Valve and steam trap

Where new boilers are married to old steam and condensate systems, similar effects occur because of the transport of debris and the resultant blockages of valves and steam traps. Where the replacement boilers are of a higher rating than the existing boilers, the problems are further exacerbated (often due to surging, faster steaming times, or increased steam velocities). 

The steam circuit is complete with automatic valves, safety relief valve, and steam traps. The supply of sterile steam is the responsibility of the customer. Steam injection is done through the CIP ports to ensure uniform steam distribution within the chamber. 

Are the control valve and steam trap functioning correctly ... 

EXHIBIT 8-31 Improper Valve and Steam Trap Location... 

K Make ond Model for Flow, Temperature and Pressure Control Volves, Hand Valves, Thermometers and Steam Traps, Eiectrieol Components and Miscellaneous Equipment. 

Coil boilers often use automatic, TDS-controlled solenoid valves to control BD. They are installed following the steam separator and steam trap. 

Valves, piping, and vessels Pumps, compressors, fans, and blowers Steam turbines and motors Heat exchangers and cooling towers Boilers and furnaces Reactors and distillation columns Instrumentation Basic hand tools Lubrication, bearings, and seals Flares, mixers, and steam traps... 

Examples of Vacuum-Related Accidents Figure 26-47 shows a jacketed tank, where the jacket was designed for low-pressure steam. When the steam was turned off and the drain valve and trap were closed, the steam condensed, causing the jacket to collapse. The jacket should have been designed for full vacuum, or a suit le vacuum relief device should have been installed on the jacket. 

Water hammer can also occur in steam mains, condensate return lines, and heat exchange equipment where steam entrapment can take place (Fig. I). A coil constructed and installed as shown here, except with just a steam trap at the outlet, permits steam from the control valve to be directed through the center tube(s) first. Steam then gets into the return header before the top and bottom tubes are filled with steam. Consequently, these top and bottom tubes are fed with steam from both ends. Waves of condensate are moved toward each other from both ends, and steam can be trapped between the waves. 

It is easy to improperly design a steam trap. The design must work for two circumstances and often a designer will check only one of these. The circumstance often overlooked is as follows On startup or upset the steam control valve can open wide so that the steam chest (assume for this discussion that we are speaking of a reboiler) pressure rises to full steam line pressure. At a... 

The incident occurred soon after the main had been brought back into use after a turnaround. It was up to pressure, but there was no flow along it. The steam trap was leaking and had been isolated. An attempt was made to get rid of condensate through the bypass valve. But steam entered the condensate header, and the line was isolated, as shown in Figure 9-9. Condensate then accumulated in the steam main. 

Moke end Model for Flow, Temperoture and Pressure Control Valves Hand Voives Thermometers, Steam Traps and Strainers, Electrical ortd other miscellaneous equipment. 

The procedure can be made more automatic by using a temperature-sensitive liquid expansion steam trap in place of the manual valve. Such an arrangement is a compromise between supervised start-up and the automatic start-up discussed below. 

Second, any valve which has been designed to operate on steam should not be expected to work at its best when supplied with a mixture of steam, water and dirt. A separator, drained through a steam trap, will remove virtually all the water from the steam entering the pressure-reducing set. The baffle type separators are found to be effective over a wide range of flow rates. 

Condensate from the low-pressure coil together with that from the flash vessel will then drain to a collecting tank, or direct to a condensate pump, for return to the boiler plant. If the pressure of the flash steam is left to find its own level it will often be sub-atmospheric. As the condensate must then drain by gravity through the steam traps these also must be sufficiently below the condensate drain points to provide an appropriate hydraulic head, and a vacuum breaker fitted above the coil. The alternatives are to allow the condensate to drain directly to a condensate pump, or to supply additional low-pressure steam through a pressure-reducing valve, to maintain a positive pressure in the coil and flash vessel. 

The second element is a device which will open or close the valve by measuring some parameter of the fluid reaching it and deciding whether this may or may not be discharged. It would be found that the controlling elements mainly fall into one of three categories. The steam trap can decide automatically whether to open or to close to the fluid reaching it on the basis of ... 

Steam lines from the boiler should always drain away from the boiler crown value to prevent condensate building up against the valve. Careless opening of this valve to allow steam to pass when the line is flooded can result in splitting the valve and pipework. If the steam line rises from the crown valve a tee trap must be installed and fitted with a steam trap and drain valve. The drain valve must be operated to check that the steam line is clear of water before the crown valve is opened. 

Carbon dioxide, from the decomposition in the boiler of temporary hardness salts present in some waters, causes corrosion of steel steam pipework and cast iron valves and traps. Corrosion inhibitors may be used, but the choice of inhibitor must take into account the other materials in the system. Neutralizing amines such as morpholine or cyclohexylamine are commonly used. 

On a single-evaporator flooded system, a float valve can be fitted which will pass any drained liquid from the condenser direct to the evaporator. The action is the same as that of a steam trap. The float chamber is at condenser pressure and the control is termed a high-pressure float (Figure 8.3). 

The condensate return system is a post-boiler section system that includes all steam traps, condensate lines, associated manifolds and valves, condensate receiving tanks, save-all tanks, condensate pumps, and other auxiliaries for condensate recovery. 

Float thermostatic steam traps employ a float valve that rises in the presence of condensate and then opens to permit the discharge of the condensate. 

Inverted-bucket steam traps contain a small bucket that becomes buoyant if steam is present and shuts off a discharge valve. The presence of condensate causes the bucket to sink and the discharge valve to open. Any entrained air is removed through a small hole in the bucket. 

Impulse steam traps rely on steam to maintain pressure on a piston and valve arrangement. When air and condensate enter the trap, the pressure is reduced above the piston and the valve opens. 

The flash vessel should be fitted with a float or inverted-bucket type steam trap to the condensate discharge line, and also a pressure relief valve to prevent excess pressure buildup, as may happen if the demand for LP steam drops below the flash steam production rate. 

An alternative way to use flash steam is to provide several, small self-contained FSHR systems, keeping the system pipework to a minimum and lagging the pipes to avoid unnecessary heat losses. Flash steam forms at the point where the pressure drops, which is at the BD valve or the valve seat of the steam trap. From this point the flash steam and condensate travel together until the flash vessel is reached. The vessel then acts as a steam-water separator. 

Carryover refers to the entrainment of BW (and the contaminating solids contained in the water) into the steam. Contamination of steam from entrained water may lead to deposits in superheaters, on turbine valves, and in steam traps, valves, and flash vessels. 

Other system problems Uncontrolled and excessive water losses Pump, valve, steam trap losses and no water meter leads to Oz pitting, Fe fouling and deposits of carbonate... 

Under these conditions, because the neutralizing amine has no effect on oxygen ingress, it is common to supplement the neutralizing amine blend with a filming amine. Thefilmer may be applied separately (usually to a steam header) or blended with the neutralizers and added to the FW, or sometimes directly to the boiler. Care should be exercised when filmers are employed in previously corroded systems because it is very likely that old corrosion debris will be transported away to cause severe blockages in steam traps and valves. 

A pipeline that passes around an injection point, valve, control point, heater, steam trap, or other device in order that repairs or other work can be carried out on the bypassed item of equipment as and when required. 

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