Engineering Solutions Since 1967 CAGE: 28017
Don’t Blame the Sealant
Don’t Blame the Sealant
When pipe joints leak, most people want to blame the pipe sealant. In many cases, however, the quality of the sealant isn’t the culprit. Other causes for leaks include not using enough sealant, cracks in the piping and joints, improperly applied PTFE tape, overtightening of joints, and dissimilar types of connections.
One of the safest ways to check for leaks is to apply soapy water to the assembly and slowly pressurize. If you see soap bubbles, you know you have a leak. Examine where the bubbles are coming from. Look carefully at the piping and joints for cracks. Common problem areas are the seams, valve stems, main connections, hose connections and bleed screws, when applicable. If the bubbles appear to come from the joint, take the joint apart to make sure there is enough sealant in the threads to form a perfect seal.
When working with plastic fittings, Fluoramics does not recommend using PTFE tape. Plastic fittings seal by dead heading and tapered wedging. When using tape with plastic fittings, more times than not, the tape gets all bunched up during the tightening, preventing a proper seal. Instead, use a thread sealant.
Proper Application of a Thread Sealant without Over Torqueing
To apply a thread sealant, start about 2 threads back from the front end of fitting to prevent paste from protruding into your product stream. Apply enough paste to fill the threads. Assemble and hand tighten with perhaps another ¼ turn and leave it there. Be careful to not over torque; it is very easy to over torque and crack or strip the threads on plastic, PVC or cast-iron fittings, causing the assembly to leak. Watch for and replace all cracked plastic nuts. This is not a sealant event but is caused by over torque.
When working with dissimilar connections, watch for different screw threads. One example is using National Pipe Tapered (NPT) fittings with National Gas Taper (NGT) fittings. The NGT is a longer screw thread than NPT. The two pieces will assemble together, but the NGT will typically have 3 more threads in the fitting area. If you mount an NPT to an NGT, you will have leaks. Also, when using dissimilar types of plastics, you may run into the threads not properly aligning. The first few threads may line up but as you continue to tighten, the threads may not align. This will cause gaps and leaks. The thread sealant will provide bulk fill and help with the leaks but the problem rests with the dissimilar types of plastics and not with the quality of the sealant.
If you are using tape vs. paste, always be sure to apply the tape in a clockwise direction so that the tape will pull down into the thread as you torque it. When using Fluoramics’ Full Density Tape, only use 1-2 wraps. Using too much tape will cause fittings to not seal properly.
Quality and Type of Sealant
Sealants come in many formulas and it is important to make sure you have the right sealant for the job. Take these factors into account when selecting a product to make sure you have the right sealant for the job.
• Mechanical Properties: What are the types of metals or plastics, size of fittings?
• Environmental Conditions: What is the range of temperatures and pressures? Is the material in a steady state or a state of rapid change?
• Chemical Resistance: What types of chemicals are you looking to seal against?
• Certifications / Agency Approvals: What types of certifications are important —NSF, oxygen service approved?
Fluoramics offers two popular paste thread sealants: LOX-8 and Formula-8.
LOX-8 Paste is a PTFE thread sealant that is highly recommended where oxygen or harsh chemicals such as chlorine or powerful oxidizers are present. Providing superior performance as a sealant, LOX-8 withstands both high extreme temperatures and high pressures. LOX-8 is stable up to 550ºF. LOX-8 has been tested and certified for use in gaseous and liquid oxygen by NASA (ASTM G72-86) and also by BAM.
LOX-8 Paste Products
Formula-8 uses PTFE in a shear-sensitive thixotropic paste to seal threaded joints with PTFE strings when torqued. The seals are formed over the entire thread length. Even fine threads in instrumentation systems are sealed effectively over the entire thread length. It won’t deteriorate from ‐400°F to +500°F and is stable in pressures up to 10,000 psi and in vacuums 10‐3 torr. Formula-8 has been tested and certified for use in gaseous and liquid oxygen by NASA (ASTM G72-86) and also by BAM (German Federal Institute for Materials Testing).