Tolley's Industrial and Commercial Gas Installation Practice

John Hazlehurst

• Publisher: Routledge
• Year: 2010
• ISBN:
  9781136434129
• Edition: 5
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

This is the third of three essential reference volumes for those concerned with the installation and servicing of domestic and industrial gas equipment. This volume explains the basic principles underlying the practical and theoretical aspects of installing and servicing gas appliances and associated equipment, from the basics of combustion, to burners, pressure and flow, transfer of heat, controls, as well as materials and processes, electrical aspects, and metering and measuring devices. Covering both Natural Gas and Liquefied Petroleum Gas, the many illustrations and worked examples included throughout the text will help the reader to understand the principles under discussion. Volume 3 of the Gas Service Technology Series will enable the reader to put into practice the safe installation and servicing procedures described in the companion volumes: Basic Science and Practice of Gas Service (Volume 1), and Domestic Gas Installation Practice (Volume 2). Combining a comprehensive reference with practical application in real-world engineering contexts, Volume 3 provides an essential handbook for all aspects of fundamental gas servicing technology, ideal for both students new to the field as well as professionals and non-operational professionals (e.g. specifiers, managers, supervisors) as an ongoing source of reference.

Chapter | one

Large Installations

Chapter 1 is based on an original draft by E. Glennon and updatd by Route OneLtd (2005)

INTRODUCTION

Large diameter pipework in non-domestic premises should be installed to comply with the requirements of the Gas Safety (Installation and Use) Regulations 1998 and the Guidance Notes on the Installation of Gas Pipework, Boosters and Compressors in Customers’ Premises, Institute of Gas Engineers document IGE/UP/2 Edition 2 (2008).

They deal with the materials and methods for installing pipework downstream from the meter control to the burners on the equipment. They apply to pipes of 35 mm or larger diameter for pressures exceeding 5 bar.

Work on large installations poses a number of problems. Some of these are also associated with pipework less than 35 mm in domestic and commercial premises and have been dealt with in Vol. 2 and reference to BS 6891 revised edition 2005.

Pipe sizing is generally carried out as described in Vol. 1 although gas flow calculators are available and offer a convenient method of calculating gas flows, velocities and pressure drops.

Velocities can be critical, particularly in unfiltered supplies where dust or debris at high velocities can cause erosion or damage to valves or controls. Generally on supplies filtered to 250 μm a maximum velocity of 40 m/s is permissible.

Pipes are usually of steel (which includes corrugated stainless steel tubing), copper, ductile iron or polyethylene (PE). In high rise buildings steel pipe is recommended for all vertical risers above 15 m.

The term ‘tightness testing’ is now used in European standards, this replaces the term ‘soundness testing’ but has an identical meaning.

IGE/UP/1 Edition 2 deals with all aspects of strength^* and tightness testing and direct purging of selected 1st, 2nd and 3rd family gasses within its wide scope and at a maximum operating pressure (MOP) not exceeding 16 bar.

IGE/UP/1A Edition 2 deals with the specific case of strength and tightness testing and direct purging of installations of volume not exceeding 1 m³ and operating pressure (OP) of not exceeding 40 mbar and a diameter not exceeding 150 mm on industrial and commercial premises and using natural gas (NG) within its scope.

IGE/UP/1B deals with tightness testing and purging of domestic-sized natural gas installations.

LPGA-TM 62 deals with the tightness of domestic-sized liquefied petroleum gas (LPG) pipework (volume not exceeding 0.02 m³). For greater volume IGE/UP/1 Edition 2 applies.

The selection of testing and purging standards

New terminology for gas pressures has been introduced to reflect those used in European standards:

STP = strength test pressure

MIP = maximum incidental pressure

OP = operating pressure

MOP = maximum operating pressure

SP= set point of the regulator

PIPEWORK LAYOUTS

The route selected for the pipework should be as short as possible without being too obtrusive. The design should allow for possible future extensions.

The installation should include valves as necessary to provide:

• section isolation

• purging

• use in emergency.

For commercial or industrial premises having two or more floors to which gas is supplied by a service pipe larger than 50 mm diameter, valves must be fitted to enable each floor to be isolated. Where a single floor is divided into self-contained areas, the pipework to each area must also be valved.

In addition, line diagrams showing all installation pipework not less than 25 mm is a statutory requirement in certain premises where the gas service is 50 mm or more and should be provided to enable isolating valves to be quickly located in case of emergency. One copy of the diagram must be fitted as near as possible to each primary meter. Other copies may be placed at the gate-house and the services engineers’ office as appropriate. The diagram must be updated whenever alterations are made to the installation.

An example of a supply diagram is shown in Fig. 1.1. It shows sufficient detail to identify the isolating valves but need not include every final connection. A key should always be provided. Diagrams are usually A4 size and protected by glass or plastic. The provision of the diagram is the responsibility of the installer and the occupier, in the case of a factory.

Figure 1.1 Gas supply line diagram.

PIPEWORK BURIED UNDERGROUND

Supplies running from one building to another may be buried or carried in ducts. A typical case is where the meter house is isolated from the main building. Where installation pipework is buried it should generally conform to the recommendations for service pipes (Vol. 2, Chapter 4) and reference should be made to relevant publications and standards. These include the Institution of Gas Engineers publication IGE/TD/3, ‘Distribution Mains’ and IGE/TD/4, ‘Gas Services’.

All pipes must be adequately protected against corrosion. Up to 50 mm, pipes are obtainable with factory-applied wrapping or sheathing. Joints or exposed sections of pipe must be covered, after testing for soundness, usually with self-adhesive PVC tape or a bandage impregnated with a petroleum grease. Larger, uncoated pipes must be wrapped after being laid. On some sites cathodic protection may be necessary or the excavation may be filled with a passive material, chalk or sand.

Exposed pipework may be painted rather than wrapped unless situated in a very corrosive atmosphere.

The route for underground pipework must be selected with the following points in mind:

• it must avoid close proximity to unstable structures

• it must be kept clear of walls which retain materials above the level of the ground in which the pipes will be laid

• pipes must not pass under load-bearing walls, foundations or footings

• in the proximity of any structure known to have unventilated voids

• areas where there may have been a recent infill, where this is impossible, welded steel or PE pipe should be used

• pipes should be laid at minimum distances from buildings as shown in Table 1.1 until a direction change is required to enter that building.

Table 1.1 Underground Pipework – Minimum Distance from Buildings

The amount of cover above the pipe for existing installations must be at least that given in Table 1.2. In special circumstances this may be reduced if the back fill is suitably reinforced.

Table 1.2 Depth of Cover on Buried Installation Pipes for Existing Installations

IGE/UP/2 Edition 2 (2008), which is applicable to new installations, states that the information on the depth of cover required for buried pipework has now been expanded depending on the maximum operating pressure and diameter of pipework. For example, for pipework up to 63 mm diameter with an MOP of up to 75 mbar, located under a path or footway, the cover should be a minimum of 375 mm. For diameters in excess of 63 mm or MOP in excess of 75 mbar the cover would be increased to 600 mm.

Where valves are fitted underground they should be provided with access to spindles and lubrication points. Valve pits should have covers of adequate strength or surface boxes to BS 5834. The position of the valve should be indicated by a marker plate, Fig. 1.2. This plate is also used to show the position of syphons or purge points.

Figure 1.2 Marker plate to show valves, syphons or purge points.

Although syphons or dip pipes are not necessary on natural gas supplies, they may be fitted to pipework which will be hydraulically tested to provide a means of removing the water.

PIPEWORK ABOVE GROUND

Pipes entering buildings should pass through the wall or floor in sleeves sealed at one...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Contents
• Preface
• Chapter One. Large Installations
• Chapter Two: Industrial and Commercial Gas Meters
• Chapter Three: Industrial Processes and Plant
• Chapter Four: Industrial Gas Burner Systems and their Control
• Chapter Five: Flame Protection Systems
• Chapter Six: Commercial Catering
• Chapter Seven: Incinerators
• Chapter Eight: Steam Boilers
• Chapter Nine: Overhead Heating
• Chapter Ten: Combined Heat and Power
• Chapter Eleven: Air Conditioning
• Chapter Twelve: Large-Scale Heating and Hot Water Systems
• Chapter Thirteen: Natural Gas and the Environment
• Appendix 1
• Appendix 2
• Index