Frequently Asked Questions | GRE, FRP & RTP Piping

Answers below are drawn from articles already published on this site. Each answer gives the short version and links to the full article, so you can read the source rather than a summary of a summary.

IFGS manufactures GRE, FRP and RTP oilfield equipment in Dongying, China. Nothing on this page invents a factory location, a listing mark, a customer name, or a rating that is not on a published product document.

Standards & specifications

What is the difference between API 15HR and API 15LR?

API 15HR addresses high-pressure fiberglass line pipe; API 15LR addresses low-pressure fiberglass line pipe. They are not a distinction between rigid and flexible thermoplastic pipe. API 15HR covers rigid glass-fiber-reinforced thermoset components and excludes thermoplastic resins. Select the applicable standard and edition against the actual pipe system and service; a standard number alone does not establish a particular IFGS product rating. Source: API official standards and program documents.

Full article: What is the difference between API 15HR and API 15LR?

What is the difference between API 15S and API 17J?

API 15S addresses spoolable reinforced plastic line pipe. API 17J addresses unbonded flexible pipe; bonded flexible pipe is addressed separately by API 17K. These scopes are not interchangeable. Confirm the construction, intended service, applicable edition and qualification evidence for the proposed system. A reference to a standard does not itself prove certification or suitability for a project. Source: API official standards and program documents.

Full article: What is the difference between API 15S and API 17J?

UL 58 vs UL 1316 vs UL 1746 — which one applies to my project?

They cover three different objects, and mixing them is the most common tank-spec error. UL 58 is the steel underground tank standard. UL 1316 is the fiberglass (FRP) underground petroleum tank standard. UL 1746 is not a tank standard at all — it covers external corrosion protection systems applied to steel tanks built to UL 58.

UL 58 is not a fiberglass tank standard, and it is not automatically a complete corrosion-protection package. UL 1316 does not by itself qualify GRE or FRP line pipe systems, which are a separate product family. UL 1746 does not replace UL 58: you still need a coherent steel tank construction path.

Full comparison: UL 58 vs UL 1316 vs UL 1746: Underground Tank Standards Buyers Actually Spec. Individual standards: What is UL 58, What is UL 1316, What is UL 1746.

What is UL 58?

UL 58 is the UL standard for underground storage of flammable and combustible liquids. It includes single-wall tanks, secondary containment tanks, multiple-compartment single-wall tanks, and multiple-compartment secondary containment tanks. These storage tanks are used in accordance with NFPA 31, NFPA 30, NFPA 30A and NFPA 37, and the Uniform Fire Code. Source: UL 58, UL Standards & Engagement.

Full article: What Is UL 58?

What is UL 1316?

UL 1316 covers Glass-Fibre-Reinforced Plastic Underground Storage Tanks for Petroleum Products, Alcohols, and Alcohol-Gasoline Mixtures. It was first published in July 1983 and covers both single- and double-wall FRP tanks, addressing protection from leakage, buckling due to external pressure, internal pressures that may develop during testing, and material compatibility with the intended fluids and ground soil conditions. Source: UL 1316, UL Standards & Engagement.

Its internal pressure test requires a tank to withstand, without rupture, 25 psi for tanks 10 feet or less in diameter and 15 psi for tanks greater than ten feet in diameter. As part of normal production, every tank is also subjected to a leakage test, an internal vacuum test and a surface cure test.

Full article: What Is UL 1316?

What is UL 1746?

UL 1746 provides requirements for corrosion protection of steel underground storage tanks, and was first published in November 1989. It covers three types of protection system — cathodically protected tanks, composite tanks and jacketed tanks — with the base tank constructed in accordance with UL 58. Source: UL 1746, UL Standards & Engagement.

Composite tanks are steel tanks complying with UL 58 that are coated with a nonmetallic coating at least 0.100 inches thick. Jacketed tanks add an external nonmetallic FRP or thermoplastic jacket, also at least 0.100 inches thick, separated from the steel by an interstitial space that acts as a secondary containment barrier. The publicly available UL scope also includes Part IV for polyurethane (PUR) coated systems.

Full article: What Is UL 1746?

What is NSF/ANSI/CAN 61?

NSF/ANSI/CAN 61 concerns the health effects of materials and components that contact drinking water — the substances that can migrate from products into drinking water. It does not establish a pipe pressure rating or general mechanical performance, and it is not an offshore oil-and-gas flexible-pipe design standard. Source: NSF/ANSI/CAN 61, NSF.

Where certification is required, ask for the current listing that identifies the manufacturer, product name, material, size range and permitted use conditions, and match those details to the pipe, fittings and joining materials in your quotation. A reference to a standard in an article is not evidence that every product from a supplier is certified.

Full article: What is NSF/ANSI/CAN 61? — that article also records that the earlier “NFS 61” label on this site was a spelling error.

What is FM 1614?

FM 1614 is a standard published by the Factory Mutual (FM) Insurance Company that covers the design, manufacture and installation of flexible reinforced thermoplastic line pipe (FRTLP) systems for use in industrial applications. It specifies requirements for materials, design, manufacture, qualification and testing, as well as installation and operation. Source: FM Approvals.

Full article: What is FM 1614?

Products

What is fiberglass line pipe?

Fiberglass line pipe is a type of non-metallic pipeline used to transport fluids — commonly in oil, gas and water service — made from fiberglass-reinforced resin, most often epoxy. In industry it is usually referred to as GRE (glass reinforced epoxy) line pipe or FRP (fiber-reinforced plastic) pipe. It is built from glass fibres that provide strength and pressure resistance, a resin (typically epoxy) that binds the fibres and gives chemical and corrosion resistance, and an optional liner that improves resistance to aggressive fluids, manufactured by filament winding or similar processes to control strength and wall thickness.

Typical uses are oilfield flowlines and gathering lines, produced-water and injection-water lines, chemical and wastewater pipelines, and onshore and offshore low-to-medium pressure services — it is especially popular where corrosion is a major problem for carbon steel. Advantages include corrosion resistance to CO₂, H₂S, saltwater and chemicals, light weight, a long service life often quoted at 20–30+ years, low maintenance with minimal scaling, and a smooth internal surface. Limitations to plan for: lower temperature and pressure limits than steel, sensitivity to impact and improper handling, specialised joints (adhesive-bonded, threaded or flanged), and a need for trained installation to meet design standards.

Full article: What is fiberglass line pipe? Product page: high-pressure fiberglass line pipe.

What is the GRE pipe material specification?

GRE means glass-reinforced epoxy: glass-fibre reinforcement in an epoxy resin system. The term identifies a material family — it does not define one universal pipe size, pressure rating or temperature limit. A material specification should identify the epoxy resin and curing system, the reinforcement and any liner or barrier; nominal size with outside and inside dimensions, wall thickness and tolerances; rated pressure and temperature for the specified size and connection; fluid compatibility, installation conditions and the required design or test standard; and document revision, traceability and the inspection records required for the order.

GRP is a broader glass-reinforced plastic term, so confirm the resin system in the offered product rather than treating GRP and GRE as interchangeable specifications. For a project review, request the material specification together with the pipe-and-joint datasheet and drawing, and have the proposed configuration checked against the fluid, temperature, pressure and mechanical loading you provide.

Full article: What is the GRE pipe material specification?

What is GRP pipe?

Glass Reinforced Plastic (GRP) pipes are strong, lightweight and corrosion-resistant pipes made from a combination of glass fibre and resin. They are available in a variety of sizes, shapes and types depending on the application, and can be used for transporting water, chemicals, oil and other liquids, as well as for structural applications such as bridges and buildings. They are particularly useful where other materials such as steel or iron would be too heavy or prone to corrosion, and they are easy to install.

Full article: What is GRP pipes? Product page: GRP pipe.

What is RTP (reinforced thermoplastic pipe)?

Reinforced Thermoplastic Pipe (RTP) is a pipe made from layers of thermoplastic and reinforcing materials such as steel, Kevlar and fiberglass. It is highly resistant to corrosion, pressure and temperature changes, and is also lightweight, easy to install and more cost-effective than traditional piping materials; it suits applications such as transporting drinking water, sewage and industrial liquids. In oilfield work, spoolable RTP is bought under API Spec 15S — see the delivered case: 6 inch API 15S RTP, 10 km at 1500 psi / 85 °C.

Full article: What is reinforced thermoplastic pipe? Product pages: reinforced thermoplastic pipe, onshore API 15S RTP pipe.

Joints & terminology

Is GRE tubing the same as GRE pipe?

Not in procurement, even though it is the same material class. GRE tubing means glass-reinforced epoxy used in well or completion-adjacent tubular strings; GRE pipe (line pipe) means the rigid surface gathering, injection or transfer line. Tubular RFQs need well duty and arrangement, fluid and temperature, internal and external pressure, axial or combined loads, and connection drawings — not a catalogue one-size rating. Line-pipe RFQs need the service, the burial or surface condition, the joint family, design pressure and temperature, and diameter, so that bids are comparable.

Full article: GRE Tubing vs GRE Pipe: Terminology Buyers Mix Up. Product pages: GRE tubing, API 15HR GRE tubing, API 15LR GRE tubing.

What is a spigot joint on fiberglass or GRE pipe?

A spigot is the male pipe end, machined or formed to enter a matching bell (the female socket). A spigot joint — also called a bell-and-spigot joint — is the assembled connection: spigot, bell and sealing system, plus a locking or restraint feature when one is specified. The common rubber-seal path seats the spigot in a belled end with an elastomeric seal, published with a catalogue envelope of up to 1,400 mm and up to 50 bar, and listed as a non-restrained joint that requires thrust blocks or hybrid systems unless you move to the locked sister product.

Full article: Spigot Joint for Fiberglass Pipe: What Buyers Spec (vs Double-Bell). Product pages: rubber-seal bell & spigot joint, rubber-seal bell & spigot locked joint.

Spigot joint vs double-bell coupler — what is the difference?

In a bell-and-spigot connection the pipe spigot enters a belled pipe end, integral or formed. In a double-bell coupler, two plain or spigot-style pipe ends enter a separate double-bell coupling sleeve — a distinct SKU and a distinct logistics item, with its own coupler count, gasket set and spare kit. The published catalogue headlines differ: bell-and-spigot up to 1,400 mm and up to 50 bar, double-bell coupler up to 4,000 mm and up to 40 bar.

Those headlines are not a combined rating claim — do not assume 50 bar at 1,400 mm without the size-specific datasheet, and do not write “spigot joint or equal” if you actually need a separate coupler sleeve for large OD.

Full guide: Spigot Joint for Fiberglass Pipe. Product pages: rubber-seal bell & spigot joint, double bell coupler joint.

Do non-restrained spigot and double-bell joints need thrust blocks?

Yes, on the published non-restrained catalogue language: thrust blocks or hybrid systems. Where the civil package cannot carry thrust blocks, the locked spigot joint is listed with the same published size and pressure headline but as a restrained joint that does not require them, typically for buried service. Adhesive-bonded and thread-joint paths are the other restrained options. Put “locked vs non-restrained” in the RFQ so civil and piping quotes stay aligned, and confirm the arrangement on the product datasheet.

Product pages: rubber-seal bell & spigot locked joint, adhesive bonded (cemented) joint, thread joint with fiberglass coupling.

Which joint families are published for GRE and FRP pipe?

Four families appear across the joint pages on this site: rubber-seal bell-and-spigot (non-restrained, with a locked/restrained version), double-bell coupler (a separate sleeve, usually for large-diameter buried flexibility), adhesive bonded or cemented (a chemically bonded restrained path), and thread joints with fiberglass or stainless-steel couplings (restrained mechanical make-up where aboveground or buried strings need restraint without thrust blocks).

Joint hardware follows the pipe family on the tender. API Spec 15HR / 15LR language belongs with GRE fiberglass tubular and line-pipe conversations, while API Spec 15S belongs with spoolable RTP and its own end fittings. Do not paste a 15S coupler list into a rigid GRE spigot RFQ, or the reverse — and if a tender only says “API 15” with no letter, stop and clarify before requesting joint datasheets.

Full guide: Spigot Joint for Fiberglass Pipe: What Buyers Spec (vs Double-Bell). Product pages: double bell coupler joint, adhesive bonded (cemented) joint, thread joint with fiberglass coupling.

Still have a question?

If the answer you need is not here, send the project data with your question and IFGS will respond against your configuration rather than a catalogue headline. Non-metallic pipe and joint selection is document-driven: fluid, design pressure and temperature, dimensions, installation mode and quantity decide the answer.

Ask IFGS.AI