Neometrix / Compressed Air Dryer Test Benches / Compressed Air Dryer Test Bench / NMX-DTB-52

NMX-DTB-52 · ENGINEERED-TO-ORDER CLASS — SPECIFY · LOAD · SENSE · CYCLE · COUNT · PROVE

Compressed Air Dryer Test Bench. Judge it at its worst.

Name: Compressed Air Dryer Test Bench
Brand: Neometrix
SKU: NMX-DTB-52

A dryer's dew point is usually given as one number. The air does not arrive as one number.

So the bench is built around three things: warm, wet inlet air at the duty flow, a fast sensor at the dryer outlet, and a run through whole tower cycles, all logged.

Discuss a dryer test bench Capability note (PDF)

A single compressed air dryer test bench in a clean test hall: a twin-tower desiccant air dryer on a grey steel frame, two upright grey towers joined by stainless steel pipe manifolds, with a pipe running to a stainless instrument manifold on a small grey stand carrying a flow section and a slim sensor housing on one black cable, and no people

Fig · 01 — A compressed air dryer test bench: a twin-tower dryer on the left and its measuring line on the right — illustrative render.

The inlet air

warm, wet, at duty flowset and held

The sensor

a fast dew point sensorat the dryer outlet

The run

whole tower cycleslogged end to end

The counts

pressure, air and powerread alongside

Status

engineered to orderno bench yet delivered

ISO 9001ISO 14001ISO 7183 dryer testing referenceISO 8573-1 air purity reference

Overview

Why a dryer is judged by its worst dew point, not its average.

Because the air only has to fail once. A dryer that holds a good average and spikes at every tower swap sends wet air downstream at each one.

Fig · 02 — The bench in one picture: warm, wet air goes in, the dryer under test does its job, and a fast sensor reads what comes out.

Judge the dryer at its worst, not on its average.

What the bench is for

It tests a compressed air dryer against the duty it is bought for. The inlet air is warmed and wetted, passed through the dryer at a set flow and pressure, and the dried air is measured at the outlet. It suits refrigeration, adsorption and membrane dryers.

Why the dew point is not one number

A pressure dew point is the temperature at which the dried air, held at line pressure, would start to form liquid water. In a twin-tower dryer one tower dries while the other is regenerated. As the online bed loads, the outlet dew point drifts wetter. When the towers swap it can spike before it settles on the fresh bed.

Why the sensor must be fast

A spike is brief. A slow sensor, or a sample line that holds moisture, smooths it away and reads close to the average, which is the number that hides it. A fast sensor on a short, dry sample line, read at line pressure, sees it.

Why the inlet air is conditioned

A dryer is fairly judged only on the air it was bought to dry. The bench warms the inlet air, makes it wet, and sets the flow and the pressure. The dryer works as it would on a hot, humid line, and the same duty can be repeated on the next dryer.

Why the run covers whole cycles

A reading taken between swaps misses the swap. The bench runs through whole tower cycles, and through reduced flow where the duty includes it, and logs the outlet dew point the whole way.

Why pressure and air are counted

A dryer that dries well can still cost too much to run. The bench reads inlet and outlet pressure, so the pressure the dryer costs is known. It also counts the regeneration air a heatless dryer spends and the power the dryer draws.

The method

Specify, load, sense, cycle, count, and prove.

Six steps in a fixed order. The two shaded steps are the ones a quick test skips.

FIG · 02COMPRESSED AIR DRYER TEST BENCH · SPECIFY / LOAD / SENSE / CYCLE / COUNT / PROVE — JUDGE IT AT ITS WORST

The step people underrate is the swap. A dryer that reads well between swaps and badly at them is not a dry dryer.

Fig · 03 — Three ways a dryer lets you down: a switchover spike, a pressure cost and a purge cost — a drawing of the idea, with no values.

1 · Specify

The duty sets the flow, the pressure and the inlet air. The customer states them, and the bench does not guess them.

2 · Load

The inlet air is warmed and wetted to the stated condition, and the flow and pressure are set and held.

3 · Sense

A fast dew point sensor reads the dryer outlet through a short sample line, at line pressure, and its response is checked before the run.

4 · Cycle

The run covers whole tower cycles, including the swap, with dew point, pressure and flow logged all the way through.

5 · Count

Inlet and outlet pressure give the pressure drop. The regeneration air and the power drawn are counted for the dryers that use them.

6 · Prove

The worst dew point of the run is reported with the average beside it, and the record is handed over with the log.

Work content

What the bench contains, element by element.

Read it as a checklist: a bench missing a row will give a good average and a wrong answer.

A single stainless steel measurement manifold on a grey bench: a short horizontal pipe with a flanged flow section, a slim cylindrical sensor housing fitted on top with one black cable, and a thin temperature probe fitted in the side of the pipe, and no people

Fig · 04 — The measuring line: a flow section, a fast dew point sensor and a temperature probe on a short stainless run — illustrative render.

Element	What it does	What matters
Air supply	feeds the bench	the customer's compressed air, or a supply engineered for the duty, with the flow and pressure set and held
Inlet conditioner	warms and wets the inlet air	brings the air to the stated temperature and humidity, so the dryer works as it would on a hot, humid line
Dryer connections	take the dryer under test	flanged ports and isolating valves that suit refrigeration, adsorption and membrane dryers, and make a change of dryer safe
Dew point sensor	reads the dried air	a fast sensor chosen for the range the dryer works in, with its response checked
Sample line	carries the sample	short, dry and stainless, from the dryer outlet, at line pressure
Flow element	measures the flow	a flow element in a straight run, with temperature and pressure taken at the same point
Pressure sensors	read inlet and outlet	give the pressure drop across the dryer at each flow
Back-pressure valve	holds line pressure and sets flow	a control valve at the end of the line that vents to a safe place through a silencer
Control & logging	run and record	PLC control of the duty, and a logger that keeps dew point, pressure, flow and power for the whole run
Power meter	counts what the dryer draws	read with the dew point, so cost and performance sit on one record
Guarding	keeps people clear of pressurised air	relief valves on every pressurised section, guarded hot parts, and a silenced vent directed away from people
Procedure	fixes the sequence	specify, load, sense, cycle, count and prove, the same for every dryer
Testing & documentation	prove the bench first	a leak test, a sensor check and a run record the customer can inspect

The element that decides whether the answer is true is the sensor and its sample line, because a slow sensor makes every dryer look better than it is.

Fig · 05 — One bench, three dryer types: adsorption, refrigeration or membrane, each read the same way.

Full specification — expand

System	An air supply with flow and pressure set and held; an inlet conditioner that warms and wets the air; flanged dryer connections with isolating valves; a fast dew point sensor on a short, dry sample line at the dryer outlet, read at line pressure; a flow element with temperature and pressure taken at the same point; inlet and outlet pressure sensors; a back-pressure valve with a silenced vent; a PLC control and a logger that keeps dew point, pressure, flow and power for the whole run; a power meter; relief valves and guarding; a written test plan; and testing and documentation before handover
The One Idea	A compressed air dryer is judged by its worst dew point, not its average.
Why The Dew Point Is Not One Number	In a twin-tower dryer one tower dries while the other is regenerated, so as the online bed loads the outlet dew point drifts wetter, and when the towers swap it can spike before settling on the fresh bed, which means a spot reading or an average can look fine while the worst reading is not
Why The Sensor Must Be Fast	A spike is brief, and a slow sensor or a long sample line smooths it away and reads close to the average, so a fast sensor on a short, dry sample line, read at line pressure, is what sees it
Why The Inlet Air Is Conditioned	A dryer is fairly judged only on the air it was bought to dry, so the bench warms and wets the inlet air and sets the flow and pressure, and the same duty can be repeated on the next dryer
Why The Run Covers Whole Cycles	A reading taken between swaps misses the swap, so the bench runs through whole tower cycles, and through reduced flow where the duty includes it, and logs the outlet dew point the whole way
Why Pressure And Air Are Counted	A dryer that dries well can still cost too much to run, so the bench reads inlet and outlet pressure to give the pressure the dryer costs, and counts the regeneration air and the power drawn
Standards	ISO 7183 is the public reference for specifying and testing compressed-air dryers, and ISO 8573-1 is the public reference for compressed-air purity classes, which include humidity. This page prints none of their reference values or conditions: those come from the standards and from the customer's duty. Approval of a dryer for use rests with the customer and the authority they name; none is claimed here
Configurations	A fixed-duty bench for one dryer size and one duty with a pass record, a programmed bench with duty steps run by a PLC and everything logged, and a range bench with test ports for a range of dryer sizes and types
Scope Boundary	This bench tests dryers. It is not a system that makes dry air for a plant (see dry and oil-free compressed air system), not a rig that tests the compressor that makes the air (see compressor test rig) and not a rig that tests parts with compressed air (see general purpose pneumatic test rig). It does not measure oil or particles: no certification is claimed here
Status	Neometrix has quoted against successive compressed air dryer test requirements, and no delivered compressed air dryer test bench is claimed.

Configurations

One method, three ways to supply the bench.

The method, the record and the worst-case rule are shared. What changes is how much of the bench is supplied.

Fixed-duty bench

Inlet air, dryer and sensor

One dryer size on one stated duty, with a fast sensor at the outlet and a pass record, to prove a dryer against the duty it was bought for.

Programmed bench

Inlet air, dryer and PLC logger

A bench whose duty steps are set and run by a PLC, with dew point, pressure, flow and power logged through whole tower cycles.

Range bench

Inlet air, test ports and logger

One bench with test ports and a conditioner for a range of dryer sizes and types, changed over with the same method.

Fig · 06 — Three ways to supply the bench, one method: a fixed-duty bench, a programmed bench, or a range bench.

And the part that is not equipment at all, yet decides all three: the test plan. It fixes the duty, the cycles to be run and the way the worst reading is reported, and it is written from the use of the dryer, not from the bench.

Where it is used

Wherever dry air has to stay dry, and a dryer has to prove it.

The common thread is air that must be dry at every moment, not on average.

Dryer makers

Where a new dryer design, or a production run, is proved against a stated duty before it leaves the works.

Plant and utility teams

Where a dryer is chosen for a compressed air line and its claimed dew point is checked before it is relied on.

Instrument and process air

Where control, instrument or process air must stay dry through every swap and every change of load.

Service and overhaul

Where a dryer is overhauled, its desiccant is changed, and its dew point and swap behaviour must be checked again.

Watch

See it in motion.

A short walkthrough video of the compressed air dryer test bench.

FAQ

Common questions.

Longer answers, for readers who want the reasoning.

Q · 01 What is a pressure dew point, and why is it measured at the outlet?

The pressure dew point is the temperature at which the dried air, held at line pressure, would start to form liquid water. The lower it is, the drier the air. It is measured at the dryer outlet because that is the air the plant actually receives. If the air is expanded before it is measured, the reading has to be converted back to line pressure, and every conversion adds doubt, so the bench reads it at line pressure from a short, dry sample line.

Q · 02 Why can a twin-tower dryer show a good average and still be a problem?

In a twin-tower dryer one tower dries while the other is regenerated, and the two swap roles at intervals. As the online bed loads, the outlet dew point drifts wetter. When the towers swap it can spike before it settles on the fresh bed. A trace that spends most of its time low and a short time high gives an average that looks good, while the equipment downstream still meets the wet moment at every swap. That is why the bench reports the worst dew point of the run with the average beside it, and not the average alone.

Q · 03 How do refrigeration, adsorption and membrane dryers differ on the bench?

A refrigeration dryer chills the air to condense out the water, so its dew point stops short of freezing. An adsorption dryer uses desiccant towers, reaches much drier air, and has the swap as the thing to watch. A membrane dryer passes water vapour through the walls of fine fibres, has no moving parts, spends a share of the dried air as sweep, and its dew point changes with flow, so more than one flow is worth running. The bench is the same for all three: the same conditioned inlet air, the same fast sensor and the same record. Each type is read where it is most likely to fall short.

Q · 04 Is this the same as the dry air system, compressor rig or pneumatic rig pages?

No, and the differences are worth stating precisely. The dry and oil-free compressed air system page is a system that makes dry air for a plant. The compressor test rig page tests the compressor that makes the air. The general purpose pneumatic test rig page tests parts with compressed air. This page tests the dryer that sits between the compressor and the user. It does not replace any of them, and it does not claim what they claim a second time.

Q · 05 What can the bench not do?

It shows how good a dryer is, and it does not make a dryer better. It reads moisture, pressure, flow and power. It does not measure oil or particles, which need their own methods, and it does not certify a dryer or itself: this page claims no certification or accreditation. A bench cannot tell the truth with a slow sensor, which is why the sensor response is checked before each run. No dew point, flow or pressure figure is printed here, and approval of a dryer for use rests with the customer and the authority they name; none is claimed here.

Q · 06 Has Neometrix built one of these?

We would rather answer this plainly than let a page imply otherwise. Neometrix has quoted against successive compressed air dryer test requirements, and no delivered compressed air dryer test bench is claimed. What stands behind the offer is adjacent: Neometrix engineers dry, oil-free compressed air systems (see the dry and oil-free compressed air system page), compressor test rigs (see the compressor test rig page) and pneumatic test rigs (see the general purpose pneumatic test rig page). The dew point sensor, flow element, valves, power meter and logger are catalogue items, bought in, not invented. What Neometrix engineers is the bench around them: the inlet conditioning, the piping and measuring line, the control and logging, the procedure and the records. So the honest position is that the bench is engineered to order, the neighbouring disciplines are in the building, and the first bench of this exact kind will be built around the customer's own dryers rather than taken off a shelf.

Q · 07 Which standards apply, and who sets the test conditions?

ISO 7183 is the public reference for specifying and testing compressed-air dryers, and ISO 8573-1 is the public reference for compressed-air purity classes, which include humidity. This page prints none of their reference values or conditions. The duty comes from the customer's air line, and the test conditions come from the standard the customer names. Acceptance of a dryer, including its proving runs on the bench, rests with the customer and whatever authority they name.

Q · 08 What do you need from us to quote?

Six things, and most of them describe your dryer and your air rather than the bench. First, the dryer: its type, its size and how many are to be tested. Second, the duty: the flow, the pressure and the inlet air, stated by the customer. Third, the run: whole cycles, reduced flow, and how the worst reading must be reported. Fourth, the connections: the ports, the space and the utilities on site. Fifth, the control and guarding: manual or programmed, and the site's rules. Sixth, the record: the logs and reports you want kept. From that we come back with a bench concept, a written test plan you can check, and a budgetary price.

The neighbouring compressed air pages, and how they differ from this one.

Three neighbours: one makes the air, one tests the compressor, one tests parts.

↗ A dry air supply

Dry & Oil-Free Compressed Air System

A system that makes dry, oil-free air for a plant - it supplies the air, it does not test a dryer.

↗ A compressor rig

Compressor Test Rig

A rig that tests rotary screw compressors - the machine that makes the air, not the dryer that follows it.

↗ A parts rig

General Purpose Pneumatic Test Rig

A rig that tests parts with compressed air - it uses the air, it does not judge a dryer.

Browse all Neometrix product lines.

Get a quotation

Tell us the dryer, the duty,
and the worst case.

The projects desk replies within two working days with a bench concept, a written test plan you can check, and a budgetary quotation. Write to [email protected] or use the form.

Enquire — compressed air dryer test bench Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED-TO-ORDER CLASS — COMPRESSED AIR DRYER TEST BENCH SPECIFY · LOAD · SENSE · CYCLE · COUNT · PROVE — JUDGE IT AT ITS WORST ENGINEERED IN NOIDA · INDIA