Reinforced thermoplastic pipe (RTP) should be selected as a complete, qualified system rather than by diameter and pressure alone. A reliable request for quotation defines the fluid, pressure and temperature envelope, pressure cycling, liner compatibility, fittings, route, installation method, inspection, testing, and required records. The manufacturer can then match a qualified pipe family to the actual duty.
For an oilfield flowline or injection line, begin with ten decisions:
- conveyed fluid and full chemical composition;
- normal, minimum, design, and upset temperatures;
- normal, maximum operating, and design pressures;
- expected pressure cycles and rapid depressurization events;
- required bore, flow rate, and allowable pressure drop;
- liner, reinforcement, cover, and seal compatibility;
- end-fitting and tie-in interfaces;
- route, burial condition, installation method, and reel limits;
- qualification, manufacturing QA, field inspection, and test requirements; and
- traceability, manuals, certificates, and closeout records.
If any of these inputs is unknown, do not compensate by choosing the highest catalog rating. Ask the supplier to identify the missing data, assumptions, and resulting limitations. A maximum pressure stated on a product family page is not automatically available at every diameter, temperature, fluid, reinforcement, or fitting configuration.
What Is RTP Pipe?
RTP is a spoolable composite line pipe with a polymeric liner, a structural reinforcement layer, and an external protective cover. Depending on the qualified product design, reinforcement may be metallic or nonmetallic. The liner carries the fluid and provides the primary fluid barrier; the reinforcement resists pressure loads; the cover protects the structural layer from handling and environmental damage.
API Specification 15S covers the manufacture and qualification of spoolable reinforced plastic line pipe for oilfield and energy applications. Its stated scope includes multiphase fluids, hydrocarbon gas and liquids, oilfield production chemicals, and nonpotable water. It covers pipe, end fittings, and couplings; conventional valves, tees, elbows, and other appurtenances remain subject to their applicable codes and project requirements.
That scope distinction matters during procurement. A compliant pipe body does not by itself qualify every connector, valve transition, branch, field assembly procedure, or completed pipeline. The purchase package needs a defined system boundary and evidence for every pressure-containing interface.
1. Define the Complete Service Envelope
Start with the conditions the line will actually experience, not a generic application label such as “oil service” or “water injection.” Two lines with the same nominal pressure can require different products because their fluids, temperatures, cycling, gas content, solids, or installation environments differ.
Provide at least the following:
| Design input | Information to provide | Why it changes selection |
|---|---|---|
| Service | Production, gathering, injection, transfer, or utility | Establishes operating mode and failure consequences |
| Fluid phase | Gas, liquid, water, oil, or multiphase | Affects qualification, permeation, decompression, and service factors |
| Composition | Water chemistry, hydrocarbons, aromatics, CO2, H2S, oxygen, solids, and chemicals | Controls liner, seal, and fitting compatibility |
| Temperature | Minimum ambient, minimum fluid, normal, maximum operating, design, upset, and installation temperatures | Ratings and handling limits are temperature-dependent |
| Pressure | Normal, maximum operating, design, shutdown, surge, vacuum, and external pressure | Defines the required qualified envelope |
| Cyclic duty | Cycle count, pressure range, frequency, pump type, and planned starts/stops | May require cyclic-service assessment |
| Depressurization | Expected blowdown rate and frequency | Gas permeation can make rapid decompression relevant |
| Design life | Required service period and operating profile | Must align with the product's qualification basis and integrity plan |
Do not treat design pressure and normal operating pressure as interchangeable. Record the source of each value and identify whether it is gauge or absolute pressure. For injection duty, include pump pulsation and shutdown behavior. For gas or multiphase duty, disclose the gas composition and anticipated depressurization scenario. For produced fluids, provide representative laboratory analysis rather than only the well or field name.
2. Verify Liner and Seal Compatibility
The liner is the fluid-contact layer, but chemical review must also include seals, end fittings, and any exposed transition materials. Compatibility is a function of concentration, temperature, pressure, exposure time, and combinations of chemicals. A material that performs well in water at ambient temperature may not be suitable for hot hydrocarbons, high aromatic content, oxidizing treatment chemicals, or mixed service.
A useful fluid data package includes:
- water cut, salinity, pH, chlorides, dissolved gases, and suspended solids;
- hydrocarbon composition and aromatic content;
- CO2 and H2S concentration or partial pressure, where applicable;
- methanol, glycol, corrosion inhibitor, scale inhibitor, biocide, solvent, or stimulation-chemical exposure;
- cleaning fluids, commissioning fluids, and temporary preservation chemicals; and
- the maximum temperature for each operating or cleaning condition.
PPI TR-19 is a screening reference for the chemical resistance of plastic piping materials, but PPI itself advises users to consult the manufacturer or material supplier for detailed application information. A generic compatibility chart should therefore start the review, not close it. Request a written, application-specific compatibility statement identifying the liner grade, seals, limits, assumptions, and excluded chemicals.
3. Match Pressure, Temperature, and Reinforcement as One Qualified Combination
RTP pressure capacity cannot be separated from temperature, diameter, reinforcement construction, fittings, and the manufacturer's qualification basis. Ask for the exact product variant proposed, not a family maximum copied from a brochure.
The technical offer should state:
- nominal inside and outside diameter;
- nominal pressure rating and maximum operating pressure for the stated service;
- lowest and maximum allowable operating temperatures;
- lowest allowable installation temperature;
- reinforcement type and pipe-layer description;
- operating, handling, and respooling minimum bend radii;
- maximum allowable installation axial tensile load, with and without fittings;
- fitting type, connector interface, and applicable limits; and
- straight-length requirements beside fittings and terminations.
CNPS's current RTP product page and a 2023 CNPS product brochure describe a broad family envelope, including products listed up to 32 MPa and 110 degrees C. These are family-level maxima, not a promise that both values apply simultaneously or to every size, fluid, construction, joint, or project. The current quotation and model-specific datasheet must establish the permitted combination.
4. Size the Bore From Hydraulics, Not Nominal Diameter Alone
Confirm whether the stated size refers to nominal pipe size, inside diameter, or outside diameter. RTP constructions with the same nominal designation can have different bores. That difference affects velocity, pressure loss, pump duty, pig selection, and tie-in geometry.
Provide design and operating flow rates, fluid density and viscosity over the temperature range, gas-liquid behavior where relevant, solids loading, elevation profile, allowable pressure drop, and pigging requirements. The supplier should return the proposed inside diameter, wall build, filled and empty unit weight, and a hydraulic basis suitable for independent checking.
Hydraulic sizing should also consider future conditions. A water-injection line may see increasing required pressure as the reservoir response changes. A gathering line may encounter changing water cut, gas fraction, wax, scale, or solids. Define credible future cases rather than sizing only for the first operating year.
5. Address Cycling, Gas Permeation, and Depressurization
Pump starts, trips, control-valve movement, reciprocating equipment, and batch operations can create repeated pressure ranges. API 15S includes specific provisions for cyclic pressure fluctuations, so the RFQ should quantify expected cycles instead of stating only “continuous service.” Ask the manufacturer to show how the proposed product is qualified for the stated cycle spectrum.
For gas and multiphase service, gas can permeate through a polymer liner and accumulate at interfaces. A rapid pressure reduction may then create a differential pressure within the pipe wall. The project team should give the manufacturer the intended blowdown rate and abnormal depressurization cases and request written operating guidance. Never infer a safe depressurization rate from a general product rating.
The same discipline applies to vacuum and external pressure. Draining, cooling, blocked-in operation, burial, groundwater, or construction loads can create conditions that are not represented by internal pressure alone.
6. Specify End Fittings and Tie-In Interfaces
The end fitting transfers load between the flexible pipe and a connector or conventional piping system. It is therefore part of the pressure-containing and structural system, not a purchasing accessory.
Define flange standard and rating, hub or thread interface, gasket and seal materials, adjacent pipe metallurgy, corrosion allowance or protection, electrical isolation, bolt access, support arrangement, thermal movement, and any imposed bending or axial loads. Identify whether fittings are factory-installed or field-installed and who is authorized to assemble them.
For every proposed fitting, request:
- a dimensional drawing and bill of materials;
- pressure and temperature limits tied to the proposed pipe;
- qualification evidence for the assembly;
- installation tooling and calibration requirements;
- operator qualification requirements;
- inspection and acceptance criteria; and
- repair or replacement instructions.
Avoid mixing pipe, fittings, and assembly procedures from unrelated product families unless the system designer and manufacturers provide a documented compatibility and qualification basis.
7. Design Around the Route, Reel, and Installation Method
Spoolability can reduce field joints, but it does not remove installation constraints. Before ordering, define the route survey, bend locations, road crossings, tie-ins, trench geometry, surface conditions, access, reel transport limits, lifting plan, payout direction, and required equipment.
API RP 15SIH is the dedicated recommended practice for onshore installation and handling of API 15S products. Its scope includes handling, layout planning, direct burial, surface lay, directional drilling, plowing, pull-through installation, post-installation inspection, and field testing. It is guidance, not a substitute for the product manufacturer's detailed procedure or the project's risk assessment.
The installation package should therefore identify:
| Installation topic | Project decision required |
|---|---|
| Reel logistics | Reel dimensions and mass, route clearances, axle limits, crane capacity, storage orientation, and chocking |
| Temperature limits | Allowable transport, handling, unspooling, fitting-installation, and test temperatures |
| Bend control | Handling and installed bend radii, roller spacing, payout geometry, and prohibited reverse bending |
| Pulling | Maximum allowable tensile load, monitoring method, pulling head, swivels, and contingency stop limits |
| Burial | Trench width, bedding, backfill, compaction, crossings, buoyancy, cover, and marker requirements |
| Surface lay | Supports, abrasion, thermal movement, UV exposure, traffic, fire, and third-party interference |
| Field fittings | Controlled work area, tooling, cleanliness, dimensions, operator qualification, and inspection hold points |
| Damage response | Quarantine, assessment, repair authority, acceptance criteria, and documentation |
Minimum bend radius is product- and condition-specific. Handling, respooling, and operating bend radii may differ, and temperature can affect permissible handling. Use the values in the approved manufacturer procedure for the exact product variant; do not copy a generic multiplier from another line or web page.
8. Define Qualification, QA, Inspection, and Field Testing
Ask the bidder to distinguish four different evidence types:
- Product qualification demonstrates that a defined product family or variant passed the applicable qualification program.
- Manufacturing quality assurance records confirm that the supplied production lot met specified controls and tests.
- Installation records show that transport, payout, field fitting, joining, inspection, and damage control followed approved procedures.
- Field test records document the completed system's test medium, pressure, temperature, stabilization, hold period, acceptance, depressurization, and restoration.
Agree the inspection and test plan before manufacturing. Define document review points, witness and hold points, marking and traceability, nonconformance handling, fitting inspection, post-installation walkdown, pressure-test boundaries, calibrated instruments, test-water quality, air removal, exclusion zones, leak acceptance, depressurization, drying, and reinstatement.
Field pressure testing is a hazardous activity and must follow the approved project procedure, applicable law, and the manufacturer's limits. The article intentionally provides no universal test pressure or duration because those values depend on the specific system, code, product, temperature, and test objective.
9. Require a Traceable Document Package
A technically acceptable pipe can still create project delay if documentation arrives late or cannot be linked to the delivered reels and fittings. Include a document register in the purchase order.
At minimum, request the following, as applicable:
- product datasheet for the proposed variant;
- qualification report or controlled summary;
- certificate of conformance;
- manufacturing QA test report;
- material and component traceability;
- reel, pipe, and fitting marking schedule;
- chemical-compatibility statement;
- transport, storage, unspooling, installation, and maintenance manuals;
- field-fitting procedure and operator qualification requirements;
- inspection and test plan;
- approved drawings and interface details;
- nonconformance and repair records;
- field installation and test forms; and
- final manufacturing record book or data book index.
API 15S requires manufacturer product information such as dimensions, layer materials, operating temperatures, nominal pressure rating, installation tensile capability, bend radii, and straight-run requirements beside connections. Use those categories as a baseline, then add project- and jurisdiction-specific requirements.
RTP Pipe RFQ Checklist
The following table can be pasted into a bid clarification or requisition:
| RFQ section | Minimum purchaser input | Required supplier response |
|---|---|---|
| Application | Flowline, gathering, injection, or transfer; onshore/offshore boundary | Suitability statement and exclusions |
| Fluid | Full composition, phase, solids, chemicals, cleaning fluids | Liner/seal/fitting compatibility statement |
| Pressure | Operating, maximum, design, surge, external, vacuum, cycles | Variant-specific ratings and qualification basis |
| Temperature | Operating, design, upset, ambient, installation | Operating and handling limits |
| Hydraulics | Flow cases, pressure-drop limit, elevation, pigging | Actual bore, hydraulic data, unit weights |
| Route | Length, profile, crossings, burial/surface conditions | Reel plan, bend limits, pulling limits, installation method |
| Interfaces | Tie-in sizes, flange/hub/thread, metallurgy, loads | Fitting drawings, limits, assembly procedure |
| QA/QC | Standard, inspection level, hold points, tests | ITP, certificates, reports, traceability plan |
| Deliverables | Data-book index, manuals, drawings, records | Document schedule and submission dates |
| Exceptions | No silent assumptions | Clause-by-clause deviation list |
Common Selection Mistakes
Selecting from a single maximum rating. A catalog maximum may apply only to a particular size, temperature, construction, or test basis. Require the exact variant and operating envelope.
Using an incomplete fluid description. “Produced water” or “crude oil” does not define aromatics, gas, salinity, solids, treatment chemicals, or cleaning exposure.
Ignoring transient duty. Surge, cycling, shutdown, vacuum, and rapid depressurization can govern even when normal pressure is modest.
Leaving installation until after purchase. Reel access, bend radius, pulling load, ambient temperature, crossings, and fitting locations can change spool length and system design.
Treating fittings as generic. The pipe-to-fitting assembly needs its own qualified limits, installation controls, and records.
Accepting a certificate without traceability. Evidence must connect the standard, product variant, manufacturing lot, reel, fittings, tests, and delivered documents.
Frequently Asked Questions
Is API 15S enough to select an RTP pipe?
No. API 15S establishes manufacturing and qualification requirements for spoolable reinforced plastic line pipe, but a project still has to define its fluid, operating envelope, route, fittings, installation, inspection, testing, and local code requirements. Offshore service may require additional provisions.
Can the highest listed pressure and temperature be used together?
Not unless the manufacturer confirms that exact combination for the proposed diameter, construction, fluid, fittings, and duty. Family-level maxima should be treated as separate boundaries until a model-specific datasheet and qualification basis are provided.
What fluid information is needed for a water-injection line?
Provide representative water chemistry, salinity, pH, dissolved oxygen, CO2, H2S, chlorides, solids, bacteria-control chemicals, scale or corrosion inhibitors, cleaning fluids, and the temperature-pressure envelope. Also describe pump pulsation and planned operating cycles.
What fluid information is needed for an oil or gas flowline?
Provide phase behavior, water cut, hydrocarbon and aromatic composition, gas composition, CO2 and H2S, solids, wax or scale risk, treatment chemicals, normal and upset temperatures, pressure cycles, and blowdown scenarios.
Is RTP minimum bend radius one fixed multiple of outside diameter?
No. The allowable radius depends on the product and whether the pipe is being handled, respooled, installed, or operated. Temperature and fittings can also affect restrictions. Use the approved values for the exact supplied product.
Does spoolable pipe eliminate field joints?
It can reduce joint count by allowing long continuous lengths, but the system still needs end fittings, reel-to-reel connections where applicable, branches, valves, tie-ins, and termination details. Route and transport limits determine practical spool lengths.
What should be checked before field pressure testing?
Confirm the approved procedure, test boundary, product and fitting limits, calibrated instruments, test medium and temperature, air removal, stabilization and hold criteria, exclusion zone, leak acceptance, depressurization method, drying, and record forms. Testing must be controlled by competent project personnel.
Build the RFQ Around the Duty, Not the Brochure
RTP selection becomes defensible when every proposed component can be traced from a real operating condition to a qualified product limit, an approved installation method, and an acceptance record. The best RFQ is not the one with the longest generic specification; it is the one that makes fluids, transients, interfaces, route constraints, evidence, and exceptions impossible to overlook.
CNPS can review a project data sheet for flowline or injection service and propose an RTP configuration for technical clarification. Send the fluid analysis, pressure-temperature profile, line size or flow cases, route length, installation method, tie-in details, applicable standards, and document requirements. Final suitability remains subject to model-specific engineering review and written confirmation.
Explore the CNPS RTP Pipe product page or contact CNPS to request a project-specific review.
Sources
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