Chain-locked open position

Many relief valves pop open above or below their set point. Such valves have to be removed from the vessel and reset in a machine shop. Often, there are isolating block valves, located beneath the relief valve, that permit the relief valve to be pulled while the vessel is still in service. These block valves are perfectly legal, provided they are chain-locked open. It in unlawful to have an isolating valve below a relief valve that is not chain-locked open or sealed open in some positive manner. 

A new sprinkler head with the same rated temperature is placed in the system by the maintenance department. Once the main water valve to the sprinkler system was shut off, the security service that provided alarm service was notified of the down time. The alarm conqiany is now contacted to report that the repair has been made and the water pressure has been restored to the system. The chain and lock is then placed back on the valve while it is in the open position. 

N-Benzoyl-Lalanine methyl ester is in turn about eight times more reactive than is its D enantiomer). The open-chain compounds may not bind to the enzyme in the same manner, however, as does the locked substrate. The conformation around the amido bond of the open-chain compounds, for example, can be transoid rather than cisoid (81). In addition, if equatorial 24 is considered to be the reactive conformer for both the Dand L enantiomers, and if the alanine methyl group is attracted to the hydrophobic aromatic binding subsite, then structures 34 and 38 would result. The L enantiomer of N-benzoyl-phenylalanine methyl ester 38 in this representation has approximately the same conformation as equatorial L-24. But attraction of the methyl of the D enantiomer to the location occupied by the methyl group of the L enantiomer causes the carbomethoxy group to move from the position it occupies in D-24. 

---