Flowline
Pup joints and hose loops
Straight lengths of flowline iron with union ends: integral pups machined in one piece for the highest ratings, threaded pups for lower-pressure lines, and steel hose loops built from swivels and pups.
A flowline pup joint is a straight length of high-pressure pipe with hammer union ends, used to make up the runs of frac, flowback, cementing and test lines. An integral pup joint is machined from one piece of AISI 4130, with the male and female union ends part of the pipe, so it carries the full rating of its figure; a threaded pup joint has union subs on pipe threads and is used where pressures are lower. We supply both, in the lengths your rig-up needs, and assemble swivels and pups into steel hose loops.
Integral and threaded pup joints
| Integral | Threaded (NPST) | |
|---|---|---|
| How the ends are made | Machined from the same piece as the pipe | Union subs threaded onto the pipe with a non-pressure-seal thread; the union seal holds the pressure |
| Connections along the pup | None: one piece from end to end | Two threaded connections between the subs and the pipe |
| Rating | The full rating of the figure, for example 15,000 psi for FIG 1502 | Set by the pipe and its threads, usually below the union rating |
| Typical use | Frac, flowback and high-pressure well service | Lower-pressure lines and connections |
Integral pups are machined from AISI 4130 bar or heavy-wall seamless tube and quenched and tempered for the figure. For hydrogen sulfide service they are made to the hardness limits of NACE MR0175 / ISO 15156-2 and rated at the sour version of the figure, for example 10,000 psi for FIG 1502.
Lengths and ends
Pups are made to the length your rig-up calls for, given face to face or center to center, with the male end carrying its wing nut and the female end its seal. The union figure, size and length are stamped on each pup with the cold working pressure and heat number. A layout of male and female ends that matches your existing iron avoids changeovers on location.
Steel hose loops
A steel hose loop is made up from long radius swivel joints and short integral pups into a loop that flexes like a hose. It is used between frac pumps and the manifold, and wherever a pump or a skid moves in service, to take up vibration and movement without straining the rest of the line. Loops are built to your sketch: the end figures, the drop between the ends, the length and the number of swivels.
Steel loops carry the full rating of their union figure, resist erosion from sand-laden fluid better than a hose and are repaired by replacing a swivel or a pup. A flexible hose is lighter and quicker to rig. The choice depends on the pressure, the fluid and the job.
Testing and documents
Each pup and each assembled loop is hydrostatically tested to the test pressure on your order, often 1.5 times the cold working pressure, and the result is recorded on the EN 10204 3.1 certificate with chemistry, heat treatment, tensile and hardness results. Magnetic particle inspection of the union threads and third-party witness can be added. See testing and documents.
We make these parts to the API 6A and API 16C requirements your order calls up: material, dimensions, tests and marking as specified. We do not hold an API license, so the parts do not carry the API Monogram. If your specification requires monogrammed equipment, the quotation says so plainly.
Ordering
Integral pup joint, 3 in FIG 1502, male by female, 10 ft face to face, AISI 4130 quenched and tempered, 15,000 psi CWP standard service, hydrostatic test at 22,500 psi, EN 10204 3.1, 12 pcs
Steel hose loop, 3 in FIG 1502, male by female, long radius swivels and integral pups to the attached sketch, 15,000 psi CWP, EN 10204 3.1, 2 pcs
Frequently asked questions
Why choose an integral pup joint over a threaded one?
An integral pup has its union ends machined from the same piece as the pipe, so there is no thread or weld between the union and the bore. It carries the full rating of the union figure, up to 15,000 psi for FIG 1502 and 20,000 psi for FIG 2002. A threaded pup is limited by its pipe thread and is used on lower-pressure lines.
What lengths can you make?
Any length your rig-up needs, within the length of bar or tube the pup is machined from. Give us the length face to face or center to center, and the tolerance if it matters for your layout.
What is a hose loop?
A flexible connection built from rigid parts: long radius swivel joints and short pup joints made up into a loop, so a pump or a manifold can move without straining the line. It takes the place of a hose where pressures, temperatures or fluids rule hoses out.
Do you mark the length and rating on each pup?
Yes. Each pup is stamped with the figure, size, length, cold working pressure and heat number, so it can be identified in the yard and traced to its certificate.