MaryFi Blog

الحمد لله والصلاة والسلام على رسول الله وعلى آله وصحبه أجمعين 

choosing HVAC PIPE WORKS AND FITTINGS Selection Tips 
DETAILED TECHNICAL SPECIFICATION

General

a) They must be installed with a view to an easy and even 
flow of fluid to and from all apparatuses without air pockets
It should be installed for quick, sure and positive drainage 
and provisions for quick and noiseless air escapement

b) All parts of the system must be capable of being vented
air vents must be provided at the highest points of all risers
vents must be piped at their points of connection to 
the piping system and to a visible drain

c) Piping must be run, in general, forming right angles with 
or parallel with walls and neatly spaced, must be installed 
so that there is clearance of at least 25 cm, between
finished coverings and the adjoining

d) Piping must be hung in ceiling void as close as possible 
to bottom of slabs, beams, etc., maintaining required 
and co-ordinated head room at all times

e) Dielectric connections must be provided for joining two 
different pipe work materials or pipes and equipment
in order to isolate cathodically the pipeline or the equipment
These connections must be rated to withstand the 
maximum medium temperature and pressure

f) All necessary line valves for the satisfactory isolation 
of components and sections of the system are to be supplied and fitted

g) Bends should be used in performance to elbows wherever possible

h) Equipment and apparatus must be installed as to be totally 
readily accessible for operation and maintenance

i) Wherever pipe work passes through walls and floors, mild steel
pipe sleeves must be provided sufficient to ensure free movements
In addition, chromium plated floor plates are to be fitted in the 
office blocks or where directed by the Engineer

j) Pipes connected to vibrating machinery must be isolated 
from the supporting structure by vibration eliminators designed 
for supports by hanger rods. Pipes must be isolated from the
vibrating machinery by use flexible metal pipeline connectors 
of metal to suit the fluids conveyed and the surrounding conditions

In all lines carrying liquids drain valves must be installed 
at all low points in the system at the end of every primary or secondary main
at intervals and not more than 75 meters in all horizontal pipe lines
and all equipment positions. The drain connections must be provided 
with a drain line leading down with drain cock to the nearest drain pit

The size of the drain lines and drain cocks must be

1- For pipelines below 4″ dia. the drain line and drain cock must be 1″
2- For pipelines 4″ dia. and above the drain pipe and drain cock must be 1.5″
3- For outside drainage points on 4″ & above pipe works drains must be 2″
4- Dirt pockets must be installed on all pipelines

the dirt pockets must be located in the pipelines at 

1- All low points in the system
2- Ahead of any rise in the piping
3- At every 120m (max) of level piping with a relative 
constant demand during design operation
4- At the end of any primary or secondary main
5- Every 60 M (max.) of level, piping with considerable 
on-off demand during design operation
6- Ahead of all pressure reducing and control valves
unless the branch feeding the valve is taken off the 
top the main and is less than 1.5 m in length

All piping, fittings and flanges must be cleaned and thoroughly 
degrease before assembly. The entire system must present a 
neat appearance for both workmanship and grouping

Welding

Welding must be done by gas or electric arc process using 
equipment and plant laid down by BS 1821 and BS 2633

The method of welding and testing must be in accordance with
the practice recommended by the BSI and AWS

All operatives must be thoroughly experienced and have 
certificate of competency. If necessary, these certificates must 
be produced for scrutiny by the Engineer and welders must be 
required to take such test as required by A.P.I.

Standard 1104 or as required by the Engineer. Lloyd’s Surveyor 
or equivalent. If necessary if there is bad workmanship in the 
opinion of the Engineer, must be instructed to:

a. Forthwith remove the operative responsible from the site
b. Replace all welding works carried out by the Operatives.

When welding is carried out, or a blowlamp used, adequate protection 
must be given to prevent damage to any part of the building 

The outside diameter and the wall thickness of butt-weld fittings 
and welding neck flanges must be the same as the outside diameter 
and wall thickness of the pipes to which they must be welded

Heat generated by welding must not be allowed to accumulate at any bearing
bearing retainer, machined surface, or dis-similar metal components
Precautions must be taken to dissipate the heat as it is generated

The joints must be tested to maximum tension required at the ambient 
temperature and pressure. The joints must also be subject to a compression
test up to a maximum deflection shown on the Data sheet, at service pressure 
and ambient temperature. At the completion of those tests, which are to be 
repeated in accordance with the required number of cycles, the joints are 
to be re-subject to a hydrostatic pressure of 1.5 times the working pressure

After completion of the above tests, the expansion joints must be rejected
if there are any leaks or sign of breakage of any point or part of the bellows

15% of all welds must be X-rayed. This identification number of the joints
must be stamped or painted on a metal sheet and fixed to the expansion joint by wire
Both wire and metal sheets are to be corrosion proof

Jointing

Up to and including 50 mm bare pipe may be either welded or screwed 
for all cold services and hot services up to a working temperature of 85 Deg. C
The pipe must be welded with flanged joints, above the size and where buried 
under ground welding must be permitted with flanged joints

The use of flanges must be limited to the flanged connections to the valves
and equipment and the following

– Location of different access, and high and low points
– Inspection holes
– On straight runs of pipe where frequent dis-assembly operations
for cleaning and maintenance may be necessary. The interval between
flanges should not normally exceed 15 m
– Positions where equipment dis-assembly requires pipe removal
All bolts must be of stainless steel as per BS requirements

Supports and Hangers

All pipe supports and hangers required for installation of the pipes 
must be provided by the contractor. Vertical risers to be provided
with suitable iron clamps. Brackets under the supports of pipes must 
be provided with sheet metal cradles to spread the load. Pipe supports 
pattern to be approved by the Engineer and must be Roller type 

Protective covering shield must be provided between all pipe supports
hangers and the insulated piping. Shield must be made of a stout gauge
galvanized mild steel of sufficient length to prevent depression of pipe covering

Additional supports must be provided and installed within 300 mm 
where pipes change direction and adjacent to flanged valves
strainers, equipment connections and heavy fittings

All vertical pipe run must be supported and laterally braced
at least once, at each building level

Unless otherwise indicated on the drawings, vertical pipes must be supported
with riser clamps, installed below hubs, couplings or lugs welded to the pipe

Hanger and supports must be prepared and painted

Insulated copper pipe must be supported by copper supports or copper plated hangers

Pipe Sleeves

All pipes passing through walls, partitions and ceiling must be provided 
with pipe sleeves. Sleeve size must allow for the free movement of pipes
Sleeves passing through the finished service or exposed to view
must be flush with the surface of the partition through which they pass
and must be provided with suitable end covers of approved pattern and finish

Expansion and Contraction of Pipes

must be dealt with by compensators. In all locations where expansion 
is not taken by piping offsets, they must have stainless steel or chromium 
melypelenum bellows and/or loop. Expansion more than 3/4″, expansion

bellows/loop must be used. They must have 3 rigid plot straps type
guides with adequate bearing surface fixed at 4 times as the 
diameters on each end and suitable to prevent any axial movement
Anchors must be provided between expansion units
These must be of sufficient strength to hold the mains tight against 
movement and withstand the thrust due to pressure and expansion 
but must not crush or injure pipe walls. consult the manufacturer for 
the precise position of the compensator and anchors and the amount 
of expansion that is to be taken by the compensators. make the calculations
of expansion bellows, guides and anchors and obtain approval of the 
Engineer prior to commencement of the works

Flanges

must be provided on both sides of each piece of equipment in the plant
and where required, having diameter 2.5″ and above must be according
to BS 10 or BS 4504 or equal approved

Unions

must be provided on both sides of each piece of equipment
in the plant having diameter less than 2.5″

Dielectric Joints

must be provided for jointing two different pipe work materials or pipe work
and equipment in order to isolate cathodically the pipeline or equipment
This connections must be rated to withstand the maximum, medium
temperature and pressure

Vibration Eliminators

Pipes connected to vibrating machinery must be isolated from the supporting
structure by vibration eliminators design for support by hanger rods
Pipes must be isolated from the vibrating machinery by use of flexible 
metal pipeline connectors of metal or rubber flexible joint, to suit the fluids
conveyed and the surrounding conditions

Valves

All valves must be factory fabricated and of types as shown on the drawings

Valves must be marked with name of manufacturer, trademark, nominal size 
and the class number, all casts in the valve body

Valves, where possible, must be of one manufacturer. Valves must be designed
for saturated steam working pressure of 861 Kpa (125 psi) and cold water 
non-shock working pressure of 1378 Kpa (200 psi) and must be manufactured 
and factory tested in accordance with the latest relevant British Standard or an equivalent
Test Certificate must be submitted for all valves
Seating surfaces of valves must be machined and finished to 
ensure tightness against leakage for the service specified and must seat freely
Hand wheels of valves must be of suitable diameter to allow 
tight closure by hand with reasonable force without additional leverage 
and without damage to stem, seat or disc
Valves located 2.4 m. or more above operating floor or platforms 
in plant rooms must be provided with a chain operated hand wheel
Flanged valves must have flanges confirming to BS 4504-NP 16/11 or ANSI 125 or equivalent
Cast iron body gate, globe and butterfly valves must be provided with position indicator
All cast iron valves must be fitted with Cast Iron indexed hand wheel clearly 
marked “Open” and “Close” with an arrow to indicate the direction of rotation

Gate Valves

Gate Valves must be used for isolating purposes, as shown on the drawings
must not be used for throttling purposes, such as regulating, balancing or controlling
must be of double-faced solid wedge disc type giving straight-line flow
Gate valves of sizes 2” mm and smaller must be of all bronze construction 
type with inside screw non-rising spindle, screwed bonnet, and screwed 
ends to ASTM B-61, B-62 or of gunmetal to BS 1400/LG2
Gate valves of size 2½” and larger must be of flanged bonnet and 
flanged ends, outside screw rising spindle type. Body, wedge and cover 
must be of cast iron, wedge facing rings and stem nut of gunmetal and
spindle of aluminium bronze. Steam seal packing must 
be of high quality suitable for Kuwait climate.
Gate valves of sizes 8” and larger must be equipped with bevel gear unit

Globe Valves

Globe valves must be used for throttling purposes to control 
the flow rate from full flow to complete shut-off
Globe valves of size 2” and smaller must be of all bronze construction 
with inside screw rising spindle, screwed bonnet and screwed ends
Globe valves of size 2½” and larger must have cast iron body, with outside
screw aluminium bronze rising spindle, renewable gunmetal or bronze disc
with gunmetal or bronze seat ring, flanged bonnet and flanged ends
Globe valve disc must be of the beveled or parabolic shape to allow throttling

Check Valves

Check valves must be silent, spring actuated lift type used to prevent 
automatically reversing of flow at pump outlets, in vertical lines and as 
indicated in the drawings or as required elsewhere
Check valves of sizes 2” and smaller must be of bronze construction, screwed ends
Check valves of sizes 2½” and larger must be of cast iron or 
ductile iron body, wafer type, stainless steel or bronze disc
stainless steel spring and renewable seats

Butterfly Valves

Butterfly valves must be used for shut-off or throttling purposes as shown on drawings
Butterfly valves must be of rubber / EPDM lined tight shut-off type
having ductile iron / ductile iron body, aluminium bronze disc
high grade stainless steel shaft, bronze bearings, monel metal
taper pins, buna-n seat liner vulcanized to the body
The butterfly valves must be wafer type or flanged type
Butterfly valves of 6” and smaller must have lever operator. Valves of 8” and larger must have manual gear operator.
All butterfly valves must be supplied with locking device and position indicator

Commissioning set must be provided on the return pipe of each 
water-cooling or heating coil and at other locations as shown on 
the drawings to facilitate balancing procedure. Commissioning set 
must consist of a double regulating valve for flow regulation and isolation 
and metering orifice station for measuring the pressure drop

The metering station must have an integral square-edged orifice plate 
fitted with a pair of pressure test plugs, which can be connected to a manometer
to measure the head loss. Bronze metering station must have cast-in flow 
direction marking, and threaded ends. The cast iron metering station must 
be supplied complete with two correctly sized gaskets and one set of flange bolting

The double regulating valve must be of the Y-pattern Oblique
globe type having a parabolic disc for allowing regular variation of the valve opening
The variation of the opening is step controlled by a graduated adjustable 
sleeve fitted with the valve to control the lift of the disc 
Each opening position is indicated by a marked number on the sleeve
At any pre-set position, the valve opening can still be regulated from
fully closed to a maximum opening at the pre-set position
The regulating sleeve is locked in the set position to prevent undesirable
interference with the setting but remaining capable of being closed 
For size 2” and smaller Commissioning Set must be of all bronze or 
gunmetal construction screwed ends and rising stem double regulating 
valve fitted with numeric indicator 

For sizes 2½” and larger, Commissioning Set materials must be as follows 

1) Metering Orifice Station
Cast iron body, stainless steel orifice plate, gunmetal retaining bush and brass test plugs 
2) Double Regulating Valve
Cast iron body, Stainless steel or bronze rising stem, gunmetal disc
gunmetal rings, anodized aluminium indicator plate and flanged ends 
Note:
No need for a separate metering Station if the DRV is provided with flow measuring provision 
DRV with pressure tapping for flow measurement will be considered 
for approval instead of independent Metering Orifice Station 
Direct reading gauge with necessary hoses and other accessories must be supplied 
in a portable sturdy metallic or plastic casing for each size of valve used 

Strainers

Strainers must be provided at the Suction side of each water circulating pump 
and at other locations as shown on drawings 
Strainers must be of Class 150 saturated steam-working pressure 
Strainers must be Y-type 
Strainers must be of same size as the connecting pipe 
Strainers for 2” pipe size and smaller must be bronze body
with stainless steel screen and screwed ends 
Strainers for 2½” pipe and larger must be cast iron 
body with stainless steel screen and flanged ends 
Screen perforation must be as follows 

Pipe size 112 B Perforation size (mm) Number of perforations per Sq. Cm. 0 B Up to 2”
2½” and larger 0.8 1.6 64 23

Automatic Air Vents

Automatic Air Vents must be provided at all high points of water piping system
irrespective of whether indicated on drawings or not to permit venting 
any air collection at high points which tends to obstruct flow 

Automatic air vents must be of the float type, and construction must be as follows 
– Body and guide cross of bronze.
– Valve seat, guide bush, upper and lower guide connecting rod
valve and guide cone of brass or stainless steel 
– Float ball of stainless steel.
– All automatic air vents must be installed with a suitable size shut-off valve 

في أمان الله