Robco Expert

  ASME PCC1-2019 : technical notes about sealing performance Lotfi Grine, Eng. – Product Specialist at Robco   In the following technical notes, you will find valuable technical extracts from the ASME PCC1 2019 ( bolted flange joint assembly (BFJA) guidelines) to help better understand sealing behaviour and produce a positive seal. - Calculating Target Torque Values are based on the root area. The root areas are based on coarse-thread series for sizes 1 in. and smaller with 8-pitch thread series for sizes 1 1/8  in. and larger (Section H). - The major long-term value of coated bolts is to protect against corrosion of the exposed threads and to minimize break-out and nut-removal torque, thereby promoting ease of joint disassembly (Section 7). - Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code requires that nuts engage the threads for the full depth of the nut (Section 8.2).   - Start-up re-torque is performed when the temperature of ...

Lotfi Grine, Eng. – Product Specialist at Robco   Causes for bolts to loosen in service: ·         Vibration: it’s an unintentional loosening, and it is the repeated relative displacements between the contact surfaces resulting in relative motion occurring in the threads. ·         Gasket creep: the gasket loses its springiness over time; it is also a permanent deformation and It’s more severe in high-temperature applications. ·          Elastic interactions between multiple bolts: Elastic interactions can either increase or decrease bolt preload. ·         Temperature fluctuation caused as a result of either differences in temperature or differences in clamped materials. ·          Low preload developed at installation: it occurs when there is no sufficient clamp force (under-tightened bolt) present on the joint interface to prevent relative motion...

Junction with leak problem, Should I suspect the fastener device...? Jocelyn Vachon - VP Busines development - Robco Uneven Bolt Stress. An incorrect bolt-up procedure or cramped working conditions near the flange can leave some bolts loose while others are overtightened and crush the gasket. This can cause in-service leaks, especially in high temperature services when the heavily loaded bolts relax. in order to close the micropores inside the gasket itself and to fill in the unevenness at the flange facing - gasket interface, the assembly bolt load should be calculated according to the ASME Code. Every bolt has a correct torque/tension elasticity range and a properly tensioned bolt works at its optimum efficiency. If the tension is too low, the nut could vibrate or work loose and if the tension is too high (overstretched), the bolt may yield. That being said, we strongly encourage you to Choose the proper fastener device (Bolts, nuts and washers) for example use a hardened washe...

One major reason your joints may be leaking... and it is not the gasket. There are a number of reasons that contribute to a seal joint failure, including weak bolt material, improper installation, inadequate bolting torque or poor flange design. Yet, if a joint fails and leaks, the immediate culprit will usually be the... gasket. Perhaps, a flange inspection would be the first analysis to do Flange face damage is an important parameter that may restrict a gasket to seal properly.  We need to take this into consideration when we analyze the sealing failure of a junction. Among flange face damages, we can find: Scratches: This type damage is narrow and elongated with sharp, shallow bottoms. However, depending on the force that created them, they can be deep. Frequently, this type of damage is created by a sharp object dragging across the flange face. These objects may include the bristles of a wire brush or a tool, such as a chisel. Gouges: These are wide and elongated with ...