A structural platform or civil platform is normally a horizontal surface at an elevated level usually provided for maintenance and easy access (operation) to required items such as valves, instruments, etc. Sometimes pipes and piping items can be supported from platforms. There is an abundant use of structural platforms in the Oil & Gas and Power Plant Industries.
Piping loads have to be transferred to the Civil and Structural Department after pipe stress analysis for taking consideration in platform design. However, heavy loads are not normally supported by platforms. At the same time, platforms are generally not designed for high horizontal loads. In such situations, some alternate structural arrangement is recommended.
Types of Structural Platforms:
Refer to Fig. 1, 2, and 3 for visualization of structural platforms. Normally 3 types of structural platforms are used in Oil and Gas/ Power Plant Industry, and those are:
OPERATING: Used for personnel movement for operating the valves/switch panels only
MAINTAINANCE: Used for maintenance of valves/equipment
MANIFOLDS: number of pipes are branching in one line
Fig. 1: Typical Structural Platform 1
Fig. 2: Typical Platform 2
Fig. 3: Typical Platform 3
Inputs for Designing Structural platform:
PIPING LAYOUT: The piping layout will reflect the needs of the platforms.
SIZE AND ELEVATIONS will be provided
PIPE SUPPORT LOADING (IF ANY)
NORMAL LIVE LOADS
Access walkways: 250 kg/sq.m
Operating floors: 500 kg/sq.m
Special case(heat exchanger): 750 kg/sq.m
Approach to Structural Platforms:
Depending on the use of structural platforms and space availability, ladders or staircases are used for ascending and descending purposes,
Standard drawings for:
ladders
staircase
Covering of Platform:
Gratings and chequered plates as the covering of platforms depending on the use
Field Welding, as the name specifies, is done outside the manufacturing shop where the outside environment is not controlled. As most of the time it is done on construction sites, it becomes very challenging to maintain the quality of the welded product. In this article, I will cover a few important points for the requirements of field welding of various components like piping, tanks, structures, etc.
Documents Applicable for Field Welding:
ASME Code SectionⅨ
ASME Code B31.1 / B31.3
AWS D1.1
General Requirements During Field Welding:
Base Metal:
Before welding, the base metal that has to be welded must be confirmed to fulfill all the requirements which are specified in the applicable codes, standards, and local/company specifications as per applicable material certificates.
Welding Consumable:
The materials of welding consumables in all applicable welding processes must meet all the requirements mentioned in the governing codes, standards, and company specifications with the applicable consumable certificates.
All Welding consumables shall be positively segregated according to grades, brands, and size. They shall be stored in facilities to prevent any moisture absorption, contamination, or rust generation. They shall be free from such harmful defects as the exfoliation or crack of covering flux, dirt, and grease.
Prior to starting the welding, covered electrodes for low-hydrogen type shall be fully dried in accordance with the manufacturer’s recommendation (e.g. between 300℃ to 350℃ for 1hr). After drying, these electrodes shall be stored in the electrode oven between 100℃ to 150℃. If 4 hours have elapsed since these electrodes were taken out of the oven, they shall be re-dried. The number of times of re-drying shall be up to 2 times.
Backing Strip:
A permanent backing strip shall not be used.
Temporary backing strips used at the welded joint shall be removed.
Shield Gas:
In accordance with applicable code and standard. Shield gas, backing gas, and trailing gas to be used for GTAW shall be Ar gas.
Requirements for Welding machine and Related Equipment:
All welding equipment such as torches, cables, grinders, and heating equipment shall be maintained in good working order and calibrated as necessary.
Earth cable for welding source shall be attached to base metal stably using cable holders. If a copper alloy cable holder is used, it shall be prevented from contact directly between the base metal and copper alloy cable holder by means of inserting a steel plate.
Field Welding at Construction Sites
Groove:
The shapes and dimensions of grooves to be welded shall be in accordance with applicable codes and standards or shall be approved in WPS and drawings.
For carbon steel, flame cutting and beveling are acceptable only if the cut surface is reasonably smooth and sound, and all oxides are removed by grinding from the flame-cut surface.
For low alloy steel, flame-cut bevels are acceptable only where machine mechanical cutting is not feasible. After flame-cutting, approximately 2.0 mm of material shall be removed from the surface of the bevel by grinding.
For stainless steel, mechanical means or plasma cutting shall be acceptable. The grooved surface shall be smoothly finished by removing completely all burrs caused by machining, and surface oxides caused by plasma cutting.
Fitting:
Parts that have to be welded shall be fixed by jigs, clamps, bridges, or direct tack welding so that required dimensions and orientations can be obtained. The materials of jigs or bridges welded to base metals shall be the same materials as the base metals.
Tack welding shall be done only by qualified welders using the approved WPS. Welding electrodes to be used for tack welding shall be the same grades or brands as those to be used for production welding.
After completion of welding, jigs or bridges shall be removed and their vestiges shall be finished smoothly by grinders to prevent any harmful defects such as under-cut in the base metal.
The allowance of dimensions and orientations for fitting-up to be welded has to be in accordance with the applicable document and the approved WPS.
Cleaning:
Prior to welding, the groove surfaces and their adjacent areas shall be completely free from oil, paint, low melting point metal, oxides, water, and all other foreign matters.
Weather:
Temperature-Welding work shall not be allowed under –10℃ of ambient conditions.
Rain / Wind-Welding works shall not be allowed, while rain, snow, or wind conditions could affect the quality of welding work unless suitable protection facilities are provided.
Requirements for Field Welding:
Welding shall be performed according to the approved WPS by qualified welders/welding operators.
The Arc starting point shall be in the bevel surface or tab plates. Arc termination and starting point shall not overlap those of the previous layer.
After completion of welding from the first side of double butt welds, the initial root pass, including root tack welds, shall be chipped, ground, or gouged to sound metal. The back-chipped welds, welding groove, and plate edges shall be examined to ensure that all cracks, laminations, pinholes, and other defects have been removed prior to commencing welding on the second side
For stainless steel, the width of weaving shall be less than approximately 2.5 times the diameter of the electrode.
Except for austenitic stainless steel, welding passes shall be performed consecutively as a rule so that there is no interruption between the start and finish of welding. The number of welding layers shall be two or more as a rule, including socket welding for piping.
Welding may be interrupted after a joint has been welded 1/2 thickness of base metal or 3rd layer or more. In the case of Cr-Mo steel, post-heating after interruption and pre-heating before restarting shall be applied in accordance with the applicable code, standard, specification, and WPS.
When the ambient temperature is not more than 5℃, pre-heating shall be applied within the temperature range of 30℃ to 50℃
Pre-heating temperature shall be measured by the use of temperature-indicating crayons, thermocouple pyrometers, or other suitable methods to assure that the required pre-heating temperature is obtained prior to and uniformly maintained during the welding operation.
For Cr-Mo steel, according to the level of Cr contents, the pre-heating temperature shall be in accordance with the following.
1/2% < Cr ≦ 2% : 150℃ or more
2% < Cr ≦ 9% : 200℃ or more
For austenitic stainless steel, pre-heating shall not be applied as a rule.
For stainless steel except for austenitic stainless steel, pre-heating shall be applied in the temperature range of 150℃ to 350℃.
Interface Temperature:
For carbon steel, the interface temperature shall be between 100℃ to 350℃.
For Cr-Mo steel, the interface temperature shall be between the temperature of pre-heating and 350℃.
For austenitic stainless steel, the interface temperature shall not be over 150℃.
For stainless steel except for austenitic stainless steel, the interface temperature shall be between 150℃ to 350℃.
Post-heating:
If the final Post Weld Heat Treatment (PWHT) cannot be carried out immediately on completion of welding, The post-heating temperature which is over its preheating temperature shall be applied.
PWHT:
All applicable codes, standards, and specifications shall be followed during the post-weld heat treatment. It must be done once all welding is completed.
PWHT has to be performed locally by means of electric induction heating, electric resistance heating, or high-frequency electric heating. Alternatively, furnace heat treatment using gas or electricity can be also acceptable. However, the use of fixed or handheld-type gas burners shall not be acceptable.
Inspection:
Governing codes, standards and specifications are to be followed while Tests and inspections are conducted at each stage of field welding.
Repair:
Before starting the repair weld, The WPS for repair weld and production WPS shall be approved. Once repair welding is finished, the repaired area has to be re-inspected by the same means previously used.
Special Field Welding Requirements for Piping:
Welding consumable:
When the operating temperature is above 345 ℃ for 2-1/4Cr-1Mo steel, each batch or heat of welding consumable and covered electrodes, including the wire flux combinations used in welding, shall be analyzed for P, Sn, Sb, and As. This analysis has to be done on the weld metal deposits. The Temper Embrittlement Factor, X-bar, must be maintained as below;
X-bar = (10P + 4Sn + 5Sb + As) / 100 ≦ 15 (PPM)
Element concentrations are in PPM i.e, parts per million.
Welding:
The welding position should be a 1G position as much as possible.
Fillet welding to pressure retaining components shall be ground to a smooth, concave contour.
Peening shall not be permitted.
Each welder/ welding operator shall mark his proper identification mark on the pipe surface near his executed welding.
Pre-heating:
For carbon steel with an operating temperature above 100℃, pre-heating shall be required for the below-mentioned services;
The thickness of the base metal is 25 mm or more.
The tensile strength of the base metal is 490N/mm2 or more.
Ceq ( = C + Mn/6 + Si/24 ) of base metal is 0.45% or more.
The width of pre-heating shall be 3 times of base metal or 25mm at both sides of the welding bead which is larger.
Post-heating:
The joint that has been welded shall not be allowed to be cooled below 149℃ before heat treatment. In case this is not practical, the weld along with the adjacent pipe shall be heated uniformly to 316℃ for 15 minutes wrapped with insulation, and then allowed to cool. Then PWHT may be performed later.
PWHT:
PWHT has to be performed for the following services;
Cr-Mo steel piping for all services
Carbon steel piping containing amines at a concentration greater than 2.0 eight %
Any other service specified in the applicable code, standard, and specification.
Process Industries uses various types of equipment for different process reasons. The main purpose of this presentation is to discuss the basic aspects related to fixing an appropriate location for the piping design of static equipment. Static equipment generally found in process plants are as follows:
The fired heater shall be located in the upwind direction or at least crosswind from sources of hydrocarbon leaks.
The minimum distance is required between the fired heater and the fractionating tower and reactor.
Provide tube removal/maintenance space within battery limits. Crane access may be necessary, especially for vertical tubes.
Provide space for removal/maintenance of burners, soot blowers, and convection sections.
Knockout drums for fuel gas supply to fired heaters shall be located as close as possible.
Fig. 1: Figure of a typical Fired Heater
Fixing the Location of Reactors
The location shall be as close as possible to Fired Heaters so that piping is short and simple.
Reactors shall be located for ease of access during catalyst unloading and loading operations.
Space shall be allowed for cranes and storage of spent and new catalysts.
A separate structure with the platform is required for catalyst loading and unloading.
Space shall be allowed for TW- removal & maintenance.
Fig. 2: Figure of a typical Reactor
Fixing the Location of Exchangers
Locate exchangers at grade unless the elevated location is required by the Client.
Shell and tube exchangers shall be located with channel end away from pipe ways to facilitate tube bundle removal.
For exchangers under drums or unit structures, where ever possible the channel end shall be clear of overhead structures for the handling of the channel end by mobile equipment.
Heat exchangers containing flammable liquids above 260 C, or their auto-ignition temperature (if lower), shall not be located beneath other equipment.
Exchangers shall be located close to the associated equipment and pipe rack, so that the piping is short, but has adequate flexibility.
Piping Thermal Insulation is very important for saving energy costs and maintaining the process fluid temperature at the required level. In case, thermal Insulation is appropriately chosen and used so that it is Non-complaining, Maintenance-free, and Patient workhouse, It looks after the economy with tremendous savings in energy costs, the safety of personnel, and smoother process control.
On the other hand, insufficient or poor piping insulation or deterioration of existing thermal insulation can be a cause of huge energy loss. So most of the time, thermal Insulation is defined as, “A major tool in improving energy availability”. The thermal insulation material is also important to achieve low thermal conductivity and low thermal inertia.
The basic objective of thermal insulation is to retard the flow of heat:
From a hot surface to a cold environment or
From a warm environment to a cold surface
Insulated Pipes
Energy Loss from Hot Surface Without Thermal Insulation
Fig. 1A and Fig. 1B below show a typical example of heat losses from the piping surface if the pipe is not insulated.
Fig. 1A: Example showing Heat Loss from Hot Surfaces
Fig. 1B: Energy loss from the pipe without thermal insulation
The heat loss values are normally corrected by the correction factor for certain applications.
Economic Reasons for Thermal Insulation:
Piping thermal insulation
Reduces fuel consumption, and hence overall operational cost so day-to-day economic benefits.
Reduces capacity requirements for heating/cooling systems (boiler, refrigeration unit, etc)
Savings in Capital costs
Even though the basic requirement for providing thermal insulation is Economic, still it is not the sole criterion. The process requirement controls the usage of thermal insulation.
Process Reasons for using thermal Insulation:
Reduces the temperature drop of fluid in a heated system
Reduces temperature gain of fluid in the refrigerated system.
Reduces boil-off rate in a volatile liquid storage system
Assist in maintaining thermal balance in the reaction system
In the heated system, it lowers temp. of exposed surfaces-protects workmen from burn hazard
Provides fire protection for plant, equipment & piping
Reduces capacity requirements for heating/cooling systems (boiler, refrigeration unit, etc)
Economic Thickness for Thermal Insulation
The thermal insulation thickness for which the total cost (insulation material cost + energy cost) is minimum is termed as economic thickness. Refer to Fig. 2 below which shows the total cost for a typical plant. Similar curves are plotted to find out the economic thermal insulation thickness.
Fig. 2: Determination of Economic Thickness
By virtue, Insulation shall resist heat transfer by:
Radiation
Convection
Conduction
Types of Thermal Insulation
Mass-type insulation: Based on interposing a mass of material with a built-in capacity to retard heat flow
Reflective Insulation: Based on providing a series of the reflective surface with the intervening space s evacuated
Microporous Insulation: Based on a combination of Mass & Reflective technologies.
Physical Properties of Thermal Insulation Materials
Significant physical parameters of thermal insulating materials can be divided into:
Thermal Properties
Chemical Properties
Commercial Factors
Thermal Properties:
The basic thermal parameters that thermal insulation materials should possess are:
Temperature resistance
Thermal conductivity
Thermal diffusivity, and
Thermal shock resistance
Chemical Properties of Insulating Material:
Major Chemical properties of insulating materials are:
Compatibility with the metal surface
Compatibility with environmental media
Deterioration arising out of the chemical action
Life of insulation material
Points to remember while selecting thermal insulating materials:
Alkalinity (pH) or acidity
Chemical Reactivity/passivity
Coefficient of Expansion / Contraction
Compressive Strength & Breaking Load
Abrasion Resistance
Combustibility
Most importantly, THERMAL CONDUCTIVITY
Thermal Conductivity Vs Density:
The thermal conductivity of a material provides the heat loss per unit area per unit insulation thickness per unit temperature difference. The unit of measurement is W-m2/m°C or W-m/°C. With an increase in temperature, the thermal conductivity of materials increases. That is why the thermal conductivity for thermal insulation materials is always specified at the mean temperature (mean of hot and cold face temperatures). Fig. 3A provides a curve showing the relation between thermal conductivity and density of the thermal insulation material.
Fig. 3A: A curve showing the relation between Thermal Conductivity and Density
Refer to Fig. 3B below which provides some typical thermal conductivity values for hot and cold insulation materials.
Fig. 3B: Thermal conductivity of hot and cold thermal insulation materials
Widely used Hot Insulating Material:
Mineral Wool
Ceramic Fibre
Calcium Silicate
Widely used Cold Insulating Materials:
Expanded Polystyrene Foam (EPS)
Extruded Polystyrene Foam (XPS)
Polyurethane Foam (PUF)
Poly-isocyanurate Foam (PIR)
Foam glass
Phenolic Foam
Thermocol
Among the above-listed materials, Polyurethane and Polyisocyanurate have assumed the highest importance because these possess many superiorities as compared to others. Both of these materials can be used as Pre-formed shapes or installed in-situ-by Pouring or by spraying.
Insulation Finishes:
The outer part of insulation is normally provided with:
Weather barriers-claddings
Weather and Vapor retarder, Indoor coverings, and finishes
All of these have only one basic function which is to protect the insulation material from severe external exposure media.
Thermal Insulating System Design
The insulation system should perform to the expected level, undiminished over its life.
This needs full data on material behavior under all conditions of exposure.
In particular, we need to know what would make a material lose its properties.
Thermal calculations need a representative value of Thermal Conductivity for the design
Standard materials like Rockwool and Calcium Silicate have well-established Design ‘k’ values.
Limiting Service Temperature of use
In pipe applications, weight becomes critical. Abrasion is also a major problem with some materials.
Calculation of Thermal Insulation Thickness
The most basic piping model with thermal insulation is shown in Fig. 4. where r1 denotes the pipe outside radius and r2 shows the radius of the Pipe including insulation.
Fig. 4: Typical Pipe Cross Section with Insulation
In the calculation of thermal insulation, the first step is to calculate the heat loss from the pipe.
Heat loss from a surface is expressed as H = h X A x (Th-Ta) Where
Th = Hot surface temperature (for hot fluid piping), ºC & Cold surface temperature for cold fluids piping)
For horizontal pipes, the heat transfer coefficient can be calculated by:
h = (A + 0.005 (Th – Ta)) x 10 W/m2-K
For vertical pipes,
h = (B + 0.009 ( Th – Ta)) x 10 W/m2-K
Here A, and B are coefficients that can be obtained from the table in Fig. 5
Tm = ( Th + Ts)/2
k = Thermal conductivity of insulation at a mean temperature of Tm, W/m-oC
tk = Thickness of insulation, mm
r1 = Actual outer radius of the pipe, mm
r2 = (r1 + tk)
Rs = Surface thermal resistance =1/h oC-m2/W
Rl = Thermal resistance of insulation =tk/k ºC-m2/W
The heat flow from the pipe surface and the ambient can be expressed as follows
H = Heat flow, Watts= (Th-Ta)/(Rl+Ra)=(Ts-Ta)/Rs
From the above equation, and for a desired Ts, Rl can be calculated. From Rl and the known value of thermal conductivity k, the thickness of insulation can be calculated.
Equivalent thickness of insulation for pipe, Etk = (r1+tk) X ln{(r1+tk)/r1}
A hose coupling is a connector that connects a hose to another hose or tap of sprinkler systems or equipment. They are manufactured in different varieties and widely used in water, chemical, and oil & gas industries. Depending on service requirements hose couplings are made of various materials like brass, steel, stainless steel, aluminum, or plastic. The purpose of this article is to provide brief information about different types of hose couplings which are used in oil & gas applications.
The following types of Hose Couplings are widely used:
Elaflex
TODO
Cam and Groove (Camlock) Couplings
Avery Hardoll dry-break couplings &
Carter couplings
Let me show them 1 by 1 in detail.
Elaflex Couplings:
These hose couplings are produced by Elaflex and are used in petrol station equipment, Tank truck equipment, Aircraft refueling, chemical and pharma industries, LPG refueling, Marine applications, Rail Tankers, and Oil & Gas applications. The main features of Elaflex hose couplings are
Elaflex hose coupling sizes – ½” to 4”
Type of pipe connection – threaded & flanged
Available Pressure classes – 150# & 300# (Working pressure up to 25 bar)
The material of construction of the Elaflex coupling – Brass (for non-sour service), SS (for sour service)
Manufacturing Std. – API RP 1004 / EN 14420
Fig. 2: Typical figure of Ela Flex Coupling
TODO Coupling:
Available sizes – 3/4” to 6”
Type of pipe connection – threaded & flanged
Pressure class – 150# & 300# (Working pressure up to 25 bar)
The material of Construction – Brass, SS, Aluminium, Hastelloy C & other on request
Manufacturing Std. – EN 13480 and EN 13445
TODO couplings are used for tanker unloading connection into a tank/vessel, because of the integral check valve.
Elaflex couplings are used for tanker loading connection from a tank/pit.
Fig. 3: Typical figure of TODO Coupling
Cam & Groove (Camlock) Couplings:
Available sizes – 1/2” to 6”
Type of pipe connection – threaded
Pressure class – 150# (Working pressure up to 17 bar)
The material of Construction – Brass, SS & Aluminium
Fig. 4: Typical figure of Camlock Couplings.
Carter Couplings:
Carter Couplings are used in the following applications:
Bolted joints are extensively used in the piping industry. Flanged joints can only be thought of with proper bolting. So the selection of appropriate bolts plays an important role in proper joining and preventing leakage. In this article, I will try to list some requirements governing the selection of bolting to complete a flanged joint.
The bolt selection criteria can be grouped into two limitation categories:
Physical Limitations.
Material Limitations.
Let me broadly classify this:
Physical Limitations during Bolt Selection
Threading Requirements: All threads shall be in accordance with ASME B1.1.
Jack Screws: Jackscrews shall be used to facilitate flange separation for maintenance. Joint assemblies that often require frequent separation include orifice plates, spectacle plates, spacers, screens, and drop-out spools. The piping layout shall be designed such that flanges can be separated without excessive force. Jackscrews shall be installed to be accessible from both sides of the pipe. For orifice flanges, jackscrews shall be installed at 3 and 9 o’clock positions. When flange separators are used, jackscrews are not required. Jack screws shall be the same material as the flange bolts.
Bolt Selection:Bolting for flanged joints shall be selected for service by service temperature, and corrosivity of the environment.
Bolt Lengths and Sizes: Bolt length and diameter are determined by the flange standard used. Each of the following flange standards has a method for the determination of bolt length.
Bolt Length: Bolts shall be expressed with inch diameters, and the length in millimeters rounded up to the nearest 5 mm.
Flanges Not Covered: Flanges not covered by the above standards shall be considered non-standard, and bolting is to be handled on an individual basis.
Washers: There are two types of washers as listed below
Flat Washers: Flat washers under the nuts are required for special cases only, such as on insulating flanges and under the nuts bearing against plastic flanges.
Belleville Washers: Belleville washers may be required for severe cyclic service, and bolt service temperatures above 4500 C.
Material Limitations for Bolt Selection
General Process: Bolting Materials for process and general services shall be ASTM A193 Grade B7 stud bolts with ASTM A194 Grade 2H nuts for service temperatures from minus 20 to plus 4500 C.
Low Temperature: Bolting Materials for low-temperature services shall be as follows:
Stud bolts conforming to ASTM A320 Grade L7 with nuts to ASTM A194 Grade 4 or 7 shall be used for bolt service temperatures from minus 18 to minus 101 deg. C.
ASTM A320 Grade L7M studs and A320 Grade 7M nuts may be used for low-temperature services from minus 18 to minus 73°C.
Stud bolts conforming to ASTM A320 Grade B8 with nuts to ASTM A194 Grade 8 shall be used for bolt service temperatures from minus 101 to minus 195 deg. C
Bolting Materials for Upper Intermediate Temperature Services:
ASTM A193 Grade B7 or B7M studs with A194 Grade 7 or 7M nuts for services up to 450 deg. C.
ASTM A193 Grade B16 stud bolts with A194 Grade 7 nuts, for bolt service temperatures from 450 to 510 deg. C.
When B8 class 2 bolts are used for temperatures over 650°C, strain-hardened bolts will be required to seat the gasket. Windings for high-temperature gaskets are most likely type 347 or Inconel.
At temperatures over 650°C, strain hardened will anneal. As long as the joint is not broken, the annealed bolts have adequate strength to hold the joint.
Materials For Sour Service:The bolting materials for sour services shall be as follows:
Standard quenched and tempered ASTM A193 Grade B7 stud bolts with 2H nuts shall be used for sour wet services when the bolting is as follows:
Not directly exposed to hydrogen sulfide
Not buried or insulated
Not equipped with flange protectors, or not deprived of direct atmospheric exposure.
ASTM A320 Grade L7 stud bolts with Grade 4 or 7 nuts can be used under the same conditions.
Stud bolts conforming to ASTM A193 Grade B7M with nuts to A194 Grade 2HM shall be used under the following conditions:
Direct exposure to sour environments
When the bolting will be buried or insulated
When the flange is equipped with flange protectors, or otherwise deprived of direct atmospheric exposure.
ASTM A320 Grade L7M bolts and Grade 7M nuts can be used under the same conditions.
Machine Bolts: Steel machine bolts conforming to ASTM A307 Grade B may be used on flat-faced cast-iron or non-metallic flanges in the non-sour environment. Nuts shall conform to ASTM A563 Grade D. This bolt and nut combination may be used in sour services when the Grade D nuts are not desulfurized. This system is also suitable when the use of “weak” bolting is specified to avoid overloading flanges. Such bolting may be zinc coated.
Expansion and Contraction: When fluid temperatures are below minus 45 deg. C, the selection of bolting material or the bolting design shall include consideration of differential contraction between flanges and bolts such that changes in gasket seating pressure will not result in leakage. Similarly, differential expansion shall be considered at operating temperatures above 300 deg. C.
Purchase Description for Bolts
The following information shall be included in the Purchase Description:
