Check Valve

Check (non-return) valves are installed in pipelines to allow flow in one direction only. It is operated entirely by reaction to the line fluid and therefore do not require any external actuation. Types including lift, disc, swing and wafer check valves.

Types of Check valves

Lift / Piston check valves

The piston-type lift check valve is a modification of the standard lift check valve. It incorporates a piston shaped plug instead of the cone, and a dashpot is applied to this mechanism. The dashpot produces a damping effect during operation, thereby eliminating the damage caused by the frequent operation of the valve, for example, in pipeline systems, which are subject to surges in pressure, or frequent changes in flow direction.

The main advantage of the lift check valve lies in its simplicity, and as the cone is the only moving part; the valve is robust and requires little maintenance. In addition, the use of a metal seat limits the amount of seat wear. The lift check valve has two major limitations; firstly, it is designed only for installation in horizontal pipelines, and secondly, its size is typically limited to 3”, above which, the valve would become too bulky.

Swing check valves

A swing check valve consists of a flap or disc of the same diameter as the pipe bore, which hangs down in the flow path. With flow in the forwards direction, the pressure of the fluid forces the disc to hinge upwards, allowing flow through the valve. Reverse flow will cause the disc to shut against the seat and stop the fluid going back down the pipe. In the absence of flow, the weight of the flap is responsible for the closure of the valve; however, in some cases, closure may be assisted using a weighted lever. As can be seen from below picture the whole mechanism is enclosed within a body, which allows the flap to retract out of the flow path.

 

Swing check valves produce relatively high resistance to flow in the open position, due to the weight of the disc. In addition, they create turbulence, because the flap 'floats' on the fluid stream. This means that there is typically a larger pressure drop across a swing check valve than across other types.

Wafer check valves

Both lift and swing check valves tend to be bulky which limits their size and makes them costly. To overcome this, wafer check valves have been developed. By definition wafer check valves are those that are designed to fit between a set of flanges. This broad definition covers a variety of different designs, including disc check valves and wafer versions of swing or split disc check valves.                                                  

                  



         

Disc check valves

The disc check valve consists of four main components: the body, a disc, a spring and a spring retainer. The disc moves in a plane at right angles to the flow of the fluid, resisted by the spring that is held in place by the retainer. The body is designed to act as an integral centering collar that facilitates installation. Where a 'zero leakage' seal is required, a soft seat can be included.

When the force exerted on the disc by the upstream pressure is greater than the force exerted by the spring, the weight of the disc and any downstream pressure, the disc is forced to lift off its seat, allowing flow through the valve. When the differential pressure across the valve is reduced, the spring forces the disc back onto its seat, closing the valve just before reverse flow occurs. This is shown in Figure above The presence of the spring enables the disc check valve to be installed in any direction.

Codes and standard used in Piping

Piping Codes

A code is a standard that has been adopted by one or more governmental bodies and has the force of law (ASME definition).

A standard can be defined as a set of technical definitions and guidelines, “how to” instructions for designers, fabricators, and operators. Standards promote safety, reliability, productivity, and efficiency in almost every industry that relies on engineering components or equipment.  Standards can run from a few paragraphs to hundreds of pages and are written by experts with knowledge and expertise in a particular field who sit on many committees. 

Standards are considered voluntary because they serve as guidelines, but do not of themselves have the force of law. ASME cannot force any manufacturer, inspector, or fabricator to follow ASME standards.  Their use is voluntary. Standards become mandatory when they have been incorporated into a contractual document (client specification requirement) or incorporated into regulations.

Standards are a vehicle of communication for producers and users. They serve as a common language, defining quality and establishing safety criteria. By following the same standard, interchangeability is assured. 

ASME codes that commonly used in piping for offshore platform are: 

ASME B31.3 - 2006 Process Piping

This ASME B31.3 code contains requirements for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, & cryogenic plants, & related processing plants terminals.

ASME B31.8 - 2007 Gas Transmission and Distribution Piping Systems

This ASME B31.8 code covers the design, fabrication, installation, inspection, testing, and safety aspects of operation and maintenance of pipeline facilities used for the transportation of gas.

ASME B31.4 - 2006 Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

This ASME B31.4 code contains requirements for piping transporting crude oil, natural gas liquids, liquefied petroleum products and other liquids between natural gas plants, refineries, and other facilities.

ASME B16.5 - 2003 Pipe Flanges and Flanged Fittings: NPS 1/2 through 24

This ASME B16.5 code covers pressure-temperature ratings, sizes, marking, materials, dimensions, and tolerances, for pipe flanges and flanged fittings of class designations 150, 300, 400, 600, 900, 1500, and 2500.

ASME B16.47 - 2006 Large Diameter Steel Flanges: NPS 26 Through NPS 60 Metric/Inch Standard

These ASME B16.47 standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges NPS 26 through NPS 60 and in Classes 75, 150, 300, 400, 600 and 900.

ASME B16.25 - 2003 Buttwelding Ends

These ASME B16.25 standard covers preparation of buttwelding ends of piping components joined into a piping system by welding, including welding bevels for heavy-wall components, and preparation of internal ends.

ASME B16.20 - 1998 Metallic Gaskets for Pipe Flanges: Ring Joint Spiral Wound and Jacketed

This ASME B16.20 standard covers materials, dimensions, tolerances, and markings for metal ring-joint gaskets, spiral-wound metal gaskets and metal jacketed gaskets used with raised face and flat face flanges.

ASME B16.21 - 2005 Nonmetallic Flat Gaskets for Pipe Flanges

This ASME B16.21 standard cover types, sizes, materials, dimensions, tolerances, and markings for nonmetallic flat gaskets used with various flange standards.

ASME B16.34 - 2004 Valves Flanged, Threaded and Welding End

This ASME B16.34 standard covers new construction including pressure-temperature ratings and dimensions for cast, forged, and fabricated flanged, threaded, and welding end, and wafer or flangeless valves.

ASME B16.10 - 2000 (R2003) Face to Face and End to End Dimensions of Valves

This ASME B16.10 standard covers face-to-face and end-to-end dimensions of straightway valves, and center-to-face and center-to-end dimensions of angle valves for assurance of installation interchangeability.

how to works Intrusive Pig Signaller?

Pig Signaller

Once a pig has been inserted into a pipe system its position cannot be visually confirmed directly. A system is therefore required to indicate a pig’s position, either continuously or intermittently at pre-determined points in the pipeline. Continuous detection is known as ‘pig tracking’ whilst intermittent detection is referred to as pig signalling. Each method involves the use of specialized equipment which, in most instances, must be incorporated into the pig or piping system before the pig is launched.

 

Pig tracking requires an active transmitting source to be attached to the pig, with various technologies being used to provide that source - electro-magnetic, acoustic and radioactive. Pig signalling, however, falls into two categories: intrusive and nonintrusive. Non-intrusive signallers are predominantly electro-magnetic and, along with pig tracking techniques, are covered more fully elsewhere. 

Intrusive pig signallers are, by definition, static, mechanically actuated and provide a momentary indication of a pig’s presence at a specific point in the pipeline. Because the actuating mechanism is a mechanical trigger that intrudes into the pipeline, a signaller must also incorporate a satisfactory means of retaining the pressure within the pipeline.

Every signaller must incorporate a mechanism that will provide a positive indication that a pig has passed. This is normally done in one of two ways:

  1.   Mechanical/Visual (a local flagged indicator)
  2.   Electrical (magnetically linked proximity switch provides an electrical signal to a controller)

Pig signallers are robust and designed to be installed for long periods. They are particularly suitable for inclusion in a pig trap system at points along the pipeline where the course of the pig must be confirmed (e.g. wyes, diverters, tees) and for providing a warning of approach at receiver and booster stations.

 


There are two types of Pig Signaller

  •     Intrusive type pig signaller
  •     Non-intrusive type pig signaller 

Intrusive Pig Signaller - Operating Principles

When a pig passes beneath a correctly installed signaller the pig discs push the protruding bi-directional trigger forward in the direction of the pig travel. The trigger is hinged at two points which converts the angular motion gained from contact with the pig into axial motion withdrawing a spring-loaded, permanent magnet holder down through the cap. At rest, the proximity of the magnet at the top of the cap retains the mechanical, spring-loaded flag and/or the contacts of an externally mounted proximity switch.


When the magnet is withdrawn, the magnetic flux influencing the components diminishes, the flag springs into an upright position and/or the proximity switch contact is broken. (This can be detected by a linked controller). Immediately after the pig has passed, the spring in the cap returns the magnet and the linked trigger to their respective resting positions ready to detect the next pig – from whichever direction it arrives. The flag of an MV/MVE must be manually reset. Proximity switches, however, will be reset at the control panel

Non-intrusive type pig signaller

Non-intrusive type pig signaller is quick and Easy for installation on the pipe. There is no hot-tapping required non-intrusive type pig signaller. Non-intrusive type pig signaller can be installed in minutes by any field technician. Non-intrusive means less maintenance and corrosion, and no possibilities of pipeline leaks.




What is gland packing?

Gland Packings

A stuffing box used for shaft sealing may be one employing gland packings or using mechanical seals. Easily replaceable without opening the whole pump, gland packings give stiff competition to mechanical seals, but the packings have to be carefully selected to be successful.

Gland Packing

Gland packing is used extensively for the sealing and restriction of leakage of the working fluid along the stem in valves and along the shaft in the case of pumps and also for stationary duties like manhole cover sealing. The technology has developed over a period. Originally old ropes and natural fiber products were used for sealing ... with varying degrees of success. The technology has now progressed to such an extent that now several combinations of artificial fibres and cutting-edge materials are used, and gland packings are even used in harsh applications like nuclear environments and in the handling of corrosive products.




 

Gland packing installation is not only a science but is also an art as its success depends on the skill of the operator installing it. The life of the gland packing greatly depends on how they were installed, no matter what grade of packing you use. Great prudence is required in the adjustment of the gland packing as a minimum leakage is to be allowed for the cooling and the lubrication purposes. An uninitiated engineer would invariably over-tighten the glands, leading to the burning of the packing and scored shaft and shaft sleeves.

Applications of Gland Packing

Gland packing are used for sealing in the following applications:

·        Stationary applications like tanks hatch cover sealing, manhole covers sealing, etc.

·        Used for reducing leakage along the stem in globe valve, gate valve, and ball valves.

·        Used for reducing leakage of the working fluid in reciprocating pumps.

·        Used for reducing leakage of the working fluid in rotating pumps like centrifugal pumps, and screw and gear pumps.

·        In propeller shaft sealing in lifeboats and on old generations of merchant ships. 

All the above are entirely different applications, and hence the type of gland packing to be used also differs. Selection also depends on the nature of the fluid to be handled like temperature, pressure, corrosiveness, and suspended solids, etc. A correct choice of gland packing has to be made by the marine engineer.

Gland Packing Vs. Mechanical Seals

There are two types of stuffing boxes used in the centrifugal pumps and other rotary pumps aboard ship. One type uses a mechanical seal, and the other type uses gland packing. Nowadays almost all new ships have mechanical seals on all the rotating pumps due to very strict pollution laws like Marpol 73/78 and others. Any fluid leakage must be further collected, treated and filtered, with oil stored for discharge to shore reception facilities. Water is to be discharged according to the regulations by approved filtering equipment under 15 parts per million guideline. It amounts to a lot of work, and any marine engineer would vouch for that.


However, in certain applications, gland packing is still used where a mechanical seal may not work properly. In certain corrosive environments, for example, where a mechanical seal may corrode and fail, a gland packing may serve better. In applications like globe, gate, ball valves, and valve cock’s gland packing is used because mechanical seals require a rotary motion for successful sealing action. It is for this reason that reciprocating pumps use gland packing. Sometimes a ship owner may want gland packing to be installed on his ships to cut costs. Also where skilled man power is not available, it is easier to open the gland to change the gland packing, than to open the whole pump for changing the mechanical seal. Also mechanical seals are very expensive as compared to gland packing. Old ships use gland packing extensively. However, a certain amount of skill is required to cut the joints and, in their installation, and removal, as otherwise it is difficult to get consistent results and long life.

The Advantages of Gland packing over Mechanical Seals

Although considered old and low-end technology, the advantages of the gland packings over the mechanical seals are as follows:

·        It is an extremely reliable sealing method.

·        It is very simple to install and maintain.

·        It tolerates poor mechanical conditions like off-center shafts and worn-down anti-friction bearings better than mechanical seals.

·        Works better in abrasive media and corrosive environments than mechanical seals.

·        Reduces the stock holding as one size packing can be used in all similar sized pumps.

·        It is very cost effective in down time as very little time is required to change a gland packing, as little as fifteen minutes.

·        They are less expensive than mechanical seals.

·        The whole pump is not required to be opened for changing the gland packing, however in mechanical seals the pump has to be opened up.

·        The gland packings are not fragile, and any amount of mishandling would not destroy them, unlike the mechanical seals.

Properties of Good Gland Packing

To be successful in its duty and to attain the objective of successful sealing and trouble free operation the gland packing must have the following properties.

·    Anti-friction properties. The gland packing basically rubs along the shaft and stationary along the stuffing box side. If the gland packing has friction, it would score the shaft or the shaft sleeve and also would heat up and fail and even burn due to consistent overheating.

·   Chemical resistance to the fluid being contained. If the gland packing reacts with the fluid, it is supposed to seal it would later disintegrate and be flushed away leading to leakage of the fluid which is not desirable.

·     Temperature resistance. The gland packing should be able to resist the working temperature of the fluid being sealed without failing.

·     Compressibility and resilience. The gland packing should be able to compress and confirm to the shaft under the force of the gland flange and when the tension is released it should come back to its original shape. The latter is important as when the gland nuts are loosened the gland packing should spring back releasing the shaft.

·   Retention of lubricants. All the gland packings are coated with lubricants like graphite, grease, petroleum products etc., also external lubricant is applied before insertion. The gland packing should be able to retain this grease for anti-friction properties.

·     Should not score the shaft. Normally on pumps a shaft sleeve is inserted over the portion where the gland packings are inserted, and which is replaceable. The gland packing should be nonabrasive to avoid the scoring on the shaft sleeve. Of course, on a long interval this is not possible, but it should at least sustain till the next overhaul

·    Should not contaminate the fluid being sealed. In some applications like food and pharmaceutical industries the gland packing should not contaminate the fluid, while in others it does not matter.

·        It should be non-corrosive to avoid damage to the shaft and the housing.

·        It should be wear resistant to last a long time.

·        It should retain its property over a time period.

Different Types of Gland Packing (Materials used)

There are many different types of gland packing depending on the type of applications such as for valve stem sealing, centrifugal pump shaft sealing, reciprocating pump shaft sealing, static duties like hatches sealing and pressure vessels manholes sealing, etc. Gland packings are made from the following basic substances and are a combination of these basic materials and are sometimes reinforced with metal wires for extreme conditions.

·        Jute

·        Flax

·        Hemp

·        Cotton

·        PTFE

·        Aramid

·        Wrapped metal foils

·        Graphite fiber

·        Carbon fiber

·        Glass fiber

·        Poly acryl nitrile fibers

All the gland packing are a combination of the above-mentioned basic materials and great research is done by the manufacturers to develop new and more efficient types of packing. The packing made of a combination of graphite, carbon, glass, etc. are used for harsh applications whereas gland packing made of materials like Jute, flax, hemp, and cotton are used for light applications like sea water, potable water etc. The compound PTFE is versatile and can be used for a wide variety of applications.

Preconditions for a Successful Gland Packing Job

No matter how many times you change the gland packing and how well you have done the job, the success of the gland packing job done would also depend on the following factors.

·   The trueness of the shaft. A shaft that is bent would eat the gland packings prematurely and there nothing you can do except change the shaft. You must make it a point to check the trueness of the shaft during each overhaul using a dial gauge.

·  Concentricity of the shaft with the stuffing box bore. The shaft might be true but if not aligned properly would again destroy the gland packings in no time.

·    Surface roughness of the shaft. If the shaft or the sleeve is pitted or unevenly worn it would again damage the gland packings very fast.

·      Whipping of the shaft due to worn bearings.

·       Consistent cooling water supply in case of pumps with a lantern ring.

Whats are the documents required for equipment layout ?

Equipment layout designing criteria 

The primary consideration in arrangement of equipment's shall be to provide an economical Facility with good weight distribution, minimum lift weight, safe and easy to operate and maintain.

1. All piping components requiring operation or maintenance where practical, shall be Located where they can be operated, serviced conveniently. Access shall be provided to such components if they are located out or reach from platform. Use of chain wheels or Extension stems for the operation of inaccessibly located valves shall be avoided.

2. Piping in banks shall be assigned specific elevation for routing in the north-south and East-west directions. These elevations shall be used throughout except where pockets are to be avoided or where space limitations do not permit use of selected elevations.

3. All piping shall be kept inside the deck area. It shall be taken out of the deck area only if it is unavoidable.

Inputs required starting with equipment layout.

  • Basic description of work (Project specific)
  • Prevailing wind and current direction
  • Maximum wave crest height
  • Installation and construction requirements- by structural dept.
  • Electrical and instrumentation panel and room dimensions with operational and maintenance clearance.
  • Inline instruments dimensions and clearances for operation and maintenance - preliminary
  • Dimensions of instrumentation skids.
  • Process design basis
  • Piping design specification
  • Mechanical and safety design specification
  • Material handling requirement specification
  • Pipeline riser location data.
  • PFD/P&ID
  • Equipment list with basic dimensions (Including Safety equipment's)
  • Vendor drawings or data- Equivalent past project data.
  • Hazardous area classification - preliminary input from electrical discipline.
  • ASME B 31.3, API RP 14E, 14J, CAP-437 and Statutory guidelines

Major parameters of an equipment layout.

  • Platform North - decided based on prevailing wind direction
  • Drill rig approach direction - applicable for wellhead platforms, decided based on prevailing wind direction.
  • Boat I Vessel approach - decided based on prevailing wind direction
  • BOS for lower most deck - considering maximum wave crest height plus specified Air gap.
  • Leg to Leg dimensions - In consultation with Structural dept., Base on project specific requirements
  • Locating Heli deck - Refer CAP 437
  • Number of levels - project specific
  • Basic segregation of Equipment's - Refer API RP 14E

Swing Spool: what is swing spool

Swing spool 

Swing spool is used to change the service/operation in the plant from one system to another system without addition of new pipe spool. Same old pipe spool is used to when switchover   the operation from one service to another service. Swing spool reduce the down time and cost of the of the running plant because existing piping spool is already in the plant within the same location.

Operation team must isolate that system and then take all the necessary approval from safety then do the changeover of swing spool. While doing the changeover of the swing spool operation team need new gaskets and bolts and nuts.  Gasket/bolts, nuts may be damage while removing that swing spool from previous connecting line because that swing spool is operation from long time. It may damage from rust or from the wear or tear while opening the nut/bolts by mechanical forces.  

what is HIPPS

High Integrity Pressure Protection System (HIPPS) valves



HIPPS valves are used as the final part of an instrumented system intended to prevent an unacceptably high pressure occurring in downstream equipment. They are always arranged to fail closed and spring/hydraulic  actuators are usually the only practical alternative for operation.



 In general, closure times should be maximized or, if times have to be short, tests should be undertaken Required closure speed depends on the closed-in volume downstream and the working fluid (e.g. if there is a high volume, gas filled system downstream, valve closure speed need not be fast).


 HIPPS applications have the following characteristics:
  • High pressure always available at time of emergency closure.
  • Low differential pressure during closure;
  • High differential pressure after closure;
  • Requirement for periodic closure (or partial closure) and seat leakage testing; (Occasionally) fast closure.
  • The first two make for particularly benign operating conditions and the temptation to specify an unnecessarily high differential pressure during closure should be resisted.

Deluge system: What is a Deluge system?

 Deluge system

A deluge system is normally the main firefighting system on any Offshore installation, used to protect process-areas, drilling-areas and other high-risk areas. A Deluge system is normally an automatic system, which is triggered by a fire detector in the protected area, and which is using water as the extinguishing agent.

A deluge system consists basically of a Deluge Control Valve, and a distribution piping network with open deluge nozzles. The Deluge Valve is normally closed, and the distribution pipework is dry. The deluge valve is activated automatically when a fire is detected. The distribution piping network is then immediately pressurized, and all nozzles in the system starts flooding the protected area with a predetermined application rate of water.


The deluge valve is usually installed on a skid together with piping, isolation valves, bypass and test/drain facility.

 

Application Deluge system.

 

A deluge system may be used to protect almost any area as it provides:

 

§ Flame extinguishment

§ Cooling

§ Fire control

Deluge systems, using water or water/foam, will extinguish fires in any, or in a combination, of the following ways:

 

§ Surface Cooling

§ Smothering, by produced steam

§ Emulsification

§ Dilution

§ Other factors

 

Except in very rare cases, where the application of water may cause certain chemicals to burn or explode, deluge systems will have a beneficial effect on all types of fires. Even in cases, such as fires in leaking, pressurized Gas equipment, where flame extinguishment cannot be achieved, the overall cooling effect, with the resulting protection of adjacent equipment, will prevent the fire from spreading and will greatly reduce the damage to both equipment and structure.

 

The extinguishing effect of water on Hydro-Carbon pool-fires can be greatly increased using various types of foaming agent, such as AFFF or ATC.

 

Hazard types where Deluge Systems are used:

  •  Hydrocarbon fires
  •  Wellhead Area
  •  Drill floor
  •  Process Areas
  •  Storage and Piping facilities
  • Gas (Jet) fires
  •  Wellhead Area
  • Drill floor

Material used for Deluge system

One of the major considerations, when specifying a Deluge System, is resistance against corrosion. A deluge system will be operated, for testing purposes, only a limited number of times per year, and yet be required to be fully functional 24 hours a day, 365 days per year. Time has proven the Norwegian Offshore environment very hostile to equipment, especially those in contact with seawater, which is stale, i.e. which is not being refreshed continuously.

 

For this reason, the material requirements are constantly under development, and there has, on the Norwegian sector, been a progression, from Steel (Galvanized) over Bronzes (CuNiFer piping, Bronze valves) and High Molybdenum (6Mo) Stainless Steels to, now, Titanium.

 

§ Titanium, all piping and valves

§ Titanium, with Deluge Valve and permanently wetted Isolation valves in Titanium and    normally dry downstream valves and accessories in Al. Bronze

§ CuNi 90/10 piping, with Deluge Valve and isolation valves in Al. Bronze

§ Stainless Steel 316L piping and valves. (Note: normally used with Cathodic protection)

§ Galvanized piping, with Bronze (Gunmetal) Deluge Valve and Rubber Lined valves.