PULP FACTORY PIPING SYSTEM STAYS SAFE IN EARTHQUAKE WITH ALGOR'S PIPEPLUS SOFTWARE

Algor's PipePlus software helps engineers design piping systems that are earthquake-resistant. Shown here is a shaded representation of a portion of the piping system found at the pulp mill in Venezuela.

When the earth shakes, miles of piping systems in factories, mills and power generation stations must shake with it or the piping will rupture, releasing gallons of potentially noxious liquids and fumes.

Piping systems perform many functions, including taking hot liquids away from power plant cores, bringing chemical soups to processing tanks and reactors and moving steam to power industrial processes.

Holding Strong During Seismic Activity

How do you tell if the piping system will withstand a violent earthquake? Neill & Gunter Limited, a Canadian engineering firm, designed an intricate piping system for a Venezuelan pulp mill using Algor's PipePlus software to demonstrate that the piping system would be earthquake-resistant.

"Using PipePlus, we put a computerized version of the design under the seismic forces required by the U.S. Nuclear Regulatory Guide to study how the system would respond to the kind of earthquakes that sometimes hit the San Felipe, Venezuela area, which has many of the same seismic characteristics as California," said Patrick LaPointe, a project engineer working on the pulp mill project for Neill & Gunter. "The results from Algor helped us make the piping and pipe support system in the factory's recovery boiler building more immune to seismic disturbances," said LaPointe.

In a typical pulp mill, the process of making pulp from wood includes a number of stages: chip preparation, mixing chips with cooking liquor that dissolves the lignin (resin that holds wood together), separation of the wood fibers from the cooking liquid and lignin and evaporation.

In this particular plant owned by Smurfit Carton de Venezuela, the company was installing a new recovery boiler, which reduces the pulp mill's emissions while saving on raw materials and providing an inexpensive source of energy.

The liquids are pumped in and out of the recovery boiler at about 220 degrees Fahrenheit in stainless steel pipes. The steam line from the recovery area is made of carbon steel piping and has an internal temperature of 850 degrees Fahrenheit at a pressure of 650 pounds per square inch.

The challenge for engineers was to design the piping system for the recovery boiler to high standards of earthquake-readiness. Some form of computer modeling and analysis is typically conducted when designing any steam-piping system.

Analysis

The pulp mill in San Felipe is located in what is called a seismic zone 4 region, a region very prone to earthquakes. Seismic analysis of the various piping systems must therefore also be performed. All of the critical piping components such as the main steam pipe, boiler feed-water, natural gas pipeline and soot blower steam piping had to receive both seismic and conventional analysis.

"We clicked on the LOAD menu and PipePlus software gave us a table to input all our data to describe a typical earthquake. The NRC regulation booklet provides guidelines for typical earthquakes, so the analysis process was extremely quick," said LaPointe.

Other piping systems in the mill were analyzed to determine the forces and moments (which are twisting or turning forces) acting on tank nozzle connections and other equipment connections. PipePlus calculated the forces and moments at all support locations and connections, which were then compared to manufacturer's allowable forces. On a few occasions the piping was rerouted to relieve a force or moment that might be too strong in an earthquake.

Results

One of the most interesting situations was uncovered at the tank nozzles. On tanks and pipes that run hot, like in a pulp mill, the piping at a nozzle connection places substantial forces and moments on the tank wall where it is attached, particularly if the pipes are more stiff than the tank. After analysis with Algor's PipePlus, if the force or moment exceeded the manufacturer's limit, the pipes were rerouted to reduce their stiffness at the point of juncture with the tank.

Engineers also used Algor PipePlus to expedite the time-consuming process of analyzing different scenarios for placing snubbers and pipe guides, which cause pipes to move in unison with the building in the case of an earthquake, thus reducing the chance of a failure. A snubber is a huge cylinder, similar to a shock absorber, which is connected to the building structure and then attached to the pipe with a clamp.

Algor software is capable of performing a number of analyses to test the design of piping systems, such as these portions from the Smurfit pulp mill in Venezuela. Shown here are the stresses and deflections that result from loading.

"With PipePlus, we had a menu of literally every imaginable pipe support, including anchors, guides, line-stops, one-way supports, supports with gaps, rod hangers, spring hangers and consistent support hangers. This vast menu of pipe supports made designing a pipe support system very fast and easy," said LaPointe.

Neill and Gunter has been using Algor's PipePlus for more than six years to analyze piping systems and size system supports. Besides the Smurfit pulp mill in Venezuela, Neill & Gunter has analyzed piping systems in breweries, composition board plants, oil refineries and coal, oil and nuclear power generating stations using Algor's PipePlus.

"The software we had previously used was no longer available, so we tried Algor's PipePlus. Algor was faster and easier to use. The amazing thing is, Algor's PipePlus was also less expensive than our former software package," said LaPointe.