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  Experienced Manufacturer of Pipe Supports since 1978
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  Webinar Archives > Engineering & Design

Engineering and Design Webinar (September 2009)

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Text Version of the Engineering and Design Webinar

This presentation covers a variety of our featured products that we have made in the past. For those unfamiliar with us, we would like to share a brief background on our company. Piping Technology & Products, Inc., also known as PT&P, has been in business since 1975. PT&P and its wholly owned subsidiaries, US Bellows, Sweco Fab, Pipe Shields, and Anchor Darling, offer a wide range of engineered products and services for various industries and applications. Our product line is extensive, from spring supports, expansion joints, pre-insulated pipe supports, and miscellaneous fabrication to various engineering and technical services, PT&P has decades of experience providing products and services for all your engineering and construction needs.

We have achieved various certifications here at Piping Technology & Products. We have the ASME U-Stamp and R-Stamp for the SWECO division of our company. We are ASME NS certified in our Fronek Anchor/Darling, Enterprises division. We are also part of the Expansion Joint Manufacturers Association through our U.S. Bellows, Inc. division. Most recently we received the ISO 9001:2000 certification for the manufacture of hot and cold supports. We are a Minority Business Enterprise granted by the City of Houston, and additionally, we are a member of the Houston Minority Business Council.

Overall we have in excess of 700 employees on staff including not only engineering employees but sales, office administration, marketing, manufacturing and accounting employees. That includes 75 engineers and designers and 4 of them have Ph.D.s. Our facility is located in Houston, Texas with over 450,000 square feet of covered shop space on a 35 acre property located near the Port of Houston.

The emphasis for todays webinar will be on engineering and design aspects required to produce and provide pipe supports from their beginning conceptual stage tofinite element analysis their final stage of delivery. Our design team has a variety of tools available to them including 3D modeling technology, Caesar II pipe stress analysis software, STAAD II for structural analysis, mesh generation software, and finite element analysis software. We also perform field testing to simulate design conditions and confirm the acceptability or usability of the final design.

Our work process flow model includes all of our four subsidiaries. Our one centralized location sends work into detailing, then planning, to cut, then fabrication, painting and galvanizing, if necessary, then assembly, layout, and finally packing and shipping of the pipe supports or products as designed. Some more of the tools available to us for design are isometric drawings, empirical calculations, load & displacement tables generated during pipe stress analysis, hardware take-off sheets, in-house developed software, and AutoCAD drawings. Another tool that we utilize is a STAAD analysis program to design auxiliary steel which is basically, the length between the structural steel designed by our engineering department and the extra supplementary steel required to support the additional supports which are being utilized to support the piping system.

We utilize 3D modeling once a conceptual design has been developed to determine the suitability of the support. This helps check that the pipe support is clear of interferences of piping, other pipe supports and structural steel. This check is only visual due to limited access to the master model. We also use an electronic data interchange between our clients and ourselves in order to reduce transcription errors and ensure that quantities, tag numbers, etc. can be incorporated into our internal system and can be transferred throughout our various departments.

All of the above mentioned tools are used for a final result which will be a detailed drawing including inside fabrication details, outside welding details, a complete bill of materials, design parameters, and the plan view that shows the exact location of the fabrication within the plant. An example of engineering and design is at one time we received a question of how to increase the life span of a standard spring support assembly. People in the field found that the spring coil itself had a much longer life span than the surrounding assembly. The containment vessel was deteriorating much faster than the coil and rendered the entire assembly unusable. One option was to modify the outer coatings of the assembly with perhaps painting, applying a zinc coating, hot-dipped galvanizing or a combination of the three. The final solution was to eliminate the last welding steps and utilize a bolting construction so that the final entire assembly could be hot-dipped galvanized as required. Another benefit was that the production time was shortened which ultimately provided a cost savings.

mini big ton spring Another example of a new design developed to meet a specific site requirement involves variable springs. The site requirements included very stringent height requirements. Although a standard variable spring could withstand loads between 4,000 lb. and 7,000 lb., it was 8-10 inches too tall to fit these height requirements. In an effort to rectify the situation, a multiple coil arrangement was used inside a single coil housing to fit the height requirements because more space was available side to side than up and down. The result was a multiple spring coil arrangement with smaller, shorter coils referred to as a mini-big ton spring assembly in a rectangular shape.

This same concept was utilized for constant spring assemblies. A plant that required constant spring assemblies had limited space between the supporting structure and the supporting element and also between some of the auxiliary structural steel between the existing framework structural steel and the available space for the constant spring assembly. A single constant could have been utilized to support the load, however, the assembly was too high for the space. Therefore, the big-ton constant assembly concept was used to support a 50,000 lb. load using two constant springs within one modified framework. This is an example of one design concept being transferred to another design as the constant spring big-tons were designed in a similar fashion as the variable spring big-tons.

We have developed in-house software to streamline some of our fabrication procedures. One component that is used in a standard clamp assembly is a heavy three boltthree bolt pipe clamp clamp. It supports loads up to 15,000 lb. for a 20 diameter. The customer required a clamp for a 20 pipe that could support 20,000 lb. Therefore calculations were made using our in-house clamp calculator in order to know the stock size, bolt sizes, material, etc. in order to withstand the 20,000 lb. load. This program drastically reduced the time required to make these calculations by hand. By using algorithms and other things, the clamp calculator can delineate all of the pertinent information required to fabricate the custom clamp needed. Also, in the process, a drawing is developed utilized not only in the manufacture of the clamp but also utilized by quality control personnel later on in the assembly process to confirm that the semi-custom design was adhered to.

An analysis of a slightly more complicated clamp design was performed using finite element analysis. In FEA, we consider not only vertical loading but axial loading as well. FEA can readily simulate all the loading conditions which are available. Likewise, FEA may be used in the special configuration of a yoke clamp designed with a u-bolt to support a pipe system. However, because of the size, in this instance a 40 pipe diameter, the yoke must be fabricated out of several different sections of material instead of one solid piece of material. Because of the complexity of all of the pieces fitting together, each piece needed to be analyzed to determine the maximum stress positions and to change, if required, to a thicker plate, add extra stiffeners, etc. The idea of this is to optimize the amount of material used, the overall amount of fabrication, and ultimately the amount of cost to create the custom yoke clamp.

Another use of finite element analysis was performed in the fabrication of a sub sea structural frame. The entire assembly was made in sub-sections and would be bolted together in the field. The most important point of this design was that the frame would be moved multiple times in and out of the water, so the stress on the lifting lugs was the main concern. FEA was performed of the initial design on the lifting lugs to make sure that they were capable of not only the static loads but also the dynamic loads that were generated in the lifting and dropping of the framework into the ocean. In the initial FEA run, it was determined that stiffeners were required to strengthen the entire assembly. A subsequent FEA was performed on the assembly after the stiffeners were added to ensure that the assembly would indeed be able to withstand the stress on the lifting lugs. In another example, both a finite element analysis and 3D model was performed on supports for a cooling towers circulatory water system at a power plant. Six of the 9 shoe assembly supports were designed for a 60" line and 50,000 lb. load, and the remaining 3 were designed for a 78" line and 75,000 lb. of load. After extensive engineering hours and structural analysis, our engineering department produced a detailed design and 3D model for the supports that would allow them to run electronic interface checks. All of the loading conditions could be simulated and the location of the stiffeners and rib plates, if required, could be modeled. Once the FEA was completed, the design was finalized and placed back into the 3D modeling program to model the existing structural steel with the newly designed shoe assemblies.

finite element analysis performed on a transition pieceA final example of finite element analysis was performed on one of our SWECO division products. This transition piece used a standard flange at the top, but had been modified to include the extra length of pipe and to eliminate two flanges. The rectangular flange was fabricated of 1.25 x 5 inch stock and was made of A36 steel. The objective was to determine the need for stiffeners in high stress areas of a transition piece and to figure out where they needed to be placed. Design conditions with internal pressure and external pressure were modeled in the FEA program. As a result, FEA analysis determined stiffeners unnecessary and yielded a saving of $30 thousand dollars.

In one case, an expansion joint failed when some adjacent line anchors failed. The petroleum company used our emergency service for the immediate replacement of this 48 expansion joint. We received the call on a Friday at 5:30pm. The next morning, the expansion joint was fabricated with tie rods to help prevent squirming in the future and was shipped that same day. Sunday, the expansion joint was installed at the petroleum plant. Modifications to the original design included incorporating tie rods to help prevent squirming in the future. This is an example of a modification to an existing design to accommodate a detrimental instance of an upset loading condition that was not initially seen as a concern.

In one instance, a customer required modifications to increase the lifespan of an existing expansion joint in order to increase its lifespan in a coal-fired power plant. The solution was to design a self-cleaning slip-type expansion joint. Several special requirements where met by a combination of design features and material specifications including an aluminum bronze bearing sleeve. The inner barrel was uniquely plated to be corrosion resistant and the outside sleeve protected the expansion joint from the potentially detrimental harsh environment.

Our U.S. Bellows, Inc. division designed a 36 gimbal expansion joint. The gimbal ring, hinges, standoff, and pins were all designed to withstand the design and hydro-test pressure thrust force. FEA was used to design this gimbal expansion joint assembly and structural FEA was performed to ensure that the product was structurally sound.

PTFE 25% glass filled slide plates disbonded from steelAnother example of design innovation was implemented on some PTFE, 25% glass filled slide plates. The necessary design parameters were not readily available, and it was not until the product was put into use, that it was revealed what would happen under those design conditions. A standard slide plate assembly, using PTFE 25% glass filled material bonded to a backing plate, was used in conjunction with a high-temperature shoe. Since the temperature gradient was sufficiently high at our operating temperature, the temperature at the intersection of the PTFE slide plate material and the base of the shoe was in excess of 350 degrees Fahrenheit. The melting temperature of the glue is approximately 325 degrees Farenheit. Therefore, when the 350 degree temperature was reached, the glue disbonded, and the PTFE slide plates were rendered useless. As a result the first attempt at modification was to utilize standard graphite slide plates to withstand the high temperatures, but since this system went through cyclic disturbances, we realized that the graphite plates might not withstand dynamic loading as readily as the PTFE material. The second idea was to use a marinite block sandwiched between stainless steel material. This provided high strength load carrying capability as well as high insulating capability, thus accomplishing both objectives necessary.

Field testing can be very beneficial in confirming or disputing some things which may be thought to be already known. In one instance we performed a case study to determine the caulking compound to be used in conjunction with a high temperature application. We set up a test facility with the original caulking compound which was 5800 and the suggested compound which is 5800C. Over a period of time, we determined the temperature at which each compound began to melt. Taking into consideration the high temperatures of this application, we determined that 5800C will be sufficient enough.

Another field example was performed to disprove an assumption. We looked at the amount of ice formation on an un-insulated pipe. It was thought that ice would continue to build up as the temperature dropped. Liquid nitrogen was allowed to fill completely the stainless steel pipe first, followed by a steady flow of liquid Nitrogen. By adjusting the control valve to a point when the liquid Nitrogen ceases to exit through the vertical outlet tube, the pipe remained completely full of liquid Nitrogen throughout the test. This flow process caused a small fraction of the flowing liquid nitrogen in the pipe to change phase to vapor by gaining latent heat of evaporation from the ambient air and exited through the outlet tube. This maintained almost a constant pipe surface temperature over an extended period of time. Metering scales were fixed radically outward at three locations (near the two ends and at the middle) along the pipe to measure the ice deposition depth as a function of time. After filling up the pipe with liquid Nitrogen, the pipes surface temperature started falling exponentially with time and it took almost 20 hours to reach an almost steady state with small variations following a trend similar to that of the ambient temperature variations during day and night. As a result, we found that ice build-up reached a cap at -295F. This disproved the original assumption that ice would continue to build as the temperature dropped. We determined that this was an acceptable amount of ice build-up without the need to add insulation.

In our final field example, over 116 hot shoes for various sizes of large bore high energy steam lines failed. This caused the Energy Center to completely shut downsupport install in the field due to safety concerns and the potential for pipe and/or equipment failure. The original vendor replaced the supports with the same type of supports, and they failed once again. PT&P was called in to survey the site and found that the type of pipe support used was not suited for the service conditions because due to the continuous cycling, the insulation was not strong enough to support during those dynamic loads and intermittent cycling. A new design was developed, and it was determined that the structural supporting member could not be the insulation itself but rather structural steel components, so that the vertical forces generated could be dissipated through a solid force transfer from the pipe supported and the steel structure below. In analyzing the entire shoe structure, finite element analysis was performed to determine the location of the stiffeners and to minimize their size and depth. After the analysis was complete, the new shoe design was fabricated and reinstalled back into the field.

We provide value-added services including product testing for a variety of our products. We can perform on-site inspection, installation and maintenance and have a 24/7 on-call engineering team for all of your emergency needs. For any of your engineering and design needs, do not hesitate to contact us at info@pipingtech.com.

 

 

 

 

 

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Mailing: P.O. Box 34506, Houston, TX 77234-4506 Location: 3701 Holmes Road, Houston, TX 77051
Our Subsidiaries: U.S. Bellows: Metallic & Fabric Expansion Joints, Bellows
Sweco Fab: ASME Vessels, Pig Launchers, Spectacle Blinds
 Pipe Shields: Pre-Insulated Pipe Supports, Slides, Guides & Anchors

Fronek Anchor/Darling
: Snubbers, Sway Struts & Sway Braces
Phone: (713) 731-0030 Toll-Free: (800) 787-5914 FAX: (713) 731-8640 info@pipingtech.com

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