Sewers seals

The loss of AM-9 as a construction tool was lamentable, but not catastrophic. The furor among grouters would have died down quickly except for one factor. Over the years since its introduction, a very specialized and sophisticated sewer sealing industry had grown around the use of AM-9 (see Chapter 20). Those involved in this industry began an immediate search for an AM-9 replacement. 

Imported acrylamide dominated the sewer-sealing industry until the acrylate grouts appeared. Both are now in use, with the acrylamides still getting the lion s share. 

A second polyurethane grout CR-260 (3M Company, St. Paul, Minnesota) was marketed primarily for sewer sealing applications. It is applied internally through a packer inside the sewer and acts as a gasket in the spigot. (This type of application is covered in greater detail in later chapters.) Newer formulations are intended for use as soil stabilizers. 

Since its introduction in the early 1980s, AC-400 (acrylate) has come into use in sewer-sealing applications. Other acrylate grouts are also claiming a share of this market. 

AH vapors, including hotweH odors, are captured in a header system linked with the incineration air of a steam boiler or hot oil vaporizer. Drain seals avoid escape of odors from the sewer lines. This completely eliminates total reduced sulfur (TRS) emissions. The SO2 emissions are subject to local regulations. 

A design pressure of 545 kPa, gage is normally specified for water disengaging drums. The water outlet system is designed to seal the drum and prevent entrainment of hydrocarbon or air into the sewer. Figure 5 indicates the normal layout incorporating a single loop seal. 

In some cases, it is possible to combine the functions of blowdown and disengaging drums in one vessel. However, PR devices discharging liquid hydrocarbons lighter than pentane should not be connected into the drum if there is a possibility that such liquids could accumulate and be released to the sewer through the seal leg. Also, the drum vent should be sized to prevent pressure buildup due to vaporization. In these applications, the design criteria for both services must be met and special attention should be paid to potential hazards and problems which may be introduced, such as ... 

The area below the stack and windbreaker is paved with concrete, surrounded by a 200 mm curb, and graded to a central drain point from which a drain line is routed to a manhole in a vented section of the oily water sewer. The water inlet should be sealed and the manhole should be located at least 15 m from the windbreaker. 

The 300 mm water seal is maintained by the location of the overflows which discharge to the oily water sewer through the primary seal loop. The water... 

However, pollution considerations may make the routing of seal water to the sewer unacceptable, in which case disposal must follow method (3) below. 

Where overfilling or leakage from the tank would contribute to a fire hazard, cause damage to property or contaminate drains or sewers, a bund wall should be constructed around the tank. This should be of brick or concrete with an oil-tight lining, and sealed to the concrete base under the tank supports. The capacity of the bunded area should be at least 10 per cent greater than that of the storage tanks contained within it. 

Openings around water pipe entries and sewer exits that pass through concrete can be easily sealed using caulks. Many builders use plastic sleeves to protect metal pipes from corrosion when they pass through concrete. In this case, an effort can be made to leave a space around the pipe that can be sealed with caulk or backer rod and caulk. The same techniques can be used for pipes passing through block walls. 

Drain to daylight if possible, or to a drywell or sewer. If you must use an interior sump pump, seal it. 

Enclosures Enclose room or equipment and place under negative pressure. Enclose hazardous operations such as sample points. Seal rooms, sewers, ventilation, and the like. Use analyzers and instruments to observe inside equipment. Shield high-temperature surfaces. Pneumatically convey dusty material. 

Normal Operational Releases Process storage or sewer vents, relief valve outlets, tank seals, which are considered normal and acceptable practices that release to the atmosphere. 

Common practice and a general guide is to prevent combustible vapors from transmitting from one process area to another process area, generally 15.2 meters (50 ft.) or more away. Usually unsealed receptacles, such as drain funnels, tundishes, drain boxes, are routed to the nearest local sealed catch basin and then into the oily water sewer main. The unsealed receptacles are only allowed in the same process area equipment where if vapors where released from an adjacent unsealed receptacle it would be "immaterial" due to the proximity to where the liquid is being drained and would normally emit vapors. 

Steam sterilization is limited in the types of medical waste it can treat, but is appropriate for laboratory cultures and/or substances contaminated with infectious organisms. The waste is subjected to steam in a sealed, pressurized chamber. The liquid that may form is drained off to the sewer or sent for processing. The unit is then reopened after a vapor release to the atmosphere, and the solid waste is removed for further processing or disposal. One advantage of steam... 

Process, chemical, or oily water sewer system branch and lateral lines should enter main lines through vapor-sealed and vented manholes. Branches and laterals in clean or storm water drainage systems may enter main lines without vapor seals if liquid-sealed catch basins are used on the inlets to these branches and laterals. 

No open process or chemical sewer drains should be under or in the drainage zone from a fired process heater since the heater could ignite flammable vapors present in the process/chemical sewer. Where pro-cess/chemical sewer drains are required at a fired heater during cleanup and maintenance, the drain openings should be sealed by a gasketed and bolted cover prior to startup of the heater. 

The major potential pollutants from the various solvent refining subprocesses are the solvents themselves. Many of the solvents, such as phenol, glycol, and amines, can produce a high BOD. Under ideal conditions the solvents are continually recirculated with no losses to the sewer. Unfortunately, some solvent is always lost through pump seals, flange leaks, and other sources. The main source of wastewater is from the bottom of fractionation towers. Oil and solvent are the major wastewater constituents. 

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