Sampling port with a no-retention valve: a piston or plug that closes flush with the reactor or pipe wall
No-retention sampling ports · Piston and plug valves that close flush with the reactor or pipe wall, seal rings, pressure class and nozzle fit
A sampling port on a reactor or process line is only as good as the first drop that comes out of it. If the valve sits at the end of a short nozzle, the liquid trapped in that nozzle between samplings is what the operator collects first. A no-retention sampling port avoids this by closing at the wall itself: a piston or plug reaches the inner surface of the vessel or pipe when shut and retracts to let live product flow when opened. For chemical reactors this matters twice over: a stale sample misreports the batch, and opening the valve can release product under pressure, which is why Strahman fits an opening indicator.
Sampling ports on chemical reactors, tanks and process pipes fitted with no-retention piston or plug valves that close at the inner wall, including seal rings, pressure and temperature ratings, body materials, piston extensions and nozzle fit. Steam- or CIP-sterilisable aseptic sampling valves for pharmaceutical, dairy and beverage lines are covered on the Sterile sampling valve page; sample taps feeding process analyzers on the PAT sampling and flow-cell module page; mechanical samplers for bulk solids on the Automated sampler for bulk solids page.
CNFX editorial research · Sources checked October 17, 2026 · 4 sources
A piston that reaches the inner wall, so the first sample is live product
Strahman's installation manual describes its piston-type sampling valve as built so that, closed, the piston extends to the inner surface of the vessel or pipe it is connected to; when the piston is retracted to open, the valve passes a sample, and because the piston takes up the whole interior of the valve no foreign material can gather in it. A pair of sealing rings around the piston gives shut-off while a gland ring keeps product out of the bonnet. [2]
The Strahman brochure adds a piston extension that breaks through crust or scale formed at the port, with standard and custom extensions for different depths of piping dead space, and an opening indicator on hand-operated valves with up to 6 in piston extensions, which warns the operator that pressurised product is about to flow so the valve can be opened slowly. [1]
Donjoy describes its no-retention sampling valve as having no dead zone at the end face connected to the container; a handwheel turns the stem with its sealing ring to open and close it, and the valve can also be fitted at the lowest point of a tank or pipeline to drain residual liquid. [3]
The background of US patent 7,389,792 (NL Technologies) explains the problem these designs address: sampling devices with crevices between component joints, or with features that let liquid pool, carry material over from one sampling episode to the next and spoil the next sample. [4]
State where the port sits (vessel wall, dished head, bottom outlet or pipe), the wall thickness and curvature, and whether solids or crust can form at the opening.
02
Pressure class, seal-ring temperature limits and body materials
Strahman gives pressure and temperature ratings for its piston sampling valves in accordance with ASME B16.34 class 600. For 316 and 316L stainless steel, its table lists 275 psig (19.0 barg) at 100 °F falling to 35 psig (2.4 barg) at 950 °F in class 150, and 1,440 psig (99.3 barg) at 100 °F falling to 775 psig (53.4 barg) at 950 °F in class 600, with 850 °F (454.4 °C) as the maximum for 316L. [1]
The same brochure lists seal-ring limits of 450° for LAM/TFE and TFM rings, 650° for medium-range (MR) rings and 1,000° for graphite rings; the unit is not printed next to these values, and the rest of the table is in °F. Bodies are 316 stainless steel as standard, with Alloy 20, nickel, Hastelloy B or C, titanium, Monel, Inconel and other alloys available. Its specification text describes a PTFE soft-seat design meeting ANSI Class VI bubble-tight shut-off. [1]
Donjoy lists −10 to 130 °C, AISI 304 or 316L bodies, PTFE seals and clamp, threaded, welded or nut connections for its no-retention valve. [3]
Strahman's manual tells the user to tighten the gland nuts to at least 50 in-lb with the valve closed and, if it leaks, to go up in 25 in-lb steps until it seals. Editorial calculation: 50 in-lb × 0.113 N·m per in-lb ≈ 5.6 N·m, and each 25 in-lb step ≈ 2.8 N·m. [2]
03
Fitting the valve to the vessel nozzle without scoring the piston
Strahman can supply a mating flange nozzle, or an adapter that pilots the valve in the nozzle so the flanges are concentric and the piston is not scored by the nozzle bore. Without such a recess or adapter it calls for 1/4 in clearance between the piston outside diameter and the nozzle bore, and asks, where required, for the pipe size and schedule or the tank wall thickness and radius. [1]
Port design
How it avoids retained product
Ask about
Piston-type sampling valve
Closed piston reaches the inner wall; extension breaks crust. [2][1]
Extension length; nozzle adapter.
Handwheel no-retention valve
No dead zone at the container end face; can drain the low point. [3]
Temperature range; connection.
Valve set back on a nozzle
Liquid can pool in crevices and carry over between samples. [4]
Flushing before each sample.
04
For each port, give
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Location: [reactor wall / dished head / bottom / pipe]; wall thickness and radius, or pipe size and schedule
Process: [medium; solids or crust; pressure; temperature]
Rating: [ASME class]
Materials: [body; seal rings]
Operation: [handwheel / crank / air or hydraulic cylinder]
Accessories: [sample bottle; flushing connection; heat jacket]
1 company lists this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
Donjoy Technology
Manufacturing site to be confirmed for the order
Lists a no-retention sampling valve with no dead zone at the container end face, 304 or 316L body and PTFE seal, −10 to 130 °C.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 17 October 2026
Buyer questions
What is a no-retention sampling valve?
A valve whose piston or plug closes at the inner wall of the vessel or pipe, so no product waits in a nozzle between samples. [2][3]
Why do dead legs spoil samples?
Crevices and pooled liquid carry material over from one sampling to the next, as US patent 7,389,792 describes. [4]
Sources and what still needs a direct check
Sources checked 2026-10-17. Ratings and installation figures are from Strahman's sample valve brochure and its installation manual, and from Donjoy's product page. The carry-over problem is described in the background of a US patent on vessel sampling and feed devices.
