Political and social context of the 1983 abortion bill

(limited to 2000 Pa positive and 750 Pa negative)

ADDITIONAL INfORMATION RELATINg TO TABLES 5.1, 5.2 & 5.3 

High Pressure class “D” Ductwork - tables 5.1 & 5.2

1) the joints and stiffeners have been rated in terms of duct longest side and maximum spacing. Manufacturers may choose to position stiffeners at un-equal distances but must ensure the maximum spacing, as listed in columns 3 to 11 and illustrated in Fig 1, is not exceeded. refer to clause 9.4 for joints and 9.5 for stiffeners.

2) in column 1, ‘A’ = Socket and spigot joints, ‘J’ = Flanged cross joint and ‘S’ = Single stiffeners.

3) in column 2, ‘PS’ = Plain sheet and ‘SS’ = Stiffened sheet (Fig 12 for examples) by means of any of the following methods:-

(a) Beading at 400mm maximum centres;

(b) cross-Breaking within the frame formed joints and/or stiffeners;

(c) Pleating at 150mm maximum centres.

4) Stiffened panels may limit the choice of insulation materials.

5) galvanized ductwork after manufacture (refer to clause 9.6 and Appendix c).

6) Aluminum ductwork (Appendix E).

7) Stainless Steel ductwork (Appendix D).

8) Although not described in this specification, due to their relatively infrequent use, cleated cross joints are an accepted constructional practice. B&ES Ductwork group should be contacted if details of their ratings and limitations are required.

9) intermediate stiffeners using roll formed profiles, illustrated in Figs. 26 to 30 of the appropriate rating may also be utilised ensuring that rigid corners are achieved.

High Pressure class “D” Ductwork – table 5.3

10) Fixings of cross joints and stiffeners to sheets to have a minimum of two fastenings per side, with a maximum distance from the corner of 50mm.

11) if ‘un-fixed’ dimpling (Fig 2 below) is used on sheet to sheet joints then one other type of fastening must be used at each end. this does not apply to self-piercing rivets as in Fig 3 below.

12) if ‘un-fixed’ dimpling (Fig 2 below) is used to secure slide-on flanges then one other type of fastening must be used at 450mm centres with a minimum of one per side.

13) Where manufacturers of proprietary flanges and stiffeners have specific

recommendations for both fixings and centres, these shall take preference over the information in table 5.3.

Fig 2 – typical ‘un-fixed’ dimple Fig 3 – typical self-piercing rivet

Longitudinal seams 

For permitted fastenings (type and spacing), see table 2.3, 3.3, 4.3 and 5.3

Sealant shall be applied either internally or externally to the seam edge or internal to the joint seam itself. the most appropriate method will be determined by the manufacturer relative to their

fig. 4 grooved seam acceptable for use on low and medium

Stiffened Sheet Panels

Dec 2013 2

Fig. 12 Typical Illustrations of panel stiffening

Cross breaking between joints and stiffeners

Pleating may also be along the duct as illustrated above Examples of

pleated cross sections

Beading may also be along the duct as illustrated above Examples of

beaded cross sections

fig. 12 Typical Illustrations of panel stiffening

flanged cross joints

note: Figures 13 to 19 above are typical examples of cross joint profiles that are in common use for connecting rectangular sheet metal ducts.

there are no set dimensions for the proprietary profiles shown in Figs. 14 to 19 provided they were certified under the B&ES testing scheme DW/tM1 “Acceptance Scheme for new products –

rectangular cross joint classification” which is now obsolete following the advent of BS En 1507

‘ventilation for buildings – Sheet metal air ducts with rectangular section – requirement for strength and leakage’.

DW/tM1 was introduced in 1987 in order that proprietary joints for rectangular ductwork (Figs 14 to 19) that were new to the market could be tested for identical strength and leakage

characteristics relative to those of rolled steel angle (rSA) flanges, Fig 13, which were predominant at that time.

type Minimum

rating Pressure

notes / corner treatments

dimensions classes

1 2 3 4 5

fig. 13 Roll steel angle-flanged joint, mm Duct ends turned up 8 mm minimum.

with welded corners

25 x 25 x 3 J3 low A turn up as illustrated is not 30 x 30 x 4 J4 Medium mandatory.

40 x 40 x 4 J5 High if not used, the toe of the angle is to be

50 x 50 x 5 J6 sealed.

Fixing bolts Fixing bolts required at each corner and 25 x 25 x 3 6 mm at 300 mm centres.

Sealant, clamps / cleats / clips and fixings omitted for clarity

fig 17 fig 18 fig 19

Clamps / cleats / clips and xings omitted for clarity Fixing bolt

a joint, these latest tests to BS En 1507 also measure deflection of a duct and the bulging and caving of the duct panel between the joint and the stiffening frame. All test results were proven to be within the new European standards defined in BS En 1507.

Such are the results of these latest tests undertaken by B&ES, certain sheet thicknesses have been reduced as the performance of these reduced thicknesses are within the new BS En 1507

standards. these reductions are in tables 2.1, 2.2, 3.1 and 3.2 and also reflected in the B&ES J-rated flange identification system as listed in table 6.

All new proprietary flanges from the date of this publication forward shall be tested to the latest BS EN 1507 standards and this includes existing proprietary profiles that wish to take advantage of the reduced sheet thicknesses referred to in the previous paragraph.

B&ES J-rated flange identification system  

in order to align to the well-established B&ES J-rated flange identification system, all new

proprietary flanges from the date of this publication forward which have been tested for strength and leakage to the latest BS En 1507 should, when tested, also meet the criteria listed in table 6 and its associated notes that follow.

note: A test must be applied to each pressure class up to the maximum rating sought as the joint may perform differently on a larger duct size at a lower pressure. e.g. a new proprietary joint that requires a J3 rating for use on a maximum of class c – High Pressure 2000Pa ductwork systems must also be tested to meet the table 6 criteria for class A – low Pressure 500Pa and class B – Medium Pressure 1000Pa.

BS EN 1507 

When undertaking BS En 1507 tests on new proprietary profiles, the manufacturer’s technical data should be followed with respect to:

• connections to duct wall

• Sheet thickness of the proprietary profile

• corner treatment

• Addition of cleats, clips and clamps

• Application of sealants

• Strength ratings – to be stamped/engraved or indelibly printed on Fig 14-16 roll formed profiles

• Application of tie bars