Steam Systems Design Pipes And Valves Pdf

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Heat transfer systems in almost any form — hot water, high temperature oil and steam — require careful design and operation because of the temperatures and pressures involved. Generally speaking, steam systems are at their safest when condensate is efficiently removed. Proper steam system design, installation, operation and maintenance significantly decrease the potential for destructive events, such as those caused by water hammer.

In many cases steam systems were designed long before there was any concern about energy efficiency. Systems are often modified over the years; equipment, pipes and valves are moved so that they no longer perform in the way they were originally intended. All of these factors and more are reasons to expect that steam piping systems could be improved when the objective is better function and energy efficiency.

Steam Systems Design- Pipes and Valves

In many cases steam systems were designed long before there was any concern about energy efficiency. Systems are often modified over the years; equipment, pipes and valves are moved so that they no longer perform in the way they were originally intended. All of these factors and more are reasons to expect that steam piping systems could be improved when the objective is better function and energy efficiency. Problems with steam systems are not always obvious as equipment may continue to function, although impaired.

Some problems lead to premature failure of equipment, but it may not be obvious what the cause of the failure was. If a facility has not had a thorough review of its steam distribution system by a competent expert, then there are likely many things that an audit would reveal.

The following examples are common problems discovered in the course of steam system audits by Duane Hagen of Merlo Steam see links below. These are real facilities that in many cases were in improper operation for a number of years prior to the audit. Steam Trap Installed Wrong. It is clear from the picture that this trap has been here a long time. What is not so obvious to the untrained eye, is that this trap is installed wrong. It must be installed so that the bolted-on flat plate is in a vertical position.

When it is horizontal as in this installation, the float is not a float but a pendulum See the sectional illustration to the right. When steam traps are improperly installed, they cannot function properly and therefore either do not remove the condensate, let steam blow through, or both. Other Components Installed Wrong.

It is common to find many types of steam system components installed incorrectly. In this example, a mechanical check valve that requires gravity to operate properly is installed upside down. It is impossible for this check valve to function when installed this way. However, it is probably a good thing that it is upside down, as it is also installed backwards. If it were installed upright, it would block flow in the wrong direction. Failed Valves. This valve is obviously stuck partly open.

However, often valves are installed with pipe on the down-stream side. High and Low Pressure Systems Interconnected. In facilities with high and low steam operating pressure systems, all steam and condensate lines should be properly identified and checked. Be sure that high and low pressure systems are not interconnected at any location, even on condensate systems. High pressure condensate can flash to steam in low pressure condensate systems causing problems with their operation and wasting steam.

Supply Lines and Condensate. Long steam supply lines should be trapped to remove condensate and keep the steam dry. In the photo to the right, there is a steam trap off the steam main, and condensate is returned to the to the top of the condensate pipe.

Because condensate is on the bottom of the pipe, this trap is doing nothing to help keep the line dry. Worse, not only is it not removing condensate, it is actually wasting energy. Steam comes off the top of the Steam Main, comes down to the trap along the vertical pipe in the left of the photo, as it is cooled by heat loss from the pipe. Note the nice insulation job however; this is probably keeping the problem from being much worse.

Condensate should always be drained from the BOTTOM of the steam line in low sections of pipe and at changes in direction, such as a 90 Degree turn. Condensate from steam traps should always be returned to the TOP of condensate lines; the maximum height of rise above the steam trap to the condensate line is a function of steam pressure and the type of trap.

A general rule of thumb is that 1 psi of steam will raise water about 2 feet. For example, a 5 psi system should not have condensate lines higher than 10 feet above the steam trap. Not only must steam traps be piped off the bottom of the steam lines, the pipe must be properly sized. If the condensate drip legs are too small, the condensate will simply blow past the drain line. Condensate drip legs should be sized according to the line they are draining. See the Chart for suggested sizes. Control Systems.

In order for steam system controls to function properly, they must be installed properly. In the photo to the right, a green-headed PRV Pressure Reducing Valve has been installed to reduce the higher pressure steam from the main steam header, to a lower pressure for use in a low pressure application — such as space heating.

This type of PRV requires a down-stream sensor line to monitor the pressure and supply a check pressure back to the PRV. The problem is that the control line is installed vertically higher than the PRV, resulting in the line going downhill back to the PRV. When this happens, the PRV cannot accurately control the low pressure and premature failure of the PRV will likely result as it constantly chatters attempting to control the pressure. The correct way to install a PRV is shown in the above diagram.

There must be a minimum distance between the PRV and sensing point, and the control line must slope down to the pipe — NOT the PRV, so that condensate will drain back to the steam line where it will be removed by a steam trap.

Therefore, do not be alarmed if the PRV has no sensing line; but if it has a line, be sure that it is installed correctly. Water Hammer. Water hammer is the result of condensate not being removed from long runs of steam lines. Steam moving through a line at high speeds picks up condensate in the bottom of the pipes, much like wind blowing across a lake forms waves.

Water Hammer can destroy controls, insulation, pipe, break fittings, and cause a lot of undesirable noise. Note that the insulation is gapping from the pipe — evidence that the pipe has been moving against the insulation, compressing it.

The grey patches show an attempt to repair the insulation. There probably needs to be a steam trap installed on this line, or if there is a steam trap, it may not be working correctly. On the other side of this wall there is a long run of steam pipe; it then makes 2 sharp 90 Degree bends. The second bend, the lower one in the photo, would be a good spot for steam trap to drain condensate from the line. Leaking Equipment. Leaking steam coils, especially in equipment less than 30 years old, can be an indicator of improper seasonal shut-down, steam trap problems, or water hammer damage.

A closer inspection of this unit heater revealed that there was no way for the condensate to be drained out at the end of the heating season. Stagnate condensate can form a mild carbonic acid when CO2 comes in contact with water. This accelerates corrosion faster than water alone. Steam systems should be piped to allow gravity drain-down when not in use, or should be blown out with compressed air at the end of each heating season.

Source: Thanks to Duane Hagen of Merlo Steam for providing these photos and an explanation of what the problem is and the best way to fix it. Duane and Merlo Steam conduct customized in-house training on steam system operation and perform steam distribution system audits. Telephone: FREE. Other Components Installed Wrong It is common to find many types of steam system components installed incorrectly. Failed Valves This valve is obviously stuck partly open.

High and Low Pressure Systems Interconnected In facilities with high and low steam operating pressure systems, all steam and condensate lines should be properly identified and checked. Supply Lines and Condensate Long steam supply lines should be trapped to remove condensate and keep the steam dry. Properly Size Steam Trap Drip Leg Lines Not only must steam traps be piped off the bottom of the steam lines, the pipe must be properly sized.

Water Hammer Water hammer is the result of condensate not being removed from long runs of steam lines. Leaking Equipment Leaking steam coils, especially in equipment less than 30 years old, can be an indicator of improper seasonal shut-down, steam trap problems, or water hammer damage.

No. 56 – Safety Items for Steam

Not only is water hammer a system issue, but it is also a safety issue. Understanding the nature and severity of water hammer in a steam and condensate system will allow plants to avoid safety risks and destructive forces. A better understanding of steam system water hammer will help the plant implement the necessary changes in steam system design, startup, maintenance, operation, and installation to eliminate water hammer. Additionally, this will help provide maximum safety for plant personnel, reduce maintenance costs, and reduce system downtime. Many mistakenly believe that water hammer is unavoidable and a natural part of steam and condensate systems, but this statement is entirely false. If the system is properly designed and correctly operated, water hammer in any form will not occur.

All Rights Reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Spirax Sarco, Inc. Blythewood, SC Phone: Fax: www. Spirax Sarco is the recognized industry standard for knowledge and products and for over 85 years has been committed to servicing the steam users world- wide. The existing and potential applications for steam, water and air are virtually unlimited. Beginning with steam generation, through distribution and utilization and ultimately returning condensate to the boiler, Spirax Sarco has the solutions to optimize steam sys- tem performance and increase productivity to save valuable time and money.

Back to Learn about steam. An efficient steam distribution system is essential if steam of the right quality and pressure is to be supplied, in the right quantity, to the steam using equipment. This tutorial looks at a typical circuit. This Module will look at methods of carrying steam from a central source to the point of use. The central source might be a boiler house or the discharge from a co-generation plant. The boilers may burn primary fuel, or be waste heat boilers using exhaust gases from high temperature processes, engines or even incinerators.


Steam Systems Design- Pipes and Valves - Free ebook download as PDF File .​pdf), Text File .txt) or read book online for free. steam systems design- pipes.


Water hammer in steam systems: cause and effect

Log In. Most steam generated today is used to produce electrical power, but this application is outside the scope of this manual. TM58 focuses on the use of steam at lower pressures and temperatures for a variety of uses in a building services environment. Steam systems are no longer installed just to heat buildings.

Log In. Most steam generated today is used to produce electrical power, but this application is outside the scope of this manual. TM58 focuses on the use of steam at lower pressures and temperatures for a variety of uses in a building services environment. Steam systems are no longer installed just to heat buildings.

You will develop an understanding of the basic concepts of steam systems including terminology, properties of a system, analysis and design. After completing the course, you will develop an understanding of:. This is an excellent course for anyone who needs information on design and analysis of steam systems. A basic knowledge of thermodynamics and psychrometrics, fundamentals of HVAC systems, and fundamentals of heating and cooling loads is assumed. The target audience is:.

Fundamentals of Steam System Design

Locations of Steam Leaks

In plants that have been constructed to consume as little energy as possible, it is rare to find steam leaking from pipes and valves. However, even in such plants, steam will start to leak after a few years as gaskets, fittings, and other areas age, unless these areas are regularly inspected and maintained. Without proper maintenance, the number of leaks and the volume of leaked steam will only increase. Leaks from valves and steam traps can be further divided into external leaks, such as those from gland packing, and internal leaks, where steam escapes through the seat and into the outlet. When pipes contract due to a drop in the temperature of the steam, the nuts and bolts of the fitting can loosen, causing a gap to open up between the two pipes from which steam will escape. If plant workers find a steam leak, they should do more than simply tighten the screws on the fitting or replace the gaskets. They should also investigate the cause of the leak and consider changing the number and location of fixed pipe supports or adding expansion joints.

Condensate that is discharged from steam traps is handled in one of two ways. It is either drained out of the system to sewer, which can result in wasted heat energy and water, or it flows into piping to be transported elsewhere, ideally for recovery. The design sizing of such piping requires significant specialization because condensate recovery piping collecting from steam traps must be designed for two-phase flow. The design should not be based on calculations for piping that transports only water because these are not valid for two-phase flow.

The role of steam distribution lines is to reliably supply steam of the highest reasonable quality to the steam-using equipment. In order for this to be achieved, condensate must be removed quickly and efficiently through steam traps installed in proper condensate discharge location CDL installations. Steam traps can't, however, simply be installed any which way and forgotten.

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Condensate Recovery Piping

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