Showing posts with label condensate return. Show all posts
Showing posts with label condensate return. Show all posts

Thursday, November 2, 2017

Steam Condensate Return Stations

duplex condensate return station
Duplex condensate return station
Image courtesy Roth Pump
Closed steam systems produce condensate, a dense source of heat. By design, the delivery of heat in a steam system is almost entirely accomplished using the heat of vaporization, with any sensible heat transfer probably being more coincidental than intentional. Condensate will contain most of the sensible heat that was added to the feedwater to get it to the boiling temperature. Conserving that sensible heat through a reuse of the hot condensate is a huge energy saving step. The condensate must be collected and returned to the boiler in a effective manner.

A condensate return station is a common means of moving condensate back to the boiler. It will generally consist of a collection vessel for the liquid condensate and one or more pumps to provide the motive force to move the liquid along its return path. Reliability is a key factor for these systems, since it is conceivable that they may need to perform on a continuous basis for years. A duplex pump arrangement can provide some backup, as well as extra capacity for accommodating large inlet flow. This is an installation where investing in rugged hardware can pay dividends in reduced maintenance burden and trouble free performance for the long term.

Roth Pump Company has been designing and manufacturing condensate return stations and other steam system related components for many years. Their experience and expertise are part of each and every system that leaves their factory. By incorporating low RPM motors, heavy duty pumps, and other features into a compact form factor, the company is able to offer a number of systems that meet a wide range of applications and deliver solid long term performance.

Share your steam system and condensate return requirements and challenges with application experts, leveraging your own experience and knowledge with their product application expertise.


Friday, July 21, 2017

Pressure Motive Condensate Pumps



In a closed steam system, condensate must be returned to the feedwater side of the boiler. Moving this condensate effectively through the system is essential to maintaining design performance levels throughout the system. Condensate can be considered "spent steam", but still retains great value as preheated and treated feedwater for the boiler.

Three general methods are employed to transport condensate from where it is collected to where it is reused. If the facility layout permits, gravity can be the motive force to move the condensate back to the boiler. A second option is a mechanical pump, unsurprisingly called a condensate pump. The third common option is to employ system steam pressure to drive the condensate through the return piping and back to the boiler.

The concept of gravity return for the condensate is easy to envision....liquid flows downhill. Mechanical pumps, as well, are a well understood means of moving liquids. When the condensate collector reaches a certain fill level, the pump is energized and the liquid is forced through the return piping.

Using pressure as the motive force for condensate return involves coordinated operation of inlet, outlet, and vent openings to the condensate collection vessel. A float inside the collection vessel and a connected mechanism provide control of the valves at the vessel openings. In the video, you can see how the valve operating sequence provides for periods of condensate collection, then condensate discharge.

Share all of your steam system challenges with application specialists, combining your own process and facilities knowledge and experience with their product application expertise to develop effective solutions.

Tuesday, May 2, 2017

Steam Traps

high pressure float type steam trap cutaway view
Cutaway view of high pressure float type steam trap
Courtesy Spirax Sarco
Steam is widely used throughout industrial, commercial, and institutional facilities and a means of transferring heat energy, as well as a wide array of other applications. Steam generation cost is a substantial line item on almost any balance sheet, so deriving the most efficient level of operation from a steam system pays tangible dividends.

Utilizing the heat content of steam, in a closed system, results in the production of condensate. Condensate is hot liquid water which can be returned to the boiler and re-vaporized. Managing the separation of the liquid condensate from the process steam and sending it to the lower pressure condensate return line is the function of a steam trap. A steam trap filters out condensate (condensed steam) via an automatic valve. The trap also removes air without letting process steam escape. By filtering out the condensate and not the steam, steam waste is minimized. Steam traps generally are self-contained automatic devices. Since steam based heating processes generally rely on latent heat transfer for rapid and efficient operation, it is necessary to continually collect and transfer condensate from the steam containing portion of the system. The condensate will reduce heat exchanger performance if allowed to accumulate.

Historically, there have been three main types of steam traps: mechanical traps, thermostatic traps, and thermodynamic traps. Most commonly used mechanisms rely on differences in temperature, specific gravity, and pressure. The mechanical trap was originally developed as a bucket trap, which was a rather large trap where a bucket floated up or down to open and close a valve. Bucket traps with a lever, which face downward – also known as ‘closed bucket’ traps – are still used today as a float type trap. Processes requiring large capacities for discharge still currently use the bucket type or float type trap, with long services lives. In the modern version of a free float trap, the condensate is continuously discharged while the valve opening is constantly controlled by the amount of buoyant force acting upon a tightly sealed float.

Thermostatic traps are a smaller, more compact design. Using a temperature sensing mechanism, and operable by mechanisms like bellows or bimetal rings, these thermostatic traps have a slower response. Processes relying on rapid condensate discharge most likely will not use thermostatic traps. An example of a trap used in the process industry today is a bimetal temperature control trap. The trap includes steam tracers and will discharge when a certain condensate temperature is reached.

The core limitation of thermostatic steam traps – the slow response time – has been addressed via the development of the thermodynamic steam trap. The thermodynamic trap operates on the expansion and contraction of an encapsulated liquid. This version of steam trap allows for the smallest amount of condensate accumulation. Early models resulted in unacceptable levels of steam loss. As a result, the commonly used disc type trap was developed for mainstream use. The disc type is compact, versatile, and relatively affordable in terms of installation costs. In the modern disc type, pressure fluctuations in the chamber above the valve result in the valve’s opening and closing. Though in use for many years, development and refinement continues on steam traps, bringing ever better performance to this ubiquitous steam specialty.

Share your challenges with a steam system specialist, combining your own process and facilities knowledge and experience with their product application expertise to develop effective solutions.

Tuesday, May 24, 2016

Understanding Condensate Pumps on a Steam Distribution System

industrial steam system
Diagram of industrial steam system
(courtesy of Watson McDaniel)
condensate pump is a specialized device intended for use in transferring condensate (water) produced in an industrial steam system. Condensate from a heating system or process is collected, then pumped to the condensate return system, where it is routed back to the boiler for reuse.

In certain cases, the steam pressure of the system may be sufficient to push the condensate through the steam traps and condensate return lines, back to the condensate holding tank in the boiler room. In most practical situations, however, one or more condensate return pumps are required to assist in overcoming gravity, pressure drops from long piping runs, and back pressure in return lines.

Condensate Return Pumps are either electrically-driven centrifugal pumps or non-electric mechanical pumps that use steam pressure as the motive force to pump the condensate. Non-electric pumps are referred to as Pressure Motive Pumps (PMPs).

A facility will often have a separate area that contains various components required for the generation of steam, such as a boiler, condensate holding or deaerator (DA) tank, boiler feed pump, water treatment, etc. Regulated by the boiler control system, the boiler feed pump sends condensate from the holding tank back to the boiler.

Pressure Motive Pumps (PMPs) are non-electric pumps which return condensate back to the boiler room; using steam pressure as the motive force. PMPs can be supplied as stand-alone units – which include a pump tank, the internal operating mechanism, and a set of inlet and outlet check valves, or: as a packaged system – which also includes the vented receiver tank (to collect the condensate) mounted on a common base.

The following is a comprehensive document, courtesy of Watson McDaniel, that provides a good general understanding of steam and condensate systems, traps and condensate pumps. 



Thursday, October 29, 2015

Steam Heat Exchanger Stall - Eliminate It For Best Performance

Steam Heat Exchanger
Industrial Steam Heat Exchanger
Courtesy JFD Tube & Coil Products
Efficient and reliable operation is always an objective of a steam system owner or operator. If your system employs heat exchangers, an understanding of heat exchanger stall will put you on a path to efficient operation, lower maintenance, and possibly longer useful life for major parts of your system.

Heat exchanger stall occurs when low load conditions reduce the steam pressure in the heat exchanger, decreasing the pressure differential across the steam trap to a point below the back pressure in the condensate line. The resulting condition causes condensate to back up into the heat exchanger, reducing its efficiency. There are other negative effects that are illustrated in the animated video below, produced by world recognized steam system experts Spirax Sarco and presented by Mountain States Engineering, a distributor in the Western US.

The video is useful and comprehensible to a wide range of  skill and knowledge levels. It takes only four minutes to view, and will leave you with a better understanding of how you can get consistent and efficient performance from your steam system.

For a steam system survey and evaluation, contact the engineers at Mountain States Engineering. They have the technical knowledge, products, and other resources to deliver solid and positive solutions for keeping your steam systems at peak operation.