General Presentation Featuring Pipe Clamps (March 2009)

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Text Version of the General Presentation Featuring Pipe Clamps

For those unfamiliar with us, we would like to share some background information on our company. Our parent 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.

Our headquarters is here in Houston, Texas. Our facility is located on a 35 acre property including additional room for future expansion. We are just miles away from the Port of Houston which allows us to quickly and conveniently ship to a variety of countries throughout the world.

Piping Technology & Products, Inc., and its wholly owned subsidiaries, (U.S. Bellows, Inc., Sweco Fab, Inc., Pipe Shields, Inc., and Anchor Darling, Ent.) collectively offer:

PT&P manufactures a range of pipe clamps, hold-down clamps which are used to restrict motion in vertical and lateral movements, riser clamps which are used to suspend and hold vertical running pipes and structural supports which are used to not only to suspend loads but to restrict motion in three dimensions. We will discuss these supports for both standard and special applications like high temperatures and non-standard dimensions.

Two-bolt clamps are standard off-the-shelf clamps that are manufactured on a daily basis. For us, a suspension of un-insulated lines can most readily be accomplished through the use of our standard two-bolt pipe clamps. They are fabricated from carbon steel and are either galvanized or left black and they are usually used to suspend lines with no insulation. The pipe size ranges from inch to 36 inches with a maximum load rating of 4,000 lb. on a 36 inch clamp. In suspension of other pipes, we offer a Figure 60, our heavy-duty clamp with a larger load rating. This particular clamp has the same configuration but with a pipe size that ranges from 3 inches to 36 inches with a maximum load rating of 28,000 lb. on a 36 inch clamp. They can be procured either unfinished or with a hot-dipped galvanized finish.

When insulation is involved, we would like to utilize a three-bolt clamp to help in instances when the pipe is insulated so that the load bolt can remain outside of the insulation. These are also standard clamps manufactured in our facility. They are manufactured from standard stock sizes, bolt sizes, and standard material. We have a Figure 70 clamp (light-duty three bolt clamp) that covers pipe sizes from inch to 36 inches with a maximum load rating of 10,500 lb. for the 36 inch pipe size. Our heavy duty clamps, figure 80, utilized for pipe sizes of 1 inches to 36 inches with a maximum load rating of 28,000 lb. for a 36 inch clamp. The three bolt clamp is also available in an unfinished condition or a hot-dipped galvanized finish.

Now that we have mentioned the standard clamps, we would like to take a look at what makes the standard clamps different from the custom clamps. We manufactured a custom-designed three-bolt clamp for a 765 MW natural gas-fired combined cycle facility. These clamps in conjunction with variable springs, will allow for vertical and axial pipe movement while restricting lateral movements. They are made for a 24 inch outside diameter pipe from 1-1/2 x 9 stock material. The standard clamp stock size would have been x 3. Based on design considerations, the clamp "E" dimension, from pipe centerline to outer load bolt, is twenty-five inches (25"). The clamps were designed for operation at one-thousand, sixty-five degrees Fahrenheit (1,065F) and per customer-supplied information. The vertical design load is one-thousand, eight-hundred and forty-eight pounds (1,848 lb.) and the maximum lateral load is nineteen-thousand, two-hundred and seven pounds (19,207 lb.) The clamp plates are made of A387 GR. 22 plate material. The stanchion pieces are made of A335 GR.22 pipe and the side stop plates are made of carbon steel.

Standard stock clamps are made for standard pipe sizes. Non-standard pipe sizes such as FRP pipes, plastic pipes, ductile iron piping, etc. would require custom made clamps because the diameter differs from a standard pipe. Additionally, you may require a specific material in order to avoid cross-contamination of the materials between the clamp and the pipe. This would require ordering a custom clamp. PT&P designed clamps that will be used in conjunction with a spring hanger and a rod to support the pipe line. By using a FEA program, the clamp was designed for an operating load of twenty-four thousand pounds (24,000 lb.) at five-hundred degrees Fahrenheit (500F). The standard load for this particular 14-18 clamp is 4,000 lb. Additionally, PT&P designed custom clamps for 66 duct work which exceeded our standard pipe size of 36. The entire assembly was custom designed and capable of a suspension load of 24,000 lb.

PT&P designed a clamp to be used in conjunction with a hydraulic snubber. Snubbers are used only when an upset or disturbance is found in the system. As a result, the clamp was not going to be used continuously but only needed when a 68,000 lb. upset load occurred within the system. It has two lower links that were joined together by an upper yoke assembly. The distance between the links was used to accommodate the pipe size. This allowed us to use the strongest portion of the pipe for suspension.

Another example of a custom clamp was used on a 97 diameter duct work. This was much greater than what a standard clamp can sustain. The duct work was also thin-walled, so stress could not be induced on the duct work by the clamp. A special clamp was designed for this unique case. Each section of the clamp assembly was formed from a continuous plate and gussets that were added at each of the bolt locations for increased strength and rigidity. Due to the ducts having a relatively thin wall, these clamps were designed wider than necessary in an effort to reduce localized stresses on the duct work.

Beam clamp assemblies are standard products. However, they too can be fabricated for special cases. One example of this is a carbon steel beam clamp designed with a clevis hanger for a 10 pipe used to suspend loads of 3600 lb. The function of the beam clamp assembly was to support the pipe and allow it to swing.

PT&P uses finite element analysis to assist in the design of pipe clamps. In one instance, PT&P designed a 42 heavy duty alloy yoke clamp for a load in excess of 70,000 lb. The FEA was first conducted to optimize the design. Using 6 thick plate, the FEA revealed that this material produced more loading in the u-bolt section rather than the yoke section of the clamp. This was a high temperature application where the operating temperature exceeded 1050 degrees Fahrenheit, and as a result, we chose chrome moly material for this design.

FEA helps us to not only optimize the materials but review what the clamp is doing to the pipe itself. In one instance, we produced a clamp for a plastic pipe and it was very necessary to reduce residual stresses on the pipe. We then had to design a clamp wherein the two center sections met. This would create stress at the pipe intersection. In this instance we were trying to overcome axial force on the pipe but at the same time, barely overcome that axial load in order to avoid extra residual stresses on the pipe.

The material we use, the bolting, etc. can be optimized for weight and cost considerations. We conducted finite element analysis on a Figure 80 heavy duty three-bolt pipe clamp for a high temperature application. Due to the high temperature, the clamps were fabricated from alloy steel, A387 Grade 91. We analyzed two different pipes one for a 68,200 lb. load and the other for a 33,500 lb. load. After the analyses, we found that the bending radius of forming the ears is 1.5 times the plate thickness. The AISC recommends that the values are three (3) times the thickness of the plates of 1 to 1 " thickness and four times the thickness for greater thicknesses. The FEA analyses demonstrate that larger radiuses would result in lower stresses. This conclusion has led to significantly lower costs to our customers by justifying the use of less steel.

PT&P designed another custom riser clamp for a power plant with a load capacity of 80,000 lb. They were fabricated to be utilized on a sixteen inch pipe with two inch flanges for added support. Riser clamps are generally used for support and steadying of steel pipe risers either insulated or bare, cast iron pipe, or conduit. Special design riser clamps may utilize four load bolts instead of two. If the clamps are to be used in a corrosive environment, we can provide special finishes like marine acrylic paint or PTFE, 25% glass filled coatings on the bolts. The main points to look at on the riser clamps are the distance between the center line of the pipe and the load bolts. This will determine the stock size and the stock thickness that we need to utilize in the design. Utilizing gusset plates at a riser clamps bend radius allows for the smallest, yet sufficient clamp stock sizes for the specified loads.

Now well discuss hold down clamps which are utilized to not only hold vertical loading but also to restrain the pipe in the lateral movement and vertical movement. Some hold downs are fabricated with PTFE, 25% glass filled, lining on the inner and lower surface. This will allow the pipe to slide axially, but restrain the pipe from moving both laterally (from side to side) and vertically (up and down). In this case it can act not as an anchor but as a guide. We also fabricate hold downs for special cases such as one we designed for a 42 pipe and utilized wedge supports as an effort to bring the pipe to a pre-designated distance from the bottom and then allowed for that height dimension to be maintained. Another special feature on hold downs is an isolation pad that can be bolted to the bottom of a hold down to absorb some vibration of the pipe line.

Special clamps were designed for an on-going project to rebuild the San Francisco-Oakland Bay Bridge. They were fabricated from carbon steel and galvanized to withstand corrosion from the ocean waters and rough winds. The supports will be welded to anchor plates which are set in a cast concrete to the bottom cavity of the bridge. This particular type of support manufactured by PT&P utilized friction holding devices known as MegaLug, which permitted attachment to the pipes without welding. The main design function of these supports is to include improvements in regards to strength and durability to withstand high loads during earthquakes and other seismic events. These supports were fabricated from carbon steel and designed for six (6"), ten (10") and twelve inch (12") ductile iron pipe. They were hot dip galvanized to protect against corrosion, and will be used in conjunction with hydraulic snubbers. The snubbers aid in protecting against axial shock loading as well as providing vertical weight support.

Now we will cover some additional products manufactured by PT&P and subsidiaries. Variables use coiled springs to support a load and allow movement. The resistance of the coil to a load changes during compression, which is why these devices are called variables. There are many different designs for variable supports. We use A through G to describe seven different physical connections to the supporting structure. A-E and G are hangers suspended from structural members and type f is a base support that rest on the supporting surface. All of our variables are available in short springs, standard springs, double springs, triple springs or quadruple springs. We also manufacture constant supports. Unlike variable springs, they have a continuous load at our load bearing condition. We provide various configurations of constant spring supports such as u-types and hanger types. Big ton springs are custom designed to meet load and travel requirements for very large loads using a multiple coil system. Usually a base-mounted support that can be designed with slide plates for lateral pipe movement. The height, width and length are also custom designed to meet space requirements.

Constants are often used in petrochemical plants. In one instance, we utilized 6 standard constants in combination to suspend a large piece of ductwork in the piping system of the plant. Additionally, we used a special application big ton support that provided an attachment point for a large diameter elbow while withstanding a load of 120,000 lb. Within this big ton spring framework were three individual coils of different sizes that helped to hold up the load. A normal variable spring withstands a maximum of 50,000 lb. so therefore, a big ton spring was required to withstand the load.

Also, to be utilized in conjunction with clamps and other pipe supports, we design and fabricate horizontal travelers. We use horizontal travelers to allow movement along either a single axis as accomplished by the single horizontal traveler, or along a dual axis, accomplished by our dual horizontal traveler.

We offer a complete line of snubber assemblies which include mechanical snubbers, hydraulic snubbers, and spring suspended load sway braces. The mechanical snubbers, as the name implies, utilize a spring and cap stand system which when a maximum velocity is reached, will lock into position. While these are suspending the line, they are not actually load carrying devices. They will allow free movement throughout the normal operating range of a line. However, only during upset conditions such as earthquakes, when a specified pre-determined maximum velocity is reached, the system will lock and the snubber will hold the line in position and act as a rigid support. When the transient condition is removed, the snubber will unlock and allow normal free movement of the line. Hydraulic snubbers, as the name implies, utilize hydraulic fluid and a valve system such that when a maximum acceleration is reached, the fluid will lock and the valve will close so that a load carrying condition for that transient loading situation to be reached once again. In sway braces we utilize springs much like a variable spring assembly to alleviate vibration in a horizontal plane. They move in either a push or pull direction to help to restrain the movement of the piping system and these, unlike variable spring assemblies, can be oriented in any horizontal, angular condition.

We also manufacture a large quantity of pre-insulated pipe supports both for high temperature and low temperature applications. They are fabricated such that the insulation is integral to the clamping or supporting structure. Instead of insulating around a clamp, the clamp goes around the insulation. The insulation is manufactured so that its load carrying capability of the insulation is enough to withstand the load generated by the pipe weight. We keep polyurethane foam in stock to be used on supports for cold applications.

Slide plates can be utilized in conjunction with clamps. They allow us to reduce the coefficient of friction between a steel to steel sliding surface for example. We offer bronzphite, marinite, and ptfe, 25% glass filled slide plates. Bronzphite slide plates use graphite impregnated into a bronze substructure and helps to eliminate the high coefficient of friction between high temperature sliding surfaces. On marinite slide plates, a sandwich concept is used in the design because marinite is a good insulator but not a good structural weight bearing component. So, a stainless steel framework is incorporated around the marinite for high temperature application, wherein the side members provide load bearing capability and the sandwiched marinite inside provides the heat transfer insulating capabilities that are required.

We manufacture expansion joints through our U.S. Bellows, Inc. subsidiary. We have the capabilities to manufacture thick wall flanged and flued head expansion joints, single metallic expansion joints, universal expansion joints, pressure balanced expansion joints, tied universal expansion joints, as well as many others. We manufactured a 47 universal expansion joint with round corners as well as 24 inline pressure balanced expansion joints. The pressure balancing helps to eliminate any residual stresses on the bellows.

In addition to expansion joints, we manufacture a large variety of custom fabricated components through our Sweco Fab division including embed plates, spectacle blinds, pressure vessels and conical strainers. Additionally, any products that require ASME codes for fabrication can be ordered through our Sweco Fab division. More items available through this division include bellmouth reducers, anchor bolts, pig launchers and receivers.

We have a large inventory of stock material including over 30,000 spring coils and a full years supply of hardware and structural components required to fabricate products quickly for our customers. At PT&P, in our engineering department, we are able to provide customers with technical services. One of those services being finite element analysis which helps us to optimize our production procedure and material requirements that we are using. We can also design and model the entire piping system and utilize our facilities in producing overall engineering assistance. We provide on-site field services including inspection and maintenance of existing supports or installation assistance with new supports.

Our web-based emergency services allow you to contact our specialists 24 hours a day, 7 days a week. One time, an expansion joint burst and failed on Friday evening. On Saturday, a replacement expansion joint was already being fabricated and that evening it was ready for shipment. On Sunday, just two days later, the new expansion joint was installed in the field. We also provide testing here at PT&P to eliminate any misgivings as a secondary option to finite element analysis or design software. All of our components can be tested to either destructive or non-destructive testing.

Any further questions can be sent to info@pipingtech.com concerning this topic.