I. Introduction
In the procurement work for chemical, oil and gas, power plant, new energy, and overseas EPC pipeline projects, standard pipe fittings and non-standard custom pipe fittings have long coexisted.Standard fittings such as elbows, tees, reducers, and flanges corresponding to standards such as GB/T12459, ASME B16.9, and EN10253 have fixed parameters and mature processes, and manufacturers usually keep them in stock and schedule batch production;Non-standard fittings, however, are mainly used in scenarios such as equipment interface connection, limited pipeline space, renovation of old installations, transition between mixed standards, and special corrosive or low-temperature working conditions. Their dimensions, reinforcement structures, and connection forms depart from standard tables and require separate design verification, process qualification, and special inspection.
A common cognitive misconception in procurement practice is to compare only the unit price quotation and simply attribute the premium of non-standard parts to higher material costs, while ignoring the design fees, tooling fees, third-party review fees, shutdown losses caused by extended lead times, and risk costs of acceptance and filing brought by non-standard parts.Some buyers blindly pursue low-priced non-standard parts and choose simple non-standard parts without strength calculations, special flaw detection, or complete documentation. Although the initial purchase price is low, the secondary costs arising from pressure test leakage, rejection by supervision inspection, on-site rework, and shutdown maintenance often far exceed the value of the fitting itself.Distinguishing standard parts, compliant non-standard parts, and inferior non-standard parts, clarifying the differences in cost composition between the two types of fittings, and establishing a total-cost evaluation mindset are the core levers for cost reduction and risk control in pipeline procurement.
II. Comparison of the Basic Cost Composition of Standard Pipe Fittings and Non-standard Pipe Fittings
The procurement cost of pipeline fittings is divided into two major components: explicit direct costs and implicit indirect costs. Raw material cost is a common baseline item, but the allocation logic for the remaining cost items is completely different.
Standard fittings are produced using large-scale assembly lines. Molds, forming tooling, welding procedure qualification, and inspection plans are developed once and then allocated across thousands of products, resulting in extremely low per-unit allocation.Raw materials are purchased uniformly in batches, giving the raw material purchase unit price a bargaining advantage;The production process is fixed, worker proficiency is high, the production takt is stable, and labor hour costs are low.The inspection stage uses sampling at the proportion specified by standards, with no need for piece-by-piece third-party review. MTR material certificates and non-destructive testing report templates are mature, so documentation costs are low.At the same time, a large number of specifications are kept in stock, lead times are short, and warehousing turnover costs are controllable.According to industry statistics, for standard carbon steel fittings of the same material and the same pressure rating, raw materials account for 60% to 70% of total cost, while the allocated costs of tooling, testing, and documentation are generally below 10%.
The cost structure of compliant non-standard fittings changes significantly.First is the upfront design cost, including working-condition input review, stress and reinforcement strength calculations, engineering drawing preparation, and drawing review. For GC1 high-hazard media non-standard parts, expert technical review must also be organized. This part of the cost cannot be apportioned and is a one-time investment.Second is the tooling and process cost. Special-angle elbows, non-standard open-hole tees, non-standard transition flanges, etc. require separate cutting, custom fixtures, and redoing welding procedure qualification WPS/PQR. For small-batch orders, tooling costs are almost entirely included in the order cost.The production stage is single-piece or small-batch trial production, without the efficiency advantage of an assembly line. Mold changeover and machine adjustment hours increase substantially, and unit labor cost rises significantly.
Inspection cost is another important source of the premium for non-standard parts.Standard parts are sampled for inspection according to the specified proportion, while high-hazard non-standard parts often require 100% non-destructive testing and piece-by-piece hydrostatic testing;Some non-standard parts for GC1 and overseas projects also require third-party supervision and type testing, and the testing costs are far higher than those for standard parts.In terms of documentation, non-standard parts cannot use standard templates and require separately issued strength calculation sheets, design review records, process documents, and special test reports, resulting in a heavy workload for document preparation, approval, and archiving.With the above factors combined, under the same material and same specification conditions, the direct purchase price of compliant non-standard pipe fittings is usually 20%~100% higher than that of standard parts, and the premium for non-standard parts made of special alloys with complex structures and small batches is even higher.
Special distinction is required: the large number of low-priced non-standard parts on the market are non-compliant products that omit strength calculations, reduce the proportion of non-destructive testing, simplify heat treatment, and reuse standard pipe fitting documentation. Their low price comes at the cost of sacrificing the safety baseline and abandoning special equipment compliance requirements. They do not fall within the scope of compliant custom non-standard parts discussed in this article and cannot be used as normal cost comparison samples.
III. Hidden costs: sources of price differences that are easily overlooked in procurement
Comparing only the unit supply price will seriously underestimate the comprehensive cost of non-standard parts. Schedule costs, installation adaptation costs, acceptance and filing risk costs, and later operation and maintenance costs constitute hidden price differences, which often have a greater impact on the total project cost.
Delivery time cost differences are prominent.Most standard parts are available from stock or have short production cycles, and can match the overall project schedule;non-standard parts require drawing confirmation, calculation review, tooling preparation, processing, and inspection, and the conventional delivery time is 2 to 4 times that of standard parts.If the pipeline construction milestone is tight, non-standard delays will cause on-site work stoppage, idle welders and hoisting equipment, and generate idle labor costs. Some overseas EPC projects will also trigger schedule breach compensation.
On-site assembly and rectification costs also cannot be ignored.The outer diameters, bevels, bending radii, and flange bolt circles of standard fittings are unified, so pipes, valves, and fittings match as complete sets, butt jointing is smooth, and the welding repair rate is low.Non-standard parts are customized to adapt to special interfaces. If deviations occur in the early surveying and parameter verification, misalignment during connection is highly likely on site, requiring grinding, cutting out, and re-fabrication, which adds substantial on-site welding, non-destructive testing, and pressure testing costs.Some modification projects use non-standard transition pieces. Once a dimensional verification error occurs, it may even be necessary to cut the existing in-service pipeline as well, carrying extremely high risk and cost.
Acceptance and filing risk costs are a cost item unique to pressure piping as special equipment.The documentation system for standard fittings is mature and highly recognized by inspection agencies and special equipment filing authorities;Non-standard parts require extensive documentation. If any of the drawings, calculation sheets, review records, or test reports is missing or logically inconsistent, it will lead to rejection by supervision inspection and stagnation of completion filing, delaying the project's commissioning time.Once non-standard parts fail to complete design review and type verification as required by TSG 31-2025, the regulatory authority may require the entire pipeline section to be removed and replaced, causing huge rework losses.
From the perspective of long-term operation and maintenance, standard fittings have strong spare-part interchangeability, making later maintenance, replacement, and procurement convenient with stable prices;Non-standard pipe fittings are custom-made exclusively, and future spare parts can only be re-customized, resulting in long procurement cycles again, unit prices that remain high, and higher long-term operation and maintenance reserve costs.Of course, in specific scenarios, reasonable non-standard parts can also reduce overall costs: when pipeline space is extremely narrow and multiple standards need to be interconnected, a set of non-standard transition fittings can avoid a large amount of on-site modification, reduce the overall pipeline modification workload, and achieve savings in the total project cost. This is also the value of the existence of non-standard customization.
IV. Procurement Selection Cost Evaluation Process and Judgment Principles
Procurement selection cannot be fixed on "prioritizing standard parts" or "prioritizing non-standard parts." An evaluation process of "technical compliance first, full-cost calculation, and tiered review" should be established.
The first step is to confirm the working conditions and interfaces, and give priority to checking whether there are standard pipe fittings that meet the requirements for parameters, interfaces, media, temperature, and pressure.As long as specifications within standards such as GB, ASME, and EN can meet the design boundaries, standard parts should be preferred, making full use of the cost advantages of bulk procurement, stock availability, and a mature documentation system, and avoiding non-standard premiums and compliance risks from the source.
The second step: when standard pipe fittings truly cannot meet assembly or process requirements and a non-standard solution must be adopted, the supplier is required to provide an itemized quotation, splitting the quotation into design review fees, tooling and fixture fees, raw material fees, processing fees, heat treatment fees, non-destructive testing fees, third-party testing fees, documentation fees, and packaging and transportation fees, so as to clearly identify the composition of the premium and avoid vague lump-sum quotations from suppliers.Procurement, technical, and supervision personnel shall jointly review: whether the entire part must be non-standard, or only the local connection structure is non-standard;Can the solution be split, with the main body using standard pipe fittings and only a small number of transition joints customized, thereby narrowing the non-standard scope and controlling costs?
Step 3: Carry out a full life-cycle cost calculation and compare the two solutions: the standard parts + on-site modification solution VS the compliant custom non-standard solution. Comprehensively calculate the pipe fitting purchase price, construction and modification costs, schedule loss, acceptance risk, and future spare parts costs, and choose the solution with the best overall total cost, rather than simply comparing pipe fitting unit prices.For non-standard parts on GC1 highly toxic, flammable high-pressure medium pipelines, technical compliance must be placed ahead of cost, and it is prohibited to choose non-standard products with simplified review and simplified testing in order to lower prices.
Step 4: For small-batch non-standard orders, mechanisms such as drawing locking, sample sealing, and first-article witness verification can be adopted to lock in dimensions, processes, and inspection plans in advance, avoiding secondary cost increases caused by design changes during manufacturing;For batch non-standard projects, specify change control clauses in the technical agreement; any changes to structure, wall thickness, or reinforcement must be recalculated for cost and schedule.
V. High-frequency procurement misunderstandings and cost control countermeasures
The first major misunderstanding is believing that the non-standard premium is simply expensive raw materials, while ignoring the one-time investment in design, tooling, review, and testing, which is especially obvious in small-batch non-standard orders.Countermeasure: At the quotation stage, require an itemized breakdown; one-time tooling costs can be apportioned across multiple batches of orders with the same drawings, and for non-standard drawings that are reused over the long term, repeated tooling costs can be deducted from subsequent orders.
The second major misconception is treating non-standard items as a universal solution: pipeline routing is not optimized during the drawing design stage, and non-standard tees and non-standard flanges are selected at will, causing a flood of non-standard items and out-of-control overall procurement costs.Countermeasure: optimize the piping layout on the design side, give priority to adapting to the standard pipe fitting specification system, and reduce non-standard points.
The third major misconception is confusing compliant non-standard items with inferior low-price non-standard items, and using low price as the core condition for winning a bid.Countermeasure: establish access thresholds for non-standard suppliers, verify special equipment manufacturing licenses, non-standard design review capabilities, and type test qualifications, list the full set of delivery document requirements in the technical agreement, and make strength calculation reports, NDT plans, and supervision requirements preconditions for acceptance.
The fourth major misconception is that the schedule evaluation for non-standard orders only counts production and processing time, omitting drawing review, third-party testing, and document approval cycles, resulting in errors in the project schedule plan.Countermeasure: break down the non-standard delivery time into multiple nodes—drawing confirmation, review, manufacturing, inspection, and document archiving—and set buffer periods.
The fifth major misconception is that in cross-border foreign trade projects, for mixed-standard transition non-standard parts, only the flange dimensions at both ends are checked while the overall stress verification is ignored; later, during the owner's supervision and inspection stage, they are rejected, causing return shipment and rework losses.Countermeasure: for cross-border non-standard parts, simultaneously carry out stress calculations according to the project's governing specification, and provide third-party inspection and bilingual technical documents recognized by the owner.
VI. Conclusion
The procurement cost difference between standard and non-standard pipe fittings is essentially the difference between the supply chain models of large-scale mature products and customized one-off products. The price gap is not just the material price, but a comprehensive reflection of a series of cost elements such as design, tooling, processes, inspection, documentation, lead time, operation and maintenance, and compliance risks.The core advantages of standard parts are low cost, fast delivery, mature documentation, and universal spare parts, making them the first choice for conventional pipeline projects;Compliant customized non-standard parts are a necessary supplement under special working conditions, suitable for equipment modification, multi-standard interfacing, confined spaces, and special medium pipeline scenarios, but they inherently have the characteristics of price premiums, long cycles, and complex control.
Procurement management personnel should move beyond the mindset of comparing prices per individual item and establish a full life-cycle cost assessment system. On the basis of meeting the safety bottom line of specifications such as TSG 31, GB/T20801, and ASME B31.3, they should reasonably control the quantity of non-standard usage, reduce unnecessary customization, and at the same time distinguish compliant non-standard parts from inferior non-standard parts that simplify work and cut corners, balancing the relationship among technical requirements, procurement costs, project progress, and long-term operation and maintenance, so as to achieve controllable safety and optimal economy in the procurement of pipe fittings.
References
[1] TSG 31-2025, Safety Technical Regulation for Industrial Pipelines [S]. State Administration for Market Regulation, 2025.
[2] GB/T 20801-2020, Pressure Piping Code—Industrial Piping [S]. Beijing: Standards Press of China, 2020.
[3] GB/T 12459-2017, Steel butt-welding seamless pipe fittings [S]. Beijing: Standards Press of China, 2017.
[4] ASME B31.3-2022, Process Piping Code [S]. New York: ASME Press, 2022.
[5] ASME B16.9-2021, Factory-Made Wrought Butt-Welding Pipe Fittings [S]. New York: ASME Press, 2021.
[6] TSG D7002-2023, Type Test Rules for Pressure Piping Components [S]. State Administration for Market Regulation, 2023.
[7] Li Gang. Design of Pressure Piping Components and Practical Review of Non-Standard Parts [M]. Beijing: Atomic Energy Press, 2021.