Penn State ME 414W Group D Website

Compressed Air System Solutions Members: James Davis, Mallory Baker, Todd Searfass

Sponsor:  Roaring Spring Paper Products

Roaring Spring Paper Products has proposed the task of redesigning their current compressed air system to improve its efficiency. Currently, there are areas in the plant that experience mild to severe pressure drops, which causes some machines to shut down due to the lack of pressure needed to sustain operation. A more efficient piping system is a potential solution which will put less of a load on the compressors, resulting in reduced energy costs for the company. Roaring Spring Paper Products has projected a three year return on this system upgrade.

It is the Penn State Design Team’s goal to modernize Roaring Spring’s compressed air system to a more efficient model. After researching, the initial approaches to re-designing the system included changing the compressor set-up, identifying leakages, and changing the piping layout of the entire system. After careful consideration to Roaring Spring’s needs, the team decided that the best approach is to change the piping layout. Increasing pipe diameters, changing pipe material, and eliminating unnecessary bends will decrease major and minor head losses; thus generating a higher efficiency.

Due to a lack of data on the volumetric flow rate being used by the various machines in the plant, the lack of documentation of the current piping layout, and the manual operation of the compressors, it is not possible to do an accurate analysis of the current system. Therefore the design team created a resistor analysis and an excel program that contains inputs for all the variables in a compressed air system and outputs the major and minor head losses. Using the program to approximate losses in the current system made is possible to easily and quickly evaluate the effectiveness of the proposed changes for new systems.

After running the excel program that was created to analyze the old system, the team concluded that re-piping the factory with the new design would be the best approach to improve the system’s efficiency. The proposed new design increases the pipe diameter 1/2”, reduces total pipe length 18%, uses ten less 90° bends, and implements Aluminum Alloy 6063-T5 smooth pipes to promote laminar flow. These changes reduce the total head loss to 135ft (11.5% of the current system headloss). The new system experiences an increase of 13.1% efficiency, which correlates to an annual cost savings of $17,260. An initial investment of $50,000 to implement the new system can be compensated by a $51,780 three year turnaround.

A change must be made to the Roaring Spring’s current compressed air system layout to improve the efficiency for energy cost savings.

The design option with the greatest total value was chosen as the design approach focused on by the group.  Therefore, for the Roaring Springs project, the group will focus on improving the piping system, which in addition to reducing pressure head losses and increasing efficiency will inherently reduce leakage, and lower the load needed by the compressors.

                                                                    (Decision Matrix)

The first step in the design process was to determine the flow rates in various sections of the current layout. A “resistor network” was set-up using the assumptions listed below:

1)      All large, critical machines were assigned a head loss factor of 3 and all small, non-critical machines were assigned a head loss factor of 2.   2)      Major head loss is negligible

          (R/C Circuit Diagram)

The second step in analyzing the current system involved creating a program on Microsoft Excel that would determine the amount of pressure head loss in each section of the system.  The program designed by the team input data such as volumetric flow rate, inlet pressure, pipe diameter, pipe length, change in elevation, roughness, number of devices and air properties.  The program then automatically calculated important parameters like pipe area, velocity, Darcy friction factor, major and minor head loss, change in pressure, and final pressure.  The following assumptions were made based on the information obtained from Roaring Springs:

1)      All drop-down piping has 50 ft. length, 0.75 in diameter, ΔZ of 20 ft., one ball valve, three 90º bends, one branch tee, and one sudden contraction.

2)      All line-flows lengths were determined from the plant layout drawing with 1.5 in. diameter piping, one ball valve, two 90º bends, and one line tee.

3)      The air properties were as follows:

a.       Density = 1.127 kg/m_­­­³

b.      Viscosity = 0.0001697 Ns/m²

c.       Gravitational constant = 9.81 m/s²

4)      Steel pipe with roughness, ε = 0.00045 m

5)      Inlet Pressure of 110 psi

By reducing head loss as much as possible, while maintaining an efficient flow model, Compressed Air System Solutions created a new pipe design.

Current Design (in blue)

New Design (in red)

Currently the effectiveness of our new system has a 2.9 year turn around that satisfies the three year return stipulated by Roaring Spring. The new system design proposed by Compressed Air System Solutions increases the pipe diameter to 2”, reduces total pipe length 18%, and uses ten less 90° bends. These changes reduce the total head loss to 135ft (11.5% of the current system headloss). The new system experiences a maximum pressure drop of 3.83 psig with two compressors running and 2.76psig with three compressors running. These pressure drops corresponds to a 13.1% increase in system efficiency. The boost of efficiency correlates to an annual savings of $17,260 on electricity and lost labor. Compressed Air System Solutions recommends changing the pipe material to SmartPipe’s Aluminum Alloy 6063-T5 to promote smooth laminar air flow as well as easy manipulation of pipes and fittings. Using a cost estimator provided by Kaeser Compressors, implementing SmartPipe will cost $50,000 after material and labor; $5,000 less than using black steel. Roaring Spring can compensate this initial investment with a $51,780 three year savings. Below is a listing of advantages and disadvantages of the proposed solution.

For future recommendations, Compressed Air System Solutions advises Roaring Springs to:

1.      Implement a bi-monthly leakage detection policy.

2.      Include venturi flow meters in the system to measure flow rates in critical pipe sections.

3.      Monitor outlet pressures at large air-use machines with pressure sensors.

4.      Use orifices at the inlets of small air-use machines to guide flow towards large air-use machines.

5.      Maintain up-to-date blue prints of new system.