Pumps, Compressors, and Fluid Power Systems

Chapter Introduction

This chapter covers the fundamental principles, installation procedures, diagnostics, and maintenance of pumps, compressors, and hydraulic and pneumatic systems. For the Red Seal exam, you must master not only the theory but also flow calculations, power calculations, performance curves, and Canadian regulatory requirements. This chapter is structured to prepare you directly for the multiple-choice questions on the exam.

1. Fundamental Principles of Fluid Mechanics

1.1 Pressure, Flow, and Total Dynamic Head

Pressure is the force exerted per unit area. It is expressed in kilopascals (kPa), pounds per square inch (psi), or bar. The fundamental relationship is:

P = F / A

Where P = pressure (Pa), F = force (N), A = area (m²).

Flow rate (Q) is the volume of fluid displaced per unit of time. It is expressed in cubic meters per second (m³/s), litres per minute (L/min), or imperial gallons per minute (GPM imp.). The continuity formula is:

Q = A × V

Where A = cross-sectional area of the conduit (m²), V = fluid velocity (m/s).

Total Dynamic Head (TDH) is the total energy imparted to the fluid by the pump, expressed in metres of liquid column. It includes:

Static elevation head (difference in geometric level)

Pressure head (discharge pressure)

Friction head losses in piping and fittings

TDH Formula:

TDH = (P₂ − P₁) / (ρ × g) + (V₂² − V₁²) / (2 × g) + (Z₂ − Z₁)

Where P = pressure, ρ = fluid density (kg/m³), g = 9.81 m/s², V = velocity, Z = elevation.

> Exam Tip: For water, 1 kPa ≈ 0.102 m of water column. A pressure of 100 kPa is equivalent to approximately 10.2 metres of water head.

1.2 Bernoulli's Theorem and Head Losses

Bernoulli's theorem states that the total energy of an incompressible fluid in steady flow remains constant along a streamline (neglecting losses):

P₁ + ½ × ρ × V₁² + ρ × g × Z₁ = P₂ + ½ × ρ × V₂² + ρ × g × Z₂

Head losses (ΔP) are caused by friction against pipe walls and by fittings (elbows, valves, couplings). They are calculated using the Darcy-Weisbach equation:

ΔP = f × (L / D) × (ρ × V² / 2)

Where f = friction factor (dimensionless), L = pipe length (m), D = inside diameter (m).

Rule of thumb: The recommended flow velocity in discharge piping is 1.5 to 3 m/s for water. Above 3 m/s, head losses and erosion increase significantly.

2. Centrifugal Pumps

2.1 Operating Principle and Components

The centrifugal pump converts mechanical energy from the motor into kinetic energy (velocity) and then into pressure energy. Fluid enters through the impeller eye (suction), is accelerated by the impeller vanes, and then slowed down in the volute or diffuser, which converts velocity into pressure.

Main Components:

Impeller: rotating element that transfers energy to the fluid. Types: open, semi-open, closed.

Volute: spiral casing that collects the fluid and converts kinetic energy into pressure.

Diffuser: ring of stationary vanes that performs the same function as the volute.

Stuffing box or mechanical seal: provides sealing between the shaft and the pump casing.

Bearing: supports the shaft and impeller.

Wear ring: sacrificial part that protects the casing and impeller against erosion.

2.2 Performance Curves and Operating Point

The performance curve of a centrifugal pump shows the relationship between flow rate (Q) and total dynamic head (TDH), brake horsepower (BHP), efficiency (η), and required NPSH (NPSHr).

Important Characteristics:

The TDH-Q curve is generally downward-sloping: as flow increases, TDH decreases.

The operating point is the intersection of the pump curve with the system curve (circuit resistance).

Maximum efficiency typically occurs at the Best Efficiency Point (BEP).

Affinity Laws (Similarity Laws):

For the same pump, if the rotational speed changes (N₁ → N₂):

Q₂ = Q₁ × (N₂ / N₁)

H₂ = H₁ × (N₂ / N₁)²

P₂ = P₁ × (N₂ / N₁)³

> Exam Tip: If the speed increases by 10%, the flow increases by 10%, the TDH increases by 21% (1.1² = 1.21), and the power increases by 33% (1.1³ = 1.331). Power varies with the cube of speed — this is a classic question.

2.3 NPSH (Net Positive Suction Head)

Available NPSH (NPSHa) is the absolute pressure at the impeller eye, minus the vapour pressure of the liquid. It depends on the installation:

NPSHa = P_atm / (ρ × g) + Z_s − h_f − P_vap / (ρ × g)

Where:

P_atm = atmospheric pressure (Pa)

Z_s = positive or negative suction head (m) — negative if the pump is above the liquid level

h_f = head losses in the suction piping (m)

P_vap = vapour pressure of the liquid at the service temperature (Pa)

Required NPSH (NPSHr) is provided by the manufacturer. To avoid cavitation, you must have:

NPSHa > NPSHr (with a safety margin of at least 0.5 m)

Cavitation: formation of vapour bubbles in the pump that implode violently, causing impeller erosion, vibrations, and performance loss.

> Exam Trap: Cavitation occurs at the suction side, not the discharge side. Symptoms include a gravel-like noise, vibrations, a drop in flow, and impeller erosion.

2.4 Priming and Installation

A centrifugal pump cannot draw air. It must be primed: the pump casing and suction piping must be filled with liquid before starting.

Priming Methods:

Manual priming through a filling port

Vacuum pump or ejector

Foot valve with strainer

Flooded suction installation (liquid level is above the pump)

Installation Rules:

The suction piping must be as short and straight as possible.

The suction piping must slope upward toward the pump (no high points where air can accumulate).

A foot valve with strainer is required if the pump is above the liquid level.

The suction piping must have a diameter greater than or equal to the pump suction opening.

2.5 Parallel and Series Pumping

In parallel: Two identical pumps feed the same discharge header. The total flow is the sum of the individual flows at the same TDH. Used to increase flow or for redundancy.

In series: The discharge of one pump feeds the suction of the next. The total TDH is the sum of the individual TDHs at the same flow. Used to increase pressure (e.g., booster stations).

> Exam Tip: In parallel, the total flow is never double the flow of a single pump because of increased head losses in the common discharge piping. The system curve is steeper.

3. Positive Displacement Pumps

3.1 Piston and Plunger Pumps

Positive displacement pumps move a fixed volume of fluid each cycle. They provide a relatively constant flow regardless of discharge pressure (within the limits of mechanical strength).

Piston Pump: The piston moves within a cylinder, drawing fluid in on the return stroke and discharging it on the forward stroke. Equipped with suction and discharge check valves.

Theoretical Flow:

Q = A × L × N × n

Where A = piston area (m²), L = stroke length (m), N = rotational speed (rev/s), n = number of cylinders.

Plunger Pump: Similar to the piston pump, but the plunger is longer and passes through the packing. Used for very high pressures.

3.2 Gear Pumps

Gear pumps use two meshing gears to move fluid between the teeth and the casing. They are used for lubricating oils and viscous fluids.

Theoretical Flow:

Q = π × D × h × b × N

Where D = pitch diameter of the gear (m), h = tooth height (m), b = gear width (m), N = speed (rev/s).

Characteristics:

Pulsating flow (smoother with more teeth)

Typical service pressure: 1 to 20 MPa (10 to 200 bar)

Does not tolerate abrasive fluids

Must have minimal clearance between gears and casing

3.3 Lobe and Screw Pumps

Lobe Pump: Two "figure-8" shaped lobes rotate in opposite directions. Used for fluids containing suspended solids (slurries, food products). Smoother flow than gear pumps.

Screw Pump (e.g., Archimedes screw, progressive cavity): A screw rotates within an elastomer stator. Used for highly viscous fluids or fluids containing particles. Very regular flow, low pulsation.

3.4 Diaphragm Pumps

The diaphragm pump uses a flexible membrane that oscillates, creating suction and discharge. The fluid only contacts the diaphragm and the check valves.

Advantages:

Perfect sealing (no shaft packing)

Can run dry without damage

Ideal for corrosive, toxic, or abrasive fluids

Can be pneumatically driven (no electricity)

Disadvantages:

Significant flow pulsation

Limited pressure (typically < 1 MPa for elastomer diaphragms)

Diaphragm is subject to wear

4. Compressors

4.1 Classification and Principles

A compressor increases the pressure of a gas by reducing its volume or increasing its velocity. Types include:

Positive Displacement Compressors:

Reciprocating (piston)

Rotary screw

Rotary vane

Lobe (blowers)

Dynamic Compressors (Turbocompressors):

Centrifugal

Axial

Key Parameters:

Compression ratio: P₂ / P₁ (absolute pressure)

Volumetric flow rate: m³/min or L/s (at suction conditions)

Brake power: kW

Isothermal and adiabatic efficiency

4.2 Reciprocating Compressors

The reciprocating compressor operates on the same principle as a piston pump, but for gases. The cycle includes four phases: suction, compression, discharge, and expansion of residual gas.

Piston Displacement:

V = A × L × N

Where A = cylinder area (m²), L = stroke (m), N = speed (rev/s).

Volumetric Efficiency (η_v):

η_v = Actual volume drawn in / Piston displacement

Volumetric efficiency decreases with compression ratio due to clearance volume (dead space between the piston and cylinder head at top dead centre).

Multi-stage Compression: For high compression ratios (> 5:1), multiple stages with intercoolers are used. This reduces gas temperature and power consumption.

> Exam Tip: The discharge temperature of a reciprocating compressor is given by the ideal gas law: T₂ = T₁ × (P₂/P₁)^((γ−1)/γ) for adiabatic compression. For air, γ = 1.4.

4.3 Screw Compressors

The screw compressor uses two helical rotors (male and female) that rotate in opposite directions within a casing. Gas is trapped between the lobes and progressively compressed.

Advantages:

Continuous flow without pulsation

Low vibration

Long service life

Can operate continuously

Disadvantages:

Higher initial cost

Requires oil injection for lubrication and sealing (except "dry" versions)

Significant noise (requires sound enclosure)

4.4 Centrifugal Compressors

The centrifugal compressor operates like a centrifugal pump, but for gases. Gas is accelerated by the impeller and then slowed in the diffuser, converting velocity into pressure.

Characteristics:

High flow, moderate pressure

Continuous and steady flow

Sensitive to surge: an instability phenomenon that occurs when flow drops below a critical threshold, causing violent flow reversals

Surge Protection: A recycle (anti-surge) valve maintains a minimum flow by returning part of the gas to the suction side.

4.5 Safety and Regulations

Canadian Electrical Code, Part I (CE Code), Chapter V (C22.1-21): Requirements for electrical installations in classified areas (hazardous locations). Air compressors in areas where flammable gases are present must use motors and electrical components rated for the appropriate zone.

CSA B149.1 (Natural Gas and Propane Installation Code): Applies to natural gas and propane compressors. Rules 6.14 to 6.22 cover compressor installation, ventilation, leak detection, and safety devices.

General Safety Rules:

Safety relief valves must be installed on each compression stage and set to the maximum service pressure.

A high-pressure switch must shut down the compressor in the event of overpressure.

Compressed air piping must be identified by colour (typically blue or grey) according to CSA Z96 or plant conventions.

Compressed air receivers must be inspected periodically in accordance with provincial requirements and CSA B51 (Boiler, Pressure Vessel and Pressure Piping Code).

5. Hydraulic Systems

5.1 Basic Principles — Pascal's Law

Pascal's law states that pressure applied to an incompressible fluid in a closed container is transmitted fully and equally in all directions.

Application: If a force F₁ is applied to a piston of area A₁, the pressure P = F₁/A₁ is transmitted to a second piston of area A₂, producing a force F₂ = P × A₂ = F₁ × (A₂/A₁).

Mechanical Advantage: F₂ / F₁ = A₂ / A₁

> Exam Tip: A hydraulic cylinder with a 100 mm diameter piston and a pressure of 10 MPa (100 bar) produces a force of:

> F = P × A = 10,000,000 Pa × π × (0.05 m)² = 10,000,000 × 0.00785 = 78,540 N ≈ 78.5 kN

5.2 Hydraulic System Components

Hydraulic Pump: Typically a positive displacement pump (gear, vane, axial piston). It converts mechanical energy into hydraulic energy (flow × pressure).

Cylinders (linear actuators): Convert hydraulic energy into linear motion. Types: single-acting (one pressurized chamber), double-acting (two chambers).

Hydraulic Motors (rotary actuators): Convert hydraulic energy into rotary motion. Types: gear, vane, axial and radial piston.

Directional Control Valves: Direct fluid to the actuators. Designated by the number of ways and positions (e.g., 4/3 = 4 ways, 3 positions).

Pressure Control Valves:

Pressure relief valve: protects the system against overpressure

Pressure reducing valve: maintains a reduced pressure in a secondary circuit

Sequence valve: controls the order of operations

Flow Control Valves:

Throttle valve: reduces flow by creating a restriction

Flow regulator: maintains constant flow despite load variations

Accumulator: A hydraulic energy reservoir that stores fluid under pressure. Types: bladder, piston, diaphragm. Used to:

Compensate for leaks

Dampen shocks

Provide an energy reserve in case of pump failure

Maintain pressure during shutdowns

Filters: Protect components against contamination. Positioned in the return line, pressure line, or suction line. ISO 4406 classifies contamination by the number of particles per millilitre.

5.3 Hydraulic Calculations

Hydraulic Power:

P_hyd = Q × ΔP

Where P_hyd = power (W), Q = flow rate (m³/s), ΔP = pressure difference (Pa).

Practical Conversion: P_hyd (kW) = Q (L/min) × ΔP (bar) / 600

Example: A pump delivers 50 L/min at 150 bar.

P_hyd = 50 × 150 / 600 = 12.5 kW

Drive Motor Power:

P_motor = P_hyd / η_total

Where η_total = pump efficiency × motor efficiency (typically 0.85 × 0.90 = 0.765).

Cylinder Speed:

V = Q / A

Where V = piston speed (m/s), Q = flow rate (m³/s), A = effective piston area (m²).

Double-acting Cylinder Force:

Extension: F = P × A_piston

Retraction: F = P × (A_piston − A_rod)

5.4 Hydraulic System Maintenance and Diagnostics

Contamination: The primary cause of hydraulic system failure (80% of breakdowns). Sources: particles, water, air, heat.

Oil Analysis: Regular oil sampling allows detection of:

Metallic particles (abnormal wear)

Oil oxidation (excessive temperature)

Water presence (condensation or cooler leak)

Common Symptoms and Causes:

Symptom	Probable Cause
Knocking noise	Air in the system, cavitation at the suction
Excessive heating	Oil too viscous, excessive pressure, faulty cooler
Slow or erratic movement	Clogged filter, dirty throttle valve, worn pump
Pressure drop	Internal leak (cylinder, valve), relief valve set too low
Milky oil	Water contamination

Air Bleeding Procedure: Open bleeders at the high points of the circuit, operate the system at low pressure, then gradually increase.

6. Pneumatic Systems

6.1 Differences Between Hydraulics and Pneumatics

Characteristic	Hydraulics	Pneumatics
Fluid	Oil (incompressible)	Air (compressible)
Typical pressure	5 to 35 MPa (50 to 350 bar)	0.4 to 1 MPa (4 to 10 bar)
Force	High	Low to moderate
Speed	Moderate	High
Positioning accuracy	Excellent	Low
Cost	High	Low
Leak risk	Pollution	Safe (air)
Energy storage	Accumulator	Air receiver

6.2 Pneumatic System Components

Compressor: Typically a reciprocating or screw compressor.

Air Dryer: Removes moisture from compressed air. Types: refrigerated, desiccant, membrane.

Filter, Regulator, Lubricator (FRL): The typical air preparation unit:

Filter: removes particles and condensed water (manual or automatic drain)

Regulator: maintains constant downstream pressure

Lubricator: adds a fine oil mist to the air to lubricate components

Directional Valves: Control pneumatic cylinders. Designated by the number of ways and positions (e.g., 5/2 = 5 ways, 2 positions).

Pneumatic Cylinders: Single-acting (spring return) or double-acting.

Exhaust: Exhaust air must be piped away or silenced to reduce noise.

6.3 Compressed Air Preparation

Air quality is essential. Compressed air contains:

Water vapour (condensation in piping)

Particles (dust, rust)

Oil (if the compressor is lubricated)

Dew Point: The temperature at which water vapour begins to condense. For outdoor applications in Canadian climates, the dew point must be below the minimum ambient temperature to prevent freezing in the piping.

Air Quality Classes (ISO 8573-1): Defines limits for particles, water, and oil. Example: Class 1-4-1 = particles ≤ 0.1 µm, dew point ≤ −20 °C, oil ≤ 0.01 mg/m³.

6.4 Pneumatic Calculations

Cylinder Air Consumption:

Q = A × L × N × (P_atm + P_gauge) / P_atm

Where Q = free air flow (m³/s), A = piston area (m²), L = stroke (m), N = number of cycles per second, P_atm = atmospheric pressure (101.3 kPa), P_gauge = gauge pressure (kPa).

Pneumatic Cylinder Force:

F = P × A × η

Where η = efficiency (typically 0.85 to 0.90 to account for seal friction).

> Exam Tip: The force of a pneumatic cylinder is calculated using gauge pressure, not absolute pressure. Atmospheric pressure cancels out on both sides of the piston.

7. Canadian Codes, Standards, and Regulations

7.1 Canadian Electrical Code, Part I (CE Code), Chapter V (C22.1-21)

This code classifies hazardous locations where explosive atmospheres may be present. Pumps and compressors installed in these areas must use electric motors and components certified for the appropriate class and division.

Classes and Divisions:

Class I: Flammable gases and vapours

Class II: Combustible dusts

Class III: Fibres and flyings

Division 1: Normal or frequent presence

Division 2: Abnormal or accidental presence

Zones (alternative system): Zone 0, 1, 2 for gases (equivalent to divisions).

7.2 CSA B51 — Boiler, Pressure Vessel and Pressure Piping Code

This standard covers the design, fabrication, and inspection of pressure vessels, including compressed air receivers and hydraulic accumulators. Requirements include:

Certified safety relief valves

Nameplates with maximum allowable working pressure

Periodic inspections by an authorized inspector

7.3 CSA B149.1 — Natural Gas and Propane Installation Code

Applies to natural gas compressors used in compression stations. Key rules:

Rule 6.14: Compressor location (ventilation, distance from ignition sources)

Rule 6.18: Safety devices (relief valves, pressure switches, gas detectors)

Rule 6.22: Grounding and bonding

7.4 CSA Piping Standards

CSA B137: Plastic piping (PVC, CPVC, PE, PEX) — used for water and fluid piping.

CSA Z662: Oil and gas pipeline systems — applies to pipelines and associated pumping facilities.

8. Installation, Alignment, and Commissioning Procedures

8.1 Pump and Motor Alignment

Proper alignment of the pump shaft with the motor shaft is essential to avoid vibrations, premature bearing wear, and seal failure.

Alignment Methods:

Straight edge: approximate method, accuracy ± 0.1 mm

Dial indicators: conventional method, accuracy ± 0.05 mm

Laser alignment: modern method, accuracy ± 0.01 mm

Typical Tolerances (parallel and angular alignment):

Rotational Speed	Parallel (mm)	Angular (mm/100 mm)
< 1500 rpm	0.10	0.05
1500 – 3000 rpm	0.05	0.03
> 3000 rpm	0.03	0.02

Procedure:

281.Verify that the foundations are solid and level.

282.Mount the pump and motor on their bases.

283.Align the parallel offset first (vertical and horizontal misalignment).

284.Then align the angularity (shaft inclination).

285.Tighten the bolts and re-check the alignment (tightening can shift components).

286.Check the end play and radial clearance of the couplings.

8.2 Couplings

Couplings transmit torque between the motor shaft and the pump shaft while compensating for minor alignment imperfections.

Common Types:

Rigid: no compensation, used for perfectly aligned shafts

Flexible (rubber, spider): compensates for minor misalignment and absorbs shocks

Gear: compensates for misalignment and transmits high torque

Disc: compensates for misalignment without backlash, used for high speeds

8.3 Centrifugal Pump Commissioning

Start-up Procedure:

296.Verify that the pump is primed (casing filled with liquid).

297.Open the suction valve fully.

298.Close the discharge valve (start with the discharge valve closed for centrifugal pumps).

299.Start the motor.

300.Gradually open the discharge valve until the desired flow is reached.

301.Check pressure, flow, vibrations, and bearing temperature.

302.Check for leaks at the seals.

Shutdown Procedure:

304.Close the discharge valve.

305.Stop the motor.

306.Close the suction valve (if necessary, to prevent backflow).

> Exam Trap: A centrifugal pump must start with the discharge valve closed to minimize starting torque. A positive displacement pump must start with the discharge valve open to avoid overpressure.

8.4 Compressor Commissioning

Procedure:

310.Check the compressor oil level.

311.Open the discharge valve (or the bypass valve).

312.Start the compressor.

313.Allow the compressor to reach rated speed.

314.Gradually close the bypass valve and open the discharge valve.

315.Check pressure, temperature, vibrations, and leaks.

316.Verify the operation of safety devices (relief valve, pressure switch).

9. Diagnostics and Troubleshooting

9.1 Centrifugal Pumps — Symptoms and Causes

Symptom	Possible Causes
No flow	Pump not primed, clogged impeller, reverse rotation, closed valve
Insufficient flow	Cavitation, partially clogged impeller, speed too low, impeller wear
Insufficient pressure	Impeller wear, speed too low, internal leak, discharge valve too far open
Excessive vibration	Misalignment, unbalanced impeller, cavitation, worn bearings, resonance
Abnormal noise	Cavitation, faulty bearing, impeller-volute contact
Bearing overheating	Poor alignment, insufficient lubrication, overload, excessive clearance
Seal leakage	Worn seal, scored shaft, incorrect gland pressure

9.2 Compressors — Symptoms and Causes

Symptom	Possible Causes
Discharge pressure too low	Internal leak, worn valves, bypass valve open, speed too low
Discharge pressure too high	Discharge valve closed, faulty relief valve
Excessive discharge temperature	Clogged cooler, compression ratio too high, insufficient lubrication
Excessive oil consumption	Worn rings, excessive piston clearance, oil level too high
Knocking noise	Excessive piston clearance, worn connecting rod, faulty valves
Compressor will not start	Electrical fault, stuck pressure switch, thermal protection tripped

9.3 Hydraulic Systems — Diagnostic Procedure

Systematic Approach:

325.Check symptoms: noise, heat, speed, pressure, leaks.

326.Visual inspection: oil level, external leaks, filters, hoses.

327.Check pressure: install a gauge at test points.

328.Check flow: use a flow meter or time the movement of a cylinder.

329.Analyze the oil: take a sample for contamination analysis.

330.Isolate the circuit: close valves to test components individually.

Internal Cylinder Leak Test: Apply pressure to one side of the cylinder, close the valve, and observe whether the piston moves. Movement indicates an internal leak past the seals.

10. Practical Calculations and Conversions

10.1 Essential Unit Conversions

Quantity	SI Unit	Imperial Unit	Conversion Factor
Pressure	1 kPa	0.145 psi	1 psi = 6.895 kPa
Pressure	1 bar	14.5 psi	1 bar = 100 kPa
Flow	1 L/min	0.22 GPM imp.	1 GPM imp. = 4.546 L/min
Flow	1 m³/h	3.67 GPM imp.	1 m³/h = 16.67 L/min
Power	1 kW	1.34 hp	1 hp = 0.746 kW
Temperature	°C	°F	°F = (°C × 9/5) + 32

10.2 Pump Power

Hydraulic Power:

P_hyd (kW) = Q (m³/s) × TDH (m) × ρ (kg/m³) × g / 1000

Brake Power (absorbed by the pump):

P_br = P_hyd / η_pump

Motor Power:

P_motor = P_br / η_motor

Example: A pump delivers 0.05 m³/s (3000 L/min) with a TDH of 40 m. ρ = 1000 kg/m³, η_pump = 0.75, η_motor = 0.90.

P_hyd = 0.05 × 40 × 1000 × 9.81 / 1000 = 19.62 kW

P_br = 19.62 / 0.75 = 26.16 kW

P_motor = 26.16 / 0.90 = 29.07 kW

10.3 Torque and Speed

Mechanical Power:

P (W) = T (N·m) × ω (rad/s)

Where ω = 2 × π × N / 60 (N in rpm).

Practical Conversion: P (kW) = T (N·m) × N (rpm) / 9550

Common Pitfalls to Avoid

354.Confusing NPSHa and NPSHr: NPSHa is calculated from the installation; NPSHr is provided by the manufacturer. Cavitation occurs if NPSHa < NPSHr.

355.Forgetting that power varies with the cube of speed: A 20% increase in speed increases power by 72.8% (1.2³ = 1.728). Always check motor power before increasing pump speed.

356.Starting a positive displacement pump with the discharge valve closed: This creates instantaneous overpressure that can damage the pump or piping. Positive displacement pumps must start with the discharge valve open or with a bypass.

357.Using absolute pressure instead of gauge pressure: In force calculations for pneumatic and hydraulic cylinders, use gauge pressure. In NPSH and gas compression calculations, use absolute pressure.

358.Ignoring compressor volumetric efficiency: Actual flow is always lower than theoretical flow due to clearance volume, leaks, and gas heating.

359.Neglecting to bleed air from hydraulic systems: Air in a hydraulic system causes erratic movement, noise, and can damage pumps through cavitation.

360.Confusing series and parallel pumping: In series, TDHs add (same flow). In parallel, flows add (same TDH).

361.Forgetting rotation direction: A centrifugal pump running in reverse delivers only about 30 to 50% of its rated flow and can overheat. Always check rotation direction before final coupling.

362.Not re-checking alignment after bolt tightening: Tightening foundation bolts can shift the pump or motor. Always re-check alignment after final tightening.

363.Using non-certified hydraulic hoses: Hoses must comply with SAE or ISO standards and have a working pressure rating higher than the maximum system pressure.

Summary

The essential points to remember for the Red Seal exam:

Centrifugal pumps: variable flow, limited TDH, start with discharge valve closed, require priming, sensitive to cavitation (NPSHa > NPSHr).

Positive displacement pumps: constant flow, high pressure, start with discharge valve open, do not require priming (they are self-priming).

Affinity laws: Q ∝ N, H ∝ N², P ∝ N³.

Compressors: compression ratio, volumetric efficiency, and discharge temperature are the key parameters. Multi-stage compression with intercooling reduces power.

Hydraulic systems: Pascal's law, hydraulic power P = Q × ΔP, contamination = primary cause of failures.

Pneumatic systems: limited pressure (4 to 10 bar), air must be filtered, dried, and lubricated.

Alignment: tighter tolerances at higher speeds; laser alignment offers the best accuracy.

Codes: CE Code Chapter V for hazardous locations, CSA B51 for pressure vessels, CSA B149.1 for natural gas.

Diagnostics: always proceed from simple to complex: visual, pressure, flow, then oil analysis.

Mastering these concepts, combined with practicing calculations and knowing Canadian standards, will prepare you effectively for the exam questions. Good luck with your preparation!

Pumps, Compressors, and Fluid Power Systems