords and status, and shows real-time licence status. Check three things: that the licence is active, that the scope covers the product you are buying, and that the certificate number on the offer matches the entry.

What is the difference between API Q1, API Q2 and ISO 9001?

ISO 9001:2015 is a general quality management standard applicable to any sector. API Spec Q1 is the quality management specification for manufacturing organisations in the petroleum and natural gas industry, and it is the prerequisite for Monogram licensing. API Spec Q2 applies to service supply organizations. API Q1 explicitly requires compliance with oil and gas legal and regulatory requirements, which ISO 9001 does not specify.

What is ISO 29001?

ISO 29001 is the sector-specific quality management system standard for the petroleum, petrochemical and natural gas industries, setting requirements for product and service supply organizations. It sits above general ISO 9001 certification for this sector. Where you are qualifying a supplier, specify ISO 29001 or the applicable API Spec Q1 or Q2, and verify that the certificate scope covers the product or service category you are buying.

What is a hazardous area zone and why does it matter to procurement?

Zone 0 means an explosive gas atmosphere is present continuously or for long periods, Zone 1 means it is likely in normal operation, and Zone 2 means it is unlikely and short-lived if it occurs. Equipment installed in any of these must carry certification matching the zone, gas group and temperature class. Specify all three on the purchase order, because equipment with the wrong marking cannot be legally installed.

What is the difference between IECEx and ATEX?

IECEx is the IEC System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres, an international scheme issuing Certificates of Conformity recognized across many jurisdictions. ATEX refers to EU Directive 2014/34/EU and is required for equipment placed on the EU market. Both reference the IEC 60079 series. In North America, NFPA 70 Articles 500 and 505 provide Class and Division and Zone systems respectively.

What belongs on an oil and gas purchase order that a generic PO would miss?

The API specification with its edition, NACE MR0175 / ISO 15156 with the applicable Part, the maximum hardness limit across parent metal, weld and HAZ, required SSC and HIC testing per NACE TM0177 and TM0284, the EN 10204 certificate type, heat treatment records, the required API Monogram with certificate number, applicable API Spec Q1 or Q2 certification, and the hazardous area zone, gas group and temperature class.

How should I approach turnaround procurement differently?

Work backward from the fixed shutdown window rather than forward from approval, so every long-lead item has a required-on-site date that precedes the window with contingency. Freeze scope early, because late additions inherit no lead time. Pre-order inspection-driven items on a probability basis, since returning unused material is almost always cheaper than extending the window. Hold consumables and gaskets locally.

Tags: Oil and Gas Procurement NACE MR0175 Sour Service API Monogram Verification Hazardous Area Certification Supplier Qualification