IQ-SP Series

Injection Quills & Sample Probes

Reotemp injection quills and sample probes are insertion assemblies that reach the center of the process flow to inject treatment chemical where it mixes or draw a representative sample. Each is built to order from 316/316L stainless steel or exotic alloys, with the process connection, isolation valve, and instrument head your line requires. Rated up to 6,000 PSIG and NACE MR0175 compliant, they are machined to the same ISO 9001 quality system as our thermowells and valves.

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Reotemp injection quill and sample probe with flanged process connection and needle isolation valve

Process ConnectionsNPT, Flanged, Socket Weld, Weld-In
Valve OptionsBall, Needle, Gate, Check
Instrument HeadFNPT, MNPT, Weld Neck Flange, Plug & Chain
Materials316 / 316L SS, Monel, Hastelloy
Max. PressureUp to 6,000 PSIG

Built in several configurations

Quill & Probe Product Types

Reotemp machines injection quills and sample probes in several standard construction types. Each pairs with the process connection, isolation valve, and instrument head your line requires.

NPT

Threaded Quills

Economical NPT-connected quills for smaller pipe sizes and lower-pressure service, with a straight or 45 deg tapered tip.

Also called sample probes or stingers

Socket Weld Quills

Welded construction for higher-pressure, higher-cycle service where a threaded joint is not suitable for the application.

Fixed, non-retractable design

Flanged Quills

Bolted, raised-face flange connections for large-diameter pipe, high pressure, or applications that call for easier removal and reinstallation.

Double-flange or slip-on flange designs

DBB

Quill & Valve Assemblies

Factory-assembled quill and valve combinations, including double block and bleed configurations, that let the quill be removed for service without a full line shutdown.

Recommended for hot-tap removal and analyzer sampling

Check Valve Quills

Quills with an integral check valve to prevent backflow into the chemical feed line and protect upstream metering pumps from pressure surges.

Common on high-pressure injection lines

P/T

Pressure & Temperature Quills

Combination assemblies that pair a quill with a pressure gauge or thermometer connection, reducing the number of penetrations into the pipe wall.

Also called multi-function quills

Reotemp Technical Reference

Understanding Quills & Sample Probes

Injection quills and sample probes look almost identical and share the same configuration choices, but they move fluid in opposite directions, and that changes the design.

Injection quill

Puts chemical in

Delivers treatment chemical to the center of the process stream so it mixes immediately, instead of running down the pipe wall and corroding it.

Discharges at the center of flow for even dispersion
Often paired with a check valve to stop backflow
Tip and bore sized to the dosing rate

Sample probe

Takes fluid out

Withdraws fluid from mid-stream so the sample reaching your analyzer or lab represents the bulk flow, not the stagnant film at the wall.

Draws from the center of flow for a true sample
Isolation valve allows clean, safe extraction
Geometry chosen to avoid dead zones

What does a quill actually do?

An injection quill or sample probe is inserted through the pipe wall so its open tip sits within the active flow path, rather than flush against the inside of the pipe. For injection service, this places the discharge point near the center of flow, so treatment chemical disperses evenly instead of running along the pipe wall, where it can cause localized corrosion or uneven treatment. For sampling, the same geometry lets the probe draw a representative sample instead of fluid that has settled near the wall.

Welded vs. retractable designs

Welded and flanged quills are fixed in place and offer the most durable, vibration-resistant construction, but they can only be removed during a line shutdown. Retractable designs use a packing gland to seal around the probe so it can be withdrawn for service while the line stays in operation, a common requirement for online process analyzers.

Design note: Probes are generally most effective in pipe sizes 2 in and larger, and are considered standard practice above 4 in. For best sampling and injection performance, industry guidance recommends roughly 10 pipe diameters of straight, undisturbed flow upstream of the quill and 2 pipe diameters downstream.

Key terminology

Stinger / probeAlternate trade names for an injection quill or sample probe.
Double block & bleed (DBB)Two isolation valves with a bleed valve between them, used to safely isolate and depressurize the quill for removal.
Insertion length ("U" dimension)How far the probe extends into the pipe, measured from the process connection to the tip.
Wake frequency calculationAn engineering check, similar to the thermowell method in ASME PTC 19.3, that confirms the probe will not resonate with flow-induced vortex shedding at process velocity.
Wall streamingAn installation defect where injected chemical runs along the pipe wall instead of mixing into the flow, often caused by insufficient insertion depth.

Common questions

Injection Quill & Sample Probe FAQ

What is an injection quill used for?

An injection quill safely introduces chemical into a flowing process stream at the center of flow, where it disperses evenly. Common uses include corrosion inhibitors, pH adjustment chemicals, biocides, anti-foaming agents, and tracer injection.

What is the difference between an injection quill and a sample probe?

The stem geometry is the same; the difference is direction. An injection quill delivers chemical into the process. A sample probe withdraws process fluid so it can be analyzed. Both need careful placement to avoid dead zones or contamination.

How do I determine the insertion length I need?

As a rule, the tip should reach roughly the center third of the flow, deep enough to inject or sample from the bulk stream rather than the boundary layer at the wall. Send us the pipe size and schedule and we will calculate insertion length "U" and confirm it on the drawing before fabrication.

Where should a quill be installed in the piping?

Quills mount directly into the pipe wall and extend toward the center of the flow path. Insertion depth, orientation relative to flow direction, and upstream and downstream straight-run distance all affect performance and should be confirmed against your P&ID before installation.

What materials are available?

316 / 316L stainless steel is standard for most process conditions. For corrosive, high-temperature, or high-pressure service, we machine quills from exotic alloys such as Monel, Hastelloy, Alloy 625/825, and Super Duplex. Share the process fluid and conditions and we will recommend a compatible alloy.

Does a quill need a check valve?

A check valve is recommended on most injection assemblies to prevent process fluid from backing up into the chemical feed line and to protect upstream metering pumps from pressure surges. Whether one is required depends on system pressure and the chemical being injected.

Can a quill be removed while the line is in service?

Welded and flanged quills are fixed and require a shutdown to remove. A quill and valve assembly with a double block and bleed or retractable packing gland design allows removal for maintenance without taking the line out of service.

What pressure can these handle?

Up to 6,000 PSIG depending on the configuration, materials, and connection type. The rating is confirmed for your specific build during quoting.

What affects the price of an injection quill or sample probe?

Material selection, pressure and temperature rating, mounting type (threaded, socket weld, or flanged), insertion length, and whether the assembly includes a valve all affect cost. Custom-engineered lengths and exotic alloys add cost over standard configurations.

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