Practical Estimation of Retorque Requirements

The initial assembly of a bolted flanged joint (BFJ) commonly includes several ramped torque steps using various bolt torque patterns, final circular pass(es) at 100% of target torque, and then the choice of whether and when to come back and retorque the just-assembled joint. The value of retorquing a newly assembled bolted flanged joint varies significantly by which gasket material and type is used in the joint. The additional maintenance costs of labor, tool rental, scaffolding, crane usage, etc. to perform a retorque on a joint can be significant, but the larger cost is generally the additional process downtime. Gaskets based on sheet materials are often retorqued. Conventional practice indicates that BFJs with gaskets made from flexible graphite or fiber sheets typically do not benefit from retorques, or at least do not benefit enough to offset the additional costs. Conversely, industry experience with many polytetrafluoroethylene (PTFE) based gaskets indicates these joints benefit significantly from retorquing a BFJ after initial assembly. This paper explores some practical methods to estimate potential retorque benefit as a function of retained gasket stress without the retorque at temperatures normally “in range” for the gasket material being considered. That is, at temperatures that would not cause thermal damage to the gasket material. For flexible graphite and fiber materials known to experience mechanical property degradation with time and/or temperature (“aging”), a typical 5-year life is used. For PTFE gaskets known to relax primarily with temperature and that do not appreciably age, use of the Hot Blowout Thermal Cycling test (HOBTC) can provide a quick evaluation of gasket stress loss as a function of temperature. Retained gasket stress in both cases can then be used to estimate tightness for the gasket material using the Room Temperature Tightness (ROTT) data. If the joint is still at or above required tightness, then retorquing the joint soon after initial assembly is of little benefit. If the gasket has lost enough stress, then a retorque can bring the gasket stress back into range to provide sufficient tightness. Knowing this, the end user can make better choices for both gasket material selection and assembly procedures in order to reduce overall job costs.

Analysis of the Gasket Damage and Sealing Performance for the Thread Ring Block Heat Exchanger

The thread ring block heat exchangers, served at the high temperature and pressure, are the key equipment in the petrochemical industry. Due to the severe operational conditions and unsuitable assemble, internal leakage problem commonly occurs, especially for the seal gasket between the tube sheet and shell. Many failed gaskets are collected. Through a series of experiments including chemical composition, metallographic analysis, SEM and fracture analysis, the gasket damage and leakage causes are analyzed. For further interpretation, the gasket stress analysis is completed by the finite element method. It shows that the gasket stress is a main factor that affects the sealing performance for the thread ring block heat exchanger. Under long term operation at high temperature and pressure, the gasket stress between the tube sheet and shell becomes loose and creep. The gasket material also deteriorates with increasing time. Therefore, in order to prevent the internal leakage, the stress should be controlled in an appropriate range. And periodical inspection must be performed.

Spiral Winding Technology for PTFE Gaskets

PTFE is used in a variety of applications that goes from wiring in aerospace to non-stick coating in cookware. Some of the PTFE properties, such as high chemical stability and good conformability, makes it excellent for use as a gasket material, especially with aggressive media, pharma and food applications. The scope of this paper is to present an innovative PTFE gasket manufacturing method for sealing aggressive media. The patented technology represents a unique production process that improves reliability, reduces cost and material waste when compared to traditional production methods. The gasket can be tailored to meet specific needs making it possible for customizations such as radial density variations, assorted colors compositions according to the gasket region and properties, or even use of distinctive fillers along its radius. Comparative data are reported among the developed technology and traditional processes.

Impact of BFJA Training on Bolted Flange Joint Assembly Reliability

A bolted flange joint assembly is a complex mechanical device, according to ASME PCC-1. A complex mechanical device’s reliability depends on many activities being performed prior and during the assembly of the bolted flange joint assembly (BFJA) being assembled. Some of these activities being; required torque calculations; gasket material selection, fastener selection, type of flange, fastener condition, lubrication, and maybe the most important activity being the assembly of the bolted flange joint. How does one ensure the correct methods and best practices being used during the assembly of the bolted flange joint? Education. Educating not only the assemblers but also the engineers, supervisors, foreman, etc. By educating more than just the assemblers we can create a proper culture to ensure BFJA reliability. We can quantify increased BFJA reliability spurred from education by using surveys completed by the assemblers who have gone through the training.

Effects of Curing Temperature and Pressure on the Mechanical Properties of Gasket Material Used for Polymer Electrolyte Membrane Fuel Cells

The long-term mechanical stability of the gasket material is critical to sealing and electrochemical performance of the polymer electrolyte membrane (PEM) fuel cells. In this paper, the silicone rubber material, which is being considered as gasket material for PEM fuel cells, was fabricated at different curing temperatures and different curing pressures. Effects of the curing temperatures and curing pressures on the mechanical properties of the silicone rubber material were investigated. The tensile test results show that tensile strength of the specimen cured at the curing temperature of 160 was larger than that for the specimens cured at the curing temperature of 150 or 170 under the same curing pressure. The test results of the compression stress-strain, compression set and compression stress relaxation show that the curing temperature and curing pressure affected significantly the compression elastic modulus, compression set rate and compression stress relaxation behavior. It is found that the silicone rubber material cured at the curing temperature of 160 under the curing pressure of 10MPa had good compression mechanical properties compared to the materials cured at the other curing temperatures and curing pressure in this work.

Design and Analysis of a Plate Heat Exchanger in the View of Performance Improvement and Cost Reduction

Redesigning of a system is a modification of existing system for reducing the disadvantages over the system and improves the features for getting more output that are desired. For redesigning the existing conventional heat exchanger by the new designed heat exchanger. Conventional heat exchanger has a major disadvantage consuming more space, high cost and maintenance is difficult. Plate heat exchanger has a major advantage over a conventional heat exchanger are that the liquid are exposed to main larger surface area because the liquids spread out over the plate. It is a specialized design well suited to transferring heat between low pressure liquids. The plate produces an extremely large surface area which allows for the fasten possible transfer and studying the plate material, gasket material, chevron angle, and surface enlargement angle. Design a plate heat exchanger by according more advantages and evaluate the cost of newly designed heat exchanger and compared to existing heat exchangers and validate the designs by flow analysis.

Bolted Flange Joint Made of Glass Fibre Reinforced Polymer (GFRP) for Oil and Gas Pipelines

The objective of this work is an experimental and numerical investigation for a bol Richard Cullen ted composite flange connection for composite pipes, which are used in the oil and gas applications, and obtain a joint with high strength and high corrosion resistance. For the experimental part, we have designed and manufactured the required mould, which ensures the quality of the composite materials and controls its surface grade. Based on the ASME Boiler and Pressure Vessel Code, Section X, this GFRP flange has been fabricated using biaxial glass fibre braid and polyester resin in a vacuum infusion process. Numerically, an investigation is carried out using 3D finite element analysis (FEA) of a bolted GFRP flange joint including flange, pipe, gasket and bolts. This model has taken into account the orthotropy of the GFRP material and the non-linear behaviour of the rubber gasket material for both the loading and non-loading conditions. Furthermore, the leakage propagation between the flange and the gasket has also been simulated in this investigation by using the pressure-penetration criteria PPNC in ANSYS. Finally, the flange has been tested under the internal pressure and the agreement between the experimental and numerical results is excellent.