Energy Efficient Steam Distribution

Discussion

Regular maintenance and good design of steam distribution systems can avoid steam losses and hence energy costs. This can save companies money. Multiplied across a region, it can help the region reduce it's greenhouse emissions.

Readings

Steam Distribution Systems

Steam Distribution Systems. Energy Smart - Energy Saving Manual

Steam is used in many industrial processes and is often a source of large amounts of wasted energy and money.

Industrial facilities can reduce steam energy consumption by 20% through simple improvements in their steam system.

Recommendations

Steam Leaks

Are there steam losses in your system?

Actively identifying and repairing steam leaks can achieve steam system efficiency improvements of 3-5%.

As well as wasting energy, leaks cause a drop in system pressure that can cause equipment to operate less efficiently by reducing the amount of heat that can be delivered to a process.

Fixing leaks may involve anything from simply tightening a connection to replacing faulty fittings.

Steam Trap Leaks

Steam traps allow the condensed steam to be removed from the steam distribution system.

It is common to find that steam distribution systems go without maintenance for three to five years.

Without adequate maintenance, 15-30 % of a plant’s steam traps are often inoperable.

Steam traps fail in the open position, which means steam passes through the condensate system and is wasted.

Energy efficiency gains of 10-15 % are common when steam traps are actively maintained, so establishing a regular maintenance program, including complete systematic inspection, testing and repairing of steam traps is imperative.

Finding Leaks

Steam leaks are easily identified visually and should be tagged when located.

Use an ultrasonic detector to locate leaks. They cost about $1300, but the cost of a detector will be repaid by the savings from fixing just one leak as an average steam leak costs around $3500 per year.

A monitoring system consisting of small control attachments to individual steam traps can be connected to a hand held computer or linked to an Energy Management System so the user can check the effectiveness of the steam traps themselves.

Calculating Costs of Steam Leaks

Steps to calculate how much steam leaks are costing:

Insulation

Can heat losses be reduced?

Insulation around pipes and valves dramatically reduces heat loss and makes the work environment much safer by reducing the likelihood of severe scalding. It can typically reduce energy losses by 90% and help ensure proper steam pressure at plant equipment. The higher the temperature of the boiler skin or pipes, the greater the radiant heat loss to the surroundings.

Often a sequence of plant upgrades leads to unnecessarily long lengths of steam pipe, which increases the heat loss.

Reducing pipe length makes good financial sense. Also, where a small steam load is located at the end of a long branch of steam pipe, it might be cost-effective to install a stand-alone piece of equipment, and to decommission that section of the steam system.

To measure the temperature of your pipes, use an infrared thermal sensor meter. They cost $600-$800 but this outlay can be repaid by the savings from insulating your system.

It is also advisable to consult a supplier of steam system monitoring equipment and they will often test your steam distribution system for free as part of a quote for work.

Any surface about 10ºC above ambient temperature should be insulated, including boiler surfaces, steam and condensate piping and fittings. Removable insulating jackets are available for valves, pressure-reducing valves, steam traps and other fittings.

Damaged, missing or wet insulation should be repaired or replaced regularly. It is important to consult an expert on steam system insulation because the thickness and type of insulation material varies according to pipe size and application.

The following example will give you an idea of the money that can be saved by insulating pipes. For example: If a 75mm bare pipe transported steam at a temperature of 150ºC above ambient temperature, 640 Watts of power would be lost per metre of pipe. By insulating this pipe, the loss could be reduced to 64 Watts, a 90% saving.

Steam Distribution

Energy Efficiency US - Industry Best Practices

The primary purpose of an effective steam distribution system is to link the output of the steam generation system to the steam end use equipment.

The distribution system should supply high-quality steam to the end use equipment at the required rate and pressure, and with the minimum heat loss.

Key components include steam distribution piping, valves, and flanges, distribution system insulation, steam traps, air vents, drip legs, and strainers.

Key Inputs and Outputs

Key inputs include steam conditions (pressure and quality) from the generation system.

Key outputs include steam distribution outlet mass flow and pressure, distribution outlet steam quality.

Opportunities for Improvements

Links

Energy Efficiency US - Industry Best Practices. Works with U.S. industry to implement energy management practices in industrial plants. Provides resources for corporate executives, plant managers, technical staff, and the general public.

2006.5.7