Neometrix / Gas Systems / SF6 Gas Handling Unit / NMX-SGH-99

NMX-SGH-99 · ENGINEERED-TO-ORDER CLASS — DUTY · GAS CIRCUIT · SCALE · SAFEGUARDS · BUILD · PROVE

SF6 Gas Handling Unit. Weigh it out. Weigh it back.

Name: SF6 Gas Handling Unit
Brand: Neometrix
SKU: NMX-SGH-99

An SF6 gas handling unit takes sulphur hexafluoride out of switchgear and puts it back. It evacuates the air, recovers the gas, dries and filters it, holds it in a storage vessel and recharges the equipment. Neometrix engineers it as a system: the gas circuit, the scale, the controls, the safeguards and the proof.

So the unit has to recover the gas without venting it, clean it of moisture and arc by-products, and count it out and back by weight.

Discuss an SF6 gas handling unit Capability note (PDF)

A trolley-mounted SF6 gas handling unit on a plain white studio background: a pale grey welded steel frame on four wheels with a long towing handle, a horizontal bright stainless steel storage vessel on the lower deck, an oil-free compressor with a finned head and a black motor, a vacuum pump, two upright bright stainless steel filter canisters, bright and copper pipework with coloured ball valve handles, a coil of black hose with quick couplings on a hook, a plain blank control cabinet at the top, and no people

Fig · 01 — An SF6 gas handling unit on a trolley: a vacuum pump, an oil-free compressor, two filter canisters, a storage vessel and hoses with quick couplings on one frame — illustrative render.

The result

gas back in servicerecovered, cleaned and returned

The air

evacuated firstbefore any gas goes back

The gas

dried and filteredmoisture and arc by-products removed

The count

weighed out and backso that a loss shows

Status

engineered to orderno delivered unit claimed

ISO 9001ISO 14001IEC 62271-4 reference for handling SF6IEC 60480 reference for re-use of SF6

Overview

What an SF6 gas handling unit has to get right, and what goes wrong when it does not.

Because the gas cannot be seen or smelled, and a mistake shows up later, in the equipment or in the air.

The gas circuit module of an SF6 gas handling unit on a plain white studio background: two tall upright bright stainless steel filter canisters on a bracket, a smaller upright particle filter housing, bright pipework with ball valves with blue and yellow handles, an oil-free compressor with a finned head and a black motor beside a finned condenser coil, all on a pale grey base frame, and no people

Fig · 02 — The gas circuit: two filter canisters and a particle filter, beside the oil-free compressor head with its condenser coil — illustrative render.

Weigh it out. Weigh it back.

What the unit is for

It takes SF6 out of gas-insulated switchgear, circuit breakers and similar equipment when they have to be opened, and puts it back afterwards. It serves substations, switchgear plants and maintenance teams.

Why the gas is recovered and not vented

SF6 is a very good insulating gas, and it is also a very strong greenhouse gas. So it is kept and reused, and it is not released to the air.

Why the air is evacuated first

Air left in the equipment dilutes the gas and brings moisture with it. So a vacuum pump takes out the air and the moisture before any gas goes back.

Why the gas is dried and filtered

Moisture, and the by-products that an electric arc makes in the gas, can attack the materials inside the equipment. So the gas passes through a dryer filter, a purification filter and a particle filter before it is stored.

Why the compressor is oil-free

Oil in the gas is a contaminant. So the compressor must not put oil into it, and the vacuum pump is kept apart from the gas by a valve.

Why the vessel is filled by weight, and never full

SF6 can be compressed to a liquid, so a small vessel holds a lot of gas. A vessel full of liquid has no room to expand when it warms, so it is filled by weight, and never full.

Why the vessel is sized for the largest compartment

The vessel has to take what is recovered from the biggest gas compartment to be emptied. So it is chosen from the equipment, and not from a catalogue.

Why the scale matters

SF6 has no colour and no smell, so a loss cannot be seen or smelled. A scale under the storage vessel counts the gas out and back, and the difference between the two is the gas that was lost.

Why the operator is protected

SF6 is heavier than air and does not support breathing, so it collects low in pits and enclosed spaces. Gas that an arc has used also carries by-products that harm the skin, the eyes and the lungs. So the connections are closed, the joints are leak-checked, and used filters are handled with care.

The method

Duty, gas circuit, scale, safeguards, build and prove.

Six steps in a fixed order. The scale and the proof are the two that a quick job skips.

1 · Duty

The equipment to be served, the largest gas compartment, where the work is done, how the unit is moved, and whether the gas is reused on site are noted.

2 · Gas circuit

The vacuum pump, the oil-free compressor, the filters, the storage vessel and the valves are arranged so that gas can be recovered, cleaned, stored and returned, and so that no oil and no air can get in.

3 · Scale and control

The storage vessel stands on load cells, and the control runs each mode in turn. The scale counts the gas out and back, and limits stop the compressor before the vessel is too full.

4 · Safeguards

Relief valves protect each part, self-sealing couplings keep the gas in when a hose is disconnected, and every joint is leak-checked.

5 · Build

The frame, the circuit, the vessel and the control are built and fitted, and the pipework is cleaned and dried before it is closed.

6 · Prove

The unit is run through all four modes, the vacuum, the leak check and the weigh-out and weigh-back are checked, the limits and the relief valves are tested, and the record goes with the unit.

Which problem, which safeguard

What can go wrong	Why it happens	What the unit does about it
The gas is released to the air	a hose is disconnected under pressure, or a joint leaks	self-sealing couplings, a closed circuit, and a leak check of every joint
Moisture stays in the equipment	the air and the moisture were not evacuated before filling	a vacuum pump that evacuates first, and a dryer filter in the circuit
Arc by-products stay in the gas	the gas was used in an arc and was not cleaned	a purification filter, and filters changed on a plan
Oil gets into the gas	the compressor or the vacuum pump puts oil into the circuit	an oil-free compressor, and a vacuum pump kept apart from the gas by a valve
The vessel is overfilled	the liquid has no room to expand when it warms	filling by weight to a limit, and a relief valve
A loss goes unnoticed	the gas has no colour and no smell	a scale under the vessel that counts the gas out and back
Gas of unknown quality goes back	nobody checked it before it was reused	sampling points, so that moisture and purity can be checked first

The step people underrate is the scale. A unit that recovers and refills without counting cannot say how much gas was lost on the way.

Work content

What the unit contains, element by element.

Read it as a checklist: a unit missing a row will move gas, but it will not move it cleanly, safely or on the record.

The storage station of an SF6 gas handling unit on a plain white studio background: a horizontal bright stainless steel storage vessel with rounded ends on a pale grey base frame that stands on four bright feet, a valve block on top with two ball valves with red and blue handles and a relief valve, a coil of black hose with a quick coupling at each end, and no people

Fig · 03 — The storage station: a horizontal vessel on a base frame that stands on four load cells, with a valve block, a safety valve and a hose with a quick coupling — illustrative render.

Element	What it does	What matters
Vacuum pump	evacuates	takes the air and the moisture out of the equipment and the circuit, and is kept apart from the gas by a valve so that its oil cannot reach it
Recovery compressor	moves the gas	an oil-free compressor that draws the gas out of the equipment and delivers it to the storage vessel, as a gas or as a liquid
Dryer and purification filters	clean the gas	a dryer filter for moisture, a purification filter for arc by-products, and a particle filter, all changed on a plan
Storage vessel	holds the gas	a vessel sized for the largest compartment to be emptied, filled by weight and never full, with a relief valve
Scale	counts the gas	load cells under the vessel, so that the gas taken out and the gas put back can be compared
Pipework and valves	carry the gas	a closed gas path, cleaned and dried before it is closed, and leak-checked at every joint
Hoses and couplings	connect the equipment	self-sealing couplings that keep the gas in when a hose is disconnected, and hoses suited to the gas
Sampling points	let the gas be checked	points at which moisture and purity can be measured before the gas is reused
Control	runs each mode	a control that runs evacuate, recover, store and fill in turn, shows the circuit, and stops the compressor at its limits
Frame and wheels	carry the unit	a frame on wheels or a skid base, that can be moved to the equipment and set up quickly
Testing & documentation	prove the unit first	a run through all four modes, a check of the vacuum, the leak tightness and the weighing, a test of the limits and the relief valves, and a record the customer can inspect

The elements that decide the result are the storage vessel on its scale and the filters. The first keeps the count, and the second keeps the gas fit to go back.

Full specification — expand

System	A frame on wheels or a skid base; a vacuum pump that evacuates the air and the moisture; an oil-free compressor that recovers the gas; a dryer filter, a purification filter and a particle filter that clean it; a storage vessel on load cells that holds it, with a relief valve; pipework, valves and self-sealing couplings; sampling points; a control that runs each mode in turn, with limits; and leak checks, trials and documentation before handover
The One Idea	Weigh it out. Weigh it back.
Why The Scale Matters	SF6 has no colour and no smell, so a loss cannot be seen or smelled; a scale under the storage vessel counts the gas out and back, and the difference between the two is the gas that was lost
Why The Gas Is Cleaned	Moisture, and the by-products that an electric arc makes in the gas, can attack the materials inside the equipment, so the gas passes through a dryer filter, a purification filter and a particle filter, and the air is evacuated before any gas goes back
Standards	IEC 62271-4 covers the handling of SF6 in high-voltage switchgear and controlgear, and IEC 60480 covers the re-use of SF6 recovered from electrical equipment. This page prints none of their requirements, and no edition year. Approval of a unit rests with the customer and the authority they name; none is claimed here
Configurations	A trolley-mounted unit, a skid-mounted station, and a unit with a large storage vessel
Scope Boundary	This page is the SF6 gas handling unit, which recovers, cleans, stores and returns the insulating gas of switchgear. It is not a halon reclamation plant, which reclaims another gas in a closed loop with a laboratory (see halon reclamation and refilling facility), not a vacuum pumping station, which takes a process chamber down to a high vacuum (see high-vacuum pumping station) and not a switchgear test bench, which proves a breaker and a relay (see circuit breaker and relay test bench). It does not decide whether the gas may be reused, and it does not replace the operator's own judgement. No certification or accreditation is claimed here
Status	Neometrix engineers SF6 gas handling units to order, and no delivered SF6 gas handling unit is claimed.

Configurations

One method, three ways to build the unit.

The method, the gas circuit, the safeguards and the proof are shared. What changes is where the unit works, and how much gas it has to hold.

Trolley-mounted unit

A unit on wheels, moved to the equipment

For a maintenance team that works at many sites: the whole circuit, the vessel and the scale on one frame, that can be wheeled to the equipment and set up quickly.

Skid-mounted station

A unit on a base frame, for a plant or a workshop

For a switchgear plant or a workshop where the unit stays: the same circuit on a base frame, joined to a fixed supply and to the equipment on the floor.

Unit with a large storage vessel

A large vessel on its scale, for a large compartment

For equipment with a large gas compartment, or many compartments in turn: a bigger vessel on a bigger scale, and a recovery compressor chosen to match.

And the part that is not equipment at all, yet decides all three: the duty and the gas handling procedure. They are written from the customer's own equipment and work, not from the unit.

The drawings

A reference set, drawn as real CAD sheets.

Two sheets of one reference configuration: the gas circuit of an SF6 gas handling unit, and its general arrangement with three details. They show the vacuum pump, the recovery train with its filters, the storage vessel on its load cells, the fill path, the unit in elevation, the filter train, the limit to which the vessel is filled and the self-sealing coupling. They carry tags and letters only. Every pressure, vacuum level, flow rate, vessel size and gas quantity is fixed by design for the customer's duty.

Reference drawing sheet one, the gas circuit of an SF6 gas handling unit. The gas compartment of the equipment is joined through a self-sealing coupling to a gas manifold with a pressure transmitter and a vacuum transmitter. A vacuum pump takes out the air and the moisture. An oil-free compressor draws the gas through a particle filter, a condenser, a dryer filter, a purification filter and a second particle filter to a storage vessel that stands on load cells, with a relief valve. A fill path with a regulator, a particle filter and a sampling point returns the gas to the equipment. A legend, a table of what each mode does, eight notes and a title block stamped reference configuration, not for construction

Fig · 04 — Sheet 01, the gas circuit: the vacuum pump, the recovery train with its filters, the storage vessel on its load cells, and the fill path, in the style of the graphical symbols of process diagrams. Reference configuration, tags only.

Reference drawing sheet two, the general arrangement and details of a trolley-mounted SF6 gas handling unit. A front elevation shows the frame on wheels, the storage vessel on its load cells on the lower deck, and the compressor, the vacuum pump, the filter canisters and the control cabinet on the upper deck, with a hose coil and a towing handle. A side elevation shows the vessel end-on. An item list numbers ten parts. Detail A shows the filter train, Detail B a vessel filled to a limit against one full of liquid, and Detail C a self-sealing coupling closed and open. A title block stamped reference configuration, not for construction

Fig · 05 — Sheet 02, the general arrangement and details: the unit in front and side elevation, the filter train, the vessel that is never filled full, and the self-sealing coupling. Reference configuration, letters only.

Every real unit is drawn for its own equipment, its own largest gas compartment and its own work. These sheets are the arrangement and the order of working that a project set starts from. Approval of any drawing rests with the customer and the authority they name; none is claimed here.

PDF · two sheets

Reference drawings — gas circuit and arrangement

PDF · capability sheet

SF6 gas handling unit — what Neometrix engineers

Where it is used

Wherever switchgear holds SF6, and the gas has to be kept.

The common thread is a gas compartment that has to be opened, a gas that must not be vented, and equipment that goes back into service.

Substations and switchgear sites

Where gas-insulated switchgear and circuit breakers are opened for maintenance or repair, and the gas has to be recovered and returned.

Switchgear plants

Where equipment is filled, tested and emptied in production, and the gas is reused and not lost.

Maintenance teams and workshops

Where one unit serves many sites and many kinds of equipment, and has to be moved and set up quickly.

Power plants and heavy industry

Where high-voltage equipment runs for years, and the gas must be checked, topped up and recovered at the end of the equipment's life.

Watch

See it in motion.

A short walkthrough video of the SF6 Gas Handling Unit.

FAQ

Common questions.

Longer answers, for readers who want the reasoning.

Q · 01 What does an SF6 gas handling unit actually do?

It takes the insulating gas out of switchgear and puts it back. A hose joins the unit to the equipment through a self-sealing coupling. The compressor recovers the gas, which passes through a dryer filter, a purification filter and a particle filter to the storage vessel. When the work on the equipment is done, the vacuum pump takes the air and the moisture out of it, and the equipment is recharged from the vessel. The scale under the vessel shows how much gas went out and how much came back. The unit does not decide what work is done on the equipment. That comes from the equipment's maker and the customer's own procedure, and the unit is built, set and proved to carry it out.

Q · 02 Why is the gas recovered and not vented?

Because SF6 is a very strong greenhouse gas, and a release does harm out of all proportion to the amount, and because the gas is costly and can be cleaned and reused. A hose that is disconnected under pressure, or a joint that leaks, lets it go, and the gas has no colour and no smell, so nobody notices. So the unit keeps the gas in a closed circuit, uses self-sealing couplings and leak-checks every joint, and a scale under the storage vessel counts the gas out and back, so that a loss shows as a difference.

Q · 03 Why are moisture and arc by-products a problem, and what removes them?

Moisture can combine with the by-products that an electric arc makes in the gas and form corrosive compounds, and those attack the materials inside the equipment. A dryer filter, which holds activated alumina, takes out the moisture. A purification filter, which holds a molecular sieve, takes out the arc by-products. A particle filter takes out the dust. The filters wear out, so they are changed on a plan, and a used filter is handled with care because it holds what it took out of the gas.

Q · 04 Why evacuate before filling, and why an oil-free compressor?

Air left in the equipment dilutes the gas and brings moisture with it, so the vacuum pump takes the air and the moisture out before any gas goes back. Oil is a contaminant of its own, so the compressor does not use oil in the gas path, and the vacuum pump is closed off from the gas by a valve while the compressor runs, so that its oil cannot reach the equipment. A unit that evacuates well but lets oil into the gas has swapped one fault for another.

Q · 05 Is this the same as the halon facility, a vacuum pumping station or a switchgear test bench?

No, and the differences are worth stating precisely. The halon reclamation and refilling facility page covers reclaiming another gas in a closed loop, with a laboratory. The high-vacuum pumping station page covers taking a process chamber down to a high vacuum. The circuit breaker and relay test bench page covers proving a breaker and a relay. This page is the SF6 gas handling unit, which recovers, cleans, stores and returns the insulating gas of switchgear. It does not replace any of them, and it does not claim what they claim a second time.

Q · 06 Has Neometrix built one of these?

We would rather answer this plainly than let a page imply otherwise. Neometrix engineers SF6 gas handling units to order, and no delivered SF6 gas handling unit is claimed. What stands behind the offer is adjacent: Neometrix engineers a halon reclamation and refilling facility (see the halon reclamation and refilling facility page), a high-vacuum pumping station (see the high-vacuum pumping station page) and special gas systems that include the recovery of gas from cylinders (see the special gas systems page). The compressor, vacuum pump, filters, vessel, valves, couplings, load cells and controls are catalogue items, bought in, not invented. What Neometrix engineers is the unit around them: the gas circuit, the scale, the controls, the safeguards and the proof. So the honest position is that the unit is engineered to order, the neighbouring disciplines are in the building, and the first unit of this exact kind will be built around the customer's own equipment and work rather than taken off a shelf.

Q · 07 Which standard applies, and what can the unit not do?

IEC 62271-4 covers the handling of SF6 in high-voltage switchgear and controlgear, and IEC 60480 covers the re-use of SF6 recovered from electrical equipment. This page prints none of their requirements, and no edition year: those come from the standard and the specification the customer names. The unit recovers, cleans, stores and returns the gas. It does not decide whether the gas may be reused, it does not open or repair the equipment, and it does not replace the operator's own judgement. This page claims no certification or accreditation. No pressure, vacuum level, flow rate, vessel size, gas quantity or limit figure is printed here, and approval of a unit rests with the customer and the authority they name; none is claimed here.

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

Six things, and most of them describe your equipment rather than the unit. First, the equipment: the kind of switchgear or breaker, and how many gas compartments. Second, the largest compartment: what the storage vessel has to take. Third, the gas: whether it is new or has been in an arc, and how clean it must be when it goes back. Fourth, the duty: how often the unit works and how fast the work must be done. Fifth, the place: a site that the unit is moved to, or a workshop where it stays. Sixth, the supply: the power and the access. From that we come back with a unit concept, a test plan you can check, and a budgetary price.

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

Three neighbours: one reclaims another gas, one pumps a chamber down, one proves a breaker.

↗ The halon facility

Halon Reclamation & Refilling Facility

Reclaims another gas in a closed loop, with a laboratory - where this page handles the insulating gas of switchgear.

↗ The vacuum station

High-Vacuum Pumping Station

Takes a process chamber down to a high vacuum - a different job from evacuating a switchgear compartment.

↗ The breaker bench

Circuit Breaker and Relay Test Bench

Proves a breaker and a relay - where this page handles the gas inside the equipment.

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and the gas it holds.

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

Enquire — SF6 gas handling unit Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED-TO-ORDER CLASS — SF6 GAS HANDLING UNIT DUTY · GAS CIRCUIT · SCALE · SAFEGUARDS · BUILD · PROVE — WEIGH IT OUT. WEIGH IT BACK. ENGINEERED IN NOIDA · INDIA