The Industrial PM VSD Low Pressure Single-Stage Screw Air Compressor is designed around a production requirement that is easy to overlook: a process may need a substantial volume of air without needing the pressure of a general factory network. SEIZE AIR's SZ-PML selection brings a dedicated low-pressure airend together with permanent-magnet variable-speed drive and a separately controlled cooling fan. The result is a package that can be specified around the process connection, rather than around the pressure setting of an unrelated utility header.
A factory can have several air duties with different pressure requirements. Supplying them all from the same high-pressure header may be convenient, but that arrangement should be reviewed when a low-pressure process represents a substantial, sustained demand. A dedicated supply allows the pressure requirement, compressor selection and distribution route to be considered together.
The starting question is practical: what pressure does the process require at its air connection while production is running? That value, the simultaneous airflow and the losses along the proposed route establish the duty to evaluate. They are more useful than copying the setting of an existing compressor that also serves unrelated machinery elsewhere in the plant.
In this oil-injected screw package, the air is compressed through a single stage. Lubricant supports sealing, cooling and lubrication during compression, after which the air-and-oil mixture passes through separation. The selected low-pressure airend is therefore part of a complete compression and fluid-management arrangement.
Low pressure does not mean that the process can accept any air condition. The compressor type, required moisture condition and permissible contamination at the user remain separate selection questions. Establish those requirements together with the pressure duty. Where a process specifies oil-free compression itself, review a suitable oil-free product instead of treating a low-pressure oil-injected machine as an equivalent.
Evaluate this series for industrial processes whose documented pressure and flow needs fit the selected SZ-PML duty. The enquiry should identify how air enters the process, whether demand is continuous or event-driven, and which equipment operates simultaneously. That operating description is a better foundation than an industry label alone.
For an existing line, identify whether a local regulator, treatment unit or long branch separates the process from the present supply. Record pressure during the operating state that matters to production. A new low-pressure package should be selected around the demand that actually reaches the process, including the intended distribution arrangement and any essential treatment.
The SEIZE AIR low-pressure catalogue describes an airend designed for low-pressure, high-flow service, with the rotor profile, internal clearances and related design choices considered for that duty. This is the technical reason to compare a purpose-selected package with a conventional-pressure system serving the process through pressure reduction.
The comparison should still use complete operating proposals. Establish the same delivered flow, process pressure, intake basis and equipment scope for each option. Then review package input and operation over the real demand pattern. That approach turns an attractive design principle into a useful purchasing comparison without assuming that every factory has the same potential result.
The following selection uses the variable-speed technical data in the English SEIZE AIR low-pressure catalogue, PDF page 5, printed pages 7–8. The values are published FAD ranges for the corresponding model and pressure row. They should be read as ranges belonging to those configurations, rather than as fixed airflow values at every operating condition.
The table covers six useful comparison points in the series. A dash marks a pressure entry that is not listed for the selected model in that source. It is a prompt for a confirmed technical proposal if your duty needs that combination. It is not a reason to estimate a value from another size or to extend an adjacent model's range.
| Model | Motor kW / Hp | FAD at 2 bar, m³/min | FAD at 2.5 bar, m³/min | FAD at 3 bar, m³/min | FAD at 3.5 bar, m³/min | FAD at 4 bar, m³/min |
|---|---|---|---|---|---|---|
| SZ-50PML | 37 / 50 | 3.4–14.0 | 3.1–12.2 | 3.5–11.5 | — | 2.5–10.1 |
| SZ-75PML | 55 / 75 | 5.2–21.0 | 4.8–19.3 | 4.4–17.6 | 4.4–17.0 | 4.0–16.0 |
| SZ-100PML | 75 / 100 | 7.1–28.0 | 6.3–25.3 | 5.8–23.1 | 5.8–22.5 | 5.2–21.0 |
| SZ-120PML | 90 / 120 | 8.6–36.5 | 8.6–34.8 | 7.9–32.0 | 7.5–29.0 | 7.0–25.6 |
| SZ-150PML | 110 / 150 | 11.6–47.2 | 9.8–38.8 | 9.2–36.8 | 8.6–34.8 | 7.9–31.0 |
| SZ-200PML | 150 / 200 | 14.0–56.5 | 12.5–55.0 | 12.5–50.0 | 11.8–47.5 | 9.8–40.2 |
The catalogue states free air delivery for the complete package in accordance with ISO 1217 Annex C. Its stated reference conditions are absolute inlet pressure of 1 bar and intake temperature of 20°C. Keep that basis attached to the flow comparison, particularly when another offer describes capacity using a different inlet or reference condition.
The motor rating is a separate field from package air delivery and electrical input. The kW values in the table identify the published motor ratings. For an energy comparison, obtain the relevant package-input information for the operating duties being compared, and keep the reference conditions and supplied equipment consistent across the proposals.
For SZ-75PML, the published motor rating is 55 kW / 75 Hp. Its FAD range is 5.2–21.0 m³/min at 2 bar, 4.8–19.3 m³/min at 2.5 bar, 4.4–17.6 m³/min at 3 bar, 4.4–17.0 m³/min at 3.5 bar and 4.0–16.0 m³/min at 4 bar.
That sequence shows why the pressure choice must accompany the model name. The maximum flow at the lower-pressure configuration should not be carried into a higher-pressure quotation. At the same time, the lower endpoint of an FAD range should not be read as a universal process requirement. It belongs to the published configuration and its operating range.
At 3 bar, SZ-50PML is listed at 3.5–11.5 m³/min with a 37 kW motor rating. SZ-75PML is listed at 4.4–17.6 m³/min with 55 kW, and SZ-100PML at 5.8–23.1 m³/min with 75 kW. Compare those entries against the production demand before deciding how much additional capacity is useful.
A larger maximum flow can help serve an identified increase in sustained demand, but it does not by itself establish the best match for long periods of reduced production. Consider the lower-demand operating states, other available supplies and the intended control role alongside the maximum requirement. The selected size should have a clear job throughout the production schedule.
Mechanical information belongs beside the flow table. The following table retains the catalogue's 3 bar entries, including the parenthesised dimensions as printed. The final offered arrangement should identify the selected configuration so that the installation drawing, connection schedule and handling information all describe the same package.
A cabinet envelope is only the beginning of the room plan. Cooling-air routes, access for service, piping interfaces and equipment handling require additional space. Use the dimensions to establish a shortlist, then coordinate the final arrangement with the surrounding equipment before the room layout is released for construction.
| Model at 3 bar | Outlet | L × W × H, mm | Weight, kg |
|---|---|---|---|
| SZ-50PML | DN80 | 2000 × 1400 × 1900 | 1900 |
| SZ-75PML | DN100 | 2300 (2300) × 1600 (1600) × 1850 (1850) | 2800 |
| SZ-100PML | DN125 | 2600 (2450) × 1750 (1750) × 2000 (2000) | 3000 |
| SZ-120PML | DN125 | 3150 (3050) × 1900 (1850) × 2100 (1950) | 4000 |
| SZ-150PML | DN125 | 3150 (3050) × 1900 (1850) × 2100 (1950) | 4100 |
| SZ-200PML | DN150 | 3550 (3450) × 2200 (2200) × 2350 (2300) | 6000 |
SZ-100PML is listed at 3 bar with a DN125 air outlet, dimensions of 2600 (2450) × 1750 (1750) × 2000 (2000) mm and weight of 3000 kg. At 4 bar, the same model's table entry changes to DN100, 2300 (2300) × 1600 (1600) × 1850 (1850) mm and 2600 kg.
Those changes affect more than the purchase description. They influence the proposed connection, handling plan and station layout. Keep the quoted pressure and the final mechanical schedule together, rather than selecting the footprint from one pressure row and the airflow from another. The configuration should remain traceable through the quotation and the approved drawing.
The Industrial PM VSD Low Pressure Single-Stage Screw Air Compressor uses a permanent-magnet main motor with variable-speed control. The low-pressure catalogue states a main-motor frequency range of 25–100%. That is a drive-frequency statement; the corresponding air-delivery range for selection is the FAD range shown in the model table.
A useful control discussion begins with the required pressure signal and the demand changes the machine must follow. Describe whether production changes gradually, switches between established recipes or introduces short demand events. This helps relate the package's variable-speed operation to a specific production pattern instead of assuming that the drive label alone resolves every pressure problem.
The catalogue describes separate variable-speed control of the cooling fan, with an airend discharge-temperature control target of 85°C. Its stated purpose is to support appropriate lubricant operating conditions. This target concerns airend discharge temperature; it should remain distinct from room temperature, process-air temperature and lubricant injection temperature.
Installation planning still has to provide a suitable cooling-air path. A separately controlled fan cannot create an effective room exhaust route when hot air is recirculating to the intake. Include the machine's location, surrounding heat sources and planned duct arrangement in the review so that control and installation support the same thermal task.
A controller can only respond to the information it receives. Establish where pressure is measured and how that point relates to the process being supplied. Treatment, valves and distribution piping between the measurement point and the user can affect the pressure that reaches production during flow.
For a dedicated process connection, draw the compressor, receiver, treatment equipment and user on a simple flow sketch. Mark the relevant pressure observation points. This gives the buyer and supplier a shared description of what the control system is intended to maintain, and helps separate supply-pressure behaviour from a restriction nearer the process.
If the new package joins an existing station, describe the other compressors and their intended operating roles. Identify whether this unit supplies a separate low-pressure header or shares a compatible network. The difference affects the connection arrangement, control sequence and isolation requirements.
Include required remote signals and operating permissions in the enquiry. Ask for the offered control functions to be identified in the technical proposal, including any external sequencing or communication scope. A visible display or inverter does not by itself define the complete integration arrangement. The objective is a machine whose response fits the intended station operation.
The open-package illustration shows the relationship between the compression assembly, motor, separation vessel and connecting circuits. It is useful for identifying why access must be preserved around more than one side of the installed machine. A compact-looking cabinet can still require a considered approach to inspection and component removal.
For the selected order, use the approved arrangement and service information to coordinate access. Check how the planned piping, cable routes and nearby equipment affect the work. Resolving that question on a drawing allows the plant to retain useful access without discovering during a service visit that a connection or adjacent structure blocks the required task.
The lubricant circuit supports the compression process, and the separation system recovers lubricant from the air-and-oil mixture. Downstream treatment addresses the delivered-air requirement of the process. These are connected parts of the air system, but they should not be treated as interchangeable functions.
Specify the required moisture and contamination condition at the point of use, together with the operating pressure and flow. Where treatment remains in an existing installation, include its identification and intended duty in the new package review. That allows pressure loss, capacity and the required delivered-air condition to be considered together.
The airend illustration highlights the component at the centre of the low-pressure design. Its application should remain linked to the selected pressure and FAD configuration. A purchasing comparison becomes less useful when an airend claim is separated from the complete package that drives, cools and controls it.
Ask for the relevant operating point and offered configuration to be stated together. The airend design, drive arrangement, separation system and cooling scope should describe a coherent product proposal. This helps the technical reviewer compare complete packages and gives purchasing a clear account of what the factory is supplying for the process duty.
A low-pressure installation still needs a practical route for intake air and heat rejection. Consider the direction of discharged cooling air, nearby machinery and the possibility of warm air returning to the compressor inlet. A machine room's overall dimensions do not reveal whether its airflow path will work as intended.
Show proposed openings and duct routes alongside the compressor position. If the installation uses a dedicated duct, coordinate the arrangement with the offered package before fabrication. Keep the manufacturer's applicable requirements with that layout, so the contractor works from the selected machine's installation information rather than a generic room sketch.
Start at the process connection and work back through the proposed supply route. Identify the pressure required during production, the treatment equipment and the restrictions introduced by piping and valves. The compressor selection can then include the relevant system losses while keeping the process requirement visible.
This is especially helpful when replacing a branch from a general factory header. The existing compressor setting may reflect the needs of other users, not the pressure needed by the process being separated. A dedicated low-pressure proposal should therefore describe its own user requirement and distribution route, rather than inherit the whole station's historical setting.
A brief consumption event and a sustained increase in flow can both produce a pressure complaint. Record when the event begins, whether other users start simultaneously and how pressure recovers after it finishes. The duration and production context help establish whether the system needs storage, distribution changes, control review or additional sustained capacity.
Receiver selection belongs in that conversation. Stored air can influence the response to a temporary event, while the compressor must still support continuing demand over time. Review storage location and usable operating conditions alongside the selected package. Adding a vessel without understanding the event can leave the underlying process requirement unresolved.
Where a plant retains a higher-pressure utility system alongside the new low-pressure supply, clearly identify the connection boundaries. The layout should show which equipment belongs to each network, where isolation is provided and how any planned alternate supply is managed under the applicable engineering design.
This prevents an ambiguous operating arrangement from entering the installation scope. A service technician should be able to understand the intended supply path from the drawings and equipment identification. Purchasing should also know whether interconnection hardware, controls and associated installation work are included in the compressor offer or remain within the plant contractor's responsibility.
A plant may need production to continue while one compressor is unavailable for planned maintenance. Define which users must remain operating and the required pressure and flow for that condition. An existing reserve source is useful only when its duty and connection arrangement are compatible with the process.
Keep the normal operating case and the reserve case distinct in the proposal. The main selected package should have a clear everyday role, while the alternative supply arrangement should identify the relevant isolation and changeover scope. This avoids treating extra motor capacity as a substitute for an organised continuity plan.
An interface schedule turns a product quotation into an installation plan. Identify the air connection, electrical supply, cooling arrangement, control interfaces and any receiver or treatment equipment included in the offer. Add the drawings and documents required by the buyer's engineering team.
For each item, record whether it is supplied with the compressor, provided by another equipment supplier or installed by the plant contractor. This gives all parties a common boundary before procurement is finalised. It is particularly useful when a dedicated process-air system is added to a running factory and several contractors share the work.
| Interface | Information to settle | Responsible scope to record |
|---|---|---|
| Process-air connection | Duty, outlet connection and distribution route | Compressor package / plant piping |
| Treatment and storage | Required air condition and installed equipment | Included units / retained equipment |
| Electrical supply | Destination voltage, frequency, phase and machine documents | Machine configuration / site electrical work |
| Cooling and access | Room airflow, duct arrangement and service access | Package requirements / installation design |
| Controls and reserve | Pressure signal, station role and changeover duty | Package controls / external integration |
The catalogue lists standard electrical supply as 380 V / 50 Hz / three-phase, with other voltages available. State the actual site supply in the enquiry and require the offered machine configuration to identify the agreed voltage, frequency and phase. The standard catalogue entry is not confirmation of a different destination configuration.
The installation team also needs the electrical documentation for the supplied package, including the relevant connection and protection requirements. The motor rating alone does not establish the complete installation design. Coordinate those requirements with the site's responsible electrical personnel and the applicable machine documents before equipment connection and commissioning.
Use the final mechanical schedule and approved handling information when planning delivery and placement. Check the route from unloading to the intended machine position, including doors, corners and any changes in floor level. The selected package's weight and configuration should be the same information used by the delivery and installation teams.
Within the room, preserve access to the operating interface and the relevant service areas. Coordinate the machine with receivers, treatment equipment, pipework and ducting on the same layout. This turns the cabinet dimensions into a practical installation plan and reduces the likelihood of alterations after equipment has arrived.
The commissioning procedure should follow the supplied machine's instructions and the authorised scope of work. In addition to confirming the delivered configuration and installed connections, establish which production state will be used to observe the intended air-supply duty. An idle process cannot demonstrate all of the behaviour expected during normal use.
Record relevant pressure observations together with the operating users and machine state. Include the treatment equipment in service and any shared-supply arrangement active at the time. This provides a useful baseline for later operation and makes it easier to understand whether a subsequent change belongs to production demand, distribution or the compressor installation.
When a process reports insufficient air, compare the pressure at the package, across relevant treatment and at the affected user during the same event. A station reading and a process reading taken at different production times can describe different demands rather than a pressure difference along one route.
The table below organises useful observations. It does not replace the supplied operating and safety instructions. Its purpose is to help the production team collect information that separates a local distribution problem from a supply or control question before components or settings are changed.
| Observation | Compare during the same event | Question to resolve |
|---|---|---|
| Process pressure falls while package pressure holds | Pressures across treatment and the affected distribution route | Where does pressure diverge under flow? |
| Package pressure changes with a new process duty | Simultaneous users, demand duration and machine state | Is demand sustained or a short event? |
| Cooling-related indication follows a room alteration | Displayed event, intake path and heat rejection route | Has recirculation or obstruction changed? |
| Unexpected response when another supply operates | Station sequence, connected pressure networks and control signal | Does actual operation match the agreed supply boundary? |
Provide the machine identification, displayed event and operating condition when requesting technical assistance. Add maintenance history and any recent changes to production, treatment, piping or the machine room. Photographs should show the relevant equipment or connection clearly enough for another person to understand the arrangement.
This makes the service discussion more specific than a general statement that pressure or temperature is unstable. Use the applicable machine documentation for maintenance tasks and consumables, and coordinate planned isolation with the plant's operating requirements. A clear record helps the service team relate the observed event to the correct part of the system.
Related SEIZE AIR low-pressure product video: SLVC-55A permanent-magnet variable-speed package.
SEIZE AIR is the brand of Seize Compressor (Shanghai) Co., Ltd., founded in 2009 and based in Shanghai. As a compressor manufacturer in China, the company brings product development, manufacturing, marketing and service into its offering. The value of that background becomes practical when the quotation connects the selected model with a defined process-air duty.
For this series, the useful technical discussion includes the low-pressure airend, pressure-specific FAD ranges, main-drive control and cooling-fan control. Ask for these to be reflected in the offered configuration and supporting documents. That gives engineering a product to assess and purchasing a consistent description of the package being ordered.
The Industrial PM VSD Low Pressure Single-Stage Screw Air Compressor should be compared with alternatives at the same process pressure, reference airflow basis and production pattern. Include downstream treatment, distribution interfaces and the relevant utilities. A comparison based only on maximum air delivery or motor power can conceal a different duty or supplied scope.
Where energy performance is part of the decision, request the relevant package-input information for the operating points being considered. Keep periods of lower production, standby arrangements and control roles visible. A plant-specific comparison can then explain the likely operating consequences of each proposal using consistent inputs, rather than a general percentage claim.
The selected model, pressure configuration, electrical supply and supplied equipment should remain consistent across the approved proposal, arrangement information and order documents. Include any inspection records or project-specific acceptance requirements in the discussion before the order is finalised.
The catalogue's ISO 1217 Annex C reference establishes the stated basis for its FAD data. The acceptance arrangement for an individual purchase should identify the applicable procedure, documentation and agreed scope. This lets the buyer relate the delivered machine to the order without relying on a photograph, a broad company statement or a motor nameplate alone.
Ask each supplier to identify included equipment, optional items and installation interfaces in the same format. Receiver and treatment scope, electrical configuration, control integration, documents and delivery arrangements should be clear enough for purchasing to compare without reconstructing the engineering intent.
For a new dedicated supply, include the required process duty and a simple layout with the quotation request. For a replacement, add the existing network arrangement and the reason the present supply is being reviewed. That context helps the factory propose a relevant configuration and reduces the risk that offers describe technically different systems under similar product names.
No. The published 25–100% figure is the main-motor frequency range stated in the catalogue. The airflow data for selection are the FAD ranges in the corresponding model and pressure rows. Use those fields for their intended purposes rather than converting one directly into the other.
For example, the selected SZ-75PML row at 3 bar lists 4.4–17.6 m³/min. That published range belongs to the model configuration. Discuss the actual production pattern and required control behaviour with the supplier when deciding how the machine will operate within the proposed air system.
Evaluate it for the users whose requirements fit the selected low-pressure duty. Identify all equipment presently connected to the proposed branch before separating it. A process-air conversion should not accidentally remove the pressure capability needed by another connected machine.
The review should cover the normal production state, temporary simultaneous demands and the required reserve arrangement. If some users continue to require a different pressure, define how those users remain supplied. The objective is a coherent pressure network, with the low-pressure package serving an identified task rather than becoming an automatic replacement for every factory air duty.
The catalogue presents mechanical entries linked to particular pressure configurations, with different outlets, dimensions and weights in some rows. Retain those associations during selection. A family name alone is not enough to finalise the connection schedule or handling plan.
Send the required duty with the enquiry and ask for the configuration-specific arrangement information. The final offered drawing should resolve which package is being supplied, including the relevant dimensions and interfaces. This is more useful for the installation team than choosing a convenient footprint from a different row of the same model table.
Send the pressure required at the process, airflow demand with its reference basis, production schedule, required air quality and destination electrical supply. Include the proposed installation location, any existing receiver or treatment equipment, and the intended relationship with other air supplies. Identify any reserve-duty, inspection or documentation requirements.
With those inputs, SEIZE AIR can discuss an Industrial PM VSD Low Pressure Single-Stage Screw Air Compressor proposal around the complete process-air task. Your engineering team can review the pressure-specific model selection and interfaces, while purchasing compares an order scope that reflects how the machine will actually be installed and used.
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