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Figure 1. Valve design considerations
Another often overlooked area of concern that is critical for sealing methane is the bolting on the valve gland. One of the most important issues that testing confirmed is that the condition of the bolts can have a significant effect on the accuracy of the gland load on the packing. Lubrication is critical, and new bolts (as compared with used bolts) can drastically affect how the valve seals operate. Depending on the condition of the bolts, a user may not be getting the correct gland load. This is because, in most cases, the applied gland load is only assessed by torque, a measurement not of tension but of force over the threads and nut. When using unlubricated used bolts compared with new bolts, the same torque will result in a much lower tension and an under-loaded gland. One way to mitigate this problem is to use a load indicator, such as disc springs height, which measures specific tension on the connection.
The work the petroleum industry, regulatory agencies, packing manufacturers and the valve industry have completed has served to reduce methane emissions.
New packing materials and formulations, new testing standards and valve design improvements have allowed the industry to lower their environmental footprint by minimizing emissions.
Next Month: Insulating Over Rubber Expansion Joints: A Good or Bad Idea?