Static joints

Static joints are the subject of a special form of Murphy s Law Pinholes and cracks appear most frequently in the least accessible places. The reason is that just because the place is accessible only with difficulty, the working of the glass during the making of the joint will have been hampered and therefore probably not well done. That is why the experienced leak hunter will first suspect a leak at the backs of joints made close to any fixtures, i.e. the parts of the joints which are difficult to see, to get the flame to, and to inspect. 

Lower Movement Caulks Oil/resin-based 5% Lowest cost easily applied and tooled primerless preparation good color stability fast skinning No recovery slow curing can stain substrate moderate shrinkage for static joints... 

Polybutene/polyisobutylene 5% Good adhesion low shrinkage excellent UV/ozone resistance low cost good water resistance Dirt pickup low cohesive strength poor solvent resistance can stain substrate for static joints... 

Low Movement Seaiants (Caulks). These include polybutene, polyisobutene, and oil and resin-based caulks. These low cost sealants have an approximate joint movement capacity of only 5%, a slow rate of cure (120 days), a low Shore A hardness, a relatively short service life (approximately 6 or 7 years on average), and only modest weather or chemical resistance. Therefore, low movement sealants are primarily utilized in static joints having minimal exterior exposure. 

The force required to overcome the static friction of the pipe in expanding or contracting on its supports, from installed to operating position. The length of pipe considered should be that located between the anchor and the expansion joint. 

The foregoing designs were discussed as ring expansion joints by Kopp and Sayre, Expansion Joints for Heat Exchangers (ASME Misc. Pap., vol. 6, no. 211). All are statically indeterminate but are subjected to analysis by introducing various simplifying assumptions. Some joints in current industrial use are of lighter wall constniction than is indicated by the method of this paper. 

After catalyst charging and the flow vs. RPM measurement is done, the reactor should be closed and flushed out with nitrogen while the impeller runs, until O2 drops below a few tenths of a percent. Then a static pressure and leak test should be made by turning off the forward pressure controller and the flow controller. If an observable drop of pressure occurs within 15 minutes, all joints and connections should be checked for leaks and fixed before progressing any fijither. 

Eqs. 1-5 hold whether failure is interfacial or cohesive within the adhesive. Furthermore, Eq. 5 shows that the reversible work of adhesion directly controls the fracture energy of an adhesive joint, even if failure occurs far from the interface. This is demonstrated in Table 5, which shows the static toughness of a series of wedge test specimens with a range of adherend surface treatments. All of these samples failed cohesively within the resin, yet show a range of static toughness values of over 600%. 

Soldered joints, especially those to be used in a static environment, are, if insufficient care is taken, liable to corrosion by residues of flux, which by their nature as oxide removers are potentially corrosive. It is, however, possible to select fluxes which are active when hot but give non-corrosive residues when cold. 

Patel et al. [70] in a recent publication have explored the adhesive action of the mbber-siUca hybrid nanocomposites on different substrates. The rubber-silica hybrid nanocomposites are synthesized through in situ silica formation from TEOS in strong acidic pH within acryhc copolymer (EA-BA) and terpolymer (EA-BA-AA) matrices. The transparent nanocomposites have been apphed in between the aluminum (Al), wood (W), and biaxially oriented polypropylene (PP) sheets separately and have been tested for peel strength, lap shear strength, and static holding power of the adhesive joints. 

Most builders use 4 in. schedule 20 PVC pipes. Other sizes can be used but 4-in. PVC is readily available and is commonly used by builders for other purposes. Fans made for use in subslab systems are available in a variety of sizes from many vendors. The fans normally used are rated in a range of 90-150 cfm at no static pressure. Manufacturers of fans used for radon reduction are fairly quick to improve their products on advice from the people who are using their products. When the radon industry first started, many of the fans leaked at seams and joints, and required disassembly of the fan to seal those openings. Most manufacturers now supply fans that do not leak, but builders should be aware that this problem did exist and may still exist in some fans. 

SDS [Sulzer Dainippon Sumitomo] A continuous process for polymerizing styrene. The reactants are mixed in a static mixer, which gives a very uniform time/temperature history for the polymer. Developed jointly by Sulzer, Dainippon Ink Chemicals, and Sumotomo Heavy Industries. Offered for license in 1990. 

---