FAQ-Valve Technical Questions

April 9th 2022

1. What’s the roughness of the body after sand blasting, of the machined flange, of the surface body/bonnet machined sealing, disc and seat?

The roughness of body after sand blasting– below Ra12.5; the roughness of the machined flange–Ra12.5; the roughness of the surface body/bonnet machined sealing, disc and seat– Ra 1.6.

2.When do you carry out the MT inspection – before or after mechanical treatment?

Before mechanical treatment.

3.What is the maximum depth of defect location, that can be detected by using of the flaw detector/defectoscope?


4.What flaw-detective magnetic material will be used: magnetic particles (fluorescent, colored or not), wet-powder developer or paste?

Colored fluorescent magnetic particles and wet powder paste can be all used according the customer’s requirements.

5.What method will be used after magnetic particle examination?


6.What instruments/tools do you use to fulfill the magnetic particle nondestructive inspection?

Yoke. The calibration accuracy of the yoke shall be verified at least annually and whenever the equipment has been subjected to major electrical repair, periodic overhaul, or damage. If the equipment has not been in use for a year or more, calibration shall be conducted before first use.

7.What is the precision of measurements / measuring inaccuracy?

Only indications with major dimensions bigger than 1.6mm shall be considered relevant.

8.The maximum acceptable indications of casting are as follows:

•Max.8mm long for material thickness less than 13mm.

•Max.13mm long for material equal to and bigger than 13mm thickness to less than or equal to 25mm thickness.

•Max.18mm long for material thickness bigger than25mm.

•The distance of linear indications must be bigger than the acceptable indication length.

9.Could you please provide us with more information concerning the defect indication?

Standard MSSSP-55.

10.What instruments/devices/tools do the NDT inspector use to indicate the defects?

Mark the defects with mark pens.

11.Have ZJCLV Butterfly Valves& Ball Valves been widely applied in cryogenic service?

Yes, our cryogenic valves have been widely used.

12.What features do ZJCLV cryogenic valves have?

Sub-zero treatment as special -196℃.

Permanent non-deformation as rigid body construction.

Zero leakage sealing as excellent seat and seal design.

No freeze-damage as long neck designed.

Firm treated stem as Chrome plating or nitriding.

Self-pressure relief struction.

Fugitive emissions control for flammable application.

Second sealing as grease.

13. What forged steel material does ZJCLV have for cryogenic valves?

LF2, LF1, LF3, LF5, LF6, LF9, LF787.Normally is forged steel LF2( -46℃) and LF3(-101℃).

14. What casting steel material does ZJCLV have for cryogenic valves?

LC1 ( -59 ℃) > LC2, LC2 – 1 ( – 73 ℃) > LC3 ( -101 ℃) > LC4 ( – 115 ℃) > LC9 ( – 196 ℃).

15.What standard does ZJCLV have for Cryogenic Flange/Wafer Metal Seat Butterfly Valves?

See bellow standards:

Design Standard GB BS EN API
Technical requirements of Cryogenic Butterfly Valves for low temperature situation GB/T24925 BS6364 MSS SP-134
Design Standard GB/T12238 BS EN593 API609
Face-to-Face GB/T12221 BS EN558 ASME B16.5
Connection End/Flanged GB/T9113 BS EN 1092-1 ASME B16.5
Test and Inspection GB/T13927 BS EN12266 API598
The end type and dimensions can be desinged and manufactured according to the buyers’ requirements.

16.What is the main parts and materials for ZJCLV butterfly valves?

The ZJCLV low temperature butterfly valves main parts and materials are as bellow:
Part Name low Temp.Steel/Stainless Steel Material
Body A352-LCB, A352-LCC, A350-LF2, A351-CF8, A351-CF8M, A182-F304,A182-F316
Disc A350-LF2+ENP, A182-F304,A182-F316
Stem A350-LF2,A276-304,A276-316
Packing PFTE, Lw emission combined packing,Graphite
Bolt/Nut A320-L7, A194-4/ A193-B8,A194-8