S.I. No. 19/1954:

STANDARD SPECIFICATION (SPARKING PLUGS) ORDER, 1954.

STANDARD SPECIFICATION (SPARKING PLUGS) ORDER, 1954.

I, SEAN F. LEMASS, Minister for Industry and Commerce, in exercise of the power conferred on me by subsection (3) of section 20 of the Industrial Research and Standards Act, 946 (No. 25 of 1946), hereby order as follows :--

1. This Order may be cited as the Standard Specification (Sparking Plugs) Order, 1954.

2.--(1) The specification set forth in the Schedule to this Order is hereby declared to be the standard specification for Sparking Plugs.

(2) The said standard specification may be cited as Irish Standard 34 : 1954 or as I.S. 34 : 1954.

SCHEDULE

SCOPE

1. This specification covers certain requirements of sparking plugs of 14 mm. nominal size intended for use in internal combustion engines other than aircraft engines.

PLUG REACH AND THREAD REACH

2. The plug reach as indicated in Fig. 1 shall be

for short reach plugs 0·500 in.±0·010 in. and

for long reach plugs 0·750 in.±0·010 in.

Alternatively the plug reach shall be as stated by the manufacturer.

The thread reach as indicated in Fig. 1 shall be such that the difference between the plug reach and thread reach shall not exceed 1/16 in.

BODY HEXAGON

3. The width across the flats of the body hexagon (Fig. 1) shall not exceed 0·81 in. The depth of the body hexagon shall be not less than 0·18 in.

GLAND HEXAGON

4. In the case of sparking plugs fitted with a gland hexagon the width across the flats of the gland hexagon (Fig. 1) shall be not more than 0·70 in. The width across the corners of the gland hexagon shall be not greater than the width across the flats of the body hexagon.

PLUG THREAD

5. The basic form of the plug thread shall be that of the Systeme International as shown in Fig. 2.

The dimensions of the thread shall be as given in the following table.

Compliance with the requirements of this clause may be determined by means of suitable ring and caliper gauges.

TERMINAL

6. Sparking plugs shall be fitted with a terminal of any of the types shown in Fig. 3.

The screw thread of the terminal shall be the American Standard thread N.C. 8-32-Class 2.

FINISH

7. The parts of the insulator which are exposed to the atmosphere shall be glazed or otherwise rendered impervious to moisture.

GASKET

8. Each sparking plug shall be supplied with a suitable gasket to prevent gas leakage and promote heat transfer between the plug and the engine cylinder head. The dimensions of the gasket shall be such that when released after subjection to compression at a torque of 25 lb. ft. the thickness shall be not less than 0·055 in. and not more than 0·080 in. and the outside diameter shall not then exceed the body diameter of the plug.

HIGH VOLTAGE TEST

9. A high voltage test shall be applied to each of the sparking plugs selected in accordance with Clause 13. The plugs shall be heated at 105°C. to 110°C. for 24 hours before testing. The body or shell electrode of the plug shall be removed or turned away from the centre electrode. The plug shall be mounted with the electrode uppermost in a glass vessel filled with oil at a temperature of 15°C. to 20°C. The plug shall be completely immersed, care being taken that the cavity of the plug is full of oil. The oil used shall comply with the requirements of B.S. 148 : 1941 " Insulating Oil for Transformers and Switchgear". An alternating 50-cycle sine wave potential difference of 15,000 volts root-men-squarea shall be applied between the body and the centre electrode for a period of one minute. The plugs shall withstand this voltage without sparking through the insulator.

GAS LEAKAGE

10. Each sparking plug selected for testing in accordance with Clause 13 together with its gasket shall be screwed into a suitable pressure bomb and tightened with a torque of 25 lb. ft. The firing end shall then be subjected to an air pressure of 225 lb. per sq. in. at room temperature. There shall be no signs of gas leakage when the assembly is immersed in transformer oil.

RESISTANCE TO TORSION

11. Each sparking plug which has been subjected to the high voltage test shall be screwed by hand into a suitably threaded hole in a steel block until the shoulder rests on the surface of the block. A gasket shall not be used. A torque of 40 lb. ft. shall be applied to the body hexagon by means of a torque wrench. When unscrewed and examined the plug shall show no signs of fracture.

MARKING

12. Every sparking plug shall be permanently and clearly marked with the name or mark of the manufacturer.

SAMPLING

13. For the purpose of testing conformity of sparking plugs with the requirements of this specification 10 plugs shall be selected at random from each lot of 1,000 or lesser number of plugs. In the case of lots of more than 1,000 plugs, 10 plugs, and in addition one plug for each 1,000 plugs contained in the lot, shall be selected.

GIVEN under my Official Seal, this 28th day of January, 1954.

SEÁN F. LEMASS,

Minister for Industry and Commerce.