Closed drain system

Prior to moving the rig and all auxiliary equipment the site will have to be cleared of vegetation and levelled. To protect against possible spills of hydrocarbons or chemicals the surface area of a location should be coated with plastic lining and a closed draining system installed. Site management should ensure that any pollutant is trapped and properly disposed of. 

Usually, the closed liquid drain header is run as a separate line to the drum and provided with a high level cut-off valve with local manual reset. In some cases the closed drain system is segregated into a number of subheaders, as described earlier. Hydrocarbon liquids may be bypassed around the drum through a connection from the closed drain header directly to the pumpout pump suction, provided that the liquid can be routed to a safe disposal location, considering its vapor pressure and temperature. Emergency liquid pulldown connections, if provided, are routed to the blowdown drum via the closed drain header. 

Another common problem area is having open and closed drain systems tied together. Liquid which drains from pressure vessels flash at atmospheric pressures giving off gas. If this liquid flows in the same piping as open drains, the gas will seek the closest exit to atmosphere it can find, causing a potential fire hazard at any open drain in the. system. 

One of the greatest challenges to do with practical risk analysis is defining the scope of the hazard term. For example, with respect to the second hazard in the above list—an overflow of T-100—more detail is needed. Clearly there is an enormous disparity between having a few drops spill into a closed drain system and having thousands of liters of the chemical pour on to the ground and then flow into the local waterways. 

Throughout this book, the importance of defining risk terms correctly is emphasized. Words such as probability, risk, and consequence have specific meanings. Yet even when risk terms are defined correctly, the words tend to have different meanings to different people and in different contexts. As discussed, the hazard of Spill from T-101 may mean that just a few drops of RM-12 flowed into a closed drain system, or it may mean that large quantities of the liquid entered an environmentally sensitive wetland area. Nonetheless, many hazards analysis teams will not thoroughly define the term Spill from T-101 in detail. 

Carbon steel—For closed drain systems, cooling, and fire water. 

Process equipment drains should be provided with a sealed drainage system where it is practical and backpressure from the system or contamination is not a concern. Open drain ports should be avoided and separate sewage and process/oily water or closed drain system capability provided. Surface drainage should be provided to remove liquid spills immediately... 

A drain system that is connected directly to pressure vessels is called a "pressure" or "closed" drain system. A drain system that collects liquids that spill on the ground is an "atmospheric," "gravity," or "open" drain. The liquid in a closed drain system must be assumed to contain dissolved gases that flash in the drain system and can become a hazard if not handled properly. In addition, it must be assumed that a closed drain valve could be left open by accident. Once the liquid has drained out of the vessel, a large amount of gas will flow out of the vessel into the closed drain system (gas blow-by) and will have to be handled safely. Thus, closed drain systems should always be routed to a pressure vessel and should never be connected to an open drain system. 

If ah systems are go, turn on the seal gas. Open the expander and eompressor ease drains to purge systems. Close drains and eheek seal gas pressure. Seal gas temperature must be 70-80°F downstream of the regulator. 

Closed Drain Header Systems for Flammable Liquids... 

Typically, the level of glycol required in a HW heating system is only 15 to 25% v/v or so (less than the 35 15% usually employed in cold and chilled-water closed-loop systems). Where glycols are added, the system must be cleaned and flushed first. The system can be partly drained to accommodate the volume of 100% glycol required or alternatively filled with a prediluted mix. If a 20% v/v strength is required, 25% v/v should be specified to allow for inaccuracies in mixing. 

Closed-loop systems should lose very little water, perhaps only 5 to 10% of the system volume per year. In practice, however, losses often tend to be much higher than this, perhaps due to unforeseen maintenance work that necessitates a system to be partially drained. A typical loss is more likely to be 50% of the system volume per season. This obviously causes problems with regard to maintaining adequate chemical treatment reserves for effective deposit and corrosion control. In fact, often the first sign that a closed-loop system is losing water is when a periodic test is undertaken and the result indicates a reduced level or complete lack of treatment reserve. 

In some cases a closed drainage system can be used which drains process components directly into the oily water sewer. This has the advantage of avoiding releases of vapors in any instance, but assurance must be obtained that back pressure from one drainage location will not backfeed liquids into another drain point when two valves are open simultaneously or other drainage valves can contain any backpressure on them from other drainage sources. 

Several series of field tests were conducted under different conditions. Row was discharged from a hydrant on EBMUD s water distribution system, through a fire hose and onto a fairly level paved and curbed street close to the curb. The water flowed down the street, into a drop inlet 160 ft downstream. The drop inlet led to an onsite storm drain system at EBMUD s wastewater treatment plant that flows into the headworks of the plant. 

Continuous treatment is understandably more demanding than the other processes, because it requires close monitoring, but it is also more efficient. For example, the particle size of the contact tartrate and the level in the crystallizer must be monitored by sampling after a few hours, using the drain system. 

Closed systems—have vent/drain systems that prevent the release of vapors, gases, and liquids into the atmosphere. 

Amine dehydration. A steam or water leak into the system will dilute the amine. Weak, rich amine becomes acidic and corrosive. To increase amine concentration, reflux water can be diverted to a closed drain. This will require piping the reflux water to a place where H2S can be safely flashed off. Do not drain this water to an open sewer it is supersaturated with deadly HjS. This is one mistake nobody makes more than once. 

Because it is possible to sudt the water se out of a P-Trap caused by the introduction of variable flow rates downstream, it is important to vent undeiground drain systems properly. ] chibit 13-49 shows how the vent is branched off the dean-out line. The vent line may discharge into the atmosphere or closed system for disposal. 

As stated in the introduction to the previous chapter, adsorption is described phenomenologically in terms of an empirical adsorption function n = f(P, T) where n is the amount adsorbed. As a matter of experimental convenience, one usually determines the adsorption isotherm n = fr(P), in a detailed study, this is done for several temperatures. Figure XVII-1 displays some of the extensive data of Drain and Morrison [1]. It is fairly common in physical adsorption systems for the low-pressure data to suggest that a limiting adsorption is being reached, as in Fig. XVII-la, but for continued further adsorption to occur at pressures approaching the saturation or condensation pressure (which would be close to 1 atm for N2 at 75 K), as in Fig. XVII-Ih. 

For low pressure pipelines that have ports open to the atmosphere, eg, sewers or closed effluent culverts, samplers are designed to sample through manholes. In a typical system, the Hquid is lifted through a suction line into the sampling chamber under vacuum. When filled, the vacuum shuts off, and the sample drains into a sample jar. A secondary float prevents any Hquid from reaching the vacuum pump. The suction line then drains by gravity back to the source. 

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