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Mar 30, 2010

Plate & Frame Heat Exchanger



 


The plate and frame heat exchanger was one of the first compact exchanger to be used in the UK process industries, being originally introduced in 1923: the first plates were made of gunmetal. It is currently second to the shell and tube heat exchanger in terms of market share.





APPLICATION


These exchangers are relatively compact and lightweight heat transfer surfaces, making them attractive for use in confined or weight-sensitive locations such as on board ships and oil production platforms. Pressures and temperatures are limited to comparatively low values because of the gasket materials and construction.he most variant of the plate and frame heat exchanger consist of a number of pressed, corrugated metal plates compressed together into a frame.




 


These plates are provided with gaskets, partly to seal the spaces between adjacent plates and partly distribute the media between the flow channels.






These exchangers are usually built of thin plates (all prime surfaces). Generally, exchangers cannot accommodate very high pressures, temperatures, and pressure and temperature differentials. The most common plate material is stainless steel.
MAIN COMPONENTS




The heat transfer surface consist of number of thin corrugated plates pressed out of a high grade metal. the pressed pattern on each plate surface induces turbulence and minimizes stagnant areas and fouling. Unlike shell and tube heat exchangers, which can be custom-built to meet almost any capacity and operating conditions, the plates of plate and frame heat exchangers are mass-produced using expensive dies and presses. Therefore, all plate and frame heat exchangers are made with may appear to be limited range of plate designs.








The plate pack is clamped together in a frame suspended from a carrying bar. Gaskets are fitted to seal the plate channels and interfaces. the frame consists of a fixed frame plate at one end and a movable pressure plate an the other. The movable plate facilitates access for cleaning or exchanging the heat transfer surfaces. The feature of this type of heat exchanger is the ability to add or remove surface area as necessary.









The plates are grouped into passes with each fluid being directed evenly between the paralleled passages in each pass. Whenever the thermal duty permits, it is desirable to use single pass, counter flow for an extremely efficient performance. Although plate and frame exchangers can accept more than two streams, this unusual. Two-pass arrangements are , however, common.














Plates can be produced from all press able materials . The most common construction materials are:
  • Stainless steel (AISI304, 316)
  • Titanium
  • Hasteloy
Usually the frame is made of coated mild steel, as it should not under normal circumstances, come into contact with the process fluids. The surface coatings vary according to the exchanger environment. Frame can be stainless steel or clad with stainless steel as an alternative to mild steel.


Gasket properties have critical bearing on the capabilities of a plate heat exchanger. in the terms of its tolerance to temperature and pressure.


Gaskets are commonly made of:
  • Hypalon
  • Nitrile rubber
  • Viton
  • Neoprene
  • EPDM
Originally, most manufacturers used glue to fix the gaskets to the plates. Proprietary fixing techniques are available that eliminate the need to use glue, and most manufacturers have adopted these methods. These so-called 'glueless' gaskets are suitable for some heavy duty industrial applications. The simplified removal and location of such gaskets can be beneficial, as it reduces downtime when on-site changing is necessary. 


Care should be taken in locating the gaskets during reassembly, as imperfect sealing is the main disadvantage of the plate and frame heat exchanger. 



OPERATING LIMITS


The operating limits of gasketed plate and frame heat exchanger vary slightly from manufacturer to manufacturer. Typically, the operating temperature range of the metal plates is from -35oC to +200oC. Design pressures up to 25 bar can be tolerated, with test pressures to 40 bar.


Heat transfer areas range 0.02 m2 to 4.45 m2 (per plate). Flow rates of up to 3500 m3/hr can be accommodate in standard units, rising to 5000 m3/hr with a double port entry. Approach temperature as low as 1oC are feasible with plate and frame heat exchangers.


The surface pattern on the plates tends to induce good mixing and turbulence, and in general this type of heat exchanger has a low propensity for fouling. Fouling resistances of typically 25% of those for shell and tube heat exchangers have been measured by Heat Transfer Research Incorporated (HTRI) in the USA.

Mar 15, 2010

Heat Exchanger (Intro)
















 A heat exchanger is a device that is used for transfer of thermal energy (enthalpy) between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at differing temperatures and in thermal contact, usually without external heat and work interactions.

The fluids may be single compounds or mixtures. Typical applications involve heating or cooling of a fluid stream of concern, evaporation or condensation of a single or multicomponent fluid stream, and heat recovery or heat rejection from a system.

Reasons for heat transfer include the following:

1. To heat a cooler fluid by means of a hotter fluid
2. To reduce the temperature of a hot fluid by means of a cooler fluid
3. To boil a liquid by means of a hotter fluid
4. To condense a gaseous fluid by means of a cooler fluid
5. To boil a liquid while condensing a hotter gaseous fluid


In other applications, the objective may be to sterilize, pasteurize, fractionate, distill, concentrate, crystallize, or control process fluid. In some heat exchangers, the fluids exchanging heat are in direct contact. In other heat exchangers, heat transfer between fluids takes place through a separating wall or into and out of a wall in a transient manner. Heat can flow only from the hotter to the cooler fluid.


In most heat exchangers, the fluids are separated by a heat transfer surface, and ideally they do not mix. Such exchangers are referred to as the direct transfer type, or simply recuperators. In contrast, exchangers in which there is an intermittent heat exchange between the hot and cold fluids via thermal energy storage and rejection through the exchanger surface or matrix—are referred to as the indirect transfer type or storage type, or simply regenerators. Such exchangers usually have leakage and fluid carryover from one stream to the other. Heat exchangers may be classified according to transfer process, construction, flow arrangement, surface compactness, number of fluids and heat transfer mechanisms or according to process functions.

We will discuss on various type of Heat Exchanger that used in Oil & Gas Industries around the world in the next post.

Apr 23, 2009

New Dawn brings New Perspectives

The oil and gas industry has to adjust to a new order where global dept and liquidity markets have all but dried up, crude prices are almost $100 per barrel than last July’s record and gas prices have slumped by even greater percentage.

National oil companies, multinationals and smaller independents alike are restructuring, shedding thousands of jobs and revamping corporate strategies while projects around the world are being deferred of shelved.

Many contractors are being hit by cancellation of drilling rig and offshore vessel newbuildings as clients find themselves unable to raise the necessary financing.
Some oil companies and contractors less able or willing to change with the times will inevitably fall by the wayside in 2009, either filing for bankruptcy or by being swallowed up by others with access to funds for acquisition.

Also, many governments will suffer as revenues, royalties and taxes from oil and gas operations this year take a slide. But is it all gloom and despondency?

History shows us that the industry has faced peaks and troughs before and will most certainly do so again. Many of the projects under way now are long-term ones where savings on capital expenditure can be achieved as a result of lower rig rates and costs for some is an opportunity for others, with the strongest and most nimble players left to sift through countless investment prospects.

The bottom line is that the world needs hydrocarbons and the recent slowdown in exploration and development activity will soon have a tangible effect on output, which in turn will drive commodities prices right back up again.

It might be years, rather than months, before the upturn is felt across the sector but there is little doubt that those which can weather the current storm will emerge leaner and meaner to rise to future challenges.

Apr 15, 2009

Does this happen to your "Project"?

please click this picture to enlarge

Apr 13, 2009

Production System on Offshore Platform

Many permanent offshore platforms have full oil production facilities onboard. It is the facility which performs processing of production fluids from oil wells in order to separate out key components and prepare them for export. Typical production fluids are a mixture of various hydrocarbons and are valuable in this natural form.



The production systems consist of the following :

  • On-boarding System
  • Oil Production Separation/Dehydration
  • Oil Export Well Cleanup and Unloading
  • Gas Compression System (i.e. Surge, LP, MP and HP Compression System)
  • Gas Reinjection System
The on-boarding system is designed to receive subsea wells production from the Drill Centers. HP Separators are designed as two-phase separator to separate out gas and liquids of the well fluids for further gas and oil processing downstream.


Oil from the HP Separators will be routed to a series of vessels for stabilization and dehydration prior to export. The MP Separator is provided to remove gas and water from the crude oil. Separated crude is routed through the Oil Heater to enable the oil to achieve the required RVP, before being transferred to the LP Separator and then the Oil Treater for dehydration to meet 0.5 BS&W. The treated oil will be routed to the Surge Vessel, which is provided (as a buffer) to hold up surge volume for the Oil Booster and Export Pumps. Oil Booster Pumps will then boost the crude oil pressure for the dry oil from Surge Vessel to be transferred to the Crude Oil Export. Crude Oil Export Pumps are designed to deliver the dry metered oil to onshore during normal operations via pipeline or tanker.
Process Flow Diagram of Typical Platform Separation Process
The Well Cleanup Separator is provided to handle well unloading fluids and containing drilling and completion fluids with spent acids.
The stages of compression (i.e. Surge, LP, MP and HP Compression Systems) are to be provided to satisfy the demand of gas gathering from various separators, fuel supply to fuel consumers and gas reinjection.
The Gas Reinjection Manifold will gather gas discharges from HP Compression System for reinjecting back to the reservoir.



Apr 9, 2009

Oilfab wins Carigali-PTTEP deal

Malaysian offshore engineering company Oilfab is primed to start work for the JDA Block B-17 development which lies in the Malaysia-Thailand joint development area after landing a 64 million ringgit ($17.7 million) deal with Carigali-PTTEP.

The contract covers the engineering, procurement, construction of topside, plus offshore hook-up and commissioning of the Muda D wellhead platform, that will lie in the joint development area 268 kilometres east of Songkhla, Thailand, or 171 kilometres north-east of Kota Baru, Kelantan, Malaysia.

The work starts immediately and is expected to be complete by the fourth quarter this year, Oilfab said today.
from upstreamonline,Wednesday, 08 April, 2009

Apr 8, 2009

Oil and Gas Production




Today oil and gas is produced in almost every part of the world, from small 100 barrels a day small private wells, to large bore 4000 barrels a day wells; In shallow 20 meters deep reservoirs to 3000 meters deep wells in more than 2000 meters water depth; In 10000 dollar onshore wells to 10 bullion dollar offshore development.











The main function of process plant on an offshore installation is to separate hydrocarbon product into liquid and gaseous phases and to remove any impurities that could inhibit transportation, such as water. The refinement process is loosely described as production.





The production processes rely on very basic principles of fluid flow and thermo-dynamics and the the reader would be justified in expecting to find a virtually standard design of offshore installation . In practice, this is certainly not the case for whilst to certain extent the process equipment must be tailored to suit individual reservoir condition, it is often Company policy which exerts the greatest influence on platform design, an aspect of offshore engineering which can be particularly frustrating. However, whilst equipment lay out may vary from installation to installation, the processes is quite similar in general principles of operation.


Process System