Piping Systems and Components

Piping Systems and Components

Chapter Introduction

This chapter covers all the essential knowledge about piping systems and their components, as required for the Red Seal exam. You must master not only component identification, but also design principles, thermal expansion calculations, support rules, and the requirements of applicable Canadian codes. This chapter is structured to follow the logical progression of a project: from material selection through to final testing.

Piping Classification According to CSA B51

The Canadian Electrical Code, Part I does not apply to piping. For pressure systems, the primary reference code is CSA B51 (Boiler, Pressure Vessel, and Pressure Piping Code). This code classifies piping into three categories based on risk level:

Essential Rule: The category determines the inspection, welding, and documentation requirements. For Category III, a piping register must be maintained and inspection by an accredited body is mandatory.

Piping Materials: Properties and Selection

Carbon Steel

Carbon steel (ASTM A53, A106) is the most common material for steam, hot water, and compressed air systems. Its maximum continuous service temperature is approximately 425 °C for A106 Grade B. Beyond this, creep becomes a limiting factor.

Stainless Steel

Austenitic stainless steels (304, 316) offer excellent corrosion resistance. Type 316 contains molybdenum (2-3%) which improves resistance to chlorides. Maximum temperature: approximately 800 °C for 304, but sensitization (carbide precipitation) between 425 °C and 870 °C can reduce corrosion resistance.

Copper and Copper Alloys

Copper (Type K, L, M) is used for potable water, heating, and refrigeration. The K, L, M designations correspond to wall thickness: K is the thickest, M is the thinnest. For steam, copper is limited to 103 kPa and 120 °C according to CSA B51.

CPVC and PVC

CPVC (chlorinated polyvinyl chloride) withstands up to 93 °C for hot water applications, while standard PVC is limited to 60 °C. These materials are not suitable for steam pressure systems.

Comparative Table of Thermal Expansion Coefficients

Thermal Expansion Calculation:

ΔL = α × L × ΔT

Where:

Example: A 30 m carbon steel pipe undergoes a temperature change of 80 °C.

ΔL = 12.1 × 10⁻⁶ × 30 × 80 = 0.029 m = 29 mm

This expansion must be absorbed by expansion joints, expansion loops, or the natural configuration of the piping route.

Piping Components

Flanges and Bolted Fittings

Flanges are classified according to their pressure class (150, 300, 600, 900, 1500, 2500 lb) and their face type:

Bolting Rule: Bolts must be tightened in a cross pattern (star pattern) in successive passes. The final torque must be achieved in at least three passes. For Class 300 and higher flanges, progressive tightening is critical to avoid flange distortion.

Gaskets

Gasket selection depends on pressure, temperature, and fluid:

Valves: Types and Functions

Check Valve Installation Rule: The check valve must be installed so that the flow direction matches the arrow indicated on the body. For swing check valves, the pivot axis must be horizontal and the valve must open upward.

Safety and Relief Valves

The distinction is important:

Installation Requirements per CSA B51:

Pipe Supports

Support Spacing

Maximum support spacing depends on diameter, material, and temperature. For carbon steel with water:

These values are based on a maximum allowable deflection of 2.5 mm between supports. For high temperatures (> 200 °C), spacing must be reduced by 10 to 15%.

Support Types

Anchor Point Rule

Between two anchor points, thermal expansion must be absorbed by expansion joints or loops. The maximum distance between anchor points is determined by the absorption capacity of the expansion joints. A bellows expansion joint must never be used to correct misalignment — this causes premature failure.

Thermal Expansion: Loop Design

Expansion Loop

The length of the loop legs (L) can be estimated using the simplified formula:

L = 2 × √(D × ΔL)

Where:

Example: DN 100 piping (D = 114 mm), expansion of 40 mm.

L = 2 × √(114 × 40) = 2 × √4,560 = 2 × 67.5 = 135 mm

This formula provides an approximate value. For precise calculations, use the methods in ASME B31.1 or B31.3.

Bellows Expansion Joints

Metallic bellows expansion joints absorb axial, lateral, or angular expansion. Their service life is limited by the number of fatigue cycles. The practical rule is to limit movement to 50% of the joint's maximum capacity to extend its service life.

Welding and Joint Preparation

Welding Standards

Pressure piping welding must be performed in accordance with the requirements of CSA W47.1 (certification of welding companies) and CSA W59 (welding of steel structures) for general aspects. For pressure piping, the reference standard is ASME B31.1 (Power Piping) or B31.3 (Process Piping).

Weld Joint Preparation

Weld Inspection

Required Inspection Percentage: For Category III piping, radiographic inspection is generally required on 100% of welds. For Category II, sampling of 10 to 20% is typical.

Testing and Commissioning

Hydrostatic Testing

Hydrostatic testing is mandatory for all new or modified piping. The test pressure is calculated as follows:

P_test = 1.5 × P_design × (S_test / S_design)

Where:

Simplified Rule: For most applications, the test pressure is 1.5 times the design pressure, with a minimum of 150 kPa at the highest point of the system.

Test Duration: The pressure must be maintained for at least 10 minutes for Category I and II piping, and 30 minutes for Category III, after stabilization.

Pneumatic Testing

Pneumatic testing is more dangerous than hydrostatic testing. It is used only when hydrostatic testing is impossible (systems that cannot be filled with water). The pneumatic test pressure is 1.1 times the design pressure. Special precautions are required: safety perimeter, gradual pressurization, and no personnel in the area during pressure buildup.

Purging and Flushing

Before commissioning, the system must be purged to remove debris, welding slag, and foreign matter. The flushing velocity must be at least 1.5 m/s for water, and the duration must be sufficient for the water to appear visually clean.

Safety and Code Rules

CSA B149.1 (Natural Gas and Propane Code)

For gas piping, CSA B149.1 applies. Key points:

Slope and Drainage

Steam piping must have a slope of 1% (10 mm/m) in the direction of flow to allow condensate drainage. Gas piping must have a slope of 0.5% toward the purge point.

Piping Identification

According to CSA Z321 (piping identification), each pipe must be identified with a label indicating the fluid, pressure, and design temperature. Standardized background colors:

Common Pitfalls to Avoid

Summary

Self-Assessment Questions

This chapter covers the fundamental knowledge of the "Piping Systems and Components" competency block of the Steamfitter/Pipefitter qualification profile. For the exam, make sure you can apply these concepts to practical situations and recognize code violations in given scenarios.