How does a restrictive network waste energy?
A machine on the shop floor may need 6 bar (87 psig) while it is consuming air, but receive that pressure only when the compressor room runs at 7.5 bar (108.8 psig). The difference is made up of treatment losses, friction in mains and branches, local losses at fittings, hoses and quick couplings, and a margin for changing demand. Some of that difference is unavoidable. The opportunity is the avoidable part, supported by measurements.
A restriction can cause several problems at once:
- Poor tool or machine performance at the end of the line.
- Operators raising the station pressure to compensate, which costs about 7% more compressor power for each extra bar.
- Higher leakage and unregulated consumption across the whole plant because of the higher pressure.
- Extra compressors starting during demand peaks because pressure collapses locally.
These effects belong to different parts of the energy balance. Measure them separately where practical and combine them without counting the same saving twice.
If a bottleneck is removed but the station pressure stays the same, users simply receive higher pressure. Unregulated users, such as blow-off nozzles and open-ended cleaning hoses, then consume more air, and leaks flow faster. Electricity use can stay the same or even rise. Every distribution project therefore needs two parts: a physical change and an operating change that lowers the generating pressure or reduces running compressors.
Start from the critical user
Identify the user that sets the station pressure. It is usually the one with the highest required pressure, the longest route or the largest intermittent demand. Ask the machine builder or process owner for the minimum dynamic pressure at the machine inlet while it is consuming air, not the static pressure when it is idle.
Then trace the route from the compressor to that user, listing every component: dryer, filters, main header, drops, isolating valves, filter-regulator-lubricator sets, hoses and couplings. Our working pressure and pressure budget page sets out how to build this route budget.
Build a synchronised measurement plan
Pressure loss depends on flow, so readings taken at different times cannot be compared. Use logging gauges with synchronised clocks at a few seconds’ resolution.
- Log pressure at the compressor discharge, after treatment, at the start of the main header, at the end of the main header and at the critical user inlet.
- Log flow at the station outlet, or power on each compressor if no flow meter is fitted.
- Cover peak demand, normal running and a low-demand period.
- Note events: shift changes, large machines starting, blowing or cleaning operations.
- Calculate the pressure drop between each pair of points at peak flow.
Our pressure profiling and pressure-drop audit pages describe the equipment and method.
Reading the pressure pattern
The shape of the pressure traces points to the cause and the right fix.
| Pattern | Likely cause | Typical fix |
|---|---|---|
| Steady large drop across one segment at all flows | Undersized pipe, partly closed valve, blocked strainer | Open or replace the valve; resize the segment |
| Drop rises sharply only at peak flow | Segment near its capacity limit | Local storage, loop main or larger branch |
| Large drop only at the last metre before the user | Small hose, coupling or regulator | Larger hose and full-bore coupling; correct regulator |
| Header pressure falls when one machine starts | Large intermittent demand | Dedicated receiver near the user; check supply pipe |
| Header steady but users complain | Point-of-use restriction or user’s own regulator | Inspect drop, FRL and hose at the user |
| Pressure at the far end lower in afternoons | Demand shift or hot, humid air affecting treatment | Review demand profile and treatment condition |
Worked example: a recoverable pressure margin
A plant runs its compressors at 7.5 bar (108.8 psig). Logging at peak flow shows 0.4 bar lost across treatment, 0.5 bar along a long undersized branch, and 0.4 bar across a 10 mm hose and two quick couplings at the critical machine, which needs 6.0 bar (87 psig) dynamic. A further 0.2 bar is control margin.
- Replacing the branch with a correctly sized pipe brings its loss to about 0.1 bar.
- A larger hose and full-bore couplings bring the local loss to about 0.1 bar.
- Total recoverable pressure: about 0.7 bar.
If the compressor setting is lowered by 0.6 bar, keeping a little extra margin, the saving is roughly 0.6 × 7% ≈ 4% of compressor power. On 110 kW of compressors loaded for 5,000 hours, that is about 22,000 kWh a year, plus some reduction in leakage and unregulated demand. The actual figure must be confirmed by logged power before and after.
Pipe sizing and pressure-loss calculations
Pressure drop in a pipe depends on flow, internal diameter, length, the number and type of fittings, and the pressure in the pipe. Flow must be converted to actual conditions at line pressure, because the same free air delivery occupies far less volume at 7 bar than at atmospheric pressure.
Standard empirical formulas and manufacturer charts give a good estimate for straight pipe, with fittings expressed as an equivalent length. They have limits: they assume clean, round pipe; old galvanised pipe that has corroded internally can be much worse; and they do not capture dynamic effects from short, large demand pulses. Use calculations to screen options, then confirm with measurement. A common design target is a total drop from compressor to the furthest user of around 0.1 bar in the main distribution, with the treatment and point-of-use losses budgeted separately. See our distribution and piping engineering page for layouts, materials and slopes.
Choose the smallest justified intervention
Large re-piping is rarely the first answer. Work through the options in order of cost and disruption:
- Open partly closed valves, remove redundant strainers and unused branches.
- Replace undersized hoses, quick couplings and regulators at the critical users.
- Repair leaks on the routes that serve the critical users.
- Add a receiver near a large intermittent user.
- Close a main into a loop or add a cross-connection to share flow.
- Replace a specific undersized segment.
- Separate a genuine high-pressure user onto its own supply or booster, so the rest of the plant can run lower.
Turning better delivery into lower station energy
After the physical changes, reduce the compressor settings in small steps, typically 0.1–0.2 bar at a time, while monitoring pressure at the critical user and production quality. Hold each step for at least a full production cycle. Adjust sequencer bands so that all machines move together and the trim machine still controls. Record the final settings and lock them where the controller allows, so they are not raised again without a reason.
If a compressor can now be switched to standby, or a smaller machine can carry the night load, the saving can be larger than the pressure reduction alone. See system pressure optimisation and unload and idle loss reduction.
Verify savings with comparable periods
Compare logged compressor energy before and after over periods with similar production, shift pattern and ambient conditions. Normalise to production output or to delivered air where a flow meter exists, and report specific power in kW per m³/min. Avoid comparing a monsoon week with a summer week, or a shutdown week with full production. Our audit reporting and verification method sets out the comparison.
Installation and keeping the gain
- Isolate, depressurise and lock off sections before any pipe work; follow your plant’s permit system.
- Use pipe materials and fittings rated for the pressure and temperature, and support them correctly.
- Flush new sections before reconnecting users, so debris does not reach filters or machines.
- Pressure-test and leak-check new joints before returning to service.
- Add the new pressure readings to routine checks and repeat leak surveys regularly.
How Reddy Compressors helps
Reddy Compressors has been in the compressed-air business since 2002, from our office in Tarnaka, Secunderabad. We work on ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other brands as an independent multi-brand specialist, not an authorised dealer. We have tie-ups with all major and reputed brands. With more than 20 service engineers and technicians, we:
- Log pressure at several points with power or flow at the compressor station.
- Identify the critical users and the restrictions on their routes.
- Recommend the smallest set of changes that recovers the most pressure.
- Adjust compressor and sequencer settings and verify the result.
- Supply receivers, compressors, dryers and filters, new, used or on rental, where the network change needs them.
Service teams cover the whole of Telangana and Andhra Pradesh; equipment and spares are supplied across India.
What to send us
- A layout sketch of the compressor room, main header and branches, with approximate pipe sizes and lengths.
- Compressor make, model, rating and pressure settings.
- The critical users, their required dynamic pressure and where complaints occur.
- Any pressure or power logging you already have.
- Shift pattern and planned shutdown dates for any installation work.
Frequently asked questions
How much pressure drop is acceptable in a compressed air pipeline?
A widely used design target is a total pressure drop of around 0.1 bar in the main distribution from the compressor room to the furthest user, with dryers, filters and point-of-use components budgeted separately. Many existing plants lose much more. The useful question is how much of the total loss between the compressor and the critical user is avoidable, which only logging at peak flow can show.
Why is pressure low at the end of my compressed air line?
The usual causes are an undersized or corroded branch, a partly closed valve, a long run without a loop, small hoses and quick couplings at the user, or a large intermittent machine nearby. Leaks along the route add flow and therefore pressure drop. Log pressure at several points during peak demand to find which segment causes most of the loss before deciding on a fix.
Does a bigger air pipe save electricity?
A larger pipe reduces pressure drop, but it saves electricity only if the compressor setting is then lowered or fewer compressors run. If the setting stays the same, users receive higher pressure and unregulated users may consume more air. Combine the pipe change with a planned, step-by-step reduction of the station pressure and verify the saving with logged power.
Is a ring main better than a straight compressed air line?
A ring or loop main lets air reach each user from two directions, which roughly halves the flow in each path and reduces pressure drop. It also helps when demand moves around the plant. It is usually a good choice for large production areas. A straight line can work well for smaller plants if it is correctly sized for peak flow with some allowance for future demand.
How do quick couplings and hoses affect compressor energy?
Small hoses and restrictive couplings can cause a large share of the pressure loss at the user, especially on high-flow tools. Operators then raise the station pressure to compensate, which costs about 7% more compressor power for each extra bar. Correctly sized hoses and full-bore couplings are often the cheapest way to recover pressure.
How do I prove a distribution improvement saved energy?
Log compressor power, and flow where possible, for a representative period before the change and again afterwards under similar production and ambient conditions. Normalise to production or delivered air, and report specific power. Record the compressor settings before and after. The saving is credible only if the settings were actually reduced and the critical users still receive their required pressure.
Related pages
Field guide
Distribution losses: Pressure lost between compressor and user
If the compressor runs at one pressure and the furthest user receives much less, the difference is being paid for at the compressor. Pipework that is too small, too long or badly laid out is a permanent energy cost.
Causes
- Main pipes undersized for today’s demand after years of expansion.
- Long dead-end runs instead of a ring main.
- Restrictive fittings, quick couplings and hoses at the point of use.
- Corroded steel pipe reducing the bore.
- Undersized drops and filter-regulators at machines.
Improvements
- Measure pressure at the compressor, after treatment, along the main and at key users.
- Fix the biggest drop first; often a single undersized section or fitting.
- Close the loop into a ring main where users are spread out.
- Upsize drops and point-of-use equipment where needed.
- Then lower generation pressure to collect the saving.
The pipe sizing calculator helps check whether a pipe is adequate for its flow and length.
What to send for a quotation
- Compressor make, model and rated power of each machine.
- Electricity tariff and annual running hours.
- Typical pressure at the compressor and at the furthest user.
- Any measurements you already have (power, flow, loaded hours).
Send it through find my part or the spare parts enquiry, or call +91 99590 60718 or +91 92468 88812.
Calculators and worked examples
These tools give indicative figures for screening, comparison and for preparing an enquiry. They run in your browser and send nothing. No prices or tariffs are assumed: enter your own to see costs. Efficiencies and other figures shown are example values: replace them with your own. Results are not a performance guarantee or a design certificate; final selection is confirmed by a service engineer against the machine data sheet and the site.
Pressure budget and the cost of excess pressure
Add up the pressure that is lost between the compressor and the point of use, and see what a lower set-point would be worth.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Pressure needed at the point of use (bar g): 6
- Dryer and filter loss (bar): 0.5
- Piping loss (bar): 0.3
- Hose, fittings and regulator loss (bar): 0.3
- Control band and safety margin (bar): 0.3
- Current compressor set-point (bar g): 8
- Compressor input power (kW): 75
- Saving per bar reduced (%): 7
- Running hours per year: 6000
Result
- Total pressure losses: 1.1 bar
- Control band and safety margin: 0.3 bar
- Compressor pressure needed: 7.4 bar g (point of use + losses + band and margin)
- Possible reduction from current set-point: 0.6 bar
- Indicative energy saving: 18,900 kWh per year
- Indicative cost saving: Enter your electricity tariff (cost per kWh) above
Method. Required compressor pressure = point-of-use pressure + sum of losses. Savings = power × (reduction in bar) × saving per bar. A saving of roughly 6–8% of compressor power per bar of pressure is commonly quoted; it is indicative and varies with machine type and control, so edit it to suit.
What to take from it. The saving is real only if the farthest and most demanding point still works at the lower set-point. Prove it before you change the setting.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.
Pipe pressure drop and sizing
Check the pressure drop and air velocity in a compressed-air line, or find the smallest bore that keeps the drop within a target.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Flow (m³/min free air): 12
- Inlet pressure (bar g): 7
- Pipe length (m): 150
- Inside diameter (mm): 80
- Roughness (mm): 0.046
- Fittings allowance (% extra length): 30
- Air temperature (°C): 30
- Target pressure drop (bar): 0.1
Result
- Pressure drop: 0.059 bar (0.839% of the inlet gauge pressure)
- Air velocity: 5.22 m/s
- Reynolds number: 2,06,066
- Smallest bore for the target drop: 73 mm inside diameter
- Velocity check: Within the common rule-of-thumb range for mains (roughly up to 15–20 m/s)
Method. Darcy–Weisbach: ΔP = f × (L/D) × ρv²/2, with the friction factor f from the Swamee–Jain relation and air density taken at mean line pressure. Fittings are allowed for as extra equivalent length. Typical commercial steel roughness is about 0.046 mm.
What to take from it. Pressure drop varies roughly with the fifth power of the bore at constant flow, so a larger main is a cheap way to hold pressure.