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Fabric Expansion Joint for Duct System

May 17, 1999

Fabric Expansion Joint for Duct System
The photograph above shows a fabric expansion joint designed and built for installation in a duct system by Piping Technology & Products, Inc. These joints can be fabricated from a variety of metals, in a variety of shapes, depending on the particular application. They are used where ducts carry hot gases at low pressures. The fabric “belt” is a combination of layers of different materials selected to withstand the high temperatures.

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U.S. Bellows Fabricates Expansion Joints for Power Plant in China

September 4, 1998

U.S. Bellows, Inc., a subsidiary of PT&P, has recently supplied four 72-inch expansion joints required for the piping system of a power plant being built in Zhuhai, China. These large expansion joints will carry the exhaust from the plant’s boiler feed pump turbines.

72" Dia. Universal Expansion Joint

72″ Dia. Universal Expansion Joint

This critical piping application often requires pressure-balanced expansion joints, but in this case a unique combination of a universal joint in one plane (left side of photo) and a hinged joint (right side of photo) was used.

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High-Temp Fabric Expansion Joints

August 2, 1998

High-Temp Fabric Expansion Joints
Shown above is a large, round fabric expansion joint designed and fabricated by U.S. Bellows. The fabric “belt” is attached between two short sections of pipe. These expansion joints are inserted in metal pipes that carry hot gases at low pressures. Layers of different materials are selected to make a belt that will function at the high temperatures required. U.S. Bellows designs and fabricates these items to meet customer requirements.

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Helium Tests for Aluminum Bellows

October 4, 1997

This photo shows a 42 inch bellows made by PT&P being tested by Leak Detection Specialist Inc. After sealing the bellows a full vacuum is pulled on the inside, then helium is sprayed over the surface of all welds. A pump pulls any gas which leaks to the interior of the bellows to a special mass spectrometer designed to detect the helium. If helium is detected, the point of the surface where it was sprayed is marked for repair. When no leaks are found, the flow rate of helium to the mass spectrometer is measured against a standard for aluminum, in this case 0.000001 cc/sec. Helium molecules are so small, they will penetrate aluminum at a slow rate when the pressure difference of a full vacuum is applied.

Leak Detection Test

Leak Detection Test

A mass spectrometer functions by accelerating a narrow beam of ions of a gas sample through a magnetic field. When they reach the magnetic field, the amount they are deflected depends on their charge-to-mass ratio. In this application the detector is set to record helium ions. In order to measure the flow rate of the helium when no leaks are detected, the entire system is sealed in a plastic “bag”. LDS can measure helium flow rates as small as 0.00000001 cc/sec.

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PT&P Acquires New Expansion Joint Capability

June 4, 1996

PT&P has acquired the metal expansion joint business of RM Engineered Products, Inc. This acquisition included the design software, drawings, business records and all the equipment used to manufacture metal bellows. The equipment was moved from their plant in Ladson, South Carolina and installed in our new building here in Houston. The move and installation efforts were managed by Rick Thompson who joined PT&P in 1995. Rick will be in charge of manufacturing and fabrication of these products.

 

Machine used in the manufacture of expansion joints to roll metal.

Photo 1

Machine used in the manufacture of expansion joints to roll metal.

Photo 2

How to Make a Simple Bellows
Photo 2 shows a roll of stainless steel next to a shear which is used to cut the starting piece for the bellows. The particular metal required depends on the temperature, pressure and other design parameters for the expansion joint. Table 1 shows the standard metals used and the corresponding ASTM specification.

Table 1
Material Type ASTM Material Specification
304 S/S A-240
304L S/S A-240
316 S/S A-240
316L S/S A-240
321 S/S A-240
Monel 400 B-127
Inconel 600 B-168
Inconel 625 B-443
Incoloy 800/H B-409
Incoloy 825 B-424
Hastelloy C-276 B-575

Rectangular pieces are rolled to form a cylinder with an open seam. The automatic TIG flat bed welding machines shown in Photo 3 require only a few minutes to produce a homogenous weld. Proper set-up of the machine is critical to the quality of the weld. One of the capabilities we have added is an x-ray machine to verify the quality of the welds.

Flat bed welding machine used to manufacture expansion joints.

Photo 3

Roll-forming machine used to manufacture expansion joints.

Photo 4

The next step is to shape the required convolutions. Convolutions provide the flexibility required and the total movement capacity of the bellows is proportional to the number of convolutions. The convolutions are formed in two steps. The first step produces a v-shaped circular expansion at the center line of each convolution. The second step extends the triangular shape and provides a flat ring shape for the convolution. This entire process is called roll-forming. Photo 4 shows a roll-forming machine. Different size convolutions require varying set-ups. The arms of a machine for much larger units can be seen in the background.

"Wedding Cake" Machine used to size the bellows.

Photo 5

Bellows are the primary “building blocks” for a variety of expansion joints. The spring rate is determined by the size of the convolutions and the metal used. The compression, extension, lateral offset, rotation etc. required for a particular application determines the design required for the entire expansion joint. Photo 5 shows a “wedding cake” machine used to size bellows when fitting them to other components of the expansion joint.

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Thick Wall Expansion Joint

October 10, 1994
Thick Wall Expansion Joint
Thick Wall Expansion Joint

The photograph above shows thick wall expansion joints fabricated by Piping Technology & Products, Inc. Thick wall joints are cost-effective for large diameter piping systems which operate at low pressures. Metals can be selected to satisfy different temperature conditions and combinations of axial, angular and lateral forces.

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Slip Type Expansion Joint for Hydrocarbon Flaring System

August 7, 1994

Slip-type Expansion Joint for Hydrocarbon Flaring System
Slip-type Expansion Joint for Hydrocarbon Flaring System

The photographs above show a special slip type expansion joint designed by the Sweco Fab Division of Piping Technology & Products, Inc. for installation in the hydrocarbon flaring system of a combination of design features and material specifications. At the top right of the picture is the inner barrel which is uniquely plated to be corrosion resistant. At the bottom right of the picture is the aluminum bronze bearing sleeve which provides strength and guidance for the inner barrel. At the left is the assembled unit shows the outer barrel which contains the six packing seals, the follower and the retaining ring. This joint is to be installed in a horizontal position in the mid span of 40 feet between guided supports. The design conditions are 12” of movements, 650oF, and 50 PSI of internal pressure.

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Thick Wall Expansion Joints for Texas Refinery

July 2, 1994
Thick Wall Expansion Joints for Texas Refinery
Thick Wall Expansion Joints for Texas Refinery

The three pictures above show thick wall expansion joints being installed in a Texas refinery. Workers are covering the expansion joints with insulation, then covering the insulation with aluminum. The 72” expansion joints, which are fabricated from 1/4” carbon steel plate, have a 10” convolution

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Twelve Foot Diameter 304 Stainless Steel Thick-Wall Duct Expansion Joint

June 29, 1994
Twelve Foot Diameter 304 Stainless Steel Thick Wall Duct Expansion Joint
Twelve Foot Diameter 304 Stainless Steel Thick Wall Duct Expansion Joint

A twelve-foot diameter 304 stainless steel thick wall duct expansion joint produced by Piping Technology & Products, Inc. is shown supported and braced ready for shipment. Special equipment had rolled the knuckles from ¼” material which is then circumferentially welded. This results in an expansion joint with the minimum stresses possibly exerted and, at the high point of the convolution, its most vulnerable area.

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Special Designed Expansion Joints with 13” of Movement

February 10, 1994
Special Designed Expansion Joints with 13” of Movement
Special Designed Expansion Joints with 13” of Movement

These expansion joints were designed for 13″ movement. They are capable of withstanding temperatures of 1100 °F. These particular joints are externally pressurized. Externally pressurizing a bellows eliminates squirm as a limitation to the design and permits the safe acceptance of large amounts of axial thermal expansion.

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5’ x 22’ Thick-Wall Tied Universal Expansion Joint

January 4, 1994
5’ x 22’ Thick-wall Tied Universal Expansion Joint
5’ x 22’ Thick-wall Tied Universal Expansion Joint

Piping Technology & Products, Inc. engineered, designed and built this 5’ x 22’ stainless steel, thick wall, tied, universal expansion joint for a major producer of agricultural chemicals in Louisiana. A special in-house CAD program was utilized in the design effort for these expansion bellows to meet the process parameters. Also, special guides and anchors were provided to facilitate proper operation of this critical unit within the system.

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Thick Wall Expansion joint for Large Diameter Piping System

October 27, 1993
Thick Wall Expansion joint for Large Diameter Piping System
Thick Wall Expansion joint for Large Diameter Piping System

The photograph above shows thick wall expansion joints fabricated by Piping Technology & Products, Inc. Thick wall joints are cost-effective for large diameter piping systems which operate at low pressures. Metals can be selected to satisfy different temperature conditions and combinations of axial, angular and lateral forces. Piping Technology is a major supplier of pipe supports, expansion joints, and related items required for large piping systems.

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