Jun. 23, 2025
Construction
All pipes will be installed at ambient temperature. Pipes carrying hot fluids such as water or steam operate at higher temperatures.
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It follows that they expand, especially in length, with an increase from ambient to working temperatures. This will create stress upon certain areas within the distribution system, such as pipe joints, which, in the extreme, could fracture. The amount of the expansion is readily calculated using Equation 10.4.1, or read from an appropriate chart such as Figure 10.4.1.
Alternatively, the chart in Figure 10.4.1 can be used for finding the approximate expansion of a variety of steel pipe lengths - see Example 10.4.2 for explanation of use.
Example 10.4.2
Using Figure 10.4.1. Find the approximate expansion from 15°C, of 100 metres of carbon steel pipework used to distribute steam at 265°C.
Temperature difference is 265 - 15°C = 250°C.
Where the diagonal temperature difference line of 250°C cuts the horizontal pipe length line at 100 m, drop a vertical line down. For this example an approximate expansion of 330 mm is indicated.
Pipework flexibility
The pipework system must be sufficiently flexible to accommodate the movements of the components as they expand. In many cases the flexibility of the pipework system, due to the length of the pipe and number of bends and supports, means that no undue stresses are imposed. In other installations, however, it will be necessary to incorporate some means of achieving this required flexibility.
An example on a typical steam system is the discharge of condensate from a steam mains drain trap into the condensate return line that runs along the steam line (Figure 10.4.2). Here, the difference between the expansions of the two pipework systems must be taken into account. The steam main will be operating at a higher temperature than that of the condensate main, and the two connection points will move relative to each other during system warm-up.
The amount of movement to be taken up by the piping and any device incorporated in it can be reduced by ‘cold draw’. The total amount of expansion is first calculated for each section between fixed anchor points. The pipes are left short by half of this amount, and stretched cold by pulling up bolts at a flanged joint, so that at ambient temperature, the system is stressed in one direction.
When warmed through half of the total temperature rise, the piping is unstressed. At working temperature and having fully expanded, the piping is stressed in the opposite direction. The effect is that instead of being stressed from 0 F to +1 F units of force, the piping is stressed from -½ F to + ½ F units of force.
In practical terms, the pipework is assembled cold with a spacer piece, of length equal to half the expansion, between two flanges. When the pipework is fully installed and anchored at both ends, the spacer is removed and the joint pulled up tight (see Figure 10.4.3).
The remaining part of the expansion, if not accepted by the natural flexibility of the pipework will call for the use of an expansion fitting.
In practice, pipework expansion and support can be classified into three areas as shown in Figure 10.4.4.
Roller supports (Figure 10.4.5 and 10.4.6) are ideal methods for supporting pipes, at the same time allowing them to move in two directions. For steel pipework, the rollers should be manufactured from ferrous material. For copper pipework, they should be manufactured from non-ferrous material. It is good practice for pipework supported on rollers to be fitted with a pipe saddle bolted to a support bracket at not more than distances of 6 metres to keep the pipework in alignment during any expansion and contraction.
Where two pipes are to be supported one below the other, it is poor practice to carry the bottom pipe from the top pipe using a pipe clip. This will cause extra stress to be added to the top pipe whose thickness has been sized to take only the stress of its working pressure.
All pipe supports should be specifically designed to suit the outside diameter of the pipe concerned.
The expansion fitting (‘C’ Figure 10.4.4) is one method of accommodating expansion. These fittings are placed within a line, and are designed to accommodate the expansion, without the total length of the line changing. They are commonly called expansion bellows, due to the bellows construction of the expansion sleeve.
Other expansion fittings can be made from the pipework itself. This can be a cheaper way to solve the problem, but more space is needed to accommodate the pipe.
Full loop
This is simply one complete turn of the pipe and, on steam pipework, should preferably be fitted in a horizontal rather than a vertical position to prevent condensate accumulating on the upstream side.
The downstream side passes below the upstream side and great care must be taken that it is not fitted the wrong way round, as condensate can accumulate in the bottom. When full loops are to be fitted in a confined space, care must be taken to specify that wrong-handed loops are not supplied.
Further reading:If you want to learn more, please visit our website pipework support manufacturer.
The full loop does not produce a force in opposition to the expanding pipework as in some other types, but with steam pressure inside the loop, there is a slight tendency to unwind, which puts an additional stress on the flanges.
This design is used rarely today due to the space taken up by the pipework, and proprietary expansion bellows are now more readily available. However large steam users such as power stations or establishments with large outside distribution systems still tend to use full loop type expansion devices, as space is usually available and the cost is relatively low.
Horseshoe or lyre loop
When space is available this type is sometimes used. It is best fitted horizontally so that the loop and the main are on the same plane. Pressure does not tend to blow the ends of the loop apart, but there is a very slight straightening out effect. This is due to the design but causes no misalignment of the flanges.
If any of these arrangements are fitted with the loop vertically above the pipe then a drain point must be provided on the upstream side as depicted in Figure 10.4.8.
The expansion loop can be fabricated from lengths of straight pipes and elbows welded at the joints (Figure 10.4.9). An indication of the expansion of pipe that can be accommodated by these assemblies is shown in Figure 10.4.10.
It can be seen from Figure 10.4.9 that the depth of the loop should be twice the width, and the width is determined from Figure 10.4.10, knowing the total amount of expansion expected from the pipes either side of the loop.
Sliding joint
These are sometimes used because they take up little room, but it is essential that the pipeline is rigidly anchored and guided in strict accordance with the manufacturers’ instructions; otherwise steam pressure acting on the cross sectional area of the sleeve part of the joint tends to blow the joint apart in opposition to the forces produced by the expanding pipework (see Figure 10.4.11). Misalignment will cause the sliding sleeve to bend, while regular maintenance of the gland packing may also be needed.
The frequency of pipe supports will vary according to the bore of the pipe; the actual pipe material (i.e. steel or copper); and whether the pipe is horizontal or vertical.
Some practical points worthy of consideration are as follows:
Table 10.4.3 can be used as a guide when calculating the distance between pipe supports for steel and copper pipework.
Factories and other industrial facilities often need to move liquids and gases from one location to the next. This requires a complex system of pipes and valves to safely transport materials where they need to go, and plumbing piping is not the right material for the job. Process piping is the safest and most effective way to move fluids and gases through an industrial or manufacturing facility.
Though it looks similar to plumbing, process piping is a different system, built with materials designed specifically for the products they will transport. Wayne Brothers Companies offers process piping as part of our industrial contracting services.
Process plant piping is found in settings where mixing or separating materials is expected. This includes industries such as:
These are just some of the types of industries where materials must pass through piping to get correctly mixed, and process piping provides the right system for the job.
Process piping may look similar to regular plumbing, but it performs a very different function. Plumbing systems take water into a facility and remove sewage from the facility after the water has been used. It also can be used for natural gas in heating systems, but its primary job is moving water into and out of a facility.
Plumbing systems have to meet building codes and regulations to safely transport water and protect the facility from wastewater and sewage exposure. Pipes are often made from plastic or copper to withstand daily exposure to water without rust or corrosion.
On the other hand, process piping moves various chemicals, including liquids and gases, to support manufacturing and processing work. It is not required to follow building codes like plumbing. Instead, it must meet the requirements for the particular operation it is designed for. This includes corrosion and heat resistance based on the product being transported. Because of this, process piping systems can be made from a wide range of materials, not just copper or plastic. Stainless steel process piping is a common choice.
Instead of being overseen by building codes, process piping designs must follow OSHA standards to ensure the manufacturing facility can operate safely.
Many municipalities require permits and inspections, especially for facilities handling hazardous materials.
When building a new industrial facility, you need to plan the process piping as part of the overall design. Wayne Brothers Companies offers a comprehensive list of industrial construction services, including process piping contractors who understand this aspect of building an industrial facility.
Want more information on Insulated pipe supports? Feel free to contact us.
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